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| Calculation of Incident energy at secondary of transformer https://brainfiller.com/arcflashforum/viewtopic.php?f=4&t=632 |
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| Author: | beenthere [ Mon Aug 24, 2009 8:10 am ] |
| Post subject: | Calculation of Incident energy at secondary of transformer |
I have a 250 MCB as the primary protection which supplies a 225KVA, 5.27% Z, the transformer is 480 to 240. There is a secondary fused switch with 250V FRS 200A. I am questioning the incident energy on the secondary side between the bushing and the actual disconnect switch. I am assuming the 250 MCB will determine the incident energy. Any thoughts on calculating this value? Thnaks for reading my post. |
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| Author: | THE CABLE GUY [ Sat Sep 12, 2009 1:14 pm ] |
| Post subject: | |
A really rough estimate on the secondary and the load side of the fused switch could be as high as 85 inch AFB, 12 cal/sm2 @ 18inch CAT#3@18" assuming a SC of 8.6ka. With my generic data the secondary SC could last a long time before tripping the breaker on a HI trip setting. However, if you have a low trip level the game changes. I get a 6" AFB .03 cal/cm2 @18" CAT0 @18". The breaker type and trip data is very important in determining your actual energy levels. The other problem is your transformer inrush which I suspect will probably be the problem to overcome. I am guessing your trip level is going to be high because of that. |
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| Author: | beenthere [ Sun Sep 13, 2009 10:37 am ] |
| Post subject: | |
Thanks for the reply My details which were not many is at a plant I am going to in mid Ocotber. I plan to get more info I will post as I get it. |
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