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 Post subject: Incident Energy - 30A Disconnect
PostPosted: Wed Nov 21, 2018 12:05 pm 

Joined: Wed Nov 21, 2018 12:00 pm
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Has anyone come across incident energy over 8 cal for a 30A 480V disconnect?


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 Post subject: Re: Incident Energy - 30A Disconnect
PostPosted: Thu Nov 22, 2018 7:53 am 
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Swizzle wrote:
Has anyone come across incident energy over 8 cal for a 30A 480V disconnect?


It can happen.

Since the arc duration is usually defined by how long it takes an upstream overcurrent device to clear the arcing current, a larger incident energy is often due to a longer clearing time from that device.

What device is upstream? Do you have a clearing time from the study result?


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 Post subject: Re: Incident Energy - 30A Disconnect
PostPosted: Fri Nov 23, 2018 10:12 am 
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Easier than that if it's fed by one big transformer like say a 1000 kva.


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 Post subject: Re: Incident Energy - 30A Disconnect
PostPosted: Mon Nov 26, 2018 8:50 am 
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we have it happen quite often in our Quarries. When you go 1500 feet of cable to a pump down in the pit the short circuit current goes low and the trip time on the Circuit breaker becomes long.


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 Post subject: Re: Incident Energy - 30A Disconnect
PostPosted: Tue Nov 27, 2018 12:57 pm 
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Typically happens at test switches or switches for power factor correction (or PQ monitoring) that are tapped off the main bus of 480 V switchgear. Why those switches are installed the way they are is another topic. ;) As many have pointed out, it's what's upstream that matters.


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 Post subject: Re: Incident Energy - 30A Disconnect
PostPosted: Wed Dec 05, 2018 8:50 pm 
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The question would be more interesting if we discussed the possibility of exceeding 1.2 cal down stream from a 30A or 60A fuse and or breaker. For those that use arc flash software try and get the incident energy above 1.2 cal down stream from a Mersen A6K200R or Buss KTSR200.


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 Post subject: Re: Incident Energy - 30A Disconnect
PostPosted: Mon Dec 10, 2018 6:58 pm 
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Flash wrote:
The question would be more interesting if we discussed the possibility of exceeding 1.2 cal down stream from a 30A or 60A fuse and or breaker. For those that use arc flash software try and get the incident energy above 1.2 cal down stream from a Mersen A6K200R or Buss KTSR200.


That seems to be the case regardless of the make or model of device once you get down below about 150%.


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