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Cadet

Circuits of ASSEMBLIES which are exempted from the verification of the short-circuit withstand strength

Could you please indicate in what cases circuits of Assemblies are exempted from the verification of the short-circuit withstand strength according to IEC 61439-1 and how we can apply this rule with limitor circuit-breaker ?

1 REPLY 1

Re: Circuits of ASSEMBLIES which are exempted from the verification of the short-circuit withstand strength

Elina

 

The Clause 10.11.2 of IEC 61439-1 exempt from doing a short circuit test in two cases:

10.11.2 Circuits of ASSEMBLIES which are exempted from the verification of the short-circuit withstand strength

A verification of the short-circuit withstand strength is not required for the following:

1) ASSEMBLIES having a rated short-time withstand current (see 5.3.5) or rated conditional short-circuit current (see 5.3.6) not exceeding 10 kA r.m.s.

2) ASSEMBLIES protected by current-limiting devices having a cut-off current not exceeding 17 kA at the maximum allowable prospective short-circuit current at the terminals of the incoming circuit of the ASSEMBLY.

 

According to the second bullet, it’s possible to use the limitation characteristics of compact NSX & NSXm to avoid a short-circuit test for prospective short-circuit current that will be limited below 17kApeak

 

NSX NSXm Limitation curves.PNG

 

So the following values can be keep as a rule:

 

 

Incomer circuit-breaker

Icu (kA)

@415V

Maximum presumed short-circuit current in kArms where IEC 61439 sort-circuit withstand test is not required

(Clause 10.11.2 -2) with specified incomer : 415Vac 50Hz

Compact NSXm 160 E

16kA

16kA

Compact NSXm 160 B

25kA

25kA

Compact NSXm 160 F

36kA

36kA

Compact NSXm 160 N

50kA

50kA

Compact NSX100-160 B

25kA

25kA

Compact NSX100-160 F

36kA

36kA

Compact NSX250 B

25kA

25kA

Compact NSX250 F

36kA

30kA

Compact NSX400 F

36kA

15kA

Compact NSX630 F

36kA

12kA

 

 

Mathieu GUILLOT

LV Power circuit-breakers