GUIDE FOR CONDUCTING FACTORY CAPABILITY ASSESSMENT FOR POWER TRANSFORMERS
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GUIDE FOR CONDUCTING FACTORY CAPABILITY ASSESSMENT FOR POWER TRANSFORMERS
Working Group A2.36
April 2013
GUIDE FOR CONDUCTING FACTORY CAPABILITY ASSESSMENT FOR POWER TRANSFORMERS WORKING GROUP A2.36 Task Force 3
Convenor: T. Breckenridge (UK) Task Force Leader: A. Manga (CA), WG Members N. Buthelezi (SA), A. Cancino (MX), L. Cornelissen ( BE), E. de Groot (NL), M. Figura (PL), T. Fogelberg (SE), T.Gradnik (SI), AC Hall (UK), J. Lackey (CA), M. Lamb (USA), A. Mjelve (NO), M. Oliva (SP), V. Podobnik (HR), S. Ryder (UK), K. Ryen (NO), C.Swinderman (USA), J.Velek (CZ), M. Zouiti (FR).
Copyright © 2013 “Ownership of a CIGRÉ publication, whether in paper form or on electronic support only infers right of use for personal purposes. Unless explicitly agreed by CIGRÉ in writing, total or partial reproduction of the publication and/or transfer to a third party is prohibited other than for personal use by CIGRÉ Individual Members or for use within CIGRÉ Collective Member organisations. Circulation on any intranet or other company network is forbidden for all persons. As an exception, CIGRÉ Collective Members only are allowed to reproduce the publication”. Disclaimer notice “CIGRÉ gives no warranty or assurance about the contents of this publication, nor does it accept any responsibility, as to the accuracy or exhaustiveness of the information. All implied warranties and conditions are excluded to the maximum extent permitted by law”. ISBN: 978-2-85873-224-1
WG A2-36
Guide for conducting factory capability assessment for power transformers
CONTENTS 1
SCOPE AND OBJECTIVES .................................................................................................1
2
REFERENCES ......................................................................................................................4
3
MANAGING QUALITY ..........................................................................................................4
4
TECHNOLOGY BASE ..........................................................................................................5 4.1 Background Description of the Business ..................................................................... 5 4.2 Transformer Type produced by the Factories ............................................................. 7 4.3 Origins of Technology Base of Factory........................................................................ 7 4.4 Familiarity and Compliance with applicable Industry Standards ................................. 7 4.5 Documentation of the Design and Manufacturing Technology Base .......................... 7 4.5.1 Investigations and R&D Reports ..........................................................................8 4.5.2 Basic Design Theory ............................................................................................8 4.6 Product Design and Manufacturing Rules and Instructions......................................... 9 4.6.1 Product Design Rules ...........................................................................................9 4.6.2 Design Methods and Tools .................................................................................12 4.6.3 Manufacturing Technology in Production Standards .........................................13 4.6.4 Testing technology .............................................................................................14 4.7 Other means of evaluating the technical capabilities of a factory ..............................14 4.8 Summary.................................................................................................................... 15
5
DESIGN PROCEDURES AND IT TOOLS ..........................................................................15 5.1 Design experience of market ..................................................................................... 15 5.2 Design experience of product range .......................................................................... 16 5.3 Specification understanding ....................................................................................... 16 5.4 Design process quotation and order .......................................................................... 16 5.5. Research and Development Activities ....................................................................... 17 5.6 Design manual, design rules ..................................................................................... 17 5.7 Design software and it’s maintenance ....................................................................... 18 5.7.1 In House Development, Outsourced ..................................................................18 5.7.2 Software Purchaser Practice ..............................................................................18 5.7.3 Software Data Base Integrity ..............................................................................18 5.7.4 Maintenance of Software ....................................................................................18 5.7.5 Computer Modelling, Dielectric, Magnetic, Thermal and Mechanical Problems 19 5.7.6 Transient Modelling ............................................................................................19 5.7.7 Engineering 2-D or 3-D Method..........................................................................19 5.7.8 Feedback from Testing .......................................................................................19 5.8 Experience level of engineers .................................................................................... 19 5.9 Engineering organisation ........................................................................................... 19 5.10 Expert technical support ............................................................................................ 19
6
SUPPLY CHAIN MANAGEMENT ......................................................................................20 6.1 Background ................................................................................................................ 20 6.2 Bushings and Tap Changers ..................................................................................... 21 6.3 Winding Conductors................................................................................................... 22 6.4 Oil ............................................................................................................................... 22 6.5 Core Steel .................................................................................................................. 22 6.6 Insulation board and insulation components ............................................................. 23 6.7 Other Components and Materials .............................................................................. 23 6.8 Summary.................................................................................................................... 24
7
MANUFACTURING METHODS .........................................................................................24 7.1 General: ..................................................................................................................... 24 7.2 Production Planning and Material Warehouse: ......................................................... 25 7.3 Main Tank and Steel Fabrication: .............................................................................. 25 7.4 Core Cutting/Stacking: ............................................................................................... 26 7.5 Winding Room: .......................................................................................................... 26
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WG A2-36 7.6 7.7 7.8 7.9
Guide for conducting factory capability assessment for power transformers Winding Sizing: .......................................................................................................... 27 Active Part Assembly: ................................................................................................ 28 Final Dry Out: ............................................................................................................. 29 Final Assembly: .......................................................................................................... 29
8
TESTING ................................................................................................................................. 8.1 Test Accuracy ............................................................................................................ 30 8.1.1 Calibration of test equipment .............................................................................30 8.1.2 Accuracy Analysis of Measurements .................................................................30 8.2 Test equipment .......................................................................................................... 30 8.3 Test engineers ........................................................................................................... 31 8.4 Standards ................................................................................................................... 31 8.5 Documentation ........................................................................................................... 31 8.6 Failure investigation ................................................................................................... 31 8.7 Others items ............................................................................................................... 32
9
WARRANTY AND SERVICES............................................................................................32 9.1 Warranty .................................................................................................................... 32 9.2 Services ..................................................................................................................... 33 9.2.1 Sales organisation ..............................................................................................33 9.2.2 After sales arrangement .....................................................................................34
10
PROJECT MANAGEMENT STRUCTURE .........................................................................35
11
HUMAN RESOURCES, HEALTH AND SAFETY MANAGEMENT ...................................35 11.1 Human resources....................................................................................................... 35 11.1.1 Aims ....................................................................................................................35 11.1.2 Legal and Cultural Aspects .................................................................................36 11.1.3 Industrial Relations .............................................................................................36 11.1.4 Recruitment ........................................................................................................36 11.1.5 Training ...............................................................................................................37 11.1.6 Vulnerable Workers ............................................................................................37 11.2 Health, Safety and Working Environment .................................................................. 37 11.2.1 Working Environment .........................................................................................37 11.2.2 Working Hours ....................................................................................................38 11.2.3 Security ...............................................................................................................38 11.2.4 Health and Safety Management .........................................................................38 11.2.5 Dangerous Chemicals ........................................................................................39
12
TRANSPORT .......................................................................................................................... 12.1 General ...................................................................................................................... 40 12.2 Delivery Terms ........................................................................................................... 40 12.2.1 Purchaser to Collect (INCOTERMS Group E) ....................................................40 12.2.2 Main Transport Arranged by Purchaser (INCOTERMS Group F) ......................40 12.2.3 Main Transport Arranged by Factory (INCOTERMS Group C) ..........................41 12.2.4 Factory to Deliver (INCOTERMS Group D) ........................................................41 12.3 Methods ..................................................................................................................... 41 12.3.1 Air .......................................................................................................................41 12.3.2 Barge/ Coastal Ship ............................................................................................41 12.3.3 Ocean Going Ship ..............................................................................................41 12.3.4 Rail ......................................................................................................................42 12.3.5 Road ...................................................................................................................42 12.4 Voyage Assessment .................................................................................................. 42 12.4.1 Assessment of the Factory’s Preparation capability...........................................43 12.4.2 Preparation and Execution of transport ..............................................................43 12.4.3 Personnel Training / Education Considerations .................................................43 12.4.4 Standards of Care for Transportation / Freight Forwarding Vendors .................43 12.4.5 Checks for All Shipments, Lifting, Ocean vessels ..............................................44 12.5 Inspection on Receipt ................................................................................................ 44
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13
INSTALLATION, COMMISSIONING AND STORAGE ......................................................45 13.1 Installation and commissioning .................................................................................. 45 13.1.1 General ...............................................................................................................45 13.1.2 Oil .......................................................................................................................45 13.1.3 Auxiliary Electrical Wiring ...................................................................................46 13.1.4 Health and Safety ...............................................................................................46 13.2 Storage ...................................................................................................................... 46
14
FINANCIAL, COMMERCIAL AND LEGAL ASPECTS ......................................................47
15
FACTORY PERFORMANCE (LEAD TIME DELIVERY, ON TIME DELIVERY…) ............47 15.1 On-time delivery performance ................................................................................... 48 15.2 Factory test failure performance ................................................................................ 48 15.3 Other factory performance measures ........................................................................ 49 15.4 Customer References ................................................................................................ 49
16
SERVICE PERFORMANCE................................................................................................50
APPENDIX 1: QUALITY MANAGEMENT SYSTEM ...................................................................52 A1.1 Quality Management System, Document Requirements (ISO9001-2000, chapter 4) .. ................................................................................................................................... 52 A1.2 Management Responsibility (ISO9001-2000, chapter 5)........................................... 52 A1.3 Resource Management (ISO9001-2000, chapter 6) ................................................. 53 A1.4 Product Realisation (ISO9001-2000, chapter 7) ........................................................ 53 A1.4.1 Planning of product realisation ...........................................................................53 A1.4.2 Purchaser related processes ..............................................................................53 A1.4.3 Review of requirements related to product .........................................................53 A1.4.4 Purchaser communication ..................................................................................53 A1.5 Design and Development .......................................................................................... 54 A1.6 Purchasing ................................................................................................................. 55 A1.7 Production and service provision ............................................................................... 55 A1.7.1 Production Control ..............................................................................................55 A1.7.2 Production Process Validation............................................................................55 A1.7.3 Product Identification, Traceability......................................................................55 A1.7.4 Purchaser property .............................................................................................56 A1.7.5 Preservation of product ......................................................................................56 A1.7.6 Monitoring and Measuring Devices ....................................................................56 A1.8 Measurement, analysis and improvement (ISO9001-2000, chapter 8) ..................... 56 A1.8.1 Customer Satisfaction ........................................................................................56 A1.8.2 Internal audits .....................................................................................................57 A1.8.3. Monitoring and measurement of processes .......................................................57 A1.8.4. Monitoring and measurement of product ............................................................57 A1.8.5. Control of non-conforming product .....................................................................57 A1.8.6 Analysis of data ..................................................................................................57 A1.8.7 Improvement .......................................................................................................58 A1.8.8 Corrective action .................................................................................................58 A1.8.9 Preventive action ................................................................................................58 APPENDIX 2: EXAMPLE OF QUESTIONNAIRE .......................................................................59
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Guide for conducting factory capability assessment for power transformers
SCOPE AND OBJECTIVES
This guide to the assessment of the capability of a manufacturers’ factory has been produced under the headline of “Transformer Procurement Process” and is one of a number of key steps in the process. A typical procurement process is shown in figure 1 and this process diagram clearly shows where this guide fits into the whole procurement process with various quality factors other than just the cost. It also represents a typical process for transformer procurement for a multi-year's contract agreement. Decisions made during the procurement process have a major impact on the future reliability of the transformer and one of the most important is the decision – which manufacturer should be considered, and which of their factories is capable of manufacturing the unit? While a good specification (refer CIGRÉ Technical Brochure 528: Guide for Preparation of Specifications for Power Transformers) is important, and the need for a thorough design review (refer CIGRÉ Technical Brochure 529: Guide for Conducting Design Reviews for Power Transformers) can never be understated, the selection of the factory at contract placement may often be the greatest risk in the whole procurement process. Before any contract is placed it is extremely important that the purchaser clearly understands what he will be getting for his money. This can only be ensured by an in-depth knowledge of the capability and competencies of the proposed manufacturer’s facility and what the manufacturer has understood and interpreted from the specified requirements. It should also be remembered that by the time the detailed design review is completed, it is often too late to change manufacturer. The importance in understanding the capability of a manufacturers’ particular factory is key to ensuring the procurement and commissioning of a quality product that is fit for purpose. This does not necessarily mean that there is a clear pass or fail criteria for the assessment system or a series of hurdles that the factory must clear, rather the assessment is intended to provide the purchaser with sufficient information on the factory’s processes and procedures in order to assist the purchaser in making an informed decision. Where the assessment highlights shortcomings in capability, these may be acceptable to the purchaser based on the balancing of the risks involved, or it may be that the purchaser can mitigate the shortcomings by committing more technical resources to work closely with the factory through the contract. It is intended that this guide will assist the purchaser to obtain most, if not all, of the information required in order to answer the key question - “Should I purchase a transformer from this facility?”; and the following question, “If I do purchase from this facility, what else do I need to do to ensure the transformer eventually delivered to site meets all the specified requirements?” This document has been prepared by CIGRÉ Working Group A2.36 as an aid to purchasers in the assessment of the capability of the manufacturer's factory. It gives guidelines and recommendations for the assessment of the whole delivery process where the purchaser and factory are acting together as a cross functional team to perform the assessment. The purpose of this guide is to serve both the purchaser and factory in the efforts to mitigate risks. It expresses the best practices in the industry to secure high quality of the delivered transformer. The guide can be applied as a pre-qualification process prior to issuing a tender to avoid unsuitable factories for being invited to tender. If used for this purpose it is unlikely to be as comprehensive as a pre-contract award
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Guide for conducting factory capability assessment for power transformers
assessment. Alternatively, it could form part of a proposed transformer purchase contract. As transformers are the key elements in the electrical infrastructure, with their requirement on highest availability, tender evaluations must be made on more factors than only first price. As minimum requirements, the guide covers many areas such as commercial risks, design and engineering, manufacturing and test facilities, transport capability, quality control etc. It does not point out specific solutions or methodologies but aims more at seeking evidence that the methods chosen are all proven by testing, measurements or simulations. The content of the guide is made with the expectation that a purchaser shall be getting some guidance to perform such an assessment on his own, where the assessment is relative among many factories. Purchasers need to develop their own check list and evaluation criteria based on their own business needs, however an example of such check list is provided in Appendix 2 for guidance.
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Identify Transformer Requirements
Prepare and Issue Technical Specifications
Determine List of Tenderers
Assess Tender Returns Technically
Issue Tender
Pre Contract Design Review
Place Contract
Yes
Assess Capability of Manufacturer Any previous Service Experiences of manufacturer?
Post Contract Design Review
On Going Manufacturers Inspections
Is Tenderer Capable of Manufacturing?
No
Factory Acceptance Testing
Do Not Use Manufacturer
On Site installation and Commissioning
Shipping to Site
Concerns over suppliers’ capability?
Post Contract Clarification of Requirements
End of Procurement Process
No
Continue to Use Manufacturer
Yes Re-assess Capability of Manufacturer
Enhanced inspection and review Is Manufacturer Capable of Manufacturing?
No
Yes Yes
Can issue be resolved with additional supervision?
No
Figure 1 - Example of a transformer procurement process
3
Terminate Contract
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Guide for conducting factory capability assessment for power transformers
REFERENCES
(Final report of CIGRÉ working group A2.05), “An international survey on failures in large power transformers in service”, Electra 88, pp 22-48, 1983 CIGRÉ Technical Brochure 528: “Guide for Preparation of Specifications for Power Transformers” CIGRÉ Technical Brochure 529 “Guide for Conducting Design Reviews for Power Transformers” IEC 60050 IEC 60076-5 IEC 60076-8 IEC 60296
all relevant parts, “International electro-technical vocabulary” Power transformers: Part 5 – ability to withstand short-circuit Power transformers: Part 8 – application guide Fluids for electro-technical applications – unused mineral insulating oils for transformers and switchgear
ILO convention 1 ILO convention 14 ILO convention 29 ILO convention 105 ILO convention 111 ILO convention 132 ILO convention 138
Hours of work (industry), 28 November 1919 Weekly rest (industry), 17 November 1921 Forced labour, 28 June 1930 Abolition of forced labour, 25 June 1957 Discrimination (employment and occupation, 25 June 1958 Holidays with pay, 25 June 1958 Minimum age, 26 June 1973
INCOTERMS 2000
ICC Official Rules for the Interpretation of Trade Terms,” ICC publication 560, 2000 edition
ISO 8501-1
Preparation of steel substrates before application of paints and related products – visual assessment of surface cleanliness Quality management systems – requirements Paints and varnishes – corrosion protection of steel structure by protective paint systems – classification of environments Environmental systems – requirements, with guidance for use Guidelines for auditing management systems
ISO 9001 ISO 12944-2 ISO 14001 ISO 19011 OHSAS 18001 requirements”
Occupational health and safety management systems –
Note: The above references can be obtained from the following web sites: IEC Standards - www.iec.ch ISO (International Organization for Standardization) standards - www.iso.org ILO (International Labour Organization) documents - www.ilo.org OHSAS (Occupational Health & Safety Advisory Services) standards - www.ohsas.org INCOTERMS (International Chamber of Commerce)- www.iccwbo.org 3
MANAGING QUALITY
Power transformer design and manufacturing is a very complex set of operations with a high percentage of manual work, where each process step should be managed in terms of quality. Essentially almost all factories have implemented a quality management system that complies with the ISO 9001 Standard. The ISO 9001 Standard defines quality management principles based on a process approach, which is applicable to all kinds of industries. That is why it defines basic 4
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Guide for conducting factory capability assessment for power transformers
processes which appear at any organisation independent of what product is manufactured. The word “product” does not necessarily mean the final product; it should be understood to be the result of any activity (process) the company performs in order to develop and manufacture the final product (transformer) that fulfils the purchaser requirements. The ISO 9001 Standard has undergone changes and developments during the past 15 years, but the basic idea has remained the same: To ensure that all operations involved in all processes are carried out under controlled conditions. The Standard covers basically the following areas:
Quality Management System
Management Responsibility
Resource Management
Product Realisation (includes Design and Purchasing)
Measurement, Analysis, Improvement
The requirements of the ISO Standard are explained in Appendix 1 in more detail with specific focus on transformer manufacture. Continual improvement and customer satisfaction are the basic prerequisites of successful Quality Management. As soon as the factory fulfils the requirements of the ISO 9001 standard, it can be certified by an external QMS certification authority. This certification procedure usually has to be repeated every three years. The certification authority issues a QMS certificate which carries the precisely defined subject of certification e.g. “Design, manufacturing, testing …of power transformers….” the quality management standard and the certificate expiration date. The certificate proves that the factory’s processes comply with the requirements of the Quality Management Standard. However, even in the case of a certified factory, it is important a purchaser makes his own assessment of the factory's capabilities before placing an order to be sure the factory is capable of meeting all requirements for a transformer, especially if the factory is new to the purchaser or otherwise unproven. The ISO 9001 certification is a necessary requirement in the evaluation of a factory, but it is not sufficient as the sole basis on which to evaluate the quality of the factory. Many transformer factories have also implemented Environment Management Systems relying on International standards ISO 14001 and/or Health and Labour Safety Management Systems based on OHSAS 18000. The rules described by these standards are similar to those given by the ISO 9001 standard for quality management systems including the certification (see appropriate chapters for details). 4 4.1
TECHNOLOGY BASE Background Description of the Business
The power transformer is a product based on fundamental technology that has been available for more than 100 years. However, continuous improvement over the years in areas such as materials, research and development advancements, design engineering capabilities, verification testing capabilities and computer modelling has led to some
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significant differences in the technologies used by the various power transformer factories engaged in today’s worldwide industry. Power Transformers are built by an electrical manufacturing industry which is characterised as an Engineering to Order (ETO) business. In simple terms it means that it is an industrial process which differs considerably from very Standardised Processes (e.g. factories producing HV and LV cables) or the Assembly to Order processes (e.g. factories producing HV & MV breakers, bushings and tap changers). In an ETO process the products are unique, almost one at each order, engineered to fulfil one specification. The production flow is very specific to each order and the factories must have very functional layouts to fit the wide variety of products. A third dimension is the complexity and size of the power transformers, see Fig.2
An ETO Business Types ofProducts Manufacturing Process T&D Complexity charter Power unique Transformers Many products: one each
Volume Many Many products: Several products: medium products: low volume volume high volume
One product: very high volume
Complexity and Size Layout and Flow
Large Power Transformers Functional layout, flow extremely varied
Job Shop
GIS Substations Small Power Transformers
Batch Flow
Cellular layout, flow varied with patterns
HV Switchgear Distribution Transformers
Large Motors Line flow, operator paced, flow mostly regular
OLTC
Operator Paced MV & HV Breakers Line Flow
Small Motors
Bushings
MV Apparatus Line flow, equipment paced, flow regular
Machining & Components
Machine Paced Line Flow
© Copyright year ABB - 4 -
LV Breakers Continuous flow: flow rigid
Insulation Materials
Continuous Flow
HV & LV Cables
ETO
ATO
STD
ETO Business = Engineering to Order Business
Figure 2 - T&D Product Complexity Charter The whole business aim is to optimise, engineer and manufacture individual transformers to lowest cost plus capitalised losses according to detailed purchaser specifications. As variations of requirements are the highest challenge in this business, purchasers and factories must find ways to mitigate all the risks in all sub-processes from specification production through to commissioning on site. The end products are expected to last for many years of service. Most of the processes involved are referred to in this guide but in this section of the guide a closer look is taken on what is required and what is meant by a Technology base, and what essential areas need to be reviewed in assessing an Engineering to Order business. 6
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4.2
Guide for conducting factory capability assessment for power transformers
Transformer Type produced by the Factories
There are two basic types of transformer core and coil assemblies which are referred to as the core-type design or the shell-type design. See IEC 60076-8 for further details. While the two types of designs can be adopted for any given transformer application, each design type does have certain basic differences that need to be understood when evaluating the technology base of a transformer factory. However the requirements of the Technology base for the two design types are fundamentally the same. 4.3
Origins of Technology Base of Factory
When evaluating a transformer factory, it is often beneficial to gain a basic understanding of the origin of a factory's technology base. Today there are three types of factories that are the owner of the technology:
belonging to a global manufacturer with factories in different countries, sharing technology or not regional manufacturers for both local and global supply local manufacturers for mainly local supply
In all above groups there can be a license agreement with a licensor. In such cases it can be worthwhile to ask for the signed license agreement and check the contents and what the licensor is obliged to give the licensee. In some cases the license agreement has been terminated meaning that the licensee is no longer supported by the licensor. In some other cases the current licensee agreement is shared with many factories and the licensee gets all the R&D results, development results, instructions and IT tools by a structured implementation system. In the last case the licensee will be provided with all results from international development work and does not need to have its own large development team. A factory with such a license agreement shall be honoured with the same assessment as one with a full R&D organisation. That means that the source of the technology can differ from the factory which is using it. Therefore when the technology is being assessed, discussions need to involve the factory which provides the technology base. 4.4
Familiarity and Compliance with applicable Industry Standards
Around the world, a number of different industry standards exist for transformers. Some standards are national standards applicable to transformers used in a given country or region, while other standards are international standards adopted by a wide range of countries around the world. Examples of industry standards are IEC and IEEE standards to name a few, while several other industry standards exist as well. If a purchaser wants to ensure that transformers utilised on their system comply with the applicable industry standards in the purchaser’s country, it is important for the purchaser to verify that potential manufacturing facilities being considered for the supply of transformers to that purchaser are capable of understanding and complying with the applicable industry standards the purchaser desires. 4.5
Documentation of the Design and Manufacturing Technology Base
Power Transformer technology must be documented. This documentation must be kept up to date as new experiences are acquired from R&D, more sophisticated programs,
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new materials, improved manufacturing methods and feedback from testing and years of field service experience. Transformer engineering is today more or less supported by integrated IT programs which are based upon these documents; well ordered documentation supported by regular updates and clarity are the basic characteristics to look for when assessing a technology. It is more important to first see the documentation structure and interrelationships in the technology descriptions before going more deeply into the technical content or details. Documentation should consist at least of the data sets or aspects below: 4.5.1 Investigations and R&D Reports Investigations and R&D Reports describing the evolution of the technology at the factory. A typical power transformer factory shall have such a library where it is possible to track the background for chosen rules, criteria, methods in design and manufacturing. These reports are of course intellectual proprieties but show the factory’s Technology base. (A licensor shall give access to the company as a licensee for the licensor’s report libraries). To go through the last 5 -10 years content of the Reports is one part of the assessment, it shows that the management understands the needs to maintain competence and knowledge as an intangible asset. If there are no Technology Report systems in the factory, enquiries need to be made to determine how the knowledge and competence is maintained and spread. It is possible in some cases that some “technical gurus” are the carrier of the Know-How but in the long term this is a very risky practice. There has been a tradition that the technology has been much related to persons but this is no longer viewed as reliable. 4.5.2 Basic Design Theory Basic Design Theory where the basis for calculation of power transformer characteristics are described (specifically how the verification of a design is documented) e.g. short circuit calculations, no load loss calculations, load losses in windings and structural parts, acoustic sound levels, windings temperature rises etc. It is also here that the dielectric design is documented from which the main insulation in windings between windings and to earth are determined
Technical Standards where a given element, component consisting of several elements, are described, (Geometry rules and parametric interrelationships). Here you can find how the core or a specific winding with its elements are built up. Very often you can find here the factory’s detailed description of the Main Insulation system (between the windings and towards the yokes) or how the winding exits or the cleats and leads are built up. Material Specifications for all Material or Components which are referred to at all Material and Component purchases. Set of Standard drawings, Corporate Standards, document and drawing numbering system. Production Standards where the manufacturing methods, processes with check and control points, tools and equipments are clearly described and visualised. Nowadays those documents can normally be found close to the work cell PC’s integrated with the drawing system.
The assessment of the Technology as described is not so much about the content, dimensions, calculation formulas, acceptance criteria etc., but more about how the documentation is built up, its structure and the responsibilities of those to edit and approve. It is important to find out how the continuous improvement process is documented and how the management of the maintenance is led and structured. The 8
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Power Transformer Technology is a slow evolution where the input is the feedback from production, final acceptance testing and field service. A modern Technology assessment today needs to focus on these aspects rather than the design elements or formulas. One of the biggest reasons for this is the interrelation between all the electrical, thermal and mechanical rules and design/component standards. If one part or chain of the interrelations is questioned the dependence to another chain may be overlooked. In this guide the aim is to depart from the more subjective assessment made by single individuals. Another most important part is to validate that above documented content is built into the design programs (IT Programs) that are used by the electrical and mechanical design engineers. Instead of questioning a rule or a formula the assessment shall concentrate more on proving the documentation is fully used and updated in the IT programs. Greater reliance on an audit where rules and criteria have a documented origin which leads to elements and combined structures is more important. 4.6
Product Design and Manufacturing Rules and Instructions
The Technology base for an ETO industry can be broken down into three major areas:
product design rules design methods and tools manufacturing/Testing methods and tools
4.6.1 Product Design Rules There are different views how to structure Transformer Design rules. Very often the rules are divided into three major areas as:
dielectric rules thermal rules mechanical rules
But it is possible to define the transformer physics according to a more practical view that takes into account the most important areas that verify the design, manufacture and testing of a transformer. a) Dielectric Rules Electric breakdown is a stochastic process and usually follows an extreme value (weakest link) statistical distribution, most commonly used is the Weibull distribution. Correct dielectric dimensioning of transformers is very important and needs to balance between the margins and failure rate. All factories must have documented evidence in how they transfer the knowledge of electrical break down strength into design rules and insulation structures. It should be clear how a distance is chosen from the knowledge of calculation of fields taking into account amplitudes, directions, durations, material borders (creep).
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Very often today the main insulation is calculated automatically from the purchaser’s specification of dielectric tests. This has been verified over years of production and fits the factory’s production and insulation sourcing procedures. It is not so meaningful today to question every stressed area if the factory has a documented insulation system and can demonstrate its application. In general, this concept applies to a continuous insulation system but where discontinuities occur, such as at winding exits, leads and bushing entries, 3-D calculation tools and the stress criteria with volume considerations need to be documented and followed by the designer. In a capability assessment it is not so helpful to argue about stresses but instead to let the factory show from factory acceptance testing (FAT) results where normally the weaknesses over many years production have normally occurred. If profound test failure analysis documentation is presented extending over many years this offers good evidence to judge the soundness of the dielectric rules. b) Magnetic Core Performance Rules The factory needs to show that it has all the tools required to calculate the no load losses from a given geometry of a core. Here it is a must to show how one calculates the core losses from the iron losses for different core steel grades. With the losses the factory must also be able to show the rules used to calculate in-rush currents, excitation currents and their harmonics. One important area is to calculate core internal and surface temperatures at rated and over rated conditions. Very often the purchasers need to know the stress in the core at dc bias or under GIC conditions. Also here the best way to assess the Magnetic Core Performance technology is to assess the accuracy between measured performance data over years versus calculated data. Such files of analysis results should be available at the factory. c) Acoustic Sound Rules Sound limitation requirements are more and more common. Nowadays both sound at load and no-load are of importance. Calculation of vibration modes, resonances at different frequencies plays an important rule to calculate the sound. Accurate calculation of the Core Noise Level and its frequency spectrum components, must include consideration of the core steel magnetostriction characteristics, type and core geometry, joints and flux density, core clamping efficiency and of course voltage frequency and form factor. Transmission of vibration and sound between core and tank is the next step and the final step is to determine the sound radiation properties of the tank. Accurate calculation of core & tank resonance frequencies allows accurate prediction of the noise level at the design stage and later avoids serious noise level problems later. There are a number of noise reduction techniques available that involve core steel, tank design, core & tank damping and vibration isolation aspects. The factory's own statistics cover calculated and measured noise levels and spectrums and are the best indicator of quality.
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Purchasers should consider requesting sound levels for both no-load and loading in the specifications. d) Load Losses and Load Temperatures This area is one of the most critical design aspects to assess as it greatly affects the long term life expectancy of the transformer. Different transformers have different loading profiles and for those units that will be loaded up to the rated power and above such as Generator Step-Up (GSU’s) must have an accurate design and accurate tests. As the Standards of verification of the thermal integrity are weaker than electrical insulation tests it is important to investigate the factory’s thermal calculation rules and comparisons to measured data. Therefore it can only be stressed here that the winding losses and the temperatures in oil and along the windings should be evenly distributed and that the factories today should be able to show how the daily order design programs are working, backed up by the physical thermal rules and design practice. Current practice is not to use CFD (Computerised Fluid Dynamics) as a common tool to be used for each particular design but rather to solve specific problems; today it is possible to fully check the thermal design programs by CFD programs that are now available on the market and measure internal hot spot measurements by fibre optic sensors. One area which is not covered by the current standards is proving the capability to calculate hot spot temperatures of the tank, core, and internal clamping structures at maximum operating ratings. The factory must demonstrate their experience by using 2D or 3D electro-thermal calculation using Finite-Element Method (FEM) coding. Again such programs are now available. It is the manufacturer’s task to prove calculations versus measurement, internally by hot spot measurements and externally by infrared cameras. e) Short Circuit Strength and Mechanical Integrity The other most critical technology area today is to show competence in verification that the factory can design and build short circuit proof transformers. The first consideration is network factors. There is an expanding cross border electricity trade bringing network operations closer to their physical limits. Transmission reserve margins are decreased. Development of wind generation parks often integrates regions without taking into account available network capacities. Load flows are varying and network components are ageing. The second consideration concerns the transformer itself. Transformers are built closer to their physical limits and as stated earlier all transformers will see more severe short circuit duty than before. Therefore short circuit strength is the key to long transformer service life and when short circuit events occur they may cause catastrophic consequences. Very few units are short circuit tested nowadays and this due to commercial and short circuit (sc) test capacity reasons. This means that one of the most critical parameters of the transformer is not tested. In a way the industry has given up and one of the most important capability assessments is therefore to go deeper into the manufactures technology base with regard to building
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short circuit proof transformers. It is therefore very important that the factory can prove by short circuit calculation and test experience that it has the capability to design short circuit proof transformers. IEC 60076-5 provides good guidelines and these should be followed. IEC 60076-5: “Ability to withstand short circuit” identifies requirements for power transformers to withstand the effects of over currents originated by external short circuits without damage. The ability to withstand the dynamic and mechanical effects of short circuits shall be demonstrated either:
by special short circuit tests by calculation, design, manufacturing considerations, given in guidelines Appendix A
There are no clear statistics of short circuit failures in the world for various reasons. This failure mode might be hidden and it might be interpreted as a dielectric failure or the evidence may be destroyed by a fire. Therefore the factory must clearly show how the axial and radial mechanical stresses in the windings during short circuits are calculated, and what radial and axial stress criteria are applied, including the maximum ratio short circuit withstand strength to short circuit force. The best method is to judge all short circuit tests the factories has made over the years, see above IEC method. It is also important to judge the manufacturer's rules to design inner tertiary and LV windings where their location makes them very sensitive to radial compression forces. The most straightforward design principle is to let them be self supporting and allow the copper strength to determine the dimensions at free buckling. There are of course other design principals and they too must then be proven by long term verifications. Axial forces should be calculated for all tap positions and the axial tolerances at winding manufacturing must be fully considered. There are numerous discussions about axial pressing methods and what they mean for short circuit strength but there is only one good way to judge and that is by examining the factory's short circuit test records. If the factory has not made many short circuit tests, one must consider investing in such tests during a longer time period of some years. Another short circuit feature in power transformers is the capability to calculate the spiralling effect, mostly in helical windings. (i.e. when the axial and radial pressures are imposed on a helical winding there is a rotational force that tends to twist the windings and move the leads exits and increase the risk of electrical break down). Finally, the capability to mitigate risks during transport and seismic stresses must be assessed. The factory must be able to state its design principles to withstand high transport accelerations and earthquakes. 4.6.2 Design Methods and Tools This section is not a technology per se, but it plays an important role when it comes to building in quality and reducing the risks for test failures and service problems. Modern industries today use simulations of all kinds to verify design, tools, building blocks, production flows etc. IT simulation tools are readily available today.
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Some very important tools used in the design and engineering process which must be taken into account in the capability assessment process are described below. One type of simulation is the Optimisation tool which can have different levels of sophistication. It is possible to optimise material cost versus losses. The more accurate the user data and updated cost factors is, the higher the purchaser value. Therefore the factory should be able to describe the way the final product is optimised to comply with the purchaser's specification. Today all factories are using 2-D electrical transient IT tools to dimension the windings for all types of impulse stresses. The accuracy may be shown by checking the analysis of dielectric test failures over the years if they are attributable to engineering and manufacturing causes. Another way is to let the factory show all the RSO (Recurrent Surge Oscillograph) measurements upon which the design calculations are based. The factory might also show if it can calculate down to single turns. Transient tools such as four poles analysis can also be a part of a complete transient analysis of the transformer. Thermal calculation tools have been mentioned to calculate oil flow velocities and the temperature gradient cross the paper wrapping from copper to oil insulation, taking into account the losses in parts and sections of the whole winding length. Another set of programs needed is to make a lot of 2-D calculations, normally based on FEM codes, of leakage flux and electrical fields between different parts in the rotational symmetries. By these means it is possible to calculate magnitudes and locations of maximum electrical stresses, leakage flux and eddy current losses and magnitudes and location of maximum short circuit forces. 3-D programs are today used to study complex 3-D structures to calculate dielectric field stresses. These programs are normally used with 3-D CAD modules for easy descriptions of the geometry. The factory's internal stress criteria should be implemented in those programs. For specific complex units and for product development factories today also use 3-D electro-thermal calculation using FEM code for tank heating and 3-D electro-mechanical calculation of short circuit forces. The results of this modelling should be verified by measurement where possible. However, just having such tools available is not enough. They must be used by well trained engineers. Simulation is also a way to give the engineers a better understanding of the transformer physics and it is much easier now to estimate the intrinsic safety margins of a design to further reduce test failures or future in service problems. The capability assessments here are of significant importance because the engineering design input constitutes some 80 % of the cost and a large part of the risk for catastrophic failures. 4.6.3 Manufacturing Technology in Production Standards Manufacturing methods will be discussed in more detail later in this guide. For the moment it is simply emphasised that the production and process methods must be documented in the same manner as for Technology and Engineering. The production
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flow and related manufacturing processes should be documented in Production Standards. Those standards describe the material flow, start up and the continuous process, tools and work cell layouts. The key here is to document checkpoints for operator control and control points where inspection from Quality and Engineering shall occur. 4.6.4 Testing Technology The purpose of Testing is to prove the product not only complies with contract obligations between purchaser and factory but also to give feedback to design and manufacturing on performance data as:
measured core losses measured load losses measured sound levels measured temperatures measured impedances measured partial discharge (pd) short circuit tests test failures
These basic performance characteristics form the base for the ongoing R&D and improvement processes this ETO business needs for a step by step evolution to higher and higher quality. Therefore the quality of the testing process is of the highest importance in the capability assessment process. The need for accuracy is paramount. Measurement accuracy (measurement quality) is a sum of best calibration and uncertainty evaluation. The requirements of calibration and uncertainty should be in line with the international standards/regulations. This need shall be proven at the assessment stage. The calibration process shall be performed according to international standards by using the best practice from available accredited calibration institutes. The Factory must provide documented evidence showing the calibration process and the certified institute. It is preferable that the whole calibration process is fully recorded, and the results correspond to the uncertainty evaluation process. An uncertainty value can be achieved based on calibration and equipment performance. The calculated uncertainty range for each measurement is provided to the purchaser and to the manufacturer's design team to establish the real level of transformer performance. 4.7
Other means of evaluating the technical capabilities of a factory
While interacting directly with the technical staff of a factory is often the best way to obtain an understanding of the technical capabilities, other more basic methods of evaluating the technical capabilities of a factory can be adopted, typically when a particular purchaser and factory are somewhat unfamiliar with each other. Such basic, fundamental methods initially employed for gaining an understanding of the technical capability of a factory include providing a questionnaire to the factory seeking 14
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information about the number of engineers and technicians employed by the factory at the production facility, as well as any supporting or shared technical resources a factory may have in their overall organisation. The purchaser may also wish to enquire how many of the technical staff described has technical education degrees or certifications from accredited organisations. This information is typically confidential for a factory, but may be provided during a qualification questionnaire exercise if the purchaser and factory are unfamiliar with each other. Given the aforementioned requirement to have the entire Technology base fully documented, the major purpose is to use the documentation as the base for engineering training and education. It is therefore important to assess how the above technology is shared and communicated to all engineers. How is the engineering training executed? How is it measured and controlled? Is there some form of certification of engineers? Other means of evaluating the technical capabilities of the factory include reviewing any industry available technical papers that have been authored or co-authored by the factory's staff members. Such industry papers often give good insight into the technical understanding and particular expertise of the factory. 4.8
Summary
An assessment of the technology starts by an in-depth examination of the documentation structure and tracing this through into the design criteria/margins, engineering IT tools and manufacturing Standards. The real purpose of assessing technology is in order to mitigate risks by judging the engineers and operators understanding and using the documented technology in this ETO business. 5
DESIGN PROCEDURES AND IT TOOLS
The factory’s capability in design should be assessed generically. Whereas specific designs are subject to design review, the factory capability assessment should cover the capability of the factory in general. This means that, unlike with a design review (refer CIGRÉ Technical Brochure 529) there is not a strong focus on a specific transformer, but a more general focus on methods, engineers, documentation etc. 5.1
Design experience of market
It is important that the factory understands the purchaser’s needs clearly and in detail, even when the specification is not clear or not sufficiently accurate. Experience with widely used standards (e.g. IEC, IEEE), market regions or specific purchasers may be of great help. This includes knowledge of the location of the transformer on the network, previous operational problems, physical limitations and specific test requirements. Some purchasers include a lot of detailed requirements in their specifications, from protection and control equipment to very specific limitations on the electrical and mechanical design, e.g. maximum allowable field strength. Other specifications are more functional, and allow greater scope for interpretation by the designer. In both cases background knowledge of the purchaser’s requirements is of benefit to the designer. An optimal solution is one which meets both the purchaser’s requirements and the factory’s standard practice. This reduces the scope for errors.
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Design experience of product range
A transformer factory may be specialised or focused on certain types of transformer. Even though the underlying physics is the same for core-form and shell-form transformers, they do have quite different properties. Very large generator transformers and transformers for certain industrial applications face challenges with very high currents. Phase-shifting transformers are rather complex to design and test. Testing of shunt reactors gives rise to rather different challenges from testing transformers. A factory may have experience or expertise in one or more of the following areas:
5.3
core-form, shell-form autotransformers large generator transformers phase-shifting transformers electric arc furnace transformers rectifier transformers HVDC Transformers shunt reactors a. fixed b. variable high current high voltage high leakage flux low sound levels a. no-load b. load mobile transformers and sub-stations, including so called Wanderer transformers Specification understanding
native languages and supported languages a. Is the factory capable of understanding the purchaser’s specification with respect to the original language? purchasers possibility to communicate directly with engineers
How is the communication between purchaser and factory organised? How direct are communication lines with engineers, how many steps, response time? 5.4
Design process quotation and order
information flow and throughput time a. What is the process of producing a new design to a purchaser’s specification for a quotation and for an order? How do the design engineers communicate with other interested parties at the factory, e.g. sales, mechanical design (drawing office), test, etc? quality assurance a. There should be clear internal quality control procedures and it should be clear who is responsible for the design. What are the detailed procedures 16
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for checking and approval of designs? How are internal and external reviews organised? How are revisions to the design controlled? 5.5.
Research and Development Activities
An important area to assess is the way the factory manages improvements in technology through research and development. What process does the factory have to make improvements in technology, build-up competences, benchmark, and share knowledge? Is there a research and development organisation? Is the factory supported by a corporate research and development organisation? Gaining an understanding of a factory’s research and development activities also provides a good gauge of the technical capability of a factory. Dedicated investment in research and development helps to ensure that a factory remains at the leading edge of technology, and suggests that the factory may be capable of adapting successfully to changing needs of purchasers. If a factory can present to the purchaser the resources used for research and development this can give a deeper understanding of the overall capabilities of the factory. The resources available for research and development vary between factories. Some factories rely completely on outside resources for research and development, whilst some use their day-to-day engineering resources to provide resources for research and development in addition to their normal responsibilities, and others have dedicated resources for research and development. Research and development resources can be used to investigate and resolve challenging problems in service. Research and development resources are also used to improve design and performance of the factory’s products and to add new features, thereby strengthening the factory’s competitiveness. Concerning licenses, purchasers are referred to section 5.3 above. The factory may be asked to provide information about:
5.6
number of engineers involves in research and development annual investment in research and development (as percentage of Turnover) number of finished R&D projects annually number of research and development reports written annually number of papers published annually participation in professional organisations and standards bodies (e.g. CIGRÉ, IEC, IEEE-PES) Design manual, design rules
The design rules used must be documented in a design manual which should be part of the quality management system. The design manual is used by design engineers to maintain consistency and improve quality. When design criteria change, the design manual must be updated immediately. The design manual is likely to contain crossreferences to research and development reports, published papers, etc. The design manual should cover all necessary aspects, and may be organised either by component (e.g. core, winding, tank, coolers, etc) or else by function/theme (dielectric, magnetic, noise, thermal, etc).
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The criteria included in the design manual may be derived from experiments, from experience with actual transformers, etc. Whatever their origin, it should be clearly documented and explained. Any criteria included in the design manual should be included in the design software, and vice versa. Design engineers should be kept fully informed of test results, and any differences between calculated and measured values, and of any test failures. Test failures should be thoroughly investigated and the results of the investigation, together with the solution, well documented. The design engineers should be completely familiar with the contents of the design manual, and able to access them easily. Note that design engineers often edit [parts of] the design manual. Any changes in the design manual should be made according to a controlled process with new versions being released only after management approval. There should also be a proper process of informing engineers of changes to the design manual. 5.7
Design software and it’s maintenance
5.7.1 In House Development, Outsourced Transformer design is a very complex process, even though the theoretical background is common knowledge. The application of physical rules in design is not only multidisciplinary, but also has factory dependent characteristics. Most factories use design software that is developed by them. Some use (partially) commercial software or outsource the development to third party companies. Source data has to be written in a structured and well documented way. Any programmer should be able to trace down the source code easily. 5.7.2 Software Purchaser Practice The design program must be easy to use, to avoid errors that can be assigned to “bad input”. The input, as well as the program release version must be stored in order to trace a result to its origin. The purchaser interface, input data and the program output must be transparent for any designer or “purchaser” of the design output. Any “fake” input, that is done to exceed the “normal” program limit, must be well documented. This is of course exceptional, because if this would happen on a regular basis, it would automatically mean a software change. All designers should know the limits of the software and if possible the software purchaser interface will indicate input errors or input limit violation. 5.7.3 Software Data Base Integrity The specific material data that is used in the design process is preferably stored in a separate data base, and not in the source code itself. This can be data like magnetic core steel properties, price information of steel, copper, oil etc. The data must be controlled by a QA system. Random changes must be impossible. 5.7.4 Maintenance of Software The designers should have a documented list where they can put on all possible suggestions for software improvements. An improvement that refers to a bug should be
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addressed by the programmer immediately. prioritised.
All other items are categorised and
Any changes in the design program must be tested before being released to the purchasers. A purchaser release means that all purchasers are informed about the new release version, and of the actual changes. 5.7.5 Computer Modelling, Dielectric, Magnetic, Thermal and Mechanical Problems What are the methods or means to tackle complex problems with finite element software? These problems can be of different kind: dielectric field plots, oil flow, mechanical strength, thermal problems, magnetic problems, noise & vibration etc. 5.7.6 Transient Modelling What are the possibilities of computing transient transformer behaviour, like impulse stresses? Are the calculated transient signals verified by measurements, like RSO (Recurrent Surge Oscillogram) on untanked active part? 5.7.7 Engineering 2-D or 3-D Method How does the engineering of active part and tank connect to the electrical design? Is there built-in intelligence in the models? Is there a product library that has proven to be the right quality? 5.7.8 Feedback from Testing In what way is data from tested transformers used to improve design and calculation algorithms to reduce the performance deviations between calculated and measured parameters? Is there regular performance deviation analysis procedures applied for core losses, load losses, temperatures, noise, impedances? 5.8
Experience level of engineers
Owing to the complex nature of large transformers, the experience of the design engineers is very important in maintaining quality and consistency alongside the design manual. Design engineers also require a sufficient level of education and professional development. 5.9
Engineering organisation
The engineering process should proceed according to documented procedures, including defined handover points between electrical and mechanical design (drawing office). There should be clearly documented procedures for both internal and external design reviews. There should also be clearly documented procedures for ordering of materials at the appropriate time. 5.10
Expert technical support
Concerning technical support during design, manufacturing and test, the factory may be asked to provide information about:
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availability of technical specialists to support the purchaser? the location of the technical specialists (e.g. based at the factory, or at another factory owned by the same company)? the ease of communication with the technical specialists?
SUPPLY CHAIN MANAGEMENT
6.1
Background
In principle, there are many good ideas on supply chain management. This document concentrates only on some very pragmatic recommendations on how to assess the supply chain management ability of a transformer factory. The following are the most important points to check:
Does the factory have up to date component and material specifications, in line with their basic technology and engineering requirements? Do the component and material specifications form part of the contract between the factory and the suppliers? Is there a continuous auditing process for supplier by the factory (possibly at a corporate level)? What are the quality requirements on the supplier? What is checked? What are the contract conditions when the supplier does not meet the factory’s requirements? (What are the incentives to improve)?
The transformer business has good international standards on how contractual performance is managed between the purchaser and the factory. This guide suggests that these standards should be mirrored in contracts between the factory and its suppliers. The most important thing to find out is whether the transformer factory is choosing suppliers solely on the basis of price or whether other quality considerations which will bring added value to the purchaser, who may operate the transformer for many years, are also taken into consideration. As the purchaser is unlikely to be informed of contract prices as part of an assessment, the assessment must focus on the role of quality in supply chain management. Instead of repeating some of the general principles of supply chain management, it is suggested that the assessment should go through some of the components and materials using a risk approach. At the time of writing, and depending on changes in raw material prices, the factory must procure components and materials comprising 60% to 80% of the value of a large transformer. Therefore supply chain management plays a very important strategic role in mitigating future risks. For many years reliability studies for transformers in service have shown that components and materials make an important contribution to problems in service, including forced outages. We shall therefore give some guidance on how these problems may be avoided. This guide therefore focuses on the following components and materials:
bushings tap changers
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winding conductor oil core steel insulating material and components
The following further components are slightly less critical, but may still contribute to service problems over the years:
steel fabrications coolers fans and pumps valves control cabinets current transformers indication and monitoring equipment
What precautions can be taken to avoid future problems? In the transformer business, a lot of changes have happened on both the factory’s side and the supplier’s side. Mergers have taken place, and production has shifted to emerging markets. It is important both to follow up old suppliers and to assess new suppliers. It is more or less impossible for the purchaser to assess individual suppliers of components and materials. Therefore the capability assessment must be an in-depth check of the factory’s supply chain management ability. 6.2
Bushings and Tap Changers
There are still a number of established suppliers left in the market, together with new suppliers entering from emerging markets. Some of the new suppliers have license agreements with the established suppliers. As part of their quality management system, it must be established that the factory has an established process for managing bushing and tap changer suppliers. It should include the following principles:
the factory should have a long term relationship with the suppliers the order documents should clearly specify the factory’s requirements the factory and the supplier should co-ordinate their production plans to meet delivery times the factory and the supplier should meet annually to discuss quality problems, e.g. delivery delays, non-conformance reports problems in service should be investigated there should be on-going development of the order and delivery process to reduce delivery times the factory should make an annual quality audit of the supplier a strong relationship is characterised by common technology and process development bushing suppliers should cover both high voltage and high current bushings the factory should check mechanical strength (seismic capability) and sealing systems (fault currents)
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Guide for conducting factory capability assessment for power transformers
Winding Conductors
There are various types of conductor used today in power transformers, including:
continuously transposed conductors (sometimes with epoxy bonding, sometimes without paper) group-insulated flat wire individually insulated flat wire
The factory must have material specifications for all types. Very often the conductors are insulated by the supplier. It is therefore very important that the supplier can show that their quality system is able to prove that the copper dimensions and properties are within the factory’s specification. The supplier must also have good control over the surface finish of the copper to eliminate problems such as burrs. It is very important that the factory has quality specifications concerning how the copper is packed and transported, to avoid damage. See also below concerning insulating material and components on how quality can be proven. The factory may be asked to provide information about: 6.4
co-ordinated production planning annual meetings to discuss quality problems, e.g. delivery delays, nonconformance reports annual quality audits Oil
It is strongly recommended for the purchaser to specify the type of oil which will be used at site. The purchaser should check that the oil to be used in the factory fully meets the requirements of the relevant standard, e.g. IEC 60296. It is important that the factory regularly checks the quality of the incoming oil, from storage tanks or from deliveries. It is especially important to check for moisture or chemical contamination. This is usually achieved by measuring DDF/tan delta and interfacial tension. In any case, the factory should have access to a transformer oil laboratory. 6.5
Core Steel
Core steel suppliers sell material of different thickness, which is graded according to the type of grain orientation (conventional, high permeability, domain refined) and the specific losses. The specific losses follow a Gaussian/normal distribution. It is important to see the factory’s material specification and to check how the core steel is purchased (annual contracts, spot market). One good way to check quality is to see whether the factory checks the supplier’s loss certificates and how they affect the calculation of no-load loss and current. Normally the no-load loss and current are measured as part of final test, and the values compared with guarantees. The scatter between calculated and measured values of noload loss may be revealing about the quality of the incoming material and the factory’s ability to keep their calculation method updated.
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There are two other factors which may affect no-load losses and long-term reliability: surface insulation (from the core steel factory) and burrs from cutting or slitting (by the core steel factory, a cutting centre or possibly at the factory itself). The factory should be able to show their specification and explain the tests they perform (e.g. Franklin test, measurement of burr height, core cross-lamination tests). The factory may also measure, or be asked to measure, no-load loss before and after dielectric test. It is anticipated that excessive burr heights may cause additional no-load loss after dielectric test. One good way to check core steel quality is for the factory to compare calculated and measured values of no-load loss, either continuously or as part of an annual review. 6.6
Insulation board and insulation components
There are very few factories of insulating material worldwide. Factories produce insulating board in different thickness and different densities. The board may also be glued to produce a laminated material. A good quality insulating board will be clean, free from voids and have good mechanical properties. The cleanliness and freedom from voids will be established by measuring partial discharge on finished transformers. The factory must have their own material specification for the insulating board, including requirements for mechanical and electrical properties. This specification should be referenced by purchase drawings for components or laminates. Production of insulation components may be made internally or contracted out. As part of the assessment, the purchaser should visit the insulation component workshop and check carefully the standards of cleanliness in production. Where insulation material and components are transported, it is important to check that it has been packed correctly to avoid contamination by dust or moisture. 6.7
Other Components and Materials
Steel fabrication, including tanks, may be made either by the factory or by a contractor who may supply steel fabrications to various transformer factories. There is a trend to buy steel fabrications from contractors. In such cases quality audits and checks on the quality of the product supplied need to be followed. Note the need for clear drawings and specifications. Purchasers are also referred to following chapter 7. Other possible suppliers to be checked include those for the following components:
coolers fans and pumps valves control cabinets current transformers indication and monitoring equipment
The general rule is to assess how the factory are specifying the components; who is supplying components; how good the relationship is between the factory and the supplier; and how the quality management system functions. The simplest method for checking how the quality management system works is to ask how quality is monitored by measurements. (If there are no measurements, there are no quality checks).
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During an assessment, the factory should be able to describe the following:
6.8
supplier qualification process for different categories of components and materials quality audits and inspections of suppliers: the purchaser may wish to see a report on a supplier quality audit supplier performance monitoring process, including what key performance indicators are used and how they are analysed continuous improvement: the purchaser may wish to ask for a description of a specific project Summary
The following points are important when assessing the supply chain management ability of a transformer factory: 7
check the factory’s procurement procedures for the most important components and materials does the factory have regular quality assurance processes in place with (say) the ten largest suppliers? ask for information about quality audits and any follow-up action required does the factory ask for information on cost of poor quality at the suppliers? what are the factory’s requirement’s from the suppliers with regard to performance monitoring what actions come from performance monitoring
MANUFACTURING METHODS
Besides distinguishing core or shell form transformers, which have fundamental different geometry, there is no significant difference in manufacturing methods between factories. Transformer manufacturing involves many manual steps that require processes and methods that need to be fully documented to ensure consistent build quality. Workers need to be properly trained for each task that they perform. The objective of this section is to provide guidance on what to look for when inspecting and evaluating factory manufacturing methods, to identify actual or potential problems, and in the end to obtain a reliable transformer as specified. It is very important to thoroughly inspect transformer manufacturing facilities close up to assess the facilities used to build the transformers and to be sure the process controls are in place that ensure uniform and reliable workmanship. Every factory is different, including those within the same parent company, and all their manufacturing and quality control processes have strengths and weaknesses. It is important to realise that you typically get what you “inspect” and not always what you “expect”. Therefore it is important to check the quality control records and the quality management effectiveness. In many cases some of the points referred to below can be regarded as design solutions/decisions more than manufacturing methods. 7.1
General:
The following conditions and work practices should be examined:
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a. tolerances b. tools c. skills of workers safe working conditions and safety equipment used, including any operational, health and safety programmes isolated clean areas (e.g. for winding, insulation, assembly) and designated "dirty" areas (e.g. for fabrication, welding, dismantling old/failed transformers) a. check cleaning routines for machines b. are there house-keeping indices c. house-keeping around work area, quality and organisation of tools building maintained properly - no roof leaks or hazards to personnel, equipment or work in progress worker experience and attitude should be appropriate for task clean and "fix as you go" mentality work areas clean, tidy and organised proper lighting examples of the "right" and "wrong" ways of doing things posted throughout the factory good communication between factory workers, inspectors, and designers Production Planning and Material Warehouse:
The following conditions and work practices should be considered:
7.3
method for project planning system and procedure for handling inventory control check workflow, work in progress, number of units in work, staging areas for part-finished items, push or pull flow goods inwards and materials storage areas structured and organised proper handling of material and components in designated areas to minimise risk of damage Main Tank and Steel Fabrication:
Some transformer factories outsource their tank fabrication work to specialised contractors. The complete procedures from engineering to outsourced production, quality systems and quality audits shall be evaluated. Purchasers are referred to section 6.7, above. The following conditions and work practices should be considered:
isolation of the steel fabrication workshop from the remainder of the factory consistent and quality welds: no main tank welds behind stiffeners that prevent visible inspection; check the Quality Plan and design drawings for welding methods inside of tank and hollow beam tank stiffeners free of any foreign material, pipes free of any foreign material; check cleaning instructions and quality control requirements has been implemented best practice for the inside of main tanks and core/coil clamping structures, to be painted white to enhance visual acuity during internal inspections 25
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tank shields and shunts either need to be insulated and grounded at one point or continuously welded on the tank wall: check for contamination risks gasket grooves smooth and within specified tolerances surface preparation should comply with ISO 8501 series or equivalent paint finishes should comply with ISO 12944 or equivalent Core Cutting/Stacking:
The following conditions and work practices should be followed:
7.5
cutting and slitting machines shall receive regular cleaning and maintenance: cutting blades shall be routinely replaced; check that maintenance routines and quality/maintenance control requirements are implemented burrs shall be within specified tolerances: no slithers, rust, or other physical damage observed any routine measurements, monitoring of incoming core steel? a. coating consistent with non-corrosive look, control cards b. core laminates routinely measured to confirm dimensions level core build table, laminations for the core build are undamaged and upending the core shall not allow movement, core deformation or core lamination damage core fully supported during stacking process core plate insulation shall remain undamaged finished core build shall be stored covered with a protective covering earthing joint mechanically strong and insulated to prevent accidental contact with core core clamping structure properly earthed with metal to metal connections cooling duct assembly shall be an integrated part of the stacking process and shall allow adequate oil flow core build routinely measured to confirm dimensions mitred joint building gaps small as possible and within least factory and Standards tolerances core stack within tolerances good practice is to confirm core inter-laminar resistance during manufacturing process use of steel hammers, mallets other metal devices directly on the core is prohibited no contaminants on or around work area workers must use protective shoes and gloves Winding Room:
The following conditions and work practices should be considered:
winding machines routinely cleaned - no contaminants inside mandrels windings manufactured on horizontal machines are to be placed on floor on clean material prior to being upended
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cable and winding conductor joints manufacture controlled to confirm that the joints are mechanically and electrically capable access controls to winding area: if necessary, environmental controls for coil winding area conductor reels free of rough edges and contaminants no conductor insulation damage or contamination: eliminate processes that could cause inadvertent insulation damage spacers, insulation blocks, oil direction washers and other winding parts correctly installed all permanent winding conductor ties/tapes non-shrinking type winding cylinders pre-dried and sized prior to winding process winding machine mandrel properly sized with adequate winding cylinder support conductors under correct tension during winding manufacture no conductor joints within windings unless an integral part of the design conductor properly supported from reels to winding machine with smooth, clean roller supports: conductors allowed to touch the floor? inner and outer winding crossovers and transpositions made correctly improper or over bending could create electrical clearance or oil flow problems apply additional insulation to all crossover bends all spacers and insulation blocks shall be made from high density insulation board and have rounded and smooth edges: no sharp edges shall be permitted adjacent to conductors all temporary blocks shall have smooth and rounded edges brazing performed in manner that minimises contamination and conductor insulation damage shield rings properly stored and handled to ensure no damage or deformation shield rings correctly installed and positioned completed windings to have protective covering oil guides installed in manner to not adversely affect oil flow through windings no tools or glue containers temporarily placed on windings windings to be protected from contamination risks from overhead structures including cranes Winding Sizing:
The following conditions and work practices should be observed:
access to sizing area should be controlled: if necessary, the sizing area environment should also be controlled no conductor insulation damage radial and axial spacer and blocks need to be properly aligned separators and blocks need to be held in place solely by winding clamping pressure or glued in place: blocks must not be glued to conductor insulation. factory shall verify the controlled and measureable winding drying, pressing, nesting and sizing processes with the aim of stabilising windings for positive axial pressure during complete service life of the transformer.
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Guide for conducting factory capability assessment for power transformers
winding lifting equipment will have cushioned supports and no chains or ropes shall be in direct contact of windings conductors shall be wound tightly so that movement cannot occur in service and harm the transformer. oil ducts shall remain properly open when sizing pressure is applied excessive winding radial build up must be avoided and not prevent correct positioning of radial and axial separators radial build up build of cross-over and transposition bends shall minimal and not exceed the maximum permitted winding inside and outside diameters winding height shall be within specified tolerance windings axial adjustments conductor ends must be covered to prevent damage to windings or injury to personnel completed windings shall be provided with a protective covering to prevent contamination Active Part Assembly:
The following conditions and work practices should be observed:
no contamination in or around work area instructions to be available on how to avoid contamination in case of cutting, crimping, brazing and top yoke stacking assembly platforms to be fitted with front barriers to prevent objects falling from the platforms into core and coil assemblies complete alignment of winding radial spacer columns and blocking protective covering applied to minimise ingress of contamination especially during brazing or crimping operations support structures for connections and leads must be mechanically sound and have rounded edges and no abnormalities use vacuum cleaners equipped with proper hose attachments to clean small openings and on no account clean these parts using compressed air hoses workers should not carry items that could accidentally fall into transformer, such as jewellery, pencils, tools, etc. upper core yoke needs to be properly stacked into position maintaining building gaps and properly supported with no waviness core lamination tips at the yoke ends must be kept separate and not bent over thus allowing contact with adjacent core plates core shall have no visible physical damage or rust: any laid up or built core having visible edge damage should be rejected. no foreign material/contamination should be visible on the core and coil assembly, including within those difficult to see areas such as the clamping structure or winding oil ducts no evidence of excessive or misuse of glue winding support blocks and pressure rings need to be properly aligned and permanently affixed in position bolted connections (electrical or mechanical) need a locking mechanism
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Guide for conducting factory capability assessment for power transformers
each electrical bolted connections shall have a two bolt fixing at least whenever possible when possible to ensure security of the fixing and minimise twisting (“scissoring”) leads and connections should not be excessively insulated and the insulation thickness must be controlled and fully documented core clamping structures need to be properly earthed with metal to metal connections, and insulated if necessary temporary use of metallic wires or ties is not acceptable insulation barriers need to be properly fixed in position pre-test check measurements on the active part during or after assembly are essential e.g. ratio, vector group, insulation resistances, winding resistance, losses, RSO, etc. Final Dry Out:
Correct processing of the completed core and coil assemblies prior to their tanking is of utmost importance. Any error in adjusting time, temperature, pressure, moisture extraction etc. can weaken the operational capability of power transformers. The following parts of the drying process (typically vapour phase) must be evaluated:
method of final drying criteria for monitoring, controlling and termination of process criteria for handling dried parts quality procedure and documentation of process variables controlled processing of core and coil assembly dry-out prior to final clamping
Verify the processed used after drying to ensure the windings are stabilised with the positive axial pressure needed to ensure the full service life of the transformer. 7.9
Final Assembly:
During the final assembly process, the core and coil assembly is clamped, retightened and tanked. Other components are then fitted to the tank, including coolers, the conservator, bushings, control cabinets, etc. Vacuum and oil filling occurs after final assembly in preparation for factory acceptance testing (FAT). The following conditions and work practices should be considered:
final winding clamping pressure applied after the final dry out process and just prior to the tanking of the active part, time tolerances for those processes to be verified the clamping process criteria, such as pressure and dimensional tolerances and jacking method, shall be verified and recorded internal bolted connections shall be properly torqued, locked, and marked to enable confirmation the tanking process within drawing dimensions to confirm accurate positioning, mounting of cover, and welding or bolting of cover to the tank vacuum time/measurement, speed of oil filling, standing time, oil filtering/circulation, particle count during the oil fill process shall be verified conduits and cable trays shall be properly secured and supported
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conduits and cable trays need to be free of internal sharp and jagged edges that could damage wire insulation during installation: conduits free of foreign material, such as shot blast cooling fans properly secured to radiators with protective pad material minimising radiator paint wear over time that could lead to radiator leaks outer tank coating touched up prior to transport control cabinets designed and manufactured per specifications
TESTING
The factory’s capability to test transformers can be assessed in various ways, considering the suitability of test equipment, the competence of the test engineers, compliance with standards, and the documented test procedures. 8.1
Test Accuracy
8.1.1
Calibration of test equipment
Reports Check on calibration reports, validity date
8.1.2 Accuracy Analysis of Measurements For the test equipment and test methods the accuracy level is normally expressed in uncertainty terms. The likelihood that the accuracy is within a specific tolerance (See e.g. Publication EA-4/02, (European co-operation for Accreditation) is calculated for each measurement (especially for Losses and Temperatures) in order to reach and provide the real level of transformers performance. Provide a report on established uncertainties of measurements. 8.2
Test equipment
The factory may be asked to provide the following information:
Is the test laboratory on-site or elsewhere? Is the test laboratory separate from other parts of the factory and shielded from them? Is it possible to test transformers without disrupting production, and vice versa (this applies especially to noise measurements and partial discharge testing)? Is the factory capable of performing all the tests and measurements that the purchaser requires, e.g. performance tests at different frequencies, dielectric tests, temperature rise test, noise measurements using different methods, testing of reactors, etc? Where are short-circuit tests performed (i.e. which external laboratory)? Is there a reference list available? Is the factory capable of performing oil analyses themselves, or are certain tests outsourced? What sampling techniques are used? Can the factory perform chemical, mechanical and thermal tests on insulating materials? These tests are needed for control of certain processes, e.g. vapour phase drying. What are the factory’s capabilities for testing transformers at site? Are tests performed by the factory themselves, or by a contractor? Typical site tests 30
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include capacitance measurements, FRA, insulation resistance measurements, etc. In some cases the purchaser may require more stringent testing, including applied voltage, induced voltage, no-load loss, and even impulse. 8.3
Test engineers
The competence level of test engineers depends very much on their experience level with transformer testing. Some theoretical background in electrical engineering as well as some basic knowledge of transformer design is also necessary. As was mentioned in sections 5.6 and 5.7 above, design engineers should be kept fully informed of test results, and any differences between calculated and measured values, and of any test failures. Pre-measurements can be particularly useful in detecting possible problems at an early stage. Does the management style support the professional development of the test engineers? 8.4
Standards
Testing according to different standards may vary. The test engineers must be aware of the procedures that are used in different standards. Some purchasers specify specific tests or test procedures that are not described in the international standards. The factory must be able to understand and execute the test procedures according to purchaser’s demand. 8.5
Documentation
The factory may be asked to provide information about: 8.6
Is there a standard format for the test programme with all the tests included in the correct order? Does the test programme include all the acceptance criteria? The quality of the test reports can be demonstrated with previous ones, showing the format, the presentation of measured data. Does the electrical designer sign the report before final approval? Is sufficient explanation given in case of abnormalities during testing? Is the generation of the test reports (partially) automated? Failure investigation
ability to investigate failures: Is knowledge and equipment, necessary for dealing with complex failure investigations, available? The nature of these problems can be very different: a. dielectric (PD, flashover) b. exceeding noise limits and or tank wall vibration limits c. overheating of windings, core, tank or other structural parts d. DGA analysis to track down failure
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8.7
9.1
procedures: Is there a procedure to follow when a test failure occurs or when there are major deviations between measured values and calculated values? This procedure should describe the way to handle and the people that are to be informed. involvement of design engineers: In what way are the design engineers part of the testing process? Do they witness testing on a regular basis, or only occasionally? communication with purchasers: What is the involvement of the purchaser and/or it’s consultant in the investigation process? documentation of failure investigation: Test failures, with nature of the problem, investigation of the fault, and final solution of the problem, must be well documented in reports. Others items
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the planning of the testing activities and scheduling should be organised properly: purchaser should be informed about the content of the test plan as well as the test schedule the factory’s ability to meet the planned schedules should be investigated an opening and closing meeting prior to, and after testing, is highly recommended to exclude any mismatch, misunderstanding or open ends in the test procedure there should be adequate facilities to accommodate purchasers during the witness testing process: a comfortable “purchasers room” with work space, and all necessary things for staying a relatively long period of time is highly recommended
WARRANTY AND SERVICES Warranty
In commercial and consumer transactions, a warranty is an obligation or guarantee that an article or service sold is as factually stated or legally implied by the seller, and that often provides for a specific remedy such as repair or replacement in the event the article or service fails to meet the warranty. A breach of warranty occurs when the promise is broken, i.e. a product is defective or not as should be expected by a reasonable purchaser. In business and legal transactions, a warranty is an assurance by one party to the other party that certain facts or conditions are true or will happen; the other party is permitted to rely on that assurance and seek some type of remedy if it is not true or followed. An important part of assessing a new factory’s capabilities is considering the warranty that is being offered. Often national legalisation makes demands on minimum requirements for mandatory warranties. Such mandatory warranties can in many cases be too weak, and reliable factories can often give better warranties than the mandatory ones. In addition purchasers of transformers should have their own opinion of their needs and demands to reduce the risk involved in acquisition of expensive equipment such as Power Transformers.
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The demands on warranty must of course be a part of the contract terms, but it could (or should) also be a part of the requirements when assessing factories in a prequalification process. A warranty should have a length that reflects circumstances like criticality of the unit, importance in the power system and anticipated lifetime of the equipment. Transformers have a life expectancy of many years and must of course operate within its limits without any operational problems. There are examples of utilities who demand a warranty period of up to five years after the unit is ready for operation at the site of operation. The actual length of the warranty a factory can offer could be an indication of the factory’s confidence in the product. When failures and operational problems occur within the warranty period, the factory must take all the necessary measures to help minimise operational difficulties and outages whenever possible. During the warranty period the factory must have a high awareness and must be prepared to immediately respond to the site in order to investigate the incident and make the necessary corrective actions in a very short duration. These items should be considered when evaluating warranties:
what terms of warranty can the factory offer, i.e. the coverage comprised by the warranty factory’s guaranteed response time in case of an incident can the factory provide a special warranty against design defects that arise after the term of the warranty access and delivery times for spare parts, such as tap-changers, auxiliary equipment, production of new windings, etc. access to transformer experts experience from other purchasers the legal situation and legislation in the country of the factory
The following additional clauses can also be considered when specifying the warranty requirements:
the factory is committed to make the necessary repairs in case of defects, failures, or in such cases when the cause of the defect is uncertain can the repair work be immediately performed by the purchaser at the cost to the factory and without foregoing notice to the factory, if operational reasons hinder the factory from performing the work? the purchaser shall be entitled to have repairs performed at the cost to the factory, if similar defects are present on other transformers
The purchaser can demand the contract work to be reversed, if defects are discovered that are the result of insufficient design, construction, materials, or works. 9.2
Services
9.2.1 Sales organisation It is important for purchasers to meet with the sales organisations during the prequalification process in order to obtain sufficient information pertaining to factory’s capabilities, including but not limited to the following:
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the range of products, ratings, design and technology, manufacturing facilities, testing, etc. any limitations in technology or capability reactions to questions regarding factory’s capabilities - is the information complete and easily understood? access to the factory’s technical experts legal aspects - fulfilment of public, global or special national requirements fulfilment of normative requirements, standards and requirements for local installations - are such known for the factory? safety standards in the country of installation - are they known and will the factory be able to fulfil these? sales staff - their competence and technical know how
9.2.2 After sales arrangement The factory’s capability regarding after sales services is also important and must be assessed carefully. A reliable factory should be able to offer condition assessment, repairs and maintenance services in all the parts of the world they are doing business. The factory must also be able to perform such services in cases where the transformer is in service at a place far away from the production site. Examples of such services are listed below: Condition assessment, repairs and maintenance services:
condition assessment a. dissolved gas analysis (DGA), other oil tests, and cellulose condition (DP and/or Furans) in-house oil laboratory or third party? experience regarding interpretation and recommendations of corrective actions. b. assessment on site regarding functionality, mechanical wear, corrosion – by means of functional testing, visual inspections or measurements c. on-site testing capabilities: voltage ratio, winding resistance, core and core-clamping grounding system, etc. frequency response analysis (FRA) winding power factor and capacitance cellulose moisture content induced with partial discharge measurement acoustic emission d. residual life analysis transformer repair capabilities and offerings a. minor or larger, such as windings, coil and core structure, tap-changer, tank, bushings, etc. b. repair locations on-site local workshop or manufacturer’s facility maintenance service offerings a. tap-changers b. tank and accessories c. auxiliary equipment
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oil maintenance: a. reclaiming b. reconditioning c. re-inhibiting d. staff experience and competence e. oil maintenance equipment - suitability, capacity, and environmental impact from the process
Other considerations to be addressed:
10
factory’s response time to service issues, such as time for experts to visit the site to perform failure investigation, anticipated lead-time for spare parts, tools and experts to perform the necessary repairs service department organisation and availability maintenance offerings training and technology transfer internally and externally spare part inventory and availability manuals detailing transport, erection, and final commissioning requirements, and maintenance/operation recommendations
PROJECT MANAGEMENT STRUCTURE
As depicted within Figure 1 of this guide, the delivery of high quality power transformers involves many steps which require a much tightened coordination and a systematic approach to determine optimally the decisions for transformer procurement. Such coordination is called power transformer project management, which is an important part to ensure the success of transformer procurement and mitigate risks for the purchaser and the factory. It is therefore critical at the stage of pre-qualification of a manufacturer or factory assessment to know how the awarded contract will be managed to secure a high quality product. Hence, project management skills shall be assessed by analysing the project management organisation of the factory. At a minimum the project management structure should contain the following items which are clearly defined: 11 11.1
communication guide project schedule contract review (how grey areas are managed?) design review risk management transport site installation and commissioning
HUMAN RESOURCES, HEALTH AND SAFETY MANAGEMENT Human resources
11.1.1 Aims As part of the inspection of a transformer factory, the purchaser may wish to gain an insight into their human resources policies and practices. This may provide reassurance
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that the factory is being managed in a responsible manner and that its employees, and any contractors are being adequately cared for. 11.1.2 Legal and Cultural Aspects Inspectors need to be aware that many aspects of human resource management are subject to legal controls. In general, these differ in scope and requirements in different jurisdictions. A degree of sensitivity and understanding may be required on the part of the inspector. Inspectors are also advised to take into account differences in culture, levels of economic development, general levels of education and other related aspects. Certain aspects of human resource management are subject to internationally agreed minimum standards in the form of International Labour Organisation (ILO) conventions. Inspectors should be conversant with the requisite standards. In the case of serious concerns, inspectors are strongly advised to seek independent local advice. 11.1.3 Industrial Relations Inspectors should seek to reassure themselves, so far as it is possible to do so, that the management of the factory are complying with all the legal and regulatory requirements of the jurisdiction where the factory is located. This can be very challenging and inspectors may wish to limit themselves to seeking assurances from the management that the factory is complying with all legal and regulatory requirements. Such assurances should preferably be obtained in writing. The inspector may wish to check the following points:
is there an independent trade union or staff association in the factory? If so, what influence does it have? are there signs of antagonism between the management and the employees or contractors? For example leaflets critical of the management being distributed, posters critical of the management on display, signs of antagonism between members of the management team and employees and contractors. has there been any strikes at the factory? Are any strikes planned or possible? is there evidence of disputes between management and employees or contractors, work disruptions, faulty work?
11.1.4 Recruitment The inspector may wish to check that the management are following good/best practices with regard to recruitment. To do so the inspector may wish to check the following points:
vacancies advertised openly (internally and externally). does the factory have an equal opportunities or non-discrimination policy? If so what is its scope? (Please refer to ILO convention 111 for further guidance). is there any obvious evidence of discrimination or favouritism? is any material on public display which might create an atmosphere that would promote discrimination or favouritism? e.g. pornographic calendars, racist or sectarian posters.
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do technicians and engineers have appropriate qualifications? Are there any specific minimum requirements.
11.1.5 Training Each transformer factory must ensure that it has available sufficient employees with the correct balance of skills. The number of employees required, and the correct balance of skills, depends on a range of factors including the output of the factory, the level of automation and the proportion of production which is sub-contracted. The amount of training required also depends on a range of factors, including the number of employees, the level of skills and education of the new employees and the turn-over of employees. Certain employees require knowledge and skills which are unique to large transformer manufacturing, e.g. design engineers, test engineers, coil winders, quality control engineers and inspectors. The inspector may wish to check the following points:
Is the transformer factory using agency or contract workers? If so, what proportion of the workforce do they represent and what is their role? Does the factory seem excessively reliant on agency or contract workers? Is the transformer factory subcontracting production which would normally be done in house? If so, to whom and what quality control procedures apply? Does the transformer factory have an adequate appraisal programme to identify training needs? Is there a system to internal candidates for promotion? Does the transformer factory have an adequate training programme for specialist staff?
11.1.6 Vulnerable Workers Use of forced labour for transformer production is not acceptable. Use of prisoners may be acceptable in certain circumstances, e.g. as part of a rehabilitation programme organised with the lawful authorities. Where this is the case a degree of transparency with the purchasers is required. For further guidance please refer to ILO conventions 29 and 105. Use of child labour for transformer production is not acceptable. Young workers may require special protection, e.g. from long working hours or from work which is inherently dangerous and too arduous. The minimum age for working and for doing dangerous work varies in different countries. Inspectors are advised that the absolute minimum age for working full-time is fourteen, in accordance with ILO convention 138. 11.2
Health, Safety and Working Environment
11.2.1 Working Environment The inspector may wish to check the following points:
Are there areas for eating and drinking separate from critical production areas, i.e. insulation components, coil winding, assembly? Are there signs of food or drink being consumed outside these areas? Is there any food waste in the bins? Are there adequate and sanitary washing facilities for all employees and contractors? 37
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11.2.2 Working Hours The inspector may wish to check the following points:
Do employees seem to be excessively tired or stressed? Is this affecting either their welfare or their ability to perform their work correctly? What is the length of the working day? What is the length of the working week? What maximum limits apply to these? (Please refer to ILO conventions 1 and 14 for further guidance). When is the weekend or weekly rest period? Are rest periods regular, adequate and observed? What public and customary holidays does the factory observe? How much paid holiday are employees entitled to? (Please refer to ILO convention 132 for further guidance). What measures have the management taken to avoid disruption to production during popular holiday periods? Is there an annual factory shut down?
11.2.3 Security Transformer factories are inherently dangerous places for members of the general public, especially children. The management should ensure that access to the factory is fully controlled. Access should be limited to employees, contractors and visitors. The inspector may wish to check the following points:
Are health and safety inductions provided for all employees, contractors and visitors? Was the inspector given such an induction? So that they can be accounted for in an emergency, is the entry and exit of all employees, contractors and visitors recorded? Was the inspector’s entry and exit recorded? Is there sufficient security to prevent the theft of valuable equipment, components or materials? What precautions are taken? Do they seem to be effective?
11.2.4 Health and Safety Management The management of occupational health and safety is the subject of OHSAS 18000, an international standard broadly similar in concept to ISO 9000 for quality management and ISO 14000 for environmental management. The general principle of OHSAS 18000 is the same as both ISO 9000 and ISO 14000 – plan, do, check, act. Planning begins with a statement of policy. As with quality and environmental management systems, top management must take responsibility for the implementation of the health and safety management system. One or more members of the top management team must be appointed to oversee the implementation of the health and safety management system and present regular reports on its operation to the rest of the top management. The inspector may wish to check the following points concerning health and safety management:
Is the factory OHSAS 18000 certified? What is the factory’s health and safety policy? Is it on prominent display? Is the health and safety policy adequate in scope? Does it seem to be used as the basis for health and safety management?
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Which member of the top management team is responsible for health and safety? Is part of the role delegated to a subordinate manager? If so, to whom and how much communication is there between the different managers? Do employees and contractors know who the health and safety manager is? Do employees have adequate access to the health and safety manager to raise concerns they might have? If they do so, will they risk disciplinary action? How do employees participate in the health and safety management system? Who are their representatives and how they appointed? Are they sufficiently independent from management? Do employees and contractors know who their health and safety representatives are? Is the health and safety management system adequately documented? Are management making good use of the hierarchy of controls, i.e.: a. elimination b. substitution c. engineering controls d. administrative controls, including signs and warnings e. personal protective equipment Are there adequate warning signs in the factory, e.g. informing of hazards in particular areas, informing what personal protective equipment is required? Are all employees and contractors equipped with adequate personal protective equipment? Is this provided free of charge? Are employees and contractors using it correctly? Was the inspector provided with personal protective equipment during his or her visit? Are there adequate numbers of trained first aiders? How are first aiders identified? Are there adequate provisions for preventing and controlling fires? Are there adequate means for raising the alarm in the event of fire? Are there adequate fire exits? Have any of them been obstructed for any reason? Are there adequate muster points? Are these suitably located, i.e. remote from oil storage areas or oil-filled equipment? Are there adequate numbers of fire marshals to help with evacuation? How are fire marshals identified? Are the fire alarms tested regularly? Are fire drills carried out regularly? Is the factory inspected regularly by the local fire service? Are the accidents reported to the local authorities? Are incidents adequately investigated? Do the management seem to learn from incidents?
11.2.5 Dangerous Chemicals Use of asbestos gaskets is widespread in certain countries. Transformer oil may contain certain dangerous chemicals, including furans, PCAs and PCBs. The factory should ensure that the oil used for manufacture and test is free from furans and PCBs and does not contain excessive amounts of PCAs. For further guidance please refer to IEC 60296.
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Guide for conducting factory capability assessment for power transformers
TRANSPORT General
This part of the guide is written with the intention of giving general information and guidance for inspectors, to reduce the possibility of damage or delays in transport. Transformers covered by this guide are not, in general, designed to be transported whilst fully assembled and are also not, in general, designed to be transported regularly. If there are no special requirements then the purchaser should expect the bushings and turrets, the coolers, conservator and associated pipe work and the control cabinets, but not the associated wiring, to be removed for transport. Power transformers covered by this guide are in general oil-immersed. It is possible to transport such transformers either drained of oil or filled with dry gas, or else partly oil filled, usually to cover the top of the core. In most cases transport drained of oil and filled with dry gas is preferable, as it reduces the transport mass and allows the oil to be transported separately using a method approved by the appropriate authorities. Where dry gas is used, this is usually at a slight positive pressure and the transformer is usually equipped with a gas cylinder for topping-up and a gauge to indicate whether any gas has been lost. These must be positioned at an accessible location on the main tank, where they are not likely to be damaged by normal handling during transport. Cigré working group A2.42 on transformer transportation will provide more details in due course. 12.2
Delivery Terms
Particular purchasers have requirements for delivery terms which do not, in general, vary from one order to the next. These can therefore be discussed, in general terms, with the factory at the time of the inspection. The exact delivery terms form part of the commercial agreement between the purchaser and the factory. The purchaser must decide where they wish responsibility to be transferred from the factory to themselves. Greatest clarity over responsibility will be obtained where there is no transfer of responsibility during transport. This is not always practical, as either the purchaser or the factory may find it very challenging to arrange local transport at the remote end of the voyage. There are four main options available: 12.2.1 Purchaser to Collect (INCOTERMS Group E) This method is suitable where the purchaser wishes to arrange for all transport separately from the factory. For transformers covered by this guide, the purchaser may require the factory to load the transformer onto the transport. 12.2.2 Main Transport Arranged by Purchaser (INCOTERMS Group F) This method is suitable where the purchaser wishes to arrange for main transport separately from the factory. Local transport to an agreed location is arranged by the factory.
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12.2.3 Main Transport Arranged by Factory (INCOTERMS Group C) This method is suitable where the purchaser wishes to arrange for local transport separately from the factory. Main transport to an agreed location is arranged by the factory. 12.2.4 Factory to Deliver (INCOTERMS Group D) This method is suitable where the purchaser requires the factory to arrange for all transport. It is particularly suitable where the purchaser also requires the factory to arrange for installation and commissioning. This is also possible with other delivery terms, although making the necessary arrangements may be more complicated. For transformers covered by this guide, the purchaser may require the factory to arrange for the transformers to be unloaded from the transport. For further guidance on different options available, please refer to INCOTERMS (International Commercial Terms). 12.3
Methods
Transformers and transformer components covered by this guide may be transported by one or more of the following methods: 12.3.1 Air This is a most unusual method for transformers of the size covered by this guide. It may be a feasible option in certain special cases, e.g. where a transformer is required urgently or when components are missing. Special limitations on mass and dimensions apply, which will require discussion between the purchaser, the factory and the transporter. Local transport by an alternative method will be required at each end of the voyage. 12.3.2 Barge/ Coastal Ship This is a popular method in countries which are well served by inland waterways, e.g. Central Europe. It is often used to move transformers from the factory to a sea port for onward transport by an ocean going ship. Limitations on dimensions and mass are not usually very restrictive. Transport by costal ship raises the possibility of damage to the transformer during adverse weather. Local transport by an alternative method is likely to be required at each end of the voyage, unless the transformer factory has direct access to a suitable inland or costal port. 12.3.3 Ocean Going Ship This is the most popular method for moving transformers long distances. In many cases there is no feasible alternative. Transformers covered by this guide are, in general, transported as hold cargo on specialised ships which are equipped with their own cranes for loading and unloading. The practice of transporting large transformers as deck cargo on container ships has now largely ceased, although it sometimes practiced for medium transformers which are first packaged into open containers. Components are usually packed first into wooden crates and then into containers. Note that certain countries may require the crates to be specially treated to prevent the introduction of pests and diseases.
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Limitations on dimensions and mass are not usually very restrictive. It raises the possibility of damage to the transformers during adverse weather. Corrosion may also be a problem, especially for transformers transported as deck cargo. Choice of routes is limited and certain routes may not available year-round owing to adverse weather, especially cyclones. Piracy has in recent years caused disruption to certain routes, especially those through the Suez Canal. Local transport by an alternative method will be required at each end of the voyage. 12.3.4 Rail This is a popular method in countries with an adequate rail infrastructure, e.g. Continental Europe, North America. Limitations on mass and especially on dimensions may be restrictive. The largest transformers must be transported using a special Schnabel wagon, which may require special tank design considerations. Severe shocks during handling are quite common. Local transport by an alternative method will be required, unless the site has its own rail siding. 12.3.5 Road This is a popular method for local transport. It may also be used over longer distances in countries where transport by other methods is impractical. Limitations on dimensions and especially on mass may be restrictive. The largest transformers must be transported using a special girder-frame trailer, which may require special design considerations. Certain factories may not be familiar with certain transport methods. Where these impose special design requirements, these should be discussed between the purchaser and the factory, preferably before the order is placed and again at the design review stage. Where local transport close to the purchaser’s site is likely to impose restrictive limits on dimensions and mass, the purchaser should inform the factory of these requirements. This is particularly important for transformers which will be installed in inaccessible locations, e.g. underground sub-stations in hydro-electric schemes. 12.4
Voyage Assessment
To be able for the purchaser to assess the risk during transport, all possible circumstances likely to be encountered during the supply chain from manufacturing site to final destination should be reviewed. The following considerations for the purchaser to its sites shall always be taken into account.
anticipated transportation equipment – ocean vessel, barge, rail, truck etc. number of lifting operations / type of lifting gear number of trans-shipments / carriers’ hubs weather and environmental circumstances during voyage infrastructure along the routing – ports, terminals and road condition necessary permits, government and local regulations expected maximum transit time including intermediate storage and storage after delivery allocation of responsibility for the transportation related to the terms of sale
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12.4.1 Assessment of the Factory’s Preparation capability
design rules of goods to be shipped, transport plan packaging rules and instructions, markings and identification numbers unit preparations closure / sealing of unit openings removal of fragile / protruding non-integral components – packed separately using packaging standards moisture protection cushioning of non-removable protrusions i.e. air pressure valves, hoses, piping, conduit, etc. shock indicators/impact recorders (registering g-forces, the time of force and duration): two impact recorders are preferable, with one installed on the core structure; the factory and the purchaser should agree on a procedure to be followed in the event of an alarm testing and inspections required when moving from one mode of transport to another: any concerns should be reported to the factory and purchaser immediately.
12.4.2 Preparation and Execution of transport
is there a transport coordinator at the factory? are there insurance policies for all sub-contractors (freighters, lifters) and other obligations? is a “Transport Manual” established for each transport by the transport coordinator? It might contain: a. transportation documents and checklists b. considerations for all lifts c. controls on cargo transfer point and securing requirements d. contracts with sub-contractors the Transport Manual should be attached to the goods before shipping from factory. is all documentation, such as photos taken before the transport, stored in the Transport Manual? is a system established for post-transport feedback on transport parameters (e.g. shocks, temperature, etc) and on damages, if any, both to increase experience as well for expeditious claim handling? It is critical to take pictures of damages and include as part of any claim.
12.4.3 Personnel Training / Education Considerations Cargo risk control requires specific knowledge of transformer transportation methods from the factory to their final destination and of the inherent risks associated with each transportation method. Are personnel involved in the transport chain trained / educated with respect to all elements of the transportation chain? 12.4.4 Standards of Care for Transportation / Freight Forwarding Vendors It is important to note that utmost care is taken by freight forwarders while executing this work. They shall be responsible for following various guidelines for the loading,
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securing, transportation and discharge during the different types of transportation methods:
Cargo securing – sea, rail and road Marine tow and barge Marine vessel
12.4.5 Checks for All Shipments, Lifting, Ocean vessels
12.5
transportation contractors, specialised in the transportation of power transformers, must be used; they must be well established and reputable, financially stable, and be able to respond to liabilities in case of sub-contracting (if mutually agreed upon) the sub-contractor should be subject to the identical standards as the contractor, but the contractor should retain liability all transportation contractors shall verify existence, adequacy and condition of their handling and transport equipment at all points throughout the course of transit unit diagram(s) and / or information to all vendors with specific dimensions, centre of gravities, spreader bar arrangements, lifting configurations, and recommended lashing / securing points shall all be provided within the transport manual all cranes and other lifting equipment shall be certified to handle safe working load capacity vessels should preferably have a tonnage of more than 10 times the weight of the transformer: if a smaller vessel is considered, insurer must be informed of the vessels IMO number the transport coordinator shall contact the captain of the vessel to fully explain the possible risks of damages and thereby to avoid high speed through rough seas Inspection on Receipt
Damage during transport can take various forms, some of which can be repaired at site and some of which will require the transformer to be returned to a factory, although not necessarily to the original manufacturing facility. Severe damage due to mishandling is usually apparent during an external visual inspection. A reputable transport contractor shall be expected to advise the factory and the purchaser if any serious problems have arisen, e.g. the transformer being dropped. Severe internal damage can result from sudden impacts or from adverse weather during sea voyages. This damage usually takes the form of the core and windings shifting in the tank or the partial collapse of the core. It can often be detected by measuring the core and frame insulation resistance. An internal inspection may be required to verify the condition of the transformer. The factory and the purchaser should agree on a procedure for inspecting the transformer upon its receipt before the transformer is shipped, preferably at the design review stage. If the transformer is trans-shipped at any point, the same procedure should also be followed. The inspection may include the following:
external visual inspection for signs of mishandling check gas pressure gauge 44
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check all impact recorder(s) measure core/frame insulation resistance: most designs have accessible core and frame earthing terminals: on many designs, these will be on the cover; means of safe access to the cover for the inspection shall therefore be required frequency response analysis, which will usually require special test bushings to be fitted for transport; it is highly likely that these will be on the cover: means of safe access to the cover for the inspection shall therefore be required
An internal inspection may be necessary if there is an indication of a problem from one of the other checks. This should be carried in a safe and responsible manner, ensuring that there is no risk to those undertaking the inspection and minimising the risk of damage to the internal parts of the transformer. Special precautions shall be followed to prevent moisture ingress during the internal inspection, and it is preferred that a continuous supply of clean dry air must be maintained during the inspection. The quality of the air should be monitored continuously during the inspection. An adequate procedure and equipment should be in place to evacuate those undertaking the inspection should any problem arise. 13 13.1
INSTALLATION, COMMISSIONING AND STORAGE Installation and commissioning
13.1.1 General Certain purchasers may prefer to make their own arrangements for installation and commissioning, separately from the factory. Where this is the case, the factory should provide written guidance concerning their requirements. It is preferable for a representative of the transformer factory to witness installation and commissioning, to ensure that these requirements are met. As part of their quality management system, the transformer factory should have in place documented procedures for storage, installation and commissioning, including a specimen or typical work plan. The inspector may wish to review this documentation, including the specimen or typical work plan (“method statement and risk assessment”), to ensure that this will meet the purchaser’s needs. If the purchaser has any special requirements concerning installation and commissioning it might be helpful to discuss these with the transformer factory as part of the capability assessment, and again at the tender stage. Various checks and tests need to be carried out before and during commissioning to ensure the safe operation of the transformer. Both the purchaser and the transformer factory should inform one another of the checks they require. Each should review the other’s requirements to ensure that all necessary checks and tests are made. 13.1.2 Oil The purchaser and the factory should confirm the suitability of the oil to be used at site and its compatibility with the oil used for manufacturing and factory tests. The oil is normally tested for contamination prior to oil-filling of the transformer at site.
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13.1.3 Auxiliary Electrical Wiring In some jurisdictions, auxiliary electrical wiring must either be done by a suitably qualified craft worker or else inspected by a suitably qualified craft worker when it is complete. In such circumstances it may be preferable for the transformer factory to work with a suitable local sub-contractor, who can ensure compliance. 13.1.4 Health and Safety The transformer factory and the site may be in different jurisdictions, and therefore subject to different health and safety legislation. Employees or contractors sent from the factory to assist with installation and commissioning may be subject to legal controls from their home jurisdiction. Where a transformer factory has little experience in the jurisdiction where the site is located the purchaser may need to inform them of local legal controls, and of suitable partners who can arrange for training etc. In such circumstances it may be preferable for the transformer factory to work with a suitable local sub-contractor, who can ensure compliance. Installation and commissioning may involve work in close proximity to energised parts. Work near energised parts is inherently dangerous and could require additional training and oversight. The purchaser shall make the factory aware of this possibility and provide any special guidelines. 13.2
Storage
Power transformers may need to be stored for short periods of time to accommodate constraints in manufacturing, transport or installation. This storage may take place at either the factory’s works, the installation site or, more unusually, a suitable storage facility at a third party location. In some cases transformers are purchased for use as spares and may need to be stored for indefinite periods. Power transformers are typically oil-immersed. There are essentially three options for storing such transformers – drained of oil, and filled with dry gas; partly oil filled, usually to cover the top of the core; and substantially or completely assembled ready for service. The first option is suitable for short-term storage to accommodate constraints in manufacturing, transport or installation. Note that no oil containment is necessary as the transformer is not oil filled. For long term storage, the core and windings must be immersed in oil and some means of accommodating changes in oil volume with temperature must be provided (e.g. pressurised gas cushion or conservator system with breather). The transformer must also be stored in a suitable oil containment area. In the case of long term storage purchaser must also consider how they wish to store the accessories, especially items such as bushings and coolers which may deteriorate if not stored correctly. Purchaser should note that oil-impregnated paper (OIP) bushings should not, in general, be stored in the horizontal position for long periods. Instead such bushings should be stored close to the vertical. Resin impregnated bushings should be stored with the oil end immersed in oil. Cooler pipe work, radiators, etc. should be securely blanked off and preferably pressurised with dry gas to prevent contamination during transport and storage. Radiator fins are made from thin steel sheet and are prone to accidental damage. Purchaser should also note that pilfering loose items for use as spares with other transformers is a widespread practice. Many purchasers therefore prefer to store spare transformers substantially or completely assembled. Note that this means they must be dismantled on deployment and so may not be the best choice in all cases.
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Where transformers are stored immersed in oil, it is prudent to make checks on the oil quality at regular intervals to check for moisture ingress. Moisture and breakdown voltage are usually considered to be required, although purchasers may wish to consider also checking resistivity or dielectric dissipation factor. 14
FINANCIAL, COMMERCIAL AND LEGAL ASPECTS
The previous chapters of this guide have described in detail many recommendations on various aspects of power transformer: design, engineering, manufacturing, transport, and storage of power transformers. In addition to those recommended technical and quality skills of the factory that need to be evaluated, it is very important to have a sound knowledge about the factory’s organisation at a corporate level. Who do we want to do business with? How reliable is the factory with regards to its financial heath, experience level and many other commercial aspects? This section highlights some key points which should be assessed to mitigate the commercial risks. Since these key points involve a certain expertise in accounting, legal aspects and risk management, the evaluation should be conducted by experts such as lawyers, account managers and risk managers. It is recommended the following minimum topics should be adopted as the basic set of pre-determined acceptance criteria to be met in any factory capability assessment: 15
acceptance by vendor of the purchaser’s terms and conditions compliance to the purchaser’s technical specifications limitation of liabilities project management skills company financial heath local representative (marketing, engineering, services) communication skills services and warranty management proven product range (voltage and power capability) location of the manufacturing and test facilities for the main product and subcontracted items and materials delivery lead time annual capacity (MVA / year) environmental policies compliance with ISO 9000, 14000, 18000
FACTORY PERFORMANCE (lead time delivery, on time delivery…)
When evaluating the overall capabilities and performance of a particular transformer factory, it is often desired by the purchaser to gain a better understanding of past performance history of the factory but also how history is influencing the continuous improvements. While there are several areas that can potentially be evaluated by a purchaser, a good understanding of a factory’s performance can often be obtained by reviewing metrics and statistics from a factory that track on-time delivery of transformers, measure the number of factory test failures prior to shipment, and the number of field failures of transformers once they are placed into service. However, it is not only about numbers 47
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alone but also about trends, i.e. the frequency of events over time and the corrective measures introduced by the factory to effect improvements. It is important to understand that due to the manufacturing complexity of such large equipment such as transformers, combined with the frequent custom designs for each application, demanding operating conditions and variable environmental factors at a given transformer installation, most factories have experienced some field problems and, more-commonly, factory test problems over the years. However, obtaining a relative comparison between different factories of similar rated transformer applications can help provide a better understanding of the overall level of relative risk in trusting the supply of a particular transformer to a given factory. When comparing these factory performance parameters of various factories, it is essential to obtain data from the factories that can be directly compared, based on similar agreed criteria and definitions that are used to gather and represent the data requested. Such common criteria and definitions must clearly be provided to the factories prior to receiving the requested data for evaluation, such that the data received can be compared most effectively. Very often such criteria differ between factories. Therefore the factory may also be able to come up with his definition. Exact comparison of such numbers between manufactures may be difficult and the assessment shall then more be concentrated on trends and corrective procedures and actions to prevent further similar problems. Such procedures and the quality among them may differ among the factories. Often the type of data requested regarding field failures, factory test failures, and on-time delivery performance is not published information by the factory, and is typically required by the factory to be treated confidentially and not shared with other competing factories or other parties outside of the particular purchaser and factory, as such data can be easily misrepresented. In some cases a confidentiality agreement may need to be created between the factory and the evaluating party in order to receive such information. Guidelines for evaluating on-time delivery performance and factory test performance are provided below. 15.1
On-time delivery performance
Often a transformer delivery is scheduled to be delivered on a just-in time basis, either to replace an existing transformer during an upcoming scheduled outage, to replace a failed transformer in a short duration, or to be delivered as part of a new substation or power station construction project, in which the transformer is one of the critical components to meet the overall construction schedule and energisation date. For these reasons, it is recommended to verify that a potential manufacturer of a critical transformer application is able to meet delivery date commitments the majority of the time, based on past performance history. 15.2
Factory test failure performance
In order to evaluate the number of test failures, test failure trends over years and test failure analysis and corrective measures, it is important to be sure the reported data is based on the same agreed universal definitions. At present no common definitions for quantifying factory test failures exist in the industry, therefore the purchaser shall have a discussion with the factory to understand what test failures have occurred within the recent past and manufacturers must discuss different ways to measure test failures.
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Measuring test failures must be a major key performance indicator at the factory. Such metrics are strategic indicators used by factories to continuously improve their product and by purchasers. Some factories count all problems or failures that occur in test whether at pre-test or at final acceptance test. It often means that all types of test values that exceed guaranteed values are included. It can also be non-conformances during other tests or that the unit needs to be drained of oil for other reasons. In that way the test failure rate is a pure quality measure. Some other factories categorise test failures into minor and major test failure categories to determine the effect on the transformer delivery times. Minor test failures for example are easy to fix and negotiate without any delay whereas major test failures will require repair with consequential delivery delays of days, weeks or months. Test failures evaluated in this way are more a measure of on time delivery capability than on quality. Other factories only give numbers from acceptance tests with purchasers witnessing the tests and keep the pre-test numbers only for internal use. Clearly therefore, there are differences that need to be resolved in order to obtain a common basis on which to evaluate the successful design and manufacture of a transformer at the point of factory test, including the traditions and procedures of the factory. One way is to engage in an in-depth dialogue with a prospective factory to better understand the failure trends, its procedures and the factory is using the data from the test failures. 15.3
Other factory performance measures
It may be desired by the evaluating party to even investigate similar on-time delivery performance measures with some of the transformer factory’s key suppliers of specialised, critical components such as bushings, tap changers and cooling equipment. In addition, reliability track-records such as field failure rates for the major components themselves could also be evaluated. This would require an additional level of effort and support by both the evaluating party and the factory, but it may be deemed worthwhile for the evaluation process on some critical transformer applications. Another item that might be considered for evaluation would be a list of major nonconformances during the manufacturing of the transformer prior to test. Sometimes significant non-conformances such as manufacturing errors and material defects can have significant impacts on the overall delivery schedule, depending on the time required to correct such non-conformances. If the purchaser is interested in such information, they should request a copy of the factory’s Quality Assurance Manual or similar system employed by the factory in order to gain a clear understanding of what constitutes a nonconformance to the factory, and any established reporting process they may have in place for such non-conformances. This data may not be readily available or easily shared by some factories, but it could be useful information if the factory has such data and is willing to share it with the purchaser. 15.4
Customer References
It is also customary to ask a factory for references from past transformer deliveries. Such references are very important when assessments of a factory’s capability and past performance are performed, because this might be the only way to get objective information regarding this capability. Other purchasers experience will always be important, especially if the factory is new and unknown. Regarding references, the
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factory should give sufficient information for a purchaser to be able to discuss the factory’s capability with the reference. Such information could be:
name of the purchaser the purchaser’s contact person with contact details (telephone number, e-mail address) technical data for the transformer, such as rated power and voltages year of manufacture number of units supplied
References typically help to provide a good understanding of the factory’s capabilities, and the following topics can be discussed relating to their experiences with the factory: 16
general experience and opinion and the capability to fulfil contracts quality assurance system technical competence of the staff, both in design, production, and service production facility capabilities experience before contract sufficient information provided during design experiences during factory visits, inspections, and factory acceptance tests on-time delivery transport, assembly. and final commissioning response and reaction time to problems and failures
SERVICE PERFORMANCE
Several surveys have been published during the last thirty years or more aimed at determining the incidence of transformer failures and identifying the generic causes. The CIGRÉ survey on transformer failures published in 1983 is notably the most comprehensive and together with other later national or regional focused surveys, the general consensus has been to separately derive the primary causes of failure from the actual types of faults e.g.:
Primary fault causes Defects in design, manufacturing, materials, poor specifications and inadequate testing, commissioning, maintenance, condition monitoring and protection; abnormal network and environmental effects, operations and events.
Transformer fault categories These are usually classified into four main categories; electrical, mechanical, thermal and operational and apply to sub-categories, comprising for example, as illustrated in table 1: Windings, core, bushings, tap changers, tank, insulating fluids, corrosion, materials, fittings and abnormal operation such; excessive harmonics, system over-voltage, overloads, ambient temperatures, weather.
It is apparent that in order to obtain some worthwhile assessment of the service performance of a transformer manufacturer’s product, some record of the performance of that product or his similar products is required. Such a record would need to be
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formulated in a regular and universally applicable manner and the duty to compile and maintain the record would appear to involve both the manufacturer and the previous purchasers of the product. Nowadays it is very difficult for factories to trace long term service data since the operators do not routinely provide service related feedback after the warranty period has ended. Therefore it is the operators that have the primary data by which to determine the Mean Time between Failure (MTBF), which must still be considered today. The data that can normally be obtained during the warranty period should be used by factories to derive a service performance summary that identifies failure frequency and causes of failure in terms of their product population and service history. Data derived from beyond the warranty period if obtainable can be considered and may indicate the way corrective actions have been introduced by the factory to improve service performance or even product design and manufacture. Part Windings
Magnetic circuit
Mechanical structure Bushings OLTC
Tank
Sub-structure HV / LV / Tapping / Tertiary Location Inner, middle, outer Axial position Radial position Insulation Major (winding to winding) (winding to ground) Minor (turn to turn) (disc to disc) Stress control Electrostatic shields Inter-disc connection Capacitance shields Core Leg (wound, unwound) Yoke (upper, lower) Magnetic shunts Tank Windings Supporting structure Clamps Windings Clamping Leads Cleat bar HV Ceramic / core / oil LV Ceramic / oil Type In-tank / separate compartment Single/double compartment Selector Drive motor / couplings Mechanical Control system Flanges Welded / bolted Shields Magnetic conducting Turrets HV / LV
Table 1 – Potential failure locations in a transformer Reference: Prof. D J Allan, Consultant: “Transformer Failures” ©. EA Technology Ltd; “Transformers for Power Systems”, March 2009.
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Appendix 1: Quality management system The ISO 9001 Standard provides common basic requirements and guidance to develop implement, use and maintain a Quality Management System leading to better performance of processes and to an acceptable level of quality of products. This means full conformity with specified requirements resulting in customer satisfaction. The following section explains the basic stipulations of the ISO 9001 Standard. A1.1
Quality Management System, Document Requirements (ISO9001-2000, chapter 4)
The Quality Management System is a set of principles, rules, documents and actions which aims at improved quality of the product and customer satisfaction. In order to manage quality, the factory should:
A1.2
define processes involved in the transformer manufacturing perform, check and monitor the processes in terms of quality establish and control quality documents: a. Quality Policy and Quality objectives b. Quality Manual c. documents required by the ISO 9001 Standard d. documents needed by the factory to influence processes (guidelines, procedures ….) e. records proving conformity and proper function of the QMS establish a quality management organisation (quality manager, auditors,…) the top management level should be personally involved in QM issues (Management Responsibility) Management Responsibility (ISO9001-2000, chapter 5)
The Quality Management System should be managed under responsibility of the Company Top Management, who should be committed to:
promote the importance of determining and meeting purchaser requirements throughout the organisation establish and promote the company quality policy ensure that the quality objectives are established conduct management reviews and decide on necessary corrective and preventive actions ensure the availability of resources necessary for quality management
A Quality Manager is appointed as a member of the company management team with clear authority and responsibility for all quality matters is to be appointed. The Quality Manager is basically responsible for:
all processes needed for the QMS and their function reporting to the top management – performance of QMS, improvement promotion of awareness of purchaser requirements 52
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Resource Management (ISO9001-2000, chapter 6)
The factory should determine and provide all resources (Human, Infrastructure, Work Environment etc.) needed for: A1.4
Quality Management System development and continual improvement, enhancing the customer satisfaction by meeting purchaser requirements Product Realisation (ISO9001-2000, chapter 7)
A1.4.1 Planning of product realisation The factory has to plan the product realisation, by determining the following, as appropriate:
quality objectives and requirements for the product necessary processes, documents and resources needed for the product realisation ways and means of verification, validation, monitoring, inspection and testing, criteria for product acceptance maintaining records needed to provide evidence that the transformer meets the above mentioned requirements
A1.4.2 Purchaser related processes The factory should determine and consider:
all requirements stated by the purchaser all requirements not specified but necessary for the intended use all statutory and regulatory requirements related to the transformer (legal, normative and other aspects) any additional requirements determined by the factory
It is recommended to use the latest CIGRÉ guides for technical specification and design review. A1.4.3 Review of requirements related to product All requirements must be reviewed prior to the factory commitment to supply the product (i.e. submission of offers, acceptance of contracts…). It must be made clear that:
all product requirements are defined all contract or purchase order requirements have been resolved the factory has the ability to meet the defined requirements
A1.4.4 Purchaser communication The factory should implement effective ways of communication with purchasers in relation to: 53
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product information enquiries, contracts and order handling purchaser feedback Design and Development
The factory has to plan and control the design and development of the product. It has to determine design and development stages, define necessary reviews, verifications and validations appropriate to every stage, determine responsibilities and authorities in the design process. It is very important to manage the interfaces (e.g. mechanical, electrical, thermal design). The design plan has to be updated as appropriate, as the design and development progresses.
Design Inputs All necessary information arising from purchaser requirements, applicable standards and regulations, previous similar designs and designer experience, have to be taken into account and reviewed for adequacy.
Design Outputs Design outputs have to be provided in a form that allows for verification against the input and shall be approved accordingly. They have to provide appropriate information for purchasing, manufacturing and servicing, set up product acceptance criteria, and specify the product characteristics that are essential for its proper use.
Design Reviews Design reviews should be performed at suitable design stages. This is one of the most important parts of the factory capability assessment which strongly influences the quality of the purchased transformer. (For details see the appropriate chapter of this guide). There is a CIGRÉ guide for design review, which is recommended for use during factory assessment.
Design Verification The purpose is to verify, that the completed or partial design meets the input requirements. Records of design verification are to be maintained.
Design Validation Design validation should prove that the manufactured product fulfils all intentions and design parameters required. Records of design validation (i.e. test reports) are to be maintained. A good proof of design validation is the reference to similar products manufactured before.
Design Changes Design changes shall be identified and records maintained. Design changes shall be reviewed, verified and validated in the same way as the original design.
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Purchasing
The factory should ensure that the requirements for the purchased product are properly specified and that the purchased product (material, service) conforms to them. This applies also to subcontractors. The factory should evaluate and select factories based on their ability to supply products in accordance with its requirements. Criteria for such evaluation should be established; records including arising actions should be maintained.
purchasing information a. specification of the product to be purchased b. requirements for approval of the purchased product, manufacturing procedures, processes and equipment c. requirements for qualification of personnel d. Quality Management System requirements
verification of the purchased product
A1.7
Production and service provision
A1.7.1 Production Control The factory should ensure:
availability of all necessary information on the required product availability of work instructions, as necessary availability and use of suitable equipment (machines, tools…) For details see the appropriate chapters of this guide. availability and use of monitoring, measuring and testing devices For details see the appropriate chapters of this guide suitably qualified trained production personnel For details see the appropriate chapters of this guide release, delivery (transport) and post-delivery (installation, commissioning and service) activities For details see the appropriate chapters of this guide
A1.7.2 Production Process Validation Results of manufacturing processes, which cannot be verified by measuring or testing directly on the transformer, should be validated. A1.7.3 Product Identification, Traceability Where appropriate, the factory should identify the product during its realisation (labelling). The label should not only identify the product, but also its status in respect to monitoring, measurement and test requirements.
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A1.7.4 Purchaser property The factory should identify, verify, protect and safeguard property provided for use or for incorporation into the product. In case of damage, loss etc. the purchaser must be notified and a record must be made. (Property may include intellectual property). A1.7.5 Preservation of product The factory has to preserve the conformity of his product during manufacture and delivery to the intended destination. The preservation should include identification, handling, packaging, storage and protection. A1.7.6 Monitoring and Measuring Devices The factory should determine the monitoring and measurement to be undertaken and the monitoring and measuring devices needed to provide evidence of product conformance to determined requirements. Where necessary to ensure valid results, measuring and testing equipment must be:
A1.8
calibrated or verified at specific intervals or prior to use against measurement standards traceable to national or international standards adjusted or readjusted as necessary the calibration and its validity (expiration) should be identified on the equipment safeguarded from adjustments that would invalidate the measurement results protected from damage and deterioration during handling, maintenance and storage Measurement, analysis and improvement (ISO9001-2000, chapter 8)
Transformer manufacturing is a plan-do-check-act process. The factory should plan and implement monitoring, measurement, analysis and improvement processes needed to:
demonstrate conformity of product with the specification and design requirements ensure conformity and effectiveness of the quality management process continually improve the effectiveness of the quality management system
Such measurement process should determine applicable methods including statistical techniques and the extent of their use. A1.8.1 Customer Satisfaction As one of the measurements of the performance of the quality management system, the factory should monitor information related to purchaser perception as to whether the factory has met the purchasers’ requirements. The factory should develop methods for obtaining and use of such information.
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A1.8.2 Internal audits The factory should conduct internal audits at planned intervals to determine whether the quality management system
conforms to the planned arrangements for the product, to the requirements of the ISO 9001-2000 standard and to the quality management requirements established by the factory is effectively implemented and maintained
The factory should establish an audit program that takes into account the importance of the processes to be audited as well as results of previous audits. Internal auditors should be selected. The auditing program should be independent and auditors should not audit their own processes. Non-conformities detected during internal audits should be eliminated together with their causes. Follow up actions should be taken in order to verify the elimination. Note: Guidance for internal auditing can be found in ISO 10011-1, 2 and 3. A1.8.3.
Monitoring and measurement of processes
The factory should apply methods that measure of the quality management process. The methods should demonstrate the ability of the processes to achieve planned results. When planned results are not achieved, corrective actions should be taken to improve the processes and ensure conformity. A1.8.4.
Monitoring and measurement of product
The factory should monitor and measure the characteristics of the product to verify that requirements have been met. Such measurements should be taken at appropriate stages of the manufacturing process and evidence of compliance with requirements and with acceptance criteria should be recorded. Records should identify the persons authorising release of the product. Final product release should not be permitted until all criteria are met and the planned checks have been completed unless otherwise approved by the purchaser. A1.8.5.
Control of non-conforming product
The factory should ensure that the product which does not conform to product requirements is identified (red tag) and controlled to prevent its unintended use or delivery. The controls and related responsibilities should be defined in a special documented procedure. A1.8.6
Analysis of data
The factory should determine, collect and analyse appropriate data to demonstrate the suitability and effectiveness of the quality management systems and to continually improve the effectiveness of the system. This data should include data obtained by monitoring and measurement of processes and products. The analysis of data should provide information on
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Guide for conducting factory capability assessment for power transformers
characteristics and trends or processes and products suppliers
A1.8.7 Improvement The factory should continually improve the effectiveness of its quality management system by improving quality policies, quality objectives, audit results, analysis of data, corrective and preventive actions and management reviews. A1.8.8 Corrective action The factory should take action to eliminate non-conformances in order to prevent recurrence. Corrective action should be taken to eliminate the consequences of nonconformances. A1.8.9 Preventive action The factory should take preventive action to eliminate the cause of non-conformances in order to prevent recurrence and avoid further non-conformances.
More information on ISO9001-2000 in Appendix 2 Examples of questions that need to be asked during the Quality Management System review are presented in the Questionnaire – Appendix 2
58
WG A2-36
Guide for conducting factory capability assessment for power transformers
Appendix 2: Example of Questionnaire A2-36
Example of Capability Assessment Questionnaire
Chapter Information required 3
Evaluation criteria Excellent
MANAGING QUALITY Does the manufacturer have a valid ISO 9001 certificate? Does the manufacturer have a valid ISO 14000 certificate? Does the manufacturer have a valid OHSAS 18000 certificate?
4
TECHNOLOGY BASE Transformer Type produced by the Factories What type of transformer design is manufactured, core and/or shell? Origin of Technology Base Is the owner of the technology a global, regional, or local supplier? Where or from whom is the origin of the technology? Is the technology owned or licensed? Familiarity and Compliance with applicable Industry Standards
4
DOCUMENTATION OF THE DESIGN AND MANUFACTURING TECHNOLOGY BASE Investigations and R&D Reports Does the factory have 5 to 10 years of R&D Reports that can be used for the assessment? How does the knowledge and competence get maintained and distributed?
59
Good
Poor
Unacceptable
Comments
WG A2-36
A2-36
Example of Capability Assessment Questionnaire
Chapter Information required 4
Guide for conducting factory capability assessment for power transformers
Evaluation criteria Excellent
Basic Design Theory Is the basis for the transformer design calculations clearly described and documented? Have origins of rules and criteria's been documented? Do technical standards provide adequate geometric details between adjacent components - windings, core, insulation systems, etc.? How are materials and components specified for purchasing? Does the factory have a drawing numbering system? Are the manufacturing methods, processes, tools and equipment clearly described and visualised? Is there documentation that confirms the validation of computer design programs?
4
Product Design and Manufacturing Rules and Instructions Product Design Rules Dielectric Rules Does the factory have documented evidence describing how the knowledge of electrical breakdown is transferred into design rules? Does the factory have a documented insulation system? Magnetic Core Performance Rules Can the factory clearly calculate no-load losses, inrush and exciting currents, harmonics, temperatures? Does the factory historically analyse performance data versus calculated values and are the results available?
60
Good
Poor
Unacceptable
Comments
WG A2-36
A2-36
Guide for conducting factory capability assessment for power transformers
Example of Capability Assessment Questionnaire
Chapter Information required 4
Evaluation criteria Excellent
Acoustic Sound Rules Does the factory have tools to calculate core vibration modes and resonances at different frequencies? Are sound levels calculated for both no-load and loading conditions? Load Losses and Load Temperature What thermal design calculation computer programs does the factory use? Have the thermal calculations been validated by fibre optic measurements? Are hot spot temperatures calculated for windings, core, internal clamping structures and the tank at worst case operating conditions? Short Circuit Strength and Mechanical Integrity Rules Does the factory demonstrate short circuit withstand capability by design calculations in accordance with IEC 60076-5? What criteria are used for axial and radial strengths of the windings? Has the factory performed short circuit tests? If yes, what has been the experience? What criteria are used to calculate transport and seismic capabilities? Design Methods and Tools How does the factory optimise the transformer designs? Does the factory calculate dielectric stresses down to single turns? Does the factory use 3-D design programs and 3-D CAD systems?
61
Good
Poor
Unacceptable
Comments
WG A2-36
A2-36
Guide for conducting factory capability assessment for power transformers
Example of Capability Assessment Questionnaire
Chapter Information required
Evaluation criteria Excellent
Manufacturing Technology in Production Standards How are production and process methods documented? What accuracy and uncertainty does the factory have in: Loss measurements? Sound level measurements? Temperature measurements? Impedance measurements? Partial discharge measurements? Does the factory have an equipment calibration process and appropriate certification for its instruments?
4
Other means of Evaluating the technical capabilities of a factory How many engineers and technicians does the factory have? Does the number seem adequate? Is there a formalized training and development program for the engineers? Has any of the factory staff written industry papers?
5
DESIGN PROCEDURES AND IT TOOLS Design Experience of Market Does the factory have experience with different specifications based on: IEC (inc. CENELEC), IEEE-ANSI, Others ?
62
Good
Poor
Unacceptable
Comments
WG A2-36
A2-36
Guide for conducting factory capability assessment for power transformers
Example of Capability Assessment Questionnaire
Chapter Information required
Evaluation criteria Excellent
Design Experience of Product Range Does the factory have experience with any of the following types of transformer : Grid step down transformers? Generator step up transformers? Transmission autotransformers? Phase-shifting transformers? Arc furnace transformers? Rectifier transformers? HVDC transformers? Shunt reactors? High voltage? High current? High leakage flux? 5
Specification Understanding and communication Is the factory capable of understanding the user’s specification in the original language? How is communication between the user and the factory’s engineers organised? How direct are the lines of communication between engineers? How many steps are there? What is a typical response time for a question?
63
Good
Poor
Unacceptable
Comments
WG A2-36
A2-36
Guide for conducting factory capability assessment for power transformers
Example of Capability Assessment Questionnaire
Chapter Information required
Evaluation criteria Excellent
Design Process Quotation and Order Is there an adequate post award review process (minutes, actions followed-up)? Internal (with commercial-, design- and manufacturing departments)? External (with customers and their representatives)? Are there defined hand-over points between electrical design and mechanical design? Is there an adequate design review process (minutes, actions followed-up)? Internal (with internal commercial and manufacturing departments)? External (with external customers and their representatives)? Are there adequate design and design revision procedures? Are there defined hand-over points between design and purchasing of material? 5
Research and Development Activities What is annual investment in R&D (as % of turn-over)? Is there an internal R&D team (permanent, dedicated, no. of engineers)? Is there external R&D collaboration (with whom, no. of engineers/ projects)? Have there been any technical publications by R&D and engineering staff? What is the factory's participation in standards bodies (e.g. IEC, IEEEANSI, National Standards etc)? What is the factory's participation in professional societies (e.g. CIGRE, IEEE, etc)?
64
Good
Poor
Unacceptable
Comments
WG A2-36
A2-36
Guide for conducting factory capability assessment for power transformers
Example of Capability Assessment Questionnaire
Chapter Information required 5
Evaluation criteria Excellent
Design Manual, Design Rules Is there an adequate design manual with the following characteristics? Is the design manual updated regularly? Are there sufficient cross-references to source material? Do the design team have good knowledge of the content of the design manual? What are the procedures for spreading new information? How are test results fed-back to the design team?
5
Software and its Maintenance Design Software Is there adequate design software with the following capabilities? Design software updated regularly? Design software documented? Is design software intuitive and user-friendly? What are the design modelling capabilities with regard to: Electric fields? Magnetic fields (including short-circuit withstand)? Noise and vibration? Transient voltages? Power system analysis? Fluid mechanics/thermodynamics (temperature distribution)? Is there adequate mechanical design software with regard to: 2-D or 3-D modelling? Library of models etc?
65
Good
Poor
Unacceptable
Comments
WG A2-36
A2-36
Guide for conducting factory capability assessment for power transformers
Example of Capability Assessment Questionnaire
Chapter Information required 5
Evaluation criteria Excellent
Experience Level of Engineers What is the age and experience profile of the design team? What are the minimum and typical levels of education of the design team? Expert Technical Support Are any technical specialists available to support the user? Where are the technical specialists based (at the factory, at another factory owned by the same manufacturer)?
6
SUPPLY CHAIN MANAGEMENT Does the manufacturer have Material/Components Specifications? Is there a continuous auditing process by the Manufacturer of the subsuppliers? What Quality requirements on the sub-suppliers are measured? What is the resolution process when non-conformances are detected? Which are the Manufacturer's 5 to 10 biggest Sub-suppliers? What is the Performance of the sub-suppliers (Report available)? Does the Manufacturer have an established relationship with important sub-suppliers? Are production plans between the Manufacturer and sub-suppliers coordinated to ensure that components are received at scheduled points in the manufacturing process to ensure the overall delivery time of the transformer is kept?
66
Good
Poor
Unacceptable
Comments
WG A2-36
A2-36
Guide for conducting factory capability assessment for power transformers
Example of Capability Assessment Questionnaire
Chapter Information required 6
Evaluation criteria Excellent
Bushings and Load Tap Changers Does the Manufacturer have an established relationship with the equipment suppliers? Is there a clear specification of the requirements in the order documents? Are the normal bushing and tap-changer suppliers of the manufacturer acceptable for the purchaser or the end-user? Does the manufacturer perform a periodic quality audit of the suppliers? Are the bushings and tap-changers inspected for specification and quality conformance upon receipt at the manufacturer's facility?
6
Copper conductors in Windings Is the quality and specification conformance of the copper conductor verified prior to use by the manufacturer? Are received copper conductor dimensions verified to be within the specified tolerances? Are controls in place to prevent burrs on the copper conductors? Are efforts taken to ensure the copper conductors are packed, transported, and stored in a safe manner to prevent damage? Oil Is the quality of the insulating oil used in assembling the transformers verified to be in accordance with relevant standards? Is the quality of the factory insulating oil checked regularly? Does the manufacturer have the capability of performing laboratory analysis of the oil?
67
Good
Poor
Unacceptable
Comments
WG A2-36
A2-36
Guide for conducting factory capability assessment for power transformers
Example of Capability Assessment Questionnaire
Chapter Information required
Evaluation criteria Excellent
Core Steel Which sources of core steel are used by the Manufacturer? Does the Manufacturer check the core steel suppliers' loss certificates? Does the Manufacturer compare the calculated and measured values of the no-load loss? Insulation board and insulation components Are the insulation board and insulation components carefully stored in a manner to avoid contamination by dust and moisture? Does the manufacturer have an established material specification for insulation board? Does the manufacturer produce the insulation components directly, or outsource the production of these components? 6
Others Components and Materials Does the manufacturer have an established relationship with components suppliers? Is main tank and/or conservator tank outsourced? Which of the following components are outsourced by the manufacturer? Main tank? Conservator and associated pipe work? Insulation parts? Other metalwork fabrication? Auxiliary control cubicles? Secondary wiring? Is the quality of the main tank and conservator tank verified by Quality Audits and inspections?
68
Good
Poor
Unacceptable
Comments
WG A2-36
A2-36
Guide for conducting factory capability assessment for power transformers
Example of Capability Assessment Questionnaire
Chapter Information required
Evaluation criteria Excellent
Are efforts taken to ensure the tanks are adequately cleaned prior to assembling the transformer, to minimize the risk of contaminants remaining in the transformer?
7
MANUFACTURING METHODS Manufacturing Procedures a) Are manufacturing tolerances documented? b) Are tools and equipment properly documented? c) Are the skills sets of the work force properly documented? d) Are the experience and attitude of the workforce documented? Are safety working conditions and safety equipment provided and correctly utilised? Are "clean areas" clearly designated and separated from "dirty areas"? Are there house-keeping indexes working? What is the general condition of the fabric of the building in which manufacture takes place? Are there any roof leaks? Are there any signs of wild life within the factory e.g. birds, vermin etc.? Does workforce experience match the tasks undertaken? Does workforce have a positive attitude to their work? Does workforce have a clean and tidy and a "fix as you go" approach? Are working areas clean and well organised? Is there good communication between factory workers, inspectors and management including designers?
69
Good
Poor
Unacceptable
Comments
WG A2-36
A2-36
Guide for conducting factory capability assessment for power transformers
Example of Capability Assessment Questionnaire
Chapter Information required 7
Evaluation criteria Excellent
Production planning and Material Warehouse: Is there a clear method for project planning? Is there an inventory control system and procedure? Is there a check workflow, push or pull flow? Are materials storage areas structured and organised? Are materials properly handled in designated areas?
7
Main Tank and Steel Fabrication: Are in-house tank and metal fabrication processes isolated from core, winding and assembly areas? For outsourced steelwork, are there systems in place covering procedures of engineering, quality system and quality audits? Is weld quality good and consistent with no main tank welds behind tank stiffeners? Is inside of the tank and any hollow beam stiffeners free from foreign material? Is the tank internal surface and the core and coil clamping structure painted white? If not: What colour is the tank internal surface? The core clamping structure? Are tank shield and shunts insulated or continuous welded? Are gasket grooves smooth and within the specified tolerance? What processes are applied to small bore pipe work regarding cleaning and preservation of the internal surfaces? Is surface preparation according to ISO 8501 or similar standard?
70
Good
Poor
Unacceptable
Comments
WG A2-36
A2-36
Guide for conducting factory capability assessment for power transformers
Example of Capability Assessment Questionnaire
Chapter Information required
Evaluation criteria Excellent
Is paint finish procedure according to ISO 12944 or similar standard? Are tank coatings according to the specification? Are tank coatings according to the specification? How is the paint thickness checked? 7
Core cutting/stacking methods Are the cutting blades routinely checked and maintained? And is this process documented? Are burrs within specified tolerance, no slithers, rust or other physical damage on the cut steel? Is the incoming core steel routine inspected, measured and monitored? a.) Is coating consistent with non-corrosive look, and indicated on control cards? b.) Are core laminates routinely measured to confirm dimensions? Are the core stacking tables stable and level? What precautions are taken to prevent core deformation during upending of the completed core? Is the core fully supported during stacking process? Is the core fully supported during stacking process? Do completed cores have protective covering to prevent contamination? Is the earthing joint mechanically strong and insulated to prevent accidental contact with core? Is the core clamping structure properly grounded with metal to metal connections? Is the core clamping structure bonded in a suitable manner to prevent circulating currents? Are core cooling ducts installed as an integrated part of the stacking process? 71
Good
Poor
Unacceptable
Comments
WG A2-36
A2-36
Guide for conducting factory capability assessment for power transformers
Example of Capability Assessment Questionnaire
Chapter Information required
Evaluation criteria Excellent
Are the mitre joint building gaps small and as uniform as possible and within factory design tolerances? Is the stacked core within the designed tolerances? Is core inter-laminar resistance confirmed during manufacturing process? Is an intermediate non-metallic block utilised for tapping the laminations, no-use of steel hammer? Are there any contaminants around the core assembly work area? Do workers have protective shoes and gloves? If yes do they wear them? 7
Winding Room: What type of winding machines does the manufacturer have? How many horizontal winding machines? How many vertical winding machines? Are winding machines routine cleaned and with no contaminants inside the mandrels? Are windings manufactured on horizontal machines placed on floor prior to being upended? Is the winding end to lead conductor jointing process controlled to confirm that the joints are mechanically and electrical capable? Has winding room access control and/or environment control? Are conductor reels free of rough edges and contaminants? Is there any sign of conductor insulation damage or contamination? Inspect for processes that could cause insulation damage. Are spacers and blocks consistently installed? Are all permanent winding conductors ties/tapes non shrinking type? Are winding cylinders pre-dried and sized prior to winding process?
72
Good
Poor
Unacceptable
Comments
WG A2-36
A2-36
Guide for conducting factory capability assessment for power transformers
Example of Capability Assessment Questionnaire
Chapter Information required
Evaluation criteria Excellent
Are winding machine mandrels properly sized and adequate for the winding support and within tolerances? Are windings manufactured with the conductor being wound held under tension? Are added splices within the windings, unless they are part of the design? Are conductors properly supported from reels to the winding machine with smooth, clean rollers supports with conductors prevented from contacting the floor? Are inner and outer crossovers and transposition bends performed correctly and in a manner to ensure all critical clearances and design oil flows are achieved? Any restrictions in oil flows observed? Have crossovers bends extra insulation wrap and pad material? Are all blocks and spacers of high density material and have been finished with rounded and smooth edges? Have all temporary blocks rounded and smooth edges? Are brazing techniques performed in a manner to minimise contamination and insulation damage? Are static rings properly stored and handled to ensure no damage or deformation? Are static rings properly installed and positioned? Are completed windings fitted with a temporary protective covering? Are oil flow guide-washers installed in a manner to not adversely affect oil flow through the windings and in accordance with design? Are tools and containers temporarily placed on windings? Is there a contamination risk from roof fabric and overhead cranes?
73
Good
Poor
Unacceptable
Comments
WG A2-36
A2-36
Guide for conducting factory capability assessment for power transformers
Example of Capability Assessment Questionnaire
Chapter Information required 7
Evaluation criteria Excellent
Winding Sizing: Is there access and/or environment control in the winding sizing area? Is there any evidence of damage to conductor insulation? Are radial spacers, sticks and blocks properly aligned? Are spacers and blocks permanently affixed into position by means of other than winding clamping pressure? Are blocks glued to conductor insulation? Does manufacturer verify, control and measure winding drying, pressing and sizing processes with the aim of stabilising windings for positive axial pressure during transformer service? Do lifts have cushioned supports and fitted with means of preventing chains or ropes in coming into direct contact with windings? Are conductors wound tightly to eliminate or minimise winding movement during service? Are oil ducts still of the correct dimensions when sizing pressure is applied? Is conductor radial build not extended beyond outer edge of radial spacer or inner edge of mitre joint to allow axial stick placement? Do any crossover radial built and transpositions bends extended beyond the edge of overall winding radial build? Is winding height within tolerance? Are conductor ends covered to prevent damage to windings or to personnel? Are complete windings fitted with temporary protective covering to prevent contamination?
7
Active Part Assembly: Is there any contamination around the work area?
74
Good
Poor
Unacceptable
Comments
WG A2-36
A2-36
Guide for conducting factory capability assessment for power transformers
Example of Capability Assessment Questionnaire
Chapter Information required
Evaluation criteria Excellent
Are there any instructions with regard to avoidance of contamination during cutting, crimping, brazing and top yoke stacking operations? Are assembly platforms fitted with a front lip to reduce the risk of contaminants falling into the Core & Coil assembly? Are the winding radial spacer columns and block correctly aligned? Are protective screens used to minimise contamination ingress especially when brazing and crimping? Are lead support structures mechanically sound with rounded edges and no visible abnormalities? Are vacuum cleaners with proper hose attachments used to clean out any small openings, e.g. winding cooling ducts? Is there any signs of the use of air hoses to clean windings? This is considered to be bad practice! Are any precautions been taken and/or instructions in place to prevent workers items falling accidentally into the transformer? e.g. pencils, jewellery, tools, etc. Is upper yoke stacked into position maintaining building gaps and properly supported without any distortion? Are core tips on ends of yokes bent over allowing contact with adjacent tips? If yes, how many? Do the cores show any signs of physical damage or corrosion, e.g. rust? Are any precautions taken to prevent contamination of winding cooling ducts during the assembly process? Are any foreign materials and contaminants on the core and coil assembly, including within areas difficult to see such as the clamping structure or winding oil ducts? Is there any evidence of too much or misuse of glue?
75
Good
Poor
Unacceptable
Comments
WG A2-36
A2-36
Guide for conducting factory capability assessment for power transformers
Example of Capability Assessment Questionnaire
Chapter Information required
Evaluation criteria Excellent
Are winding support blocks and pressure rings aligned and permanently fixed into position? Are any bolted connections (both electrical and mechanical) fitted with suitable locking mechanisms? Are electrical bolted connections fitted with at least two bolts (where possible) to prevent "scissoring"? Are leads suitably insulated and insulation thickness fully documented? Are core clamping structures properly grounded with metal to metal connections in a manner to prevent circulating currents? Are any temporary metallic wires or ties used? Are any insulation barriers properly fixed in position? Are pre-measurements made on active part during assembly (ratio, losses, RSO, etc.)? 7
Final Dry Out: What methods of drying are employed during the final drying process of the transformer? What criteria are used to monitor, control and terminate the process? Are there any special instructions in place with regard to the handling of dried components? How are drying process variables indicated on quality procedures and documentation? How is the process of dry-out of the core and coil assembly controlled prior to final clamping? What methods are used after drying, direct impregnation, maintaining dryness until final oil filling with the aim of stabilising the windings to ensure positive axial pressure during the transformer service
76
Good
Poor
Unacceptable
Comments
WG A2-36
A2-36
Guide for conducting factory capability assessment for power transformers
Example of Capability Assessment Questionnaire
Chapter Information required 7
Evaluation criteria Excellent
Final Assembly: How is the final winding clamping pressure applied after the final dryout process prior to the tanking of the active part? What are the time tolerances? What are the clamping force criteria? Is the clamping pressure, dimensional tolerances and the jacking method recorded? Are the internal bolted connections properly torqued, locked and marked to facilitate confirmation of correct clamping pressure? Is the core and coils positioned accurately inside the tank, according to drawing dimensions? Are vacuum time, speed of oil filling, standing time, oil filtering/ circulation time and particle count measured and recorded? Are conduits and wires properly secured and supported, and designed to minimise ingress of moisture? Are conduits and wires free of internal sharp and jagged edges and free of foreign materials? Are cooling fans properly secured to radiators with protective pad material minimising radiator paint wear over time that could lead to radiator leaks? Is tank paint work touched up prior to shipment? Are control enclosures designed and manufactured as per specifications?
8
TESTING Test Accuracy Are all pieces of test equipment properly calibrated, certified and currently valid? Is the test equipment calibration status clearly marked on each
77
Good
Poor
Unacceptable
Comments
WG A2-36
A2-36
Guide for conducting factory capability assessment for power transformers
Example of Capability Assessment Questionnaire
Chapter Information required
Evaluation criteria Excellent
instrument of piece of test equipment? Is there a documented accuracy level for each piece of test equipment? Test Equipment Is the factory capable of performing all routine tests at the manufacturing facility? Is the test facility shielded and physically isolated from the rest of the factory? Is the factory capable in performing all required tests? Where are short circuit tests typically performed? Is there a short circuit test reference list available? Can the factory perform dissolved gas analysis on-site or is it performed by 3rd party? Can the factory perform thermal, mechanical, and chemical tests on insulating materials? Can the factory perform routine tests in the field (capacitance, power factor, TTR, frequency response analysis, etc? Does the factory have the capability to perform no-load, applied potential, induced, or impulse tests in the field? 8
Test Engineers Is there a formalised training and development program for the test engineers?
78
Good
Poor
Unacceptable
Comments
WG A2-36
A2-36
Guide for conducting factory capability assessment for power transformers
Example of Capability Assessment Questionnaire
Chapter Information required
Evaluation criteria Excellent
Standards Are the test engineers fully conversant with the latest industry test standards (IEC, IEEE, etc) and customer specific test requirements? Do they understand them? Documentation Does the factory provide a detailed test plan showing test circuit, test procedure including voltages to be applied and acceptance criteria? Is there a standard format for the test plan and sequence of tests? Does the test plan typically include all acceptance criteria? Does the transformer design engineer review and sign the test reports before final approval? Are abnormalities that arise during testing sufficiently explained to the purchaser? Is the generation of test reports partially or totally automated? 8
Failure investigation Is there in-house technical expertise, personnel, and equipment available for dealing with test failure investigations? Are there procedures in place to support test failure investigations? Do the transformer design engineers typically participate in investigations? Are customers promptly notified of a test failure and asked to participate in investigations? Are test failure investigations fully documented?
79
Good
Poor
Unacceptable
Comments
WG A2-36
A2-36
Guide for conducting factory capability assessment for power transformers
Example of Capability Assessment Questionnaire
Chapter Information required
Evaluation criteria Excellent
General Are customers typically notified in a timely manner about the test plan and the test schedule? Are there opening and closing meetings with the customers included in the test procedures? Are there adequate facilities to accommodate customers during the test witness process?
9
WARRANTY AND SERVICES Warranty What terms of warranty can the manufacturer offer, i.e. the coverage comprised by the warranty? What is the manufacturer’s guaranteed response time in case of an incident, how is the access to the manufacturers' experts? Can the manufacturer provide a special warranty against design defects that arise after the term of the warranty? e.g. latent defects? Access and delivery times for spare parts, such as tap-changers, auxiliary equipment, production of new windings, etc... What is the legal situation and legislation in the country of the manufacturer?
9
Services Sales organisation What is the range of products, ratings, design and technology, manufacturing facilities, testing, etc. (limitations in technology or capability) Are fulfilment of normative requirements, standards and requirements for local installations known for the manufacturer? What is the competence and technical know-how of the sales staff?
80
Good
Poor
Unacceptable
Comments
WG A2-36
A2-36
Guide for conducting factory capability assessment for power transformers
Example of Capability Assessment Questionnaire
Chapter Information required
Evaluation criteria Excellent
After sales arrangement Can the manufacturer offer support in terms of condition assessment, DGA sampling and analysis, on site testing etc. Can the manufacturer carry out transformer repairs? Is the manufacturer prepared to do so? Can the manufacturer offer any added value maintenance service products? 10
PROJECT MANAGEMENT Will there be a single or multiple point of contact? Will there be direct or indirect communication? What project languages are understood and can be used? What is the typical project management structure used by the manufacturer? What is a typical project schedule and how is it updated? What is the method of contract review? What methods of risk management are used? What is a typical inspection and test plan?
11
HUMAN RESOURCES MANAGEMENT Human Resources Aims Does the manufacturer manage human resources responsibly? Legal and Cultural Aspects Is human resource management subject to the International Labour Organisation (ILO)?
81
Good
Poor
Unacceptable
Comments
WG A2-36
A2-36
Guide for conducting factory capability assessment for power transformers
Example of Capability Assessment Questionnaire
Chapter Information required
Evaluation criteria Excellent
Industrial Relations Is there an independent trade union in the factory, how much influence does it have? Are there signs of antagonism between the management and the employees? Have there been any strikes at the factory? Are any strikes planned or possible? Recruitment Are vacancies openly advertised? Does the manufacturer have an equal opportunities or nondiscrimination policy? Is there any obvious evidence of discrimination or favouritism? Is there any material or public display which might create an atmosphere that would promote discrimination? Do technicians and engineers have appropriate qualifications and minimum requirements? 11
Agency Workers Is the factory using agency or contract workers? In case of agency workers, what proportion of the workforce do they represent? Does the factory seem excessively reliant on agency or contract workers? Vulnerable Workers Is any special forced labour used for transformer production? Is any child labour used for transformer production? Training and Development Is there adequate opportunities for the workforce to be provided with suitable training and development? 82
Good
Poor
Unacceptable
Comments
WG A2-36
A2-36
Guide for conducting factory capability assessment for power transformers
Example of Capability Assessment Questionnaire
Chapter Information required
Evaluation criteria Excellent
Health, Safety and Working Environment Working Environment Are there separate areas for eating and drinking away from critical production areas? Is there any evidence of food or drink being consumed outside these areas? e.g. at the work place? Are there adequate and sanitary washing facilities for all employees and contractors? 11
Working Hours and Holidays Do employees seem to be excessively tired or stressed? What is the length of the working day, week, and maximum limits that apply to these? When is the weekend or weekly rest period? What public and customary holidays does the factory observe? How much paid holiday are employees entitled to? What measures have the management taken to avoid disruption to production during holidays? Is there an annual factory shut down? Security Are health and safety inductions provided for all employees, contractors and visitors? Was the inspector given such an induction? Is the entry and exit of all employees, contractors and visitors recorded and/ or controlled? Was the inspector's entry and exit recorded/ controlled?
83
Good
Poor
Unacceptable
Comments
WG A2-36
A2-36
Guide for conducting factory capability assessment for power transformers
Example of Capability Assessment Questionnaire
Chapter Information required
Evaluation criteria Excellent
Is there sufficient security to prevent the theft of valuable equipment, components or materials? What precautions are taken? Do they seem to be effective? 11
Health and Safety Management Is the factory OSHAS 18000 certified? What is the factory health and safety policy? Is it prominently displayed? Is the health and safety policy adequate in scope? Does it seem to be used as basis for health and safety management? Which member of the top management team is responsible for health and safety? Is part of role delegated to a sub-ordinate manager? How much communication is there between the different managers? Do employees and contractors know who the health and safety manager is? How do employees participate in the health and safety management system? Do employees and contractors know who their health and safety representatives are? Is the health and safety management system adequately documented? Is management making good use of the hierarchy of controls, i.e.: elimination, substitution, engineering and administrative controls?
11
Personal protective equipment Are there adequate warning signs in the factory about hazardous areas and protective equipment requirements? Are all employees and contractors equipped with adequate personal protective equipment? Are they using it correctly? Was the inspector provided with personal protective equipment during his or her visit? 84
Good
Poor
Unacceptable
Comments
WG A2-36
A2-36
Guide for conducting factory capability assessment for power transformers
Example of Capability Assessment Questionnaire
Chapter Information required
Evaluation criteria Excellent
Is there an adequate number of trained first aiders? How are first aiders identified? Are there adequate provisions for preventing and controlling fires? Are there adequate fire exits? Have any of them been obstructed for any reason? Are there adequate numbers of fire marshals to help with evacuation? How are fire marshals identified? Are the fire alarms tested regularly? Is the factory inspected regularly by the local fire service? Are all accidents reported to the local authorities? Are incidents adequately investigated? Do the management seem to learn from incidents? 11
Dangerous Chemicals Does the manufacturer use any asbestos in the gasket material? Does the factory ensure that oil is free from furans and PCB's?
12
TRANSPORT General Do purchasers know which parts are removed for shipment (bushings, turrets, coolers, conservator, pipes, etc.)? Delivery Terms Do the exact delivery terms agree (Incoterms 2000 group E, F, C or D)? How well does the factory know their transport companies? Methods Air What limitations on mass and dimensions apply? 85
Good
Poor
Unacceptable
Comments
WG A2-36
A2-36
Guide for conducting factory capability assessment for power transformers
Example of Capability Assessment Questionnaire
Chapter Information required
Evaluation criteria Excellent
Barge (Coastal Ship) How is the transformer protected against adverse weather? 12
Ocean-Going Ship Are wooden crates specially treated to prevent the introduction of pest and diseases? How is the transformer protected against adverse weather? Rail What limitations on mass and dimensions apply? Does the manufacturer have a Schnabel wagon design? Road What limitations on mass and dimensions apply? Voyage Assessment Are the following considerations taken into account? Transportation equipment - ocean vessel, barge, rail, truck? Number of lifting operations and type of lifting gear? Number of trans-shipments and carrier's hubs? Weather and environmental circumstances? Infrastructure along the routing as ports, terminal and road conditions? Permits and government regulations? Expected maximum transit time including intermediate storage and storage after delivery? Responsibility for the transportation?
86
Good
Poor
Unacceptable
Comments
WG A2-36
A2-36
Guide for conducting factory capability assessment for power transformers
Example of Capability Assessment Questionnaire
Chapter Information required
Evaluation criteria Excellent
Assessment of the Factory's Preparation capability Are there design rules for goods to be shipped? Is there a transport plan? Are there packaging rules and instructions including identification numbers? Is the transformer prepared taking in consideration: Closure/sealing of unit openings? Removal of fragile and protruding non integral components? Moisture protection? Cushioning of non-removable protrusions, i.e.: valves, hoses, pipe work, conduits, etc? Shock indicators / impact recorders. How is the factory using them?, What is their duration?, Is there a shock sensor on the core structure? 12
Preparation and Execution of transport Is there a transport coordinator located at the factory? Are there insurance policies for all sub-contractors and their obligations? Is a "Transport Manual" established for each transport? If so does it contain: Transportation documents and checklists? Considerations for all lifts? Controls on cargo transfer points including photos from each diagonally opposite corner? Is there a strong suggestion to ensure transport contractors include these requirements? Contracts with sub-contractors?
87
Good
Poor
Unacceptable
Comments
WG A2-36
A2-36
Guide for conducting factory capability assessment for power transformers
Example of Capability Assessment Questionnaire
Chapter Information required
Evaluation criteria Excellent
Is the "Transport Manual" attached to the goods before shipment from the factory? Are documentation, such as photos taken before the transport, stored in the "Transport Manual"? Is a system established for post-transport feedback on transport parameters, damages and claim handling? 12
Personnel Training / Education Considerations Are personnel involved in the transport chain trained / educated with respect to all elements of the transportation chain? Standards of Care for Transportation / Freight Forwarding Vendors Does the freight forwarder follow various guidelines for loading, securing, transportation and discharge? Check for All Shipments, Lifts, Ocean Vessels Are transportation contractors specialised in handling power transformers? Are transportation contractors financially stable to be able to respond to liabilities? Do sub-contractors retain liability? Do contractors verify existence, adequacy and condition of their handling and transport equipment at all points of the transit? Are all cranes and gears used in lifting certified to required safe working load capacities? Do vessels have a tonnage of more than 10 times the weight of the transformer? If not, is the relevant insurer informed? Does transport coordinator contact the captain of the vessel to fully explain possible risks for damage of transformers? In case of Rail and Truck, Is a qualified operator selected and utilised?
88
Good
Poor
Unacceptable
Comments
WG A2-36
A2-36
Guide for conducting factory capability assessment for power transformers
Example of Capability Assessment Questionnaire
Chapter Information required
Evaluation criteria Excellent
Inspection and Receipt Is an internal inspection performed to verify the condition of the transformer at purchaser's delivery location? Do purchaser and manufacturer agree to a procedure for inspecting the transformer? Does the inspection include: External visual inspection? Check gas pressure gauge? Check all impact recorders? Measure core/frame insulation resistance? Frequency response analysis, with special test bushings? When an internal inspection may be necessary: Is the quality of air injected during the internal inspection monitored continuously? What maximum shocks does the design permit?
13
INSTALLATION, COMMISSIONING AND STORAGE Installation and commissioning General Does the factory provide written guidance and requirements relating to installation and commissioning? Can the factory perform the installation and final commissioning? Does a factory service engineer/supervisor typically witness installation and commissioning?
13
Oil Does the factory confirm the suitability and compatibility of the final oil?
89
Good
Poor
Unacceptable
Comments
WG A2-36
A2-36
Guide for conducting factory capability assessment for power transformers
Example of Capability Assessment Questionnaire
Chapter Information required
Evaluation criteria Excellent
Auxiliary Electrical Equipment Can the factory perform the required electrical wiring and meet all local compliance requirements? Health and Safety Does the factory have experience in the jurisdiction where the site is located? Will the factory contract a local sub-contractor? Does a factory representative visit the sites prior to the installation work to identify specific hazards? Storage Does the factory have a written procedure for storage? Can the transformers be stored at the factory or 3rd party location? If so, for what duration? What state do transformers need to be stored: drained of oil and gas filled, partly oil filled to top of the core, etc? How do accessories need to be stored, especially bushings and coolers which may quickly deteriorate if not stored correctly? Are there periodic checks required during the storage period?
14
FINANCIAL, COMMERCIAL AND LEGAL ASPECTS Who do we want to do business with? Does the manufacturer accept the purchaser's terms and conditions? Does the manufacturer comply with the purchaser's technical specifications? Does the manufacturer agree in the Limitation of Liabilities? Does the manufacturer have suitable project management skills?
90
Good
Poor
Unacceptable
Comments
WG A2-36
A2-36
Guide for conducting factory capability assessment for power transformers
Example of Capability Assessment Questionnaire
Chapter Information required
Evaluation criteria Excellent
Does the manufacturer have sound financial health? Does the manufacturer have local representatives (marketing, engineering, services)? What is the language of communication? Does the manufacturer have services and warranty management? What is the range of the manufacturer's product portfolio? Where is the location of the manufacturing factory? Where is the location of the test facility? What is the current delivery lead time? What is the manufacturer's annual capacity (MVA/year)? What are the manufacturer's environmental policies? 15
FACTORY PERFORMANCE On-time delivery What is the ex-works on-time delivery rate? What is the trend ex-works in on-time delivery rate? Works test What is the works test failure rate? How is the works test failure rate defined? Major/serious failures (transformer removed from tank for repair)? What is the effect of the failure rate on the on-time delivery rate? What is the trend in failure rate? Other Performance Measures What is the on-time delivery performance by suppliers of critical components/materials? What is the rate of non-conformances during manufacturing? What are the reporting processes for non-conformances?
91
Good
Poor
Unacceptable
Comments
WG A2-36
A2-36
Example of Capability Assessment Questionnaire
Chapter Information required 15
Guide for conducting factory capability assessment for power transformers
Evaluation criteria Excellent
References Can the factory supply a full reference/experience list? Can the factory supply testimonials?
16
SERVICE PERFORMANCE What is the failure rate during warranty period? All failures Major/serious failures (transformer returned to works)? What is the trend in the failure rate? What is the failure rate outside warranty period (where known)? All failures Major/serious failures (transformer returned to works)? Can the factory provide the classification of major/serious failures? By root cause? By component(s) involved?
92
Good
Poor
Unacceptable
Comments
WG A2-36
A2-36 Chapter A1
Guide for conducting factory capability assessment for power transformers
Example of Capability Assessment Questionnaire Information required
Evaluation criteria Excellent
QUALITY MANAGEMENT SYSTEM Quality Management System, Documentation Requirements (ISO9001, chapter 4) Are all transformer manufacturing processes identified and defined? Are the processes regularly checked in terms of quality? Are the following Control Quality Documents established? - Quality Policy and Objectives - Quality Manual - Documents required by ISO-9001 Management Responsibility (ISO9001, chapter 5) Does the Quality Manager promote the importance of customer requirements awareness? Is the importance of meeting customer requirements promoted throughout the organisation? Is the Quality Policy issued and promoted throughout the organisation? Are the Quality Objectives established? Do employees know them? Are Management Reviews conducted to decide on QMS improvements, corrective and preventive actions? Are necessary resources for quality management available? Resource Management (ISO9001, chapter 6) Are there all resources available (human, infrastructure, working conditions) for achieving continual improvement? Are there all resources available for achieving Purchaser Satisfaction by meeting all his requirements?
93
Good
Poor
Unacceptable
Comments
WG A2-36
A2-36 Chapter A1
Guide for conducting factory capability assessment for power transformers
Example of Capability Assessment Questionnaire Information required
Evaluation criteria Excellent
Product Realisation (ISO9001, chapter 7) Planning of product realisation Are quality objectives / requirements taken as basic for the product? Are there all necessary processes, documents and resources available for the product realisation? Has the organisation set criteria for product acceptance by means of verification, validation, monitoring, inspection and testing? Are there records made and maintained to provide evidence that the Transformer meets the above criteria? Customer related processes Are all requirements stated by the customer discussed and taken into account when contracting a Transformer? Are all requirements not specified but necessary for the intended use known and achievable (legal, normative, other aspects)? The use of the latest CIGRÉ Guide to Specifications” is highly recommended for Review of Customer Requirements. Is it known and used?
A1
Review of requirements related to product Are all requirements defined and clear? Are all Contract or Order requirements discussed? Purchaser communication Are there effective ways established to keep the purchaser informed during order handling and to have his feedback?
94
Good
Poor
Unacceptable
Comments
WG A2-36
A2-36 Chapter
Guide for conducting factory capability assessment for power transformers
Example of Capability Assessment Questionnaire Information required
Evaluation criteria Excellent
Customer communication A1
Design and Development Are the Design Inputs taken into account when discussing Customer requirements? Are the Design Outputs provided in a form that allows for verification against the Input? Are the Design Reviews taken at suitable design stages (see latest CIGRÉ guide for Design Review")? Are Design Verifications organised to prove whether the Design meets the Input requirements? Does Design Validation (Test Reports) prove that the finished Transformer (or its part) fulfils the designed parameters required? Are the Design Changes identified and records maintained? Purchasing Purchasing Information Is there always a clear specification of the product to be purchased? Is there always a requirement for approval of the purchased product? Are there Quality Management System requirements defined and checked when contracting a supplier? Is there a Supplier Assessment done during the purchasing process?
A1
Verification of the purchased product Is there a system for checking purchased products on receipt? Production and service provision Production Control Is there all necessary information on the required product (Transformer) made available? 95
Good
Poor
Unacceptable
Comments
WG A2-36
A2-36 Chapter
Guide for conducting factory capability assessment for power transformers
Example of Capability Assessment Questionnaire Information required
Evaluation criteria Excellent
Are all necessary work instructions and procedures available, known and used? Production Process Validation Are there any processes that cannot be directly verified validated? If so, which ones? Product Identification, Traceability Is the product identifiable throughout the whole production process? Customer property Does the manufacturer verify and protect any customers’ property to be used in the Transformer? Preservation of product How does the manufacturer manage identification, storing, handling, packaging and protecting the product before delivery?
A1
Monitoring and Measuring Devices Does the manufacturer have a traceable measuring and testing instrument calibration program? Do the instruments have calibration validity labels stating calibration validity dates? Measurement, analysis and improvement (ISO9001, chapter 8) Can the manufacturer demonstrate conformity of the product with specifications and design requirements? Can the manufacturer demonstrate conformity and effectiveness of his quality management system?
96
Good
Poor
Unacceptable
Comments
WG A2-36
A2-36 Chapter A1
Guide for conducting factory capability assessment for power transformers
Example of Capability Assessment Questionnaire Information required
Evaluation criteria Excellent
Customer Satisfaction Is there a questionnaire or another tool to check the Customer Satisfaction? Internal audits Is there a plan of internal audits available? How many audits are there in a year? Do they cover all processes? Monitoring and measurement of processes Does the manufacturer apply corrective actions to ensure conformity of the processes? Monitoring and measurement of product In what stages does the manufacture measure the characteristics of the product? Do records indicate the person(s) authorising the release of the product? Control of nonconforming product Does the manufacturer use non-conforming product identification tags or any other means to prevent from further use of a non-conforming product? Analysis of data Does the manufacturer have data on: Customer satisfaction? Conformance to product requirements? Quality Characteristics and trends or processes and products? Suppliers Quality?
97
Good
Poor
Unacceptable
Comments
WG A2-36
A2-36 Chapter
Guide for conducting factory capability assessment for power transformers
Example of Capability Assessment Questionnaire Information required
Evaluation criteria Excellent
Improvement Does the manufacturer continually improve the effectiveness of the quality management system? Corrective action Does the manufacturer apply corrective actions to eliminate the cause of non-conformities? Preventive action Does the manufacturer apply preventive actions to in order to prevent recurrence?
98
Good
Poor
Unacceptable
Comments
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