Introduction:

IEC 60439, the standard for low-voltageswitchgear and controlgear assemblies,was under restructuring from the lastdecade. The new series of IEC 61439standards were published in January2009. This standard has broughtconsiderable clarity in technicalinterpretation.

The new standard follows thephilosophy of IEC 60947 series i.e. IEC61439-1 is ‘General Rules’ standard tobe referred to by subsidiary product partsof IEC 61439 series. (Refer Table 1)

The IEC 60439 standards wereambiguous about how to assesscompliance of partially type testedassemblies. As a result manufacturersand testing bodies often treatedpartially type-tested assemblies

NOVEMBER 2008 - MARCH 2009

Introduction to IEC 61439: A new standard onSwitchgear & Controlgear Assemblies

- Mr. A P Rao; Mr. D A Chavan; Mr. P Patel; Mr. T N ShahSwitchgear Design & Development Center

differently. One of the main featuresof IEC 61439-1 is that thediscrimination between Type TestedAssemblies (TTA) and Partially TypeTested Assemblies (PTTA) has beeneliminated by the verification approach.

The three different but equivalent typesof verification methods are introducedand these are;

a) Verification by Testing.

b) Verification by Calculation/Measurement.

c) Verification by Design rules.

The requirements regarding short circuitperformance, temperature rise, dielectricproperties and rated diversity factorhave been covered in more detail.

Verification of Requirements:

Table 2 gives the characteristics to be

verified and options available forverification.

Salient features of IEC 61439

1. Verification of temperature rise

� For multiple compartmentassembly, verification bycalculation can be done up torated current of 1600 A only.

� Assemblies, verified by designrule from a similar testedassembly, should comply withthe following:

� Functional units shallbelong to the same groupas functional unit selectedfor test.

� Same type of construction.

� Same or increased overalldimensions.

� Same or reduced internalseparation.

� Same or reduced powerlosses in the same sectionof assembly.

� Same or reduced numberof outgoing circuit for everysection.

� Rated diversity factor (RDF) iselaborated in more details withincoming and outgoing circuitdiagrams.

� The average ambient tempe-rature for the duration of test

shall not exceed 35o

C.

Table 1: Parts of IEC 61439 series

IEC 61439-1 General rules

IEC 61439-2 Power switchgear and control gear ASSEMBLIES(Replacing IEC 60439-1)

IEC 61439-3 Distribution boards (to supersede IEC 60439-3)

IEC 61439-4 ASSEMBLIES for construction sites(to supersede IEC 60439-4)

IEC 61439-5 ASSEMBLIES for power distribution(to supersede IEC 60439-5)

IEC 61439-6 Busbar trunking systems(to supersede IEC 60439-2)

2. Short circuit withstand test

Verification of assembly by designrules is permitted, if;

� Following requirements are greaterthan or equal to reference design

� Cross-sectional dimensions ofthe busbars and connections

� Spacing of the busbars andconnections

� SCPDs are equivalent, i.e. ofthe same make with the sameor better I2t based on thedevice manufacturer’s data

� Following requirements are lessthan or equal to reference design

� Short circuit rating of each circuit

� Busbar supports spacing

� Length of unprotected liveconductors of each non-protected circuit

� Following requirements are sameas that of reference design

� Conductor material and itsproperties

� Enclosure design, type anddimensions

� Compartment mechanicaldesign and dimensions

If all the above requirements aresatisfied, then further verification bycalculation or actual testing is notrequired.

3. Power frequency withstandvoltage

The values of dielectric test voltage

are reduced corresponding to ratedinsulation voltage (Refer Table 3)

4. Impulse voltage withstand test

� Verification is mandatory eitherby test or by design rules.

� Test is not required whenclearances in the assembly are1.5 times the specified valuein Table - 4.

5. Degree of protection

� The IPX1 to IPX6 tests on anassembly are deemed to befailure if water comes intocontact with electricalequipment housed within theenclosure.

� Requirements for ‘emptyenclosures for assemblies (IEC62208)’ have been incorporatedin the standard.

6. Mechanical operation

� Rated numbers of operatingcycles have been increasedfrom 50 to 200.

7. Protection provided by barriers

The protection provided by horizontaltop surfaces of easily accessiblebarriers is changed from IPXXB (theprotection of person against access tohazardous parts with finger) to IPXXD(the protection of person againstaccess to hazardous parts with wire).

8. Cross-section area of neutral

� 100% - for phase cross sectionarea upto 16 mm2

� 50 % - for phase cross sectionarea above 16 mm2, with aminimum of 16 mm2

� For conductor other thancopper, the cross sectionshould be greater thanequivalent copper conductor

9. Additional Tests in IEC 61439

� Resistance to corrosion Test

Purpose:

To ensure that deterioration ofmetallic component caused bycorrosion shall not impair themechanical strength ofswitchboard.

Procedure:

The test is carried out on a typicalswitchboard enclosure or on arepresentative sample showing thesame constructional details.

� 6 cycles of 24 hr each to DampHeat Cycling Test according toIEC 60068-2-30 at (40±3)

o

C &relative humidity of 95%.

Table-2

No. Characteristic Verification options

Testing Calculation Designrules

1 Degree of protection of enclosures � � �

2 Clearance and creepage distances � � �

3 Effectiveness of assembly � � �(protective circuit) for external faults

4 Incorporation of switching � � �devices and components

5 Internal electrical circuits � � �and connections

6 Terminals for external conductors � � �

7 Impulse withstand voltage � � �

8 Temperature rise limits � � �

9 Short-circuit withstand strength � � �

10 Electromagnetic compatibility (EMC) � � �

11 Effective continuity between the � � �exposed conductive parts of theassembly and the protective circuit

12 Power frequency withstand voltage � � �

13 Mechanical operation � � �

The following characteristics are newly introduced in IEC 61439

14 Resistance to corrosion � � �

15 Thermal stability of enclosure � � �

16 Resistance of insulating material � � �to heat

17 Glow wire test � � �

18 Resistance to UV radiation � � �

19 Lifting � � �

20 Mechanical impact test (IK) � � �

21 Marking � � �

� 2 cycles of 24 hr each to SaltMist test according to IEC60068-2-11 at temperature of(35±2)

o

C.

Assessment Criteria:

� The mechanical integrity shallnot be impaired.

� Doors, hinges, locks, etc. shallwork without abnormal effects.

� Seals shall not damage.

� There shall be no iron-oxide,cracking or other deteriorationmore than that allowed by ISO4628-3 for degree of rustingRi1.

� Verification of Thermal stability

Purpose:

To check the thermal properties ofthe enclosure

Procedure:

� The specimen is kept in aheating chamber at 70

o

C for 7days.

� After that the sample is keptat ambient temperature for 4days.

Assessment criteria:

� The sample shall show nocracks nor shall the materialbecome sticky or greasy

� Sample is pressed with theforefinger wrapped in a dry clothwith a force of 5 N; no tracesof cloth shall remain on thesample.

� Verification of resistance ofinsulating materials to heat

Purpose:

To ensure the properties ofinsulating material to normal heat

Procedure:

� A ball pressure test apparatusis used to verify the suitabilityof insulating materials.

� The test shall be carried outon an insulating material ofminimum 2 mm thickness.

� The test shall be made in aheating cabinet at atemperature as stated below:

v parts supporting livecomponents – 125

o

C

v other parts – 70o

C

� After 1 hr, the sample isremoved and cooled within 10s to approx. room temperatureby immersion in cold water.

Assessment criteria:

� The diameter of the impressioncaused by the ball shall bemeasured and shall not exceed2 mm.

� Resistance to abnormal heat &fire (Glow Wire Test)

Purpose:

Glow wire test checks thecapability of insulation material tohandle thermal stresses producedby sources of heat or ignition.

Procedure:

� Sample: Thinnest wallthickness of the completedapplication.

� Pre-treatment: 24 hours at 23o

Cat 50% RH.

� Temperatures of glow wire:550, 650, 750, 850 or 960degrees C (depending on therelevant specification).

� Force: 1 N

� Contact time: 30 s

Assessment criteria:

� There is no flame and glowingon the sample or flames/glowing of the sampleextinguish within 30 s.

� The cotton or the paperunderlay doesn’t ignite or burn.

� Resistance to UV radiation

Purpose:

The UV radiation causesdeterioration of synthetic materialuse for enclosures.

Procedure:

� UV Test according to ISO4892 – 2 method A; 1000cycles of 5 min of watering and25 min. of dry period withxenon lamp providing a totaltest period of 500 hrs.

� The value of temperature andhumidity for the test are(65±3)

o

C and (65±5) %.

Assessment criteria:

� Adherence of syntheticmaterial (according to ISO2409) shall have minimum 50%retention.

� Sample shall not show cracksor deterioration visible tonormal or corrected visionwithout any additionalmagnification.

� This test is not required ifsynthetic material supplierdemonstrates that materials ofsame thickness or thinnercomply with this requirement.

NOTE: This test is applicable only forenclosures and external parts ofASSEMBLIES intended to be installedoutdoors.

Table - 3

Rated insulation voltage (Ui) Dielectric test Dielectric test(line to line a.c or d.c) voltage (a.c) r.m.s voltage (d.c)

V V V

Ui ≤ 60 1000 (1000) 1415

60 < Ui ≤ 300 1500 (2000) 2120

300 < Ui ≤ 690 1890 (2500) 2670

690 < Ui ≤ 800 2000 (3000) 2830

800 < Ui ≤ 1000 2200 (3500) 3110

1000 < Ui ≤ 1500* — 3820

Note 1: * For d.c only.Note 2: the values in parentheses are according to IEC 60439-1.

Table - 4

Rated impulse Minimumwithstand voltage clearance

Uimp

(kV) mm

≤ 2.5 1.5

4.0 3.0

6.0 5.5

8.0 8.0

12.0 14.0

Based on inhomogeneous field condition andpollution degree 3.

� Lifting:

Purpose:

To ensure that there should be nodamage to the panel duringtransportation & installation.

Procedure:

� The test is carried out on asample having weight 1.25times its maximum shippingweight.

� From a standstill position, theASSEMBLY shall be raisedsmoothly without jerking in avertical plane to a height of(1±0.1) m and lowered in thesame manner to a standstillposition. This test is repeateda further two times.

� After this the ASSEMBLY israised up and suspended for30 min at a height of (1±0.1)m without any movement.

� Following this test theASSEMBLY shall be raisedsmoothly without jerking froma standstill position to a heightof (1±0.1) m and moved(10±0.5) m horizontally, thenlowered to a standstill position.

� This sequence shall be carriedout three times at uniformspeed, each sequence beingcarried out within 1 min.

Assessment criteria:

� During the test, with the testweights in place, theASSEMBLY shall show nodeflections and after the testshow no cracks or permanentdistortions visible to normal orcorrected vision withoutadditional magnification, whichcould impair any of itscharacteristics.

� Mechanical Impact Test

Purpose:

This test measures resistance ofan enclosure towards externalMechanical Impact.

The degree of protection providedby an enclosure against impactsis indicated by the letters IKfollowed by two digits dependingon its ability to withstand theimpact (as per IEC 62262).

Procedure:

� Number of impacts on eachexposed face shall be fiveunless otherwise specified inrelevant product standard.

� The impacts shall be evenlydistributed on the faces of theenclosure under test.

� At the surrounding of any pointof enclosure, not more thanthree impacts shall be applied.

Assessment Criteria:

� Structural integrity shall bemaintained.

� Degree of protection (IP) shallbe unaffected.

� Functionality of electricalproducts shall not behampered.

NOTE: Mechanical Impact test is notapplicable to low voltage powerswitchgear and controlgear (PSC)assemblies.

� Marking:

Purpose:

To ensure that the markings arelegible.

Procedure:

� Marking made by moulding,pressing, engraving or similarshall not be submitted to thefollowing test.

� The test is made by rubbingthe marking by hand for 15 swith a piece of cloth soaked inwater and then for 15 s with apiece of cloth soaked withpetroleum spirit.

Assessment criteria:

� After the test the marking shallbe legible to normal orcorrected vision withoutadditional magnification.

Validity of certificates as per

IEC 60439:

Where tests on the ASSEMBLY havebeen conducted in accordance with theIEC 60439 series, prior to thepublication of relevant product standardin the IEC 61439 series, and the testresults fulfill the requirements of therelevant part of IEC 61439, theverification of these requirements neednot be repeated.

Conclusion:

The 4th edition of IEC 60439-1 waspublished in 1999 with a subsequentamendment in 2004. This standard didnot mandate compliance to stringentsafety requirements (such as impulsewithstand and resistance to abnormalheat and fire i.e. glow wire) which arepresent in other LV product standards.

In the new standard (IEC 61439-1)these safety requirements have beenincluded in addition to others pertainingto satisfactory performance underapplicable environmental conditions.

Hence, with these additions IEC 61439series becomes the most updateddocument from a technologicalperspective.

Relation between IK code & Impact energy.

IK IK IK IK IK IK IK IK IK IK IK IKcode 00 01 02 03 04 05 06 07 08 09 10

Impact * 0.14 0.2 0.35 0.5 0.7 1 2 5 10 20Energy

J

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