IEC61439-1 doesn't warrant for short circuit performance evaluation under the following conditions:
Assemblies protected by short circuit protective devices whose cut off current is not more than 17kA with prospective current set at the incoming terminals of the assembly under test.
Assemblies protected by frequency converters where the outputs are provided with electronic short-circuit protection that limits the cut-off current with in 17 kA,
Assemblies whose rated short-time withstand rating or rated conditional short-circuit current are not not more than 10 kA .
Control power circuits that are fed by control transformers whose rating doesn't exceed 10kVA for a rated secondary voltage of not less than 110v or of an 1.6 kVA transformer for a rated secondary voltage less than 110 V, and whose short-circuit impedance is not less than 4 %.
For further information on the topic, kindly refer to clause 10.11.2 under short circuit performance.
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Needs small clarifications in respect of the following...
Clause 10.10.2.3.7 a) Main bus-bars shall be tested separately.
In this case shall the main breaker to be taken in the circuit (or) shall we have to test only on HBB alone bypassing Main breaker ?
The test shall be carried out at the rated current. The test current shall pass through the full length of the bus bars. Q:Can this current be different from rated current of the Assembly?
Where the design of the assembly permits, and, to minimize the influence of the external test conductors on the temperature rise,the length of the main bus bar within the enclosure for the test shall be a minimum of 2 m and include a minimum of one joint when the bus bars are extendable. Q: Can the main bus bar length can be less than 2m due to design constraints.