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

[Elina]

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 ?

[MathieuGuillot · Accepted solution]

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

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