TNB Planning Guide LV

Low Voltage Planning Guidelines

Asset Management Department Distribution Division Tenaga Nasional Berhad

LOW VOLTAGE PLANNING GUIDELINES November 2012

Asset Management Department Distribution Division, Tenaga Nasional Berhad Wisma TNB Jalan Timur, Petaling Jaya Selangor Disclaimer This guidebook does not confer legal rights or impose legal obligations upon any member of the public. While TNB has made every effort to ensure the accuracy of the discussion in this presentation, the obligations of the regulated community are determined by statues, regulations or other legally binding requirements. In the event of a conflict between the discussion in this presentation and any statute or regulation, this presentation would not be controlling.

LV PLANNING GUIDELINES

ACKNOWLEDGEMENT We would like to express our deepest gratitude to the management of the Distribution Division, for the successful publication of this Low Voltage Planning Guidelines. Our special thanks to Hj. Ismail Mohd Din, Senior General Manager, Asset Management Department for his full support and motivation to establish the revision of this guide book. We would like to express our gratitude to the ever-committed LV Planning Guideline workgroup members, comprising Ir. Tan Siew Hwa, Mr. Kok Sheng Kheun, Mr Ideris Shamsudin, Mr Lim Chia Yih and Dr Rahman bin Khalid for their 2 years of hardwork in successfully completing this new edition of Low Voltage Planning Guidelines. Our appreciation also goes to Assoc. Prof. Dr. Ir. Au Mau Teng, Ir. Lau Chee Chong, Ms Teo Siow Kim, Mr Ruslam Hussin, Mr Azmi bin Husin, Ir Rekha A/P Perumaloo, Ms Fadhlillah Adnan, Mr Fazely Haron and Ir Woo Chiew Chonng for their guidance and feedback in developing the guidelines. Special thanks to Dr. Marayati Marsadek for her untiring efforts in proof-reading this guide book. Lastly, acknowledgement and thanks to all other distribution planning community members whose names are not listed above for their valuable contributions and ideas in preparing the contents of this handbook.

Thank you.

Dr. Abu Hanifah bin Azit Chief Engineer System Planning & Development, Asset Management Department, Distribution Division, TNB

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LV PLANNING GUIDELINES

FOREWORD Objective of the power distribution system is to deliver electrical power to customers in a safe, reliable and most economical way. Several parameters of electricity supply such as frequency, continuity of supply, voltage level etc. should be within allowable limits to ensure that customers obtain satisfactory performance for their electrical equipment while ensuring that the demands of the customers are continuously met. The capital and operating costs of doing so should be kept at the most optimum level, taking into account the total cost of ownership and losses in the system. This document details out and standardizes planning methodology in TNB Distribution, which provides TNB Distribution Planners with a basic understanding of theory and practical application. This latest edition of Low Voltage Planning Guidelines also introduces additional requirement to adopt the changes in technology and expansion of network. With this revised Low Voltage Planning Guidelines, I am confident that TNB Distribution Planners would be able to produce the most efficient LV network to meet customer’s service expectation.

Hj. Ismail bin Mohd Din Senior General Manager Asset Management Department TNB Distribution

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LV PLANNING GUIDELINES

TABLE OF CONTENTS ACKNOWLEDGEMENT......................................................................................................... i FOREWORD ...........................................................................................................................ii TABLE OF CONTENTS........................................................................................................... iii CHAPTER 1 GENERAL INTRODUCTION.............................................................................. 1 1.0 INTRODUCTION ..................................................................................................... 1 1.1 SCOPE ..................................................................................................................... 1 1.2 DOCUMENT LAYOUT ............................................................................................ 2 CHAPTER 2 QUALITY OF SUPPLY ........................................................................................ 3 2.0 OBJECTIVE .............................................................................................................. 3 2.1 DEFINITION OF QUALITY OF SUPPLY ................................................................... 3 2.2 SYSTEM AVERAGE INTERRUPTION DURATION INDEX (SAIDI) ......................... 4 2.3 SUPPLY SYSTEM STANDARDS ............................................................................... 5 CHAPTER 3 LOADS ............................................................................................................... 7 3.0 OBJECTIVE .............................................................................................................. 7 3.1 TYPES & CHARACTERISTICS OF LOAD ............................................................... 7 3.2 LOAD GROWTH ..................................................................................................... 7 3.3 LOAD DEMAND ..................................................................................................... 8 3.3.1 Typical Load Demand for Domestic Residential Premises ................. 9 3.3.2 Typical Load Demand for Commercial Premises ................................ 9 3.3.3 Typical Load for Commercial Complex................................................. 9 3.3.4 Typical Load Demand for Industries ..................................................... 10 3.4 COINCIDENT FACTORS ...................................................................................... 10 3.4.1 Sample Calculation of Coincident Factor .......................................... 10 3.5 LOAD FACTOR ..................................................................................................... 11 3.6 ALTERNATIVE SUPPLY .......................................................................................... 12 CHAPTER 4 DISTRIBUTION SUBSTATIONS ........................................................................ 13 4.0 OBJECTIVE ............................................................................................................ 13 4.1 DEFINITION............................................................................................................ 13 4.2 SUBSTATION SELECTION CRITERIA .................................................................... 14 4.2.1 Indoor Substation ...................................................................................... 14 4.2.1.1 Indoor Standalone Substation .................................................. 14 4.2.1.2 Indoor Attached Substation ..................................................... 15 4.2.2 Outdoor and Semi-Indoor Substation .................................................. 15 4.2.3 Pad-Mounted Switchgear H-Pole .......................................................... 15 4.2.4 Compact Type Substation ...................................................................... 16 4.2.5 Summary of Substation Characteristics and Usage .......................... 17 4.3 SUBSTATION REQUIREMENT & TRANSFORMER SIZING ................................... 18 4.3.1 Domestic Development .......................................................................... 18 4.3.2 Commercial Development .................................................................... 20 4.3.3 Industrial Development ........................................................................... 22

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LV PLANNING GUIDELINES

4.3.4 Multi-tenanted Buildings/ Development.............................................. 23 CHAPTER 5 LOW VOLTAGE NETWORKS .......................................................................... 24 5.0 OBJECTIVE ............................................................................................................ 24 5.1 DISTRIBUTION NETWORK COMPONENTS ......................................................... 24 5.2 DISTRIBUTION TRANSFOMERS ............................................................................ 25 5.2.1 Configuration............................................................................................. 25 5.2.2 Transformer Cable Tail ............................................................................. 25 5.3 LV FEEDER PILLARS .............................................................................................. 26 5.3.1 Configuration............................................................................................. 26 5.4. LV FEEDERS ........................................................................................................... 28 5.4.1 Loading Limits ............................................................................................ 28 5.4.2 Configuration............................................................................................. 28 5.5 FIVE FOOT WAY MAINS ...................................................................................... 29 5.5.1 Configuration............................................................................................. 29 5.6 SERVICE CABLES .................................................................................................. 29 5.7 STREET LIGHTING.................................................................................................. 29 5.7.1 Configuration............................................................................................. 29 5.8 DISTRIBUTION NETWORK TYPES ......................................................................... 30 5.8.1 Domestic Overhead ................................................................................ 32 5.8.2 Domestic Underground ........................................................................... 33 5.8.3 Commercial Overhead ........................................................................... 33 5.8.4 Commercial Underground ..................................................................... 34 5.8.5 Industrial Overhead.................................................................................. 34 5.8.6 Industrial Underground ............................................................................ 34 5.8.7 LV Supply for Premises with Separate Owner / Landlord and Tenant Meters ..................................................................................................... 34 5.8.8LV Ring System ............................................................................................ 35 5.8.9 LV Auto Transfer Switch System.............................................................. 35 5.9 ECONOMICS ....................................................................................................... 36 5.9.1 Initial Cost of Implementation ................................................................ 36 5.9.2 Operation and Maintenance Cost....................................................... 37 5.9.3 Replacement Cost ................................................................................... 37 5.9.4 Technical Losses ........................................................................................ 37 5.10 OTHER CONSIDERATIONS .................................................................................. 37 CHAPTER 6 LOW VOLTAGE PROTECTION AND EARTHING .......................................... 38 6.0 OBJECTIVE ............................................................................................................ 38 6.1 DEFINITION............................................................................................................ 38 6.2 PROTECTION PLANNING.................................................................................... 38 6.3 FUSE PROTECTION ............................................................................................... 39 6.4 SURGE ARRESTORS .............................................................................................. 41 6.5 NEUTRAL EARTHING IN LV SYSTEM ................................................................... 41 6.5.1 Feeder Earthing for Overhead Lines..................................................... 41 6.5.2 Feeder Earthing for Underground Cables ........................................... 42

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LV PLANNING GUIDELINES

CHAPTER 7 LOW VOLTAGE METERING ........................................................................... 43 7.0 OBJECTIVE ............................................................................................................ 43 7.1 DEFINITION............................................................................................................ 43 7.2 CUSTOMER SUPPLY AND METERING ................................................................ 44 7.2.1 Metering Criteria ....................................................................................... 44 7.2.2 Whole Current Metering.......................................................................... 44 7.2.3 C.T. Metering ............................................................................................. 44 7.2.3.1 C.T. Meter Loading ...................................................................... 45 CHAPTER 8 LOW VOLTAGE TECHNICAL LOSSES ........................................................... 46 8.0 OBJECTIVE ............................................................................................................ 46 8.1 DEFINITION............................................................................................................ 46 8.2 POWER FACTOR CORRECTION ........................................................................ 46 8.3 TYPES OF TECHNICAL LOSSES ........................................................................... 47 8.4 CONTRIBUTORS OF TECHNICAL LOSSES IN LV NETWORK ............................ 47 8.4.1 Strategies .................................................................................................... 47 8.4.1.1 Reactive Power Management - Supply Side ......................... 48 8.4.1.2 Reactive Power Management - Customer side................... 48 8.4.1.3 Efficient Low Voltage System Design ...................................... 48 8.4.1.4 LV Load Monitoring..................................................................... 49 8.4.1.5 Smaller Transformer Design Rating and Initial Installation Practise........................................................................................................ 49 CHAPTER 9 POWER QUALITY ............................................................................................ 50 9.0 OBJECTIVE ............................................................................................................ 50 9.1 DEFINITION............................................................................................................ 50 9.2 VOLTAGE DIPS ..................................................................................................... 50 9.3 HARMONICS ........................................................................................................ 51 9.4 VOLTAGE UNBALANCE ...................................................................................... 51 9.5 TRANSIENTS ........................................................................................................... 51 9.6 VOLTAGE FLUCTUATION AND FLICKER ........................................................... 51 9.7 REMEDIES .............................................................................................................. 52 9.8 POWER QUALITY MANAGEMENT MONITORING ........................................... 53 CHAPTER 10 DATA MANAGEMENT ................................................................................. 54 10.0 OBJECTIVE ............................................................................................................ 54 10.1 DATA CATEGORIES ............................................................................................. 54 10.2 LOAD AND DEMAND DATA .............................................................................. 54 10.3 SYSTEM NETWORK DATA .................................................................................... 55 10.4 SYSTEM PERFORMANCE DATA.......................................................................... 55 10.5 DATA MANAGEMENT MONITORING ............................................................... 56 10.6 INTERACTION BETWEEN VARIOUS UNITS IN AN AREA ................................... 57 APPENDICES ....................................................................................................................... 58 APPENDIX 1: TYPES OF LOADS AND THEIR CHARACTERISTICS .................................. 59 APPENDIX 2: TRANSFORMER SIZING COMPUTATION.................................................. 60 APPENDIX 3: STANDARD MULTI-TENANTED BUILDINGS DESIGN ................................ 62

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LV PLANNING GUIDELINES

3A Multi-Tenanted Buildings (< 5 storey) without Substation .................... 62 3B Multi-Tenanted Buildings (< 5 storey) with Substation .......................... 63 3C Multi-Tenanted Buildings (> 5 storey) without Substation ..................... 64 3D Multi-Tenanted Buildings (> 5 storey) with Substation (Landlord & Tenant takes LV supply) .................................................................................... 65 3E Multi-Tenanted Buildings (> 5 storey) with Substation (Landlord & Tenant takes MV supply) .................................................................................. 66 3F Multi-Tenanted buildings (> 5 storey) with Substation (Development takes MV supply with Landlord load >1600A) .............................................. 67 3GMulti-Tenanted Buildings (> 5 storey) with Substation (Development takes MV supply with Landlord load 850 kVA

(Domestic Development) Transformer capacity at 85% loading 1 substation @ 100kVA (for rural supply) 1 substation @ 300kVA 1 substation @ 500kVA 1 substation @ 750kVA 1 substation @ 1000kVA More than 1 substation is required

For MD >850 kVA, the number of substations required can be computed as below:Step 1:Calculate the minimum installed capacity (a) based on the principle of 85% transformer loading using the following relationship: a=

MD (in KVA) 0.85

(4.1)

Step 2:Determine the number of 1000kVA transformer required to meet the capacity calculated in step 1 using the following formula: Page | 18

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DISTRIBUTION SUBSTATIONS

a 1000 kVA Number of substations = roundup (b) b=

(4.2) (4.3)

Step 3:Transformer capacity is selected based on the closest match of kVA to a, taking into account the possible MSVR in the area. Example 1: Computation on Number of Substations Required (Domestic Development) Each terraced house in a housing scheme which consists of 250 terraced houses has an MD of 4 kW. The total MD by considering 0.9 group coincident factor is 900 kW (i.e (4 x 250)x 0.9 = 900kW). Assuming 0.85 p.f., the MD in kVA is 1059 kVA. The number of substations required is determined using the following procedures: Step 1:

a=

MD (in KVA) 1059 = = 1246 kVA 0.85 0.85

Step 2:

b=

1246 kVA a = = 1.25 1000 kVA 1000 kVA

Number of substations = roundup (1.25)= 2 Step 3:

Required transformer capacity 1 nos 1000kVA + 1 nos 300kVA Or 2 nos 750kVA

Example 2 : Computation on Number of Substations Required (Domestic Development) Each single-storey semi-detached house in a housing scheme which consists of 500 single-storey semi-detached houses has an MD of 5 kW. The total MD by considering 0.9 group coincident factor is 2,250 kW (i.e (5 x 500)x 0.9 = 2,250 kW). Assuming 0.85 p.f., the MD in kVA is 2647 kVA. The number of substations required is determined using the following procedures: Step 1:

a=

MD (in KVA) 2647 = = 3114 kVA 0.85 0.85

Step 2:

b=

3114 kVA a = = 3.11 1000 kVA 1000 kVA Page | 19

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Number of substations = roundup (3.11)= 4 Step 3:

Required transformer capacity 3 nos 1000kVA + 1 nos 300kVA OR 3 nos 750kVA + 1 nos 1000kVA

4.3.2 Commercial Development For commercial development (tariff B), transformer size must be planned according to the load requirement with maximum of 2 transformers at each substation site. The utilization of installed transformer capacity will reach 100% in 15 years assuming that the average growth rate as stated in Appendix 2. The planned transformer capacity is computed based on 60% of transformer loading. Table 4.3 provides the detail of the number of substation required in commercial development based on this principle. Table 4.3: Computation on the Number of Substation Required (Commercial Development) MD Up to 180 kVA Up to 3000 kVA Up to 450 kVA Up to 600 kVA > 600 kVA

Transformer capacity at 60% loading 1 substation @ 300kVA 1 substation @ 500kVA 1 substation @ 750kVA 1 substation @ 1000kVA Require > 1 substation with 1 substation or double chamber substation

For MD >600kVA, the number of substation can be computed as below: Step 1:Calculate the minimum installed capacity (a) based on the principle of 60% transformer loading by using the following relationship: a=

MD (in KVA) 0.60

(4.4)

Step 2:Determine the number of 1000kVA transformer required to meet the capacity calculated in step 1 by using the following formula:

a 1000 kVA Number of substations = roundup (b) b=

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(4.5) (4.6)

LV PLANNING GUIDELINES

DISTRIBUTION SUBSTATIONS

Step 3:Transformer capacity is selected based on the closest match of kVA to a, taking into account the possible MSVR in the area.

Example 1: Computation on Number of Substation Required (Commercial Development) Each single-storey shop house in a commercial development which consists of 80 units of single-storey shop houses has an MD of 10 kW. The total MD by considering 0.87 group coincident factor is 696 kW (i.e (10 x 80)x 0.87 = 696 kW). Assuming 0.85 p.f., the MD in kVA is 819 kVA. The number of substation required is determined using the following procedures: Step 1:

a=

MD (in KVA) 819 = = 1365 kVA 0.60 0.60

Step 2:

b=

1365 kVA a = = 1.365 1000 kVA 1000 kVA

Number of substations = roundup (1.365)=2

Step 3:

Required transformer capacity. 1 nos 1000kVA + 1 nos 500kVA

Table 4.4: Transformer Loading Computation (Individual Commercial Customer) MD 300kVA up to 500kVA >500kVA up to 750kVA >750kVA up to 1000kVA >1000kVA

Transformer capacity base on customer’s maximum demand Nearby substation (LV 4C Al cable 1 substation or double chamber substation

Table 4.6: Computation on the Number of Substations Required (Individual Industrial Customer) MD 300kVA up to 500kVA >500kVA up to 750kVA >750kVA up to 1000kVA >1000kVA

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Transformer capacity base on customer’s maximum demand Nearby substation (LV 4C Al cable 1000kVA shall take 11kV bulk supply. This is to eliminate multiple transformers connected to a common busbar at the customer’s side. Separate MSB must be installed at the customer’s intake side for the owner and tenant supply when it involves multiple tenants and owner intake, such as condominiums, apartments or shopping complexes. Detailed design scheme is shown in Appendix 3: Multi Tenanted Building Design. However, multi-tenanted building customers are encouraged to take bulk supply with Independent Distributor license from Energy Commission. Independent Distributor is licensed to sell electricity to the tenants in a building / development. In the case where multi-tenanted building requires supply through LV service connection from two transformers to customer MSB, interlocking facility must be provided at customer’s incomers to prevent parallel operation of two transformers.

5.2.2 Transformer Cable Tail Table 5.1 indicates standard cable sizes used to connect the transformers to the TNB network.

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LV PLANNING GUIDELINES

LOW VOLTAGE NETWORKS

Table 5.1: "Transformer Tail" Cables Transformer kVA Rating

LV Tail HT Tail 11/.4 kV Phase(sq mm)

Neutral(sq mm)

100

70 mm 2 1C XLPE 1x300 AI 1C PVC/PVC 1x300 AI 1C

300

70 mm 2 1C XLPE 1x500 AI 1C PVC/PVC 1x500 AI 1C

500

70 mm 2 1C XLPE 2x300 Al 1C PVC/PVC 1x300 Al 1C

750

70 mm 2 1C XLPE 2x500 AI 1C PVC/PVC 1x500 AI 1C

1000

70 mm 2 1C XLPE 2x500 Cu 1C PVC/PVC 1x500 Cu 1C

The recommended LV connections summarized in Table 5.1 are applicable to both connections to the feeder pillars or directly to the bulk customer's installations.

5.3 LV FEEDER PILLARS LV feeder pillars are used to split the output from the secondary winding of the distribution transformers to several different circuits. LV feeder pillars provide fusing facilities for each circuit as protection where it can be used to disconnect or isolate supply to that particular circuit. The usage of LV feeder pillars are not restricted to after the secondary transformer tail but can also be used to further split the circuit from main feeder pillar. The usage of LV Distribution Board has been discontinued since it does not comply with the Factory and Machinery (Fencing of Machinery and Safety) Regulation 1970, and Regulation 11 (Revised -1983), due to existence of exposed busbar. In the current substation design, LV Distribution Board has been replaced with Feeder Pillars. All new substation layouts have been designed to enable the Feeder Pillar usage.

5.3.1 Configuration LV feeder pillars should accommodate a sufficient number of outgoing feeders in order to allow optimal distribution of LV system to meet the expected customer demand. The number of outgoing feeder pillars with respect to feeder pillar current carrying capacity is given in Table 5.2.

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LV PLANNING GUIDELINES

LOW VOLTAGE NETWORKS

Table 5.2: Typical Number Of Incoming & Outgoing Feeders In Feeder Pillar Feeder Pillar Current carrying capacity (A)

Typical Number of incoming feeders

400A (Mini) 800A (Main / Sectional) 1600A (Main / Sectional)

2 2 2

Typical Number of outgoing feeders 6 5 8

At the planning stage (for commercial, industrial or mix development), it is recommended that spare feeders are made available at every substation, for customer upgrades in the future. The number of minimum spare feeders for each type of customer is listed in Table 5.3. Table 5.3: Minimum Spare Feeders at the Planning Stage Customer type Group Commercial Group Industrial Mix Development

Minimum Spare feeders per substations 2 2 2

However, Planners should determine the necessity of spare feeders according to the needs of a particular development area. If the development area has the potential to become a busy commercial hub, then the Planner should plan for a higher spare capacity to cater the increase in the commercial customers like banks, eateries or convenient stores. If a double chamber is planned, the number of minimum spares made available at the planning stage is required from one (1) of the transformers only. Appendix 4 shows typical outlook of different sizes Feeder Pillar. A typical LV underground network design entails the following: i. Transformer tail to main feeder pillar. ii. Main feeder pillar to sectional feeder pillar • Incoming cable 2 x 300mmp 4T Al. XLPE (max fuse Amp = 250A) • J-slotted fuse / DIN type fuse iii. Main/Sectional feeder pillar to mini feeder pillar • Incoming cable 1 x 185mmp 4T Al. XLPE (max fuse Amp = 200A) iv. From mini Feeder Pillar, lay LV service cable 70mmp or 25mmp XLPE Al 4C cable (depending on MD per unit) to individual unit. Page | 27

LV PLANNING GUIDELINES

LOW VOLTAGE NETWORKS

v. Loads connected must not exceed incoming feeder fusing rating. vi. Location of feeder pillar must comply with local authority requirements and location agreed by developer. Planners should take into account the extention of LV networks at the planning stage. To reduce the length of LV network, Planners should consider acquiring additional substation if high numbers of feeders or feeder pillars are needed. This requirement should be prompted during Ulasan Pembangunan stage.

5.4. LV FEEDERS The outgoings from main feeder pillars which are used to distribute supply to customers are called LV feeders. LV feeders include underground and / or overhead cables.

5.4.1 Loading Limits All LV conductors’ mains loading at planning stage must be at a maximum of 50% of their thermal capacity in order to achieve distribution technical losses at 4%, To avoid having joints in the circuit, the length of LV underground cables must not exceed 240m. The length of LV underground and overhead cables are also limited by maximum voltage drop of 5% from reference voltage of 415V at the end of the circuit. Effective and efficient planning of the LV distribution network is critical as: i. It affects the cost of LV network, which forms a substantial portion of the project capital cost and is described in Section 5.9. ii. It influences the magnitude of technical losses in the system. iii. It has an impact to the reliability of supply to customers.

5.4.2 Configuration LV network is designed with security level 4. However, higher level of security can be designed based on consumer request at an additional cost and with special agreement from TNB.

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LV PLANNING GUIDELINES

LOW VOLTAGE NETWORKS

5.5 FIVE FOOT WAY MAINS From the LV feeders, the circuit is further extended to LV services or Five Foot Way Mains, which is the last section of the circuit before terminating to the customers intake point. “Mains” along terraced premises are often in the form of Five Foot Way Mains comprising of PVC single core insulated conductors or ABC insulated cables.

5.5.1 Configuration Five Foot Way Mains configuration is currently standardised to three phase plus neutral in which it consists of four wire layout throughout its length using 7/.083 (25mm2) for PVC Al. or 3 x 16mm2, 3 x 95mm2 and 3x185mm 2 for ABC cables. Due to the increasing load demand by customers, it is necessary to use high capacity conductors. To facilitate the increasing load demand by customers, larger ABC cables are used instead of single core conductors. Five Foot Way Mains normally do not include feed back supply features.

5.6 SERVICE CABLES Service cable includes all means of connection from TNB mains to customers’ installations. This consists of overhead cables, underground cables inclusive of direct connections from transformer terminals to the customer’s switch board.

5.7 STREET LIGHTING Street lighting, given at a special tariff to local authorities, is part of the “local government’s” provision of public amenities. The intention is to encourage lighting up the public area, especially roads or streets at night. TNB has recently extended the provision of street lighting to include such supply to domestic customers, also at a special tariff. The lighting equipment used can be of standard TNB design, or of special design at the Local Authority’s cost.

5.7.1 Configuration The configurations of street lighting are divided into three categories.

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LV PLANNING GUIDELINES

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i. Street Light for individual domestic customers and maintained by TNB • The application of street lighting in this category is by individuals and billed to the customer’s account at a determined flat rate per month. • It is installed by TNB on the existing LV lines (i.e. 5-wire Aeriel Bundled Cables (ABC)) ii. Street Lighting for Local Authority but maintained by TNB • This category of street lighting is installed by TNB upon request by the Local Authority. • It is installed on TNB poles and is maintained by TNB. • It is metered and paid by Local Authority unlike the previous category which is paid by individual customer iii. Street Light for Local Authority and maintained by Local Authority • For this category of street lighting, a dedicated LV underground cable is used to supply to the street lighting system • It is metered and paid by Local Authority • It can be supplied from TNB feeder pillars, existing or new substation Planners should plan for the street lighting supply at the initial stage so that the distance from the source to the street light meter panel can be optimized. The distance is restricted by voltage drop and technical loss of the service cable. Refer Appendix 5 for typical streetlight configuration.

5.8 DISTRIBUTION NETWORK TYPES Network configurations with respect to types of premises and metering locations are designed to suit a particular development. Table 5.4 summarizes the network configuration associated with customer type, meter board location and design requirement. Table 5.4: Network Configuration Associated with Customer Type, Meter Board Location and Design Requirement Customer Type Residential Overhead

Residential Overhead

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Meter Board Location Five Foot Way

Pole

Design requirement Conductor PVC Al 1C 35mm2 (19/.064) as the five foot way mains Services drop Conductor PVC Al 1C 25mm2 (7/.083) into 3 houses (max) with meters installed at the pole

LV PLANNING GUIDELINES

Customer Type

Meter Board Location

Domestic Overhead (with gate pillar)

Gate Pillar

Domestic SemiUnderground

Five Foot Way

Domestic Fully Underground

Gate Pillar

Domestic Fully Underground

Meter Pillar

Group Commercial (U/G)

Stair case

Group Commercial (U/G)

Group Commercial (U/G)

Bulk Commercial

Group Industrial (U/G)

Upper front wall of the commercial premise Supporting vertical pillar of the building Meter Room in TNB Substation. Upper front wall of the industrial premise

Domestic Fully Underground

Gate Pillar

Domestic Fully Underground

Meter Pillar

Bulk Industrial

Meter Room in TNB Substation.

LOW VOLTAGE NETWORKS

Design requirement Use LV underground service cable from pole and junction box if looping of service cable is required (3 houses max). The bottom of meter must be >3 feet from floor level. UG Cable LV XLPE Al 4C 185mm 2 terminated on the pole with service drop 35mm 2 Conductor PVC Al 1C 35mm2 (19/.064) as the five foot way mains Fully underground design with junction box for looping of 3 houses max. The bottom of meter must be >3 feet from floor level. Fully underground design where developers prefer centralized metering scheme Ensure grill gate installations at staircase is after the centralized meter panel (by developer, before V.P. stage) 3 phase & 1 phase meters installed between 0.7m to 1.65m from floor level Aesthetic design by the developer’s architect. 3 phase & 1 phase meters installed between 0.7m to 1.65m from floor level C.T. & voltage input to meter tapped from transformer tail 3 phase & 1 phase meters installed between 0.7m to 1.65m range from floor level Fully underground design with junction box for looping of 3 houses max. The bottom of meter must be >3 feet from floor level. Fully underground design where developers prefer centralized metering scheme C.T. & voltage input to meter tapped from transformer tail

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LV PLANNING GUIDELINES

Customer Type

Owner / tenant (LV)

Meter Board Location Owner’s main meter installed at TNB Metering Room, tenant’s meter installed at centralized meter room at ground floor (5 storey & below) or every floor (> 5 storey)

LOW VOLTAGE NETWORKS

Design requirement

Splitting of owner and tenant feeders at TNB’s installations

Different types of premises need different types configurations. LV networks types can be grouped into:

of

network

i. Residential Overhead. ii. Residential Underground. iii. Commercial Overhead. iv. Commercial Underground. v. Industrial Overhead. vi. Industrial Underground. vii. LV Multi Tenant and Owner. viii. LV Ring Circuit.

5.8.1 Domestic Overhead LV reticulation using overhead lines to housing developments are the method preferred by TNB. Reticulation using this method is the most costeffective when compared to other methods and also the easiest to maintain and repair. Ring system through overhead should be provided, wherever possible, as it can be easily incorporated into the system via jumper or connection at sectional poles. Services can be distributed mainly using five foot way mains or directly from poles to individual premises.

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Detailed design is shown in Appendix 6 Standard Design O/H Dom A: Consists of 185mmp XLPE 4C from feeder pillar in substation to pole; 3x185+120+16mmp LV ABC as Overhead Mains; 7/.083 PVC/PVC as Five Foot Mains; Metered at five foot way. Alternative Design O/H Dom B is shown in Appendix 7: Consists of LV ABC as Overhead Mains; 7/.083 PVC as Five Foot Mains; Metered at pole. Alternative Design O/H Dom C is shown in Appendix 8: Consists of LV ABC as Overhead Mains; 25mmp 4C underground cable as service cables to the meters; Metered at gate pillar (pipings are required and provided by developers. Loopings to 2 other units are allowed through junction box)

5.8.2 Domestic Underground This method is used upon request by developers or as per the requirement of the Local Authority. Both would request for this method due to aesthetic reason of not having poles and overhead lines along the road. However, this method is expensive to construct due to extensive road excavation and involves erection of large numbers of feeder pillars to serve the customers. It is also difficult to maintain and repair. Hence, this method is treated as special features and the cost difference compared to overhead method (O/H Dom A) is chargeable to developer. The meter is required to be installed outside the premise and normally at the gate pillar or metering pillar. Detailed design is shown in Appendix 9 Standard Design U/G Dom A: Consists of 2x300mmp XLPE Al 4C cable from main 1600A Feeder Pillar in a substation to 800A Feeder Pillar; 1x 185mmp XLPE Al 4C from 800A Feeder Pillar to 400A mini Feeder Pillar; LV service cable 25mmp XLPE Al 4C or 70mmp XLPE Al 4C from mini Feeder Pillar to customer meter panel; Looping of 3 houses max is allowed through junction box.

5.8.3 Commercial Overhead For shoplots at sub-urban area or rural area, supply can be distributed to commercial customers using overhead poles from the source to the shoplots. Overhead lines can be used for this situation if the load requirement is of low to medium density. The Planner must decide whether sufficient spare capacity is available to cater load growth for the shoplots.

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Five foot way mains for commercial lots will not pose a problem because meters and cut outs are accessible to TNB. Detailed design is shown in Appendix 10 Standard Design O/H Com A (meter at individual lots).

5.8.4 Commercial Underground This is the main method used to distribute electricity to shoplots in urban areas. The design fully utilizes underground cables with feeder pillars providing distribution outgoing to MSB of each lot. Detailed design is shown in Standard Design U/G Com A of Appendix 11: Meters at individual lots.

5.8.5 Industrial Overhead For industrial customers, it is seldom supplied through the overhead line unless it is small scale industries producing things like clay pots, ice plant, rubber products etc. Most of these factories are located sparsely and this is the reason supply is given through overhead system. The design is similar to commercial overhead network design.

5.8.6 Industrial Underground The LV network design for this category is usually planned at early stage and it is found mostly in dedicated small and medium industrial area. Initially numbers and location of sub stations are determined during Ulasan Pembangunan stage and each factory is supplied with 100A 3 phase or 200A 3 phase. Spare capacity for this category is important as growth potential is tremendous. Customers requiring loads beyond the available spare capacity shall be required to provide additional substation. Detailed design is shown in Appendix 12 Standard Design U/G Ind A where meter pillar is located at customer’s front gate.

5.8.7 LV Supply for Premises with Separate Owner / Landlord and Tenant Meters This type of customer consists mostly of apartments, condominiums or shopping complexes. It is required to have separate MSB for landlord / owner and tenants for ease of disconnection. Detailed design is shown in pin Appendix 3 Standard Multi-tenanted Buildings Design.

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5.8.8 LV Ring System LV ring system is an LV network designed with N-1 element. N-1element is the possibility of distribution system to feed back from a different feeder when the main feeder is down. It is installed only upon customers request and the customers or developers must have special agreement with TNB. It is considered as special features and cost difference is chargeable to the customers. For ring system, labeling of feeders is very important in order to ensure safe operation. Detailed design is shown in Standard Deisgn “U/G Ring” as shown in Appendix 13.

5.8.9 LV Auto Transfer Switch System LV auto-transfer switch (LV-ATS) system is an LV ring system which enables automatic switching of source when an interruption occurs. Two (2) LV feeders from different substations with different MV supplies need to be connected to the LV-ATS. The design principle is as follows: i.

To ensure the shortest possible service cable, the LV-ATS panel is to placed as near to customer’s MSB / meter panel as possible. ii. Lay 2 circuits of LV feeders to ATS panel from 2 different substations. iii. These 2 substations should be connected from different MV source. iv. The transformer capacity of both substations is sufficient to provide the customer load when LV-ATS operates. The sample network with LV-ATS is shown in Appendix 14. Similar to LV ring system, LV-ATS is installed only upon customers request and the customers or developers must have special agreement with TNB. It is considered as special features and cost difference is chargeable to the customers. Proper labeling of feeders at ATS and substation is very important in order to ensure safe operation. This system is suitable to provide secured supply to VIP customers such as Istana, Prime Minister’s or Chief Minister’s residents.

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5.9 ECONOMICS The decision of selecting a certain network design in a project will have an economic impact to TNB throughout lifecycle of the installation. The economic consideration shall include: i. The initial cost of implementation. ii. The operation and maintenance cost. iii. The replacement cost. iv. Technical losses. v. Other cost such as aesthetic, safety.

5.9.1 Initial Cost of Implementation Initial cost of implementation for LV network depends upon the network design. This cost includes : i. ii. iii. iv.

Land acquisition cost. Material cost. Contract cost. Supervision cost.

TNB standard design for LV system is overhead network since it is the most cost effective network design. Overhead network system reduces the need to acquire wayleave and permits for road excavation from local authorities and therefore shorten the duration of construction. Furthermore, the unit price of ABC is cheaper when compared to the underground cable. Any change from the standard overhead network design is treated as Special Features and is chargeable to customers. Table 5.5 shows the summary of the cost comparison between an overhead system design and an underground system design taken from a project supplying 38 units of 3 storeys semi-detached and 1 unit of bungalow. From the example shown in Table 5.5, the initial cost of implementation for underground system LV network is 131% higher than the overhead system. Table 5.5: Network Design Cost Comparison Type of cost Land cost Staff cost Material cost Contract cost Permit cost TOTAL Page | 36

Overhead system (RM) 10 2200 76000 34562 0 112772

Underground system (RM) 10 1700 162000 82270 15000 260980

Difference (%) 0 23 -113 -138 -1,500,000 131

LV PLANNING GUIDELINES

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5.9.2 Operation and Maintenance Cost The operation and maintenance cost of an LV network depends on the type of system design. The cost of repair which is part of the operation and maintenance cost differs significantly between the overhead and underground systems. For example, a fault in the underground system requires specialised equipment such cable fault locating equipment and cable tracer in order to pinpoint the fault location whereas fault in the overhead system can be detected visually. The material used to repair the fault for underground cable is more expensive compared to overhead line and its accessories. Furthermore, repairing underground cable fault may require permits from local authorities and contractors for excavation works.

5.9.3 Replacement Cost All materials will deteriorate after a particular period in operation and need to be replaced. The cost of replacement for underground system is higher compared to overhead system.

5.9.4 Technical Losses Generally, underground system has more losses than overhead system due to method of construction. Underground cable will be affected by rate of heat dissipation where high operating temperature will increase the technical losses. The heat dissipation depends on the depth and laying methods (in ducts or directly in soil).

5.10 OTHER CONSIDERATIONS There are other considerations for Planners to explore and advice customers during the network design stage. Planners should lead in determining decisions listed below: i. ii. iii. iv. v. vi.

Supply security requirement. Location of installation (such as LV poles and feeder pillars). Utility reserves such as manhole and ductings. Wayleave for cables. Meter location. Advising customers on power factor control such as requirement of capacitor bank where applicable.

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CHAPTER

6 LOW VOLTAGE PROTECTION AND EARTHING 6.0 OBJECTIVE The objective of this chapter is: i. To describe the protection and earthing requirements for the LV distribution system, and to be employed as standard TNB practice.

6.1 DEFINITION System protection is the combination of devices and features that ensure safe operation of the system when abnormal conditions occur by isolating the fault, or dangerous components to eliminate potentially dangerous incidents. System earthing, or grounding is the intentional electrical connection to ground of the neutral or star point of four wire LV system. Effective earthing is an essential requirement for system protection. Commonly, TNB practise multiple earthed neutral (MEN) system in LV network. The neutral conductor is grounded at all poles. Besides that, the star points of substation transformer and the end of each LV feeder are also grounded.

6.2 PROTECTION PLANNING Planning of the LV system protection must address the following issues: i. Safe operation of the system. ii. Adequate capacity to meet customers load. Page | 38

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iii. Definite operation of the protection devices. iv. Proper discrimination of protection settings.

6.3 FUSE PROTECTION Fuses are TNB’s standard LV distribution protection system, usually with time delay characteristics, or thermal detectors. They are normally used for short circuits and over-current. Fuse protection uses various “housing”, such as feeder pillar carriers, fuse switches, cut outs etc. Fuses provide low cost and effective protection for short circuit and over load. The types of fuses used in TNB LV distribution system are of HRC (high rupturing capacity) J-slotted, HRC NH (or Blade type) and barrel fuse. Table 6.1 presents the types of fuses used in TNB distribution system and its respective usage. Table 6.1: Fuses in TNB network Fuse Type HRC (J slotted type) HRC (NH type)

Usage Feeder pillar Feeder pillar, black box

The Low Voltage ABC Manual provides detail guidelines on the selection of fuse sizing and location as well as the examples of short circuit current calculation. The sizing and location of fuses must satisfy the following criteria so as to conform to the LV protection philosophy: i. ii. iii. iv.

v.

The fuse rating must be higher than the maximum load to be carried. The fuse rating must permit fuse failure under the “minimum” fault current occurrence. The fusing current must not exceed the conductor current carrying capacity. Fuses in series along a feeder must be suitably graded to provide discriminated failure so as to limit the supply outage extent to the minimum. Fuse rating selection is based on the following, whichever is lower:1 • × ( Lowest short circuit current of the feeder ) 3 - This is with reference to Pekeliling Timbalan Pengurus Besar Kejuruteraan (Perkhidmatan Pengguna), Kejuruteraan Bil 3/1991

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LV PLANNING GUIDELINES

•

LOW VOLTAGE PROTECTION AND EARTHING

1 × ( Conductor current carrying capacity) 1 .5 - This is with reference to mean HRC fuse time-current characteristic

For proper fuse grading: i. J-slotted type and NH type fuse requires up stream fuse to be 2 times higher than down stream fuse ii. NH type and NH type fuse requires up stream fuse to be 1.5 times higher than down stream fuse The grading Table for LV overhead system is shown in Table 6.2. Table 6.2: Grading Table for LV Overhead System Nearest location Fuse Fuse Fuse Size allowed Fuse Size Size Size Transformer Conductor (J-slotted for (NH at (NH) (NH) Size ABC at 1st Substation) 1st 2nd Substation) Section Section Section Fuse 16mm2 Tiang 1 n/a n/a 50 n/a 100kVA 95mm2 Tiang 1 n/a n/a 100 50 H/Pole 2 185mm Tiang 1 n/a n/a n/a n/a 16mm2 Tiang 1 60 50 n/a n/a 100kVA 95mm2 Tiang 1 160 160 50 n/a G/Mounted 185mm2 Tiang 1 n/a n/a n/a n/a Tiang 1 n/a n/a 50 n/a 16mm2 300kVA 2 95mm Tiang 2 n/a n/a 125 50 H-Pole 185mm 2 Tiang 3 n/a n/a 200 125 16mm2 Tiang 2 60 50 n/a n/a 300kVA 2 95mm Tiang 2 160 160 50 n/a G/Mounted 185mm 2 Tiang 3 200 200 100 50 2 16mm Tiang 2 60 50 n/a n/a 500kVA 95mm2 Tiang 3 160 160 50 n/a 185mm 2 Tiang 5 200 200 100 50 2 16mm Tiang 2 60 50 n/a n/a 750kVA 95mm2 Tiang 4 160 160 50 n/a 185mm 2 Tiang 6 200 200 100 50 2 16mm Tiang 2 60 50 n/a n/a 1000kVA 95mm2 Tiang 4 160 160 50 n/a 185mm2 Tiang 6 200 200 100 50 * Source from LV ABC Manual

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6.4 SURGE ARRESTORS Surge arrestors are used on TNB overhead LV system to minimise possible risks from lightning strikes causing serious damage to the utility’s or customers’ installations. Surge arrestors must be installed at cable terminators, connections to other installations (e.g.: transformers, feeder pillars, five foot way mains), at the T-off and end of LV overhead mains. The satisfactory performance of surge arrestors depends to some extent, on the integrity of the system earthing. In TNB LV system, the surge arrestors are installed at every phase and neutral conductor is of metal oxide varistor (M.O.V) type.

6.5 NEUTRAL EARTHING IN LV SYSTEM Earthing of the LV Distribution system neutral is of paramount importance to ensure safety to users and equipment connected to the system, as well as its operation. Neutral earthing provides a deliberate earth path for fault current to be directed back to the source to operate the protective devices. The protective devices segregate the faulty components from the supply, so that the rest of the electricity supply system operates in a safe and stable condition. The system neutral is grounded so as to: i. Provide constant reference for the supply voltage. ii. Enable safe ground leakage path for fault currents to clear the faults. iii. Minimize unbalanced voltages due to “floating neutral”, if the neutral earth path becomes disconnected.

6.5.1 Feeder Earthing for Overhead Lines For LV overhead lines, the system is grounded at the distribution substations, via transformer neutral, and at every LV pole. With ABC cables, the MEN practice still applies, with the earthing via pre-installed SWG stay wire inside the pole. This stay wire needs to be connected to the neutral and make up at the bottom of pole. ABC cable installation is designed to prevent breakage by allowing the cables to fall off their supports through mechanical fusable link.

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6.5.2 Feeder Earthing for Underground Cables For underground cable feeders, the system is grounded through substation neutral busbar at feeder pillar.

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CHAPTER

7 LOW VOLTAGE METERING 7.0 OBJECTIVE The objectives of this chapter are to: i. Provide guidelines on LV supply metering methods according to customer categories and load demand. ii. Summarises TNB’s policy on metering schemes, especially for LV customers, including LPCs.

7.1 DEFINITION Metering of electricity for billing is the measurement of the amount of electrical energy that is consumed by the installation. Metering in TNB is based on measurement of active energy as kilowatt-hours (KWH), and reactive energy as kiloVAR-hours (KVARH), where power factor penalty applies on the supply tariffs concerned. Meters used are of several types: i. Whole current meters for single & three phase customers. ii. LV current transformer (C.T.) meters for the LV customers. iii. HV C.T. meters for the customers. TNB customers with C.T. operated meter are classified as Large Power Customers (LPCs). In TNB, power factor penalty charge is imposed for all customers’ with monthly average load at power factor value < 0.85, except for domestic customers and street lighting.

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7.2 CUSTOMER SUPPLY AND METERING The mode of supply connections to customers is dependent on the load demand as indicated in Chapter 3, i.e.: i. Direct (whole current) • Single phase • Three phase ii. Through LV C.Ts via : • LV from mains • from dedicated Substation • MV or HV supply

7.2.1 Metering Criteria The metering criteria depend on the: i. Mode of supply ii. Supply voltage iii. Respective tariff iv. Magnitude of load fed (i.e. energy consumed)

7.2.2 Whole Current Metering In TNB LV distribution system, for loads not exceeding 100 amps, whole current meters (single phase and three phase up to 100 Amp) are used. Currently, the whole current meters are all electronic type and their designated accuracy tolerances are: i. kWH meters – class 2.0 ii. kVARH meters – class 3.0

7.2.3 C.T. Metering For load exceeding 100A, supply must be metered through Current Transformer (C.T.), with 5 Amp secondary windings in order to enable the supply to be measured within relevant accuracy class tolerances. The accuracy class standard adopted by TNB is presented in Table 7.1. Table 7.1: Accuracy Class Standard for C.T Meter Category Voltage

Description

1 2 3 4

CT size 400/5 and below CT size 500/5 and above CT size 50/5 and above CT size 100/5 and above

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400V 400V 11kV 33kV and above

Meter Class 2 2 0.5 0.2

CT Class 0.5 0.2 0.2 0.2

PT Class

0.5 0.2

LV PLANNING GUIDELINES

LOW VOLTAGE METERING

Check meter is required for all Category 2 customers and Category 1 customer with more than 50,000kWh monthly consumption. Details of metering installations required for LPCs are set out in Arahan Naib Presiden Pembahagian C4/2007. 7.2.3.1 C.T. Meter Loading Meter has a limited overload capacity with regard to their accuracy range, which is 120 % of the nominal rating. This means that the measurement accuracy can be severely affected if the input current exceeds the limit value. For planning of supply connection and selection of metering installation, the primary current of C.T. metered installations must not exceed 120 % of their nominal rating. Thus planning of supply must ensure that for C.T. metered customers, their protection trip settings do not exceed the metering C.T.’s accurate measurement limit.

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CHAPTER

8 LOW VOLTAGE TECHNICAL LOSSES 8.0 OBJECTIVE The objective of this chapter is to: i.

Provide a brief overview on LV technical losses from the planning perspective in TNB Distribution.

8.1 DEFINITION Losses in TNB distribution systems are divided into 2 main categories:i. Technical losses. ii. Non technical losses. Technical losses are the electrical energy dissipated in the conductors and transformers while supplying electricity to the customers. These losses are inherent in the processing and delivery of power but can be minimized in order to maximise returns. Losses represent a considerable operating cost, estimated to add 6-8% to the cost of electricity and some 25% to the cost of delivery. Non technical losses are due to un-audited account or billing, meter errors or theft of electricity.

8.2 POWER FACTOR CORRECTION Indoor substations serving residential and commercial loads are planned to accommodate switched LV capacitor banks for power factor correction. Currently, 3 phase supply to commercial and industrial customers are imposed with power factor penalty for load with p.f. 5 storey) without Substation

Landlord Account1 bill = M(landlord1) Landlord Account2 bill = M(landlord2) – summation (m) TNB FEEDER PILLAR

1. CT (landlord) installed at TNB feeder pillar 2. Meter (landlord) installed at TNB Outdoor Meter Panel M(landlord1)

M(landlord2)

TNB Water pump load

M4

Tenant & water pump MSB

LANDLORD MSB

Supply to Landlord

Tenant meter at centralized meter room at each level

Tenant Lateral Riser to individual tenant at each level

M1

m

m

m

M2

m

m

m

M3

m

m

m

To tenant units

Tenant Landlord is recommended to install M1, Vertical Riser M2, Mn.. for landlord to check with individual tenant bills for any irregularity

Figure A3.3: Standard Design for Multi-Tenanted Buildings > 5 storey without Substation

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3D Multi-Tenanted Buildings (> 5 storey) with Substation (Landlord & Tenant takes LV supply)

TNB SUBSTATION

Owner bill = M(landlord1) – summation (m) Substation & Feeder pillar dedicated to this multitenant building

TNB FEEDER PILLAR

M(landlord)

TNB Water pump load

1. CT (landlord) installed at TNB transformer tail 2. Meter (landlord) installed at Meter Room in PE TNB M4 LANDLORD MSB

TENANT MSB

Tenant Lateral Riser to individual tenant at each level

Tenant Vertical Riser Supply to Landlord

M 1 M 2 M 3

Landlord is recommended to install M1, M2, Mn.. for landlord to check with individual tenant bills for any irregularity

m m m m m m

To tenant units

m m m Tenant meter at centralized meter room at each level

Figure A3.4: Standard Drawing Diagram for Multitenanted Buildings with Substation (Landlord & Tenant takes LV supply)

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APPENDIX 3

3E Multi-Tenanted Buildings (> 5 storey) with Substation (Landlord & Tenant takes MV supply)

1. CT & PT installed at TNB VCB 2. Meter installed at Meter Room in PE TNB

TNB SUBSTATION

VCB (B2) With slot for metering CT

M(Landlord)

M(Tenant)

TNB

LANDLORD MV PANEL TENANT MV PANEL

TO LANDLORD

TO TENANT

Figure A3.5: Standard Design for Multi-Tenanted Buildings > 5 storey with Substation (Landlord & Tenant takes MV supply)

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APPENDIX 3

3F Multi-Tenanted buildings (> 5 storey) with Substation (Development takes MV supply with Landlord load >1600A)

Figure A3.6: Standard Design for Multi-tenanted Buildings > 5 storey with Substation (Development takes MV supply with Landlord load >1600A)

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3G Multi-Tenanted Buildings (> 5 storey) with Substation (Development takes MV supply with Landlord load 5 storey with Substation (Development takes MV supply with Landlord load