vector march2013 new

7/30/2019 Vector March2013 New

1/4March 2013 - Vector - Page 40

D R I V E S &S W I T C H G E A R

New standard for LV switchgear,

controlgear assemblies

The IEC 61439, the new standard for low-voltage (LV) switchgear

and controlgear assemblies, was published in 2009 to harmoniseand define all general requirements for LV electrical assemblies.

Information from ABBOnly two parts of the standard arenecessary to determine all requirementsfor each type of electrical assembly:the basic standard IEC 61439-1General rules and the specific assemblystandard.

The current IEC 60439

The current IEC 60439 standard

applies to enclosures with the ratedvoltages under or equal to 1000 VAC (at fr equenc ies no t exceed ing1000 Hz) or 1500 V DC. The standardmakes a distinction between type-tested assemblies (TTAs) and partiallytype-tested assemblies (PTTAs).Thefollowing parts are mentioned andhave equal weighting. There is nota formal hierarchy. Each part is acomplete entity and can be used onan individual basis:

IEC 60439-1: Type-tested andpartially type-tested assemblies.

I E C 6 0 4 3 9 - 2 : P a r t i c u l a r requirements for busbar trunkingsystems (busways).

IEC 60439-3: Particular requirementsfor low-voltage switchgear andcontrolgear assemblies to beinstalled in locations where unskilledpersons have access.

IEC 60439-4: Particular requirementsfor assemblies for construction sites(ACSs).

I E C 6 0 4 3 9 - 5 : P a r t i c u l a r requirements for assemblies to beinstalled outdoors in public places cable distribution cabinets (CDCs)for power distribution in networks.

The new IEC 61439

The new standard applies to enclosuresfor which the rated voltage is under1000 V AC (at frequencies not exceeding1000 Hz) or 1500 V DC. The standarddefines the design verified assembliesand eliminates completely the categories

TTA and PTTA. To conform to thestandard, type tests have been replacedby a design verification which canbe carried out by the three followingequivalent alternative methods: testing,calculation/measurement or applicationof design rules.

The following parts are mentioned anddo not have equal weighting. There is aformal hierarchy. Individual parts cannotbe used individually:

IEC 61439-1: General rules.

IEC 61439-2: Power switchgear andcontrolgear assemblies.

IEC 61439-3: Distribution boards.

IEC 61439-4: Assemblies forconstruction sites.

IEC 61439-5: Assemblies for powerdistribution.

IEC 61439-6: Busbar trunkingsystems.

Part 1 is the general rules part andcannot be used alone to specify anassembly. Part 2 defines the specific

requirements of power switchgear andcontrolgear assemblies (PSC assemblies)and must be used with part 1. This isthe only part that has a double roleas it covers PSC ASS emblies and anyassembly which is not covered by anyother specific parts.

Parts 3 X are still under preparationbut are already mentioned in Part 1.These could total more than four asadditional parts may be developed asthe need arises.

To summarise, with the currently usedIEC 60439, the rule is one part foreach type of assembly. With the newIEC 61439 the rule is two parts foreach type of assembly. The compliance

IEC 60439-1 +

IEC 61439-2 replacesIEC 60439-1

(still valid until 2014)

IEC 61439-6 will replace IEC 60439-2 (still valid)

IEC 61439-3 will replace IEC 60439-3 (still valid)

IEC 61439-4 will replace IEC 60439-4 (still valid)IEC 61439-5 will replace IEC 60439-5 (still valid)

Table 1: The relationship between the two standards.


2/4

March 2013 - Vector - Page 41

of an assembly is declared referring tothe specific assembly standard (e.g.IEC 61439-2), and the compliancewith the general rules (IEC 61439-1)is always implicit. The phrase TTAswitchgear according to IEC 60439-1is now replaced by Power switchgear

and controlgear assemblies accordingto IEC 61439-2, design veri f iedassembly.

The validity of the two standards willoverlap until 2014, and prior to thisdate assemblies can be manufacturedaccording to IEC 61439 or IEC 60439.The relationship between the twostandards is shown in Table 1.

Main changes

The new IEC 61439 includes thefollowing significant technical changeswith respect to the last edition ofIEC 60439.

Responsibility split

New terms have been introduced andthere is a split in product responsibilitybetween the original manufacturer(responsible for carrying out theoriginal design and the associatedverification of an assembly) and theassembly manufacturer (e.g. panelbuilder using an assembly system froman original manufacturer) assumingresponsibi l i ty for the completedassembly.

The assembly manufacturer maybe a different organisation to theoriginal manufacturer. Where the

assembly manufacturer introduceschanges to the assembly configurationtested by the original manufacturer,he is deemed to be the originalmanufacturer in respect of thesechanges and he has to carry out thedesign verification.

Design verification replacesTTA and PTTA categories

Design verification replaces type tests sothe discrimination between type-testedassemblies and partially type-testedassemblies is eliminated.

Three different but equivalent typesof verification of requirements areintroduced:

Ver i f ica t ion by tes t ing : Testconducted on a sample of anassembly or on parts of assemblies

to verify that the design meets theappropriate requirements. Thismethod is equivalent to the currentlyimplemented type tests.

Ver i f i ca t ion by ca lcu la t ion/measurement: Calculations appliedto a sample of an assembly or toparts of assemblies to show thatthe design meets the appropriaterequirements.

Verification by application of designrules: Specified rule to verify thedesign of an assembly.

The selection of the appropriateverification method must be doneaccording to Annex D which explains theavailable verification options for eachcharacteristic to be verified, as shownin Table 2.

Tes t s tha t have been made inaccordance with IEC 60439 whichfulfill the requirements of the newIEC 61439 need not be repeated.

The second stage verification is routineverification, performed to verify thatthe materials and workmanship arein accordance with the requirements

of the standard. Routine verificationreplaces the current routine test. It ismore detailed but, essentially, the newrequirements are the same as in theIEC 60439. This verification mustbe carried out for each completedassembly and it is the responsibilityo f t he a s semb l y manu fac tu re r (see Fig. 1).

Additional verification

New requirements from the standardIEC 62208: Empty enclosures for

assemblies, have been added: Verif ication of resistance to UV

radiation for outdoor plasticenclosures.

Verification of corrosion resistance.

Mandatory dec la ra t ion andconfirmation of an impulse rating.

Lifting, mechanical impact andmarking.

Other changes

Temperature rise: Temperature rise

requirements are explained moreclearly and are adapted to the stateof the art.

One of the following methods isallowed for verification:

Testing with current.

Derivation (from a tested design)of ratings for similar variants.

Calculation.

RDF: The rated diversity factor(RDF) is covered in more detail. Inpractice, it is assumed that multiple

functional units are not fully loadedsimultaneously.

Labels: Labels must be subjected totesting to verify their legibility. Thefollowing information is required onthe label:

Assembly manufacturers name.

Identification number.

Date of manufacture .

IEC 61439-X (part X must bespecified).

Grey areas: A number of greyareas have been clarified:

Neutral conductors will havea current rating equal to 50% ofthe corresponding phases if notspecified otherwise.

Fig. 1: Comparison between the current and the new verification flow.


3/4


Agreements between customerand manufacturer have been moredetailed, extended and listed inannex C.

It is mandatory to specify the ratedcurrent of the assembly.

A technical report IEC 61439-0:Guide for specifying assembliesis under development for a betterunderstanding of the new standard.

Questions regarding the internalform of separation have beenclarified (e.g. a moulded casecircuit breakers casing providesseparation from other functionalunits).

Responsibilities

With regard to responsibilities, thegeneral and obvious rule is thatthe manufacturer of the assemblyis responsible for i t. One couldalso say the original manufacturerusually makes design verificationsand assumes responsibility for theproper functionality of prototypeassemblies. He provides a portfolioof veri f ied assemblies and eachplayer in the electrical market who

becomes the assembly manufacturercan manufacture a design-verifiedassembly by following the instructionssupplied in the original manufacturersinstruction manual or catalogue; theassembly manufacturer assumesresponsibility for the assembly, labelsit and declares that the assemblycomplies with the relevant standards.In practice, he has two options:

He decides to manufacture theassembly according to the rules ofthe original manufacturer. In this

case, the assembly manufacturermust perform only the secondstage verification, namely routineverification.

He decides not to manufacture theassembly according to the rules of

the original manufacturer. In thiscase, the manufacturer incorporateshis own arrangements so thathe is deemed to be the original

manufacturer. He must then carry outboth the first and the second stageverification: design verification androutine verification.

Hypothetical examples

An original manufacturer assemblesa complete assembly and sells it to apanel builder.

The panel builder is only the assemblymanufacturer if he installs the assemblyas is. The panel builder is the assemblymanufacturer and becomes the original

manufacturer i f he makes somemodifications to the assembly.

A panel builder assembles a completeassembly according to the rules of theoriginal manufacturer.

The panel builder is the assemblymanufacturer and is responsible for theassembly provided that the electricalinstaller installs the assembly withoutmaking any alterations.

A panel builder assembles a completeassembly (according to the rules of the

original manufacturer) which has beenassembled partially by an externalsupplier.

The panel builder is the assemblymanufacturer and is responsible for theassembly.

FAQ

Until what point is it possible tomanufacture and to install assembliesin accordance with IEC 60439?

The validity of the two standards willoverlap until 2014, and prior to thisdate assemblies can be manufactureda c c o r d i n g t o I E C 6 1 4 3 9 o r IEC 60439.

If tests on the assembly have beenconduc ted in acco rdance w i t h

IEC 60439, is it necessary to repeatthem in accordance with the newIEC 61439?

No, if the conducted test resultsfulfill the requirements of the newIEC 61439 it is not necessary to repeatthem. It is necessary to test only theadditional verification that has beenintroduced by the new standard.

Is i t possible to manufacture anassembly in accordance with the newIEC 61439, with enclosures, busbars,circuit breakers etc. from differentmanufacturers?

Yes, it is possible but it is not easy andit is expensive. The panel builder who

decides to mix different elementsfrom different manufacturers is notonly the assembly manufacturer, butbecomes the original manufacturerand has to perform both first andsecond stage verification: designverification and routine verification.

The routine verification is similarto the present routine test and isrelatively straightforward. The designverification, however, includes somecharacteristics which are easily verified,

and others which can only be verifiedthrough laboratory testing.

What is the rated diversity factor(RDF)?

The RDF is the per unit value of therated current, to which outgoingcircuits of an assembly can be loadedcontinuously and simultaneously (themutual thermal influences must betaken into account). It can be declaredfor groups of circuits or for the wholeassembly. The RDF has to be assigned

by the assembly manufacturer (if notspecified it is assumed to be equal to 1).In practice, it is recognised that not allcircuits in an assembly operate at ratedcurrent continuously and this allowsefficient use of materials and resources.

Characteristics to be verifiedVerification options available

Verification by testing Verification by calculation Verification by design rules10.2 Strength of material and parts Yes No No10.3 Degree of protection of enclosures Yes No Yes10.4 Clearances and creepage distances Yes Yes Yes10.5.2 Effective continuity between parts and PE Yes No No10.5.3 Effectiveness of the assembly for external faults Yes Yes Yes10.6 Incorporating of apparatus No No Yes10.7 Internal electrical circuits and connections No No Yes10.8 Terminals for external conductors No No Yes10.9.2 Power frequency withstand voltage Yes No No10.9.3 Impulse withstand voltage Yes No Yes10.10 Temperature rise limits Yes Yes Yes10.11 Short-circuit withstand strength Yes Yes Yes10.12 EMC Yes No Yes10.13 Mechanical operation Yes No No

Table 2: Characeristics to be verified.


4/4


Is it possible to substitute a device withinan assembly? What about temperaturerise and short circuit strength?

The new IEC 61439 clearly definesa device substitution in respect oftemperature rise and short circuitstrength.

In terms of temperature rise, it is

possible to substitute a device withoutrepeating design verification, providedthat the new device from the same oranother series has identical or bettervalues regarding power loss andterminal temperature rise comparedwith those of the original device, astested in accordance with the productstandard.

In terms of short circuit, it is possibleto substitute a device without repeatingthe design verification, provided thatthe new device is identical. If different,

it must from the same manufacturerwho has to certify that it is equivalent orbetter with regard to all relevant shortcircuit characteristics.

Is the verification of the short circuitwithstand strength required for allcircuits of an assembly?

No, it is not required for:

Assembl ies with rated short-t imewithstand current or rated conditionalshort circuit current not exceeding10 kA rms.

Assemblies protected by current-limiting devices with cut-off currentnot exceeding 17 kA at the maximum

permitted prospective short-circuitcurrent at the terminals of theincoming circuit of the assembly.

Auxi llary ci rcui ts of assembliesintended to be connected totransformers whose rated powerdoes not exceed 10 kVA for ratedsecondary voltages of no lessthan 110 V, or 1,6 kVA for a ratedsecondary voltage less than 110 V,and whose short circuit impedanceis not less than 4%.

All other circuits must be verified.

Does the verification of temperaturerise remain unchanged?

Temperature rise requirements areexplained in further detail. Threedifferent methods are now allowed forverification (the original manufacturer

is responsible for choosing the suitableverification methods):

Testing with current: Three differenttest methods are permitted andthe original manufacturer mustdetermine the best method. When anumber of variants of an assemblymust be verified, the most onerousconfiguration has to be tested andthe ratings of the less onerous (andsimilar) variants can be derivedwithout testing.

Derivation: (from a tested design)of ratings for similar variants. Thestandard defines a series of sub-clauses that help define how non-tested variants can be verified byderivation from similar arrangementsverified by test.

Calculation: Two calculation methodsare allowed: single compartment

assembly with rated current notexceeding 630 A (done by calculatingthe total power loss of the assembly ifcertain conditions are fulfilled), andmultiple compartment assembly withrated current not exceeding 1600 A(done by calculation in accordancewith the method of IEC 60890 ifcertain conditions are fulfilled).

Conclusion

The new s tanda rd I EC 61439introduces important modifications in

comparison with the current standardIEC 60439 on low voltage switchgearand controlgear assemblies.

The structure of the new standardis clearer with a general part andproduct-specific parts. New definitionshave been written (e.g. originalmanu fac tu re r and a s semb l ymanufacturer). New compulsorycharacteristics must be specified (e.g.rated current of the assembly).

A new design veri fied assembly

concept has been specified. Thisnew concept completely discards thecategories TTA and PTTA, and thecompliance of an assembly can nownot only be verified by means of tests,but also with alternative methods:calculation/measurement and designrules.

The new standard is more precise,eradicating the grey areas containedin the prev ious s tandard . Theresponsibilities for an assembly areclearly defined, making the job of eachactor on the electrical market easiernowadays.

Contact Kovilan Chinnathambi,ABB South Africa, Tel 010 202-5097,[email protected]

vector march2013 new

Documents