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Fault Current Limiter application

Fault Current Limiter application

Fault Current Limiter application

(OP)
Hello

I'm looking for reference and opinion about Fault current limiter.

Question Is there any papers or reference that allow to calculate, to compute, to quantify peak short-circuit reduced by a current limiter on all the load side assemblies?

Context :
Arc-Flash, short-circuit and coordination study.
CSA, IEEE, ANSI zone. (Canada)
Installation details : The factory is powered throught two 2000kVA 25kV/600V 4.1% Xmer parallely connected.
It feeds a main switchgear. The main protection is provide by a 4000A breaker with Westinghouse Amptector 1 trip unit. Short-circuit rating at 85kA.
It feeds two circuit. Protection device in each are short-circuit rated at 50kA. Each are combined with current limiters rated 200kA
One circuit feeds a secondary distribution switchgear. The derivations protection device short-circuit rating are not higher than 22kA.
Issue: I statuated that the secondary distribution protection device are under rated for short-circuit. My chief disagree. My point is that current limiters benefits are restricted to the limits of the assembly. In this case, the main switchgear cells. This is how it is viewed according by the Buff Book and a IEAI arcticle about the 2005 NEC. That a current limiting device connected line side allow the protective device to share the current limiter rating if that series-combination had been tested with approved method (UL).
My colleagues argument is that a current limiter effectively reduce the current default and thus the default is lowered for all the load side and for all the assembly. They used as reference many recent papers and new current limiters application. Althought I agree with the logic, my answer to the reference is to ask about the context. For some it ends the application is limit to an assembly. For other papers, I can't statuated on them.

My wish : I agree with my colleagues about the presumed impact of the current limiters. I'm confront with the angle of the published standards. If I look at it as an inspector, I stay on my position. If I follow my colleagues, I'm looking for a way to calculated those reduced by current limiters short-circuit peak levels.
    

Danny Garant, ing.jr
Groupe Stavibel Inc.
www.stavibel.qc.ca
 

RE: Fault Current Limiter application

In my opinion The Secondary Distribution Switchgear has to be rated for more than 22 kA and tested for its rated Short-circuit current.
If you doubt the Manufacturer test you may invite an UL assistant during the test. The cables have to be calculated and chosen accordingly .The cable accessories have their rated current and have to be tested prior delivery.
Some time the current limiter could be damaged. If the damage will be between turns then this could reduce the limiter reactance and increase the short-circuit current at Secondary Distribution Switchgear level. You may ask from the limiter Manufacturer if this could happened and how much the reactance would decrease.
 

RE: Fault Current Limiter application

Morquea:
I agree with your own assessment.

RE: Fault Current Limiter application

It must be a tested combination.  Fault impedance during a fault is not constant and the impedance of the circuit breaker can have a big impact on the fault current.  

The old "up over down" method has long been discredited.   

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