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SKM Arc Flash Circuit Device Max Arcing Duration Reached
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Author:  cteoh2 [ Mon Jan 15, 2024 8:15 pm ]
Post subject:  SKM Arc Flash Circuit Device Max Arcing Duration Reached
I am new to SKM and I am I am puzzled with the condition as below:
I have a power circuit with main circuit breaker 4000A. The downstream have another 600A circuit breaker before go to the bus. I expect the circuit should be tripped with a lower IE compared to the main feeder. I check the TCC curve and AF analysis result, the fault current is 10kA. It should trip the 600A circuit breaker with delay time around 0.015 sec. But, the result given by SKM is 2 sec, which cause the IE jump up 32Cal/cm^2. SKM software only given warning "Max Arcing Duration Reached" but I dont know which setting cause this component not able operate. I emailed SKM, but so far no reply from them. Anyone can help?

I attached some information here. Please help. Thousand thanks.

Attachments:
Device Arcing Duration Reached.pdf [186.78 KiB]
Downloaded 880 times
Author:  mpparent [ Tue Jan 16, 2024 6:21 am ]
Post subject:  Re: SKM Arc Flash Circuit Device Max Arcing Duration Reached
Did you check the arcing fault current against your TCC? There is a difference between the available fault current vs. the arcing fault current the device will see.

Mike
Author:  bbaumer [ Tue Jan 16, 2024 8:02 am ]
Post subject:  Re: SKM Arc Flash Circuit Device Max Arcing Duration Reached
Mike is right but it looks like CH-01A LD/600 is in no man's land and the upstream device may be in short time. The reason the upstream 4000A main is picking it up quicker is because the upstream available fault current is much higher and into the instantaneous region of that breaker.

Attachment:
SKM question.jpg
SKM question.jpg [ 180.12 KiB | Viewed 4270 times ]
Author:  cteoh2 [ Tue Jan 16, 2024 5:50 pm ]
Post subject:  Re: SKM Arc Flash Circuit Device Max Arcing Duration Reached
Hi Mike and bbaumer,

Thanks for your reply to clear my doubt. It means the analysis use the device arcing fault current to determine the trip delay time. In my case is 7.11kA. The delay time is higher than 2 sec. SKM use Max Arcing Duration (2sec) for calculation. But, in real case, the upstream circuit breaker will trip first due to higher fault current.

Many thanks.
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