IEC 61439

Introduction to IEC 61439:  A new standar standard d on Switchgear & Controlgear  Assemblies  An effort by Virendra Sahdev

IEC 60439 vs IEC IEC 61439 61439

Introduction  The

new series of IEC 61439 6 1439 standards were were published in January Januar y 2009. The new standard follows the philosophy of IEC 60947 series i.e. IEC 61439-1 is ‘General Rules’ standard to be referred to by subsidiary product parts of IEC 61439 series. (Refer Table Table 1 below) bel ow)

Introduction  One

of the main features of IEC 61439-1 is that the discrimination between Type Tested Assemblies (TTA) and Partially Type Tested Assemblies (PTTA) has been eliminated by the verification approach. The three different but equivalent types of verification methods are introduced and these are; a) Verification by Testing. b) Verification by Calculation/ Measurement. c) Verification by Design rules. The requirements regarding short circuit performance, temperature rise, dielectric properties and rated diversity factor have been covered in more detail.

Main Functions

Main Functions

Main Functions

Main Functions

 Verification Requirements 

 Verification Requirements

 Verification Requirements Examples of the limitations and margins applied to  verification without type test include:  All

assemblies connected to a supply with a prospective short circuit current in excess of 10kA rms or having a cut-off current of 17kA peak must be of a type-tested design or the verification must be an interpolation from a reference design. Under no circumstances can the assigned short circuit current rating be higher than that of the reference design. So as to take account of the air temperature within the enclosure, thermal interactions and possible hot spots; components within a circuit that has not been temperature rise tested, must be de-rated to 80% of their free air current rating. Comparison of the power loss of the components within an assembly with the known heat dissipation capability of an enclosure, is restricted to assemblies having a rating of 630A. Confirmation of temperature rise performance by calculation is limited to assemblies with a rating not exceeding 1600A. Test or interpolation from a tested design must be used to verify higher ratings.

Salient features of IEC 61439 Verification of temperature rise For multiple compartment assembly, verification by calculation can be done up to

rated current of 1600 A only.  Assemblies, verified by design rule from a similar tested assembly, should comply with the following: oFunctional units shall belong to the same group as functional unit selected for test. oSame type of construction. oSame or increased overall dimensions. oSame or reduced internal separation. oSame or reduced power losses in the same section of assembly. oSame or reduced number of outgoing circuit for every section. Rated diversity factor (RDF) is elaborated in more details with incoming and outgoing circuit diagrams. The average ambient temperature for the duration of test shall not exceed 35 oC.

Salient features of IEC 61439 Rated divers1ty factor (RDF): The rated diversity factor is the per unit value of the rated current, assigned by the assembly manufacturer, to which outgoing circuits of an assembly can be continuously and simultaneously loaded taking into account the mutual thermal influences. Rated diversity factor can be stated: • for groups of circuits; • for the whole assembly. The rated diversity factor multiplied by the rated current of the circuits shall be equal to or higher than the assumed loading of the outgoing circuits. The assumed loading of outgoing circuits shall be addressed by the relevant assembly standard, The rated diversity factor is applicable with the ASSEMBLY operating at rated current (lnA)

Salient features of IEC 61439 Short circuit withstand test Following requirements are greater than or equal to reference design: oCross-sectional dimensions of the busbars and connections o Spacing of the busbars and connections o SCPDs are equivalent, i.e. of the same make with the same or better I2t based on the device manufacturer’s data Following requirements are less than or equal to reference design: oShort circuit rating of each circuit o Busbar supports spacing o Length of unprotected live conductors of each nonprotected circuit Following requirements are same as that of reference design o Conductor material and its properties o Enclosure design, type and dimensions o Compartment mechanical design and dimensions If all the above requirements are satisfied, then further verification by calculation or actual testing is not required.

Salient features of IEC 61439 Short circuit withstand test Following requirements are greater than or equal to reference design: oCross-sectional dimensions of the busbars and connections o Spacing of the busbars and connections o SCPDs are equivalent, i.e. of the same make with the same or better I2t based on the device manufacturer’s data Following requirements are less than or equal to reference design: oShort circuit rating of each circuit o Busbar supports spacing o Length of unprotected live conductors of each nonprotected circuit Following requirements are same as that of reference design o Conductor material and its properties o Enclosure design, type and dimensions o Compartment mechanical design and dimensions If all the above requirements are satisfied, then further verification by calculation or actual testing is not required.

Salient features of IEC 61439 Short circuit withstand test Following requirements are greater than or equal to reference design: oCross-sectional dimensions of the busbars and connections o Spacing of the busbars and connections o SCPDs are equivalent, i.e. of the same make with the same or better I2t based on the device manufacturer’s data Following requirements are less than or equal to reference design: oShort circuit rating of each circuit o Busbar supports spacing o Length of unprotected live conductors of each nonprotected circuit Following requirements are same as that of reference design o Conductor material and its properties o Enclosure design, type and dimensions o Compartment mechanical design and dimensions If all the above requirements are satisfied, then further verification by calculation or actual testing is not required.

Salient features of IEC 61439  Power frequency withstand voltage The values of dielectric test voltage are reduced corresponding to rated insulation voltage (Refer Table 3)

Salient features of IEC 61439 Impulse voltage withstand test  Verification is mandatory either by test or by design rules. o Test is not required when clearances in the assembly are 1.5 times the specified value in Table - 4. o

Salient features of IEC 61439 Degree of protection The IPX1 to IPX6 tests on an assembly are deemed to be failure if water comes into contact with electrical equipment housed within the enclosure. o Requirements for ‘empty enclosures for assemblies (IEC 62208)’ have been incorporated in the standard. o

Mechanical operation  Rated numbers of operating cycles have been increased from 50 to 200.

o

Protection provided by barriers The protection provided by horizontal top surfaces of easily accessible barriers is changed from IPXXB (the protection of person against access to hazardous parts with finger) to IPXXD (the protection of person against access to hazardous parts with wire). o

Cross-section area of neutral 100% - for phase cross section area upto 16 mm2 o 50 % - for phase cross section area above 16 mm2, with a minimum of 16 mm2 o For conductor other than copper, the cross section should be greater than o

Salient features of IEC 61439 Degree of protection The protection provided by horizontal top surfaces of easily accessible barriers is changed from IPXXB (the protection of person against access to hazardous parts with finger) to IPXXD (the protection of person against access to hazardous parts with wire). o

Salient features of IEC 61439 dditional Tests in IEC 61439 Resistance to corrosion Test Purpose: oTo ensure that deterioration of metallic component caused by corrosion shall not impair the mechanical strength of switchboard. Procedure: oThe test is carried out on a typical switchboard enclosure or on a representative sample showing the same constructional details.  6 cycles of 24 hr each to Damp Heat Cycling Test according to IEC 60068-2-30 at (40±3) o C & relative humidity of 95%. •

Salient features of IEC 61439 dditional Tests in IEC 61439 Verification of Thermal stability Purpose: oTo check the thermal properties of the enclosure Procedure: o The specimen is kept in a heating chamber at 70 o C for 7 days. After that the sample is kept at ambient temperature for 4 days. ssessment criteria: o The sample shall show no cracks nor shall the material become sticky or greasy Sample is pressed with the forefinger wrapped in a dry cloth with a force of 5 N; no traces of cloth shall remain on the sample.

Salient features of IEC 61439 dditional Tests in IEC 61439 Verification of resistance of insulating materials to heat Purpose: To ensure the properties of insulating material to normal heat

Procedure:  A ball pressure test apparatus is used to verify the suitability of insulating materials. The test shall be carried out on an insulating material of minimum 2 mm thickness. The test shall be made in a heating cabinet at a temperature as stated below: o parts supporting live components – 125 o C o other parts – 70 o C o After 1 hr, the sample is removed and cooled within 10 s to approx. room temperature by immersion in cold water. o

ssessment criteria: The diameter of the impression caused by the ball shall be measured and shall not exceed 2 mm.

Salient features of IEC 61439 dditional Tests in IEC 61439 Resistance to abnormal heat & fire (Glow Wire Test) Purpose: Glow wire test checks the capability of insulation material to handle thermal stresses produced by sources of heat or ignition.

Procedure: Sample: Thinnest wall thickness of the completed application. Pre-treatment: 24 hours at 23 o C at 50% RH. Temperatures of glow wire: 650, 850 or 960 degrees C (depending on the relevant specification). 960 degrees C for parts necessary to retain cur rent carrying parts in position; 850 degrees C for enclosures intended for mounting in hollow walls: 650 degrees C for all other parts, including parts necessary to retain the protective conductor. Force: 1 N Contact time: 30 s ssessment criteria: There is no flame and glowing on the sample or flames/glowing of the sample extinguish within 30 s. The cotton or the paper underlay doesn’t ignite or burn. •

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Salient features of IEC 61439 dditional Tests in IEC 61439 Resistance to UV radiation Purpose: The UV radiation causes deterioration of synthetic material used for enclosures.

Procedure: UV Test according to ISO 4892 – 2 method A; 1000 cycles of 5 min of watering and 25 min. of dry period with xenon lamp providing a total test period of 500 hrs. The value of temperature and humidity for the test are (65±3) o C and (65±5) %.

ssessment criteria: Adherence of synthetic material (according to ISO 2409) shall have minimum 50% retention. Sample shall not show cracks or deterioration visible to normal or corrected vision without any additional magnification. This test is not required if synthetic material supplier demonstrates that materials of same thickness or thinner comply with this requirement. NOTE: This test is applicable only for enclosures and external parts of ASSEMBLIES intended to be installed Outdoors.

Salient features of IEC 61439 dditional Tests in IEC 61439 Lifting: Purpose: To ensure that there should be no damage to the panel during transportation & installation.

Procedure:  The test is carried out on a sample having weight 1.25 times its maximum shipping weight. o From a standstill position, the ASSEMBLY shall be raised smoothly without jerking in a vertical plane to a height of (1±0.1) m and lowered in the same manner to a standstill position. This test is repeated a further two times. o After this the ASSEMBLY is raised up and suspended for 30 min at a height of (1±0.1) m without any movement. o Following this test the ASSEMBLY shall be raised smoothly without jerking from a standstill position to a height of (1±0.1) m and moved (10±0.5) m horizontally, then lowered to a standstill position. o This sequence shall be carried out three times at uniform speed, each sequence being carried out within 1 min. o

ssessment criteria: During the test, with the test weights in place, the ASSEMBLY shall show no deflections and after the test show no cracks or permanent distortions visible to normal or corrected vision without additional magnification, which could impair any of its characteristics.

Salient features of IEC 61439 dditional Tests in IEC 61439 Mechanical Impact Test Purpose: This test measures resistance of an enclosure towards external Mechanical Impact. The degree of protection provided by an enclosure against impacts is indicated by the letters IK followed by two digits depending on its ability to withstand the impact (as per IEC 62262).

Procedure:  Number of impacts on each exposed face shall be five unless otherwise specified in relevant product standard. o The impacts shall be evenly distributed on the faces of the enclosure under test. o At the surrounding of any point of enclosure, not more than three impacts shall be applied. o

ssessment Criteria:  Structural integrity shall be maintained. o Degree of protection (IP) shall be unaffected. o Functionality of electrical products shall not be hampered. NOTE: Mechanical Impact test is not applicable to low voltage power switchgear and controlgear (PSC) assemblies. o

Salient features of IEC 61439 dditional Tests in IEC 61439 Marking: Purpose: To ensure that the markings are legible. Procedure: Marking made by moulding, pressing, engraving or similar shall not be submitted to the following test. The test is made by rubbing the marking by hand for 15 s with a piece of cloth soaked in water and then for 15 s with a piece of cloth soaked with petroleum spirit. ssessment criteria: After the test the marking shall be legible to normal or corrected vision without additional magnification.

 Ambiguities clarified Previously

a manufacturer had to assign a current rating to each circuit, but they were never required by the standard to prove its rating. In accordance with the new standard, the manufacturers have to verify the rating of each type of circuit. Each type of circuit will have its rating verified within the assembly and the capability of the assembly as a whole will be proven by loading adjacent outgoing circuits to their rated current, multiplied by the diversity factor. Historically it has been assumed that if nothing was said, the neutral could have a current rating equal to 50% of that of its associated phase. However, because this has not been stipulated in any low-voltage standards for many years, any query could only be answered by it’s custom and practice. IEC 61439 includes a default current rating in accordance with custom and practice for circuits with conductors above 16mm², but a specifier can ask for a higher rating to suit the needs of his application. In addition the ongoing question in respect of forms of separation has been answered. device’s integral enclosure, for example the case of a moulded case circuit breaker, is defined as a means of providing separation from an adjacent

Classification of assemblies Open-type and enclosed assemblies - Enclosed assembly n assembly is enclosed when there are protected panels on all its sides so as to provide a degree of protection against direct contact not lower than IPXXB . Assemblies intended to be installed in common environments shall be of enclosed type - Open-type assembly n assembly, with or without front covering, in which the live parts of the electrical equipment are accessible. Such assemblies can be used only in places where skilled persons have access for their use.

External design - Cubicle-type (column) Used for large distribution and control equipment; mechanically joined multi-cubicle-type assemblies are obtained by combining side by side more cubicle-type assemblies. - Desk-type Used to control complex machines or plants in mechanical, iron and steel and chemical industries. - Box-type Intended to be mounted on a vertical plane, both jutting out as well as built-in; such assemblies are used mainly for the department or area distribution in industrial or service sector environments. - Multi-box-type combination of boxes, generally of protected type and with fixing flanges, each housing a functional unit which may be an automatic circuit-breaker, a starter, a

Classification of assemblies Conditions of installation - Assembly for indoor installation ssembly which is designed for use in locations where the normal service Conditions for indoor use as specified in the Std. IEC 61439-1 are fulfilled. - Assembly for indoor installation ssembly which is designed for use in locations where the normal service conditions for outdoor use as specified in the Std. IEC 61439-1 are fulfilled. - Stationary assembly ssembly which is designed to be fixed at its place of installation, for instance to the floor or to a wall, and to be used at this place. - Movable assembly ssembly which is designed so that it can readily be moved from one place of use to another.

Conclusion With the ever-increasing pressures of demand for higher network utilization, assembly design optimization and more stringent safety, the changes included in the assembly standard IEC 61439-2 are important and overdue. ll assemblies that do not have a specific product standard are covered and there is no opportunity to avoid compliance. In the new standard, the methods of confirming design performance are practical and pragmatic, reflecting the different market needs and ways in which assemblies are produced. Several alternative and equivalent means of verifying a particular characteristic of an assembly are included. These are defined and their use restricted. Where alternatives to type tests are used, a compensatory approach is taken and margins are added to ensure equivalence. Overall, the standard is performance based.

Bibliography IEC

61439-1 - Low-voltage switchgear and controlgear assemblies – Part 1: General Rules IEC 61439-2 - Low-voltage switchgear and controlgear assemblies – Part 2: Power switchgear and controlgear assemblies Introduction to IEC 61439: A new standard on Switchgear & Controlgear ssemblies by Mr. A P Rao; Mr. D A Chavan; Mr. P Patel; Mr. T N Shah Switchgear Design & Development Center Improving safety and performance in electrical assemblies - A guide to IEC 614392 by Schneider Electric IEC 61439 The new Standard for Low-Voltage Switchgear Assemblies – Changes and Effects in respect of Tests by GE Ronald Borchert, IPH Berlin The new IEC 61439 Series – Technical Seminar, 10 th November, 2010 – Singapore, KEMA Quality