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 Post subject: Normal vs Emergency PowerPosted: Sun Jun 28, 2015 8:16 am

Joined: Mon Jun 09, 2014 9:19 am
Posts: 43
At all of our facilities we have stand by/ emergency generators with transfer switches tied into our electrical systems. When performing our arc flash analysis at our stations we have found that on Normal Power we usually have less than 4cal/cm^2 incident energy. On Emergency power we have greater than 12cal/cm^2. Several or our stations had greater than 25cal/cm^2 but we are replacing the breaker at the generator with current limiting breakers to lower the hazard down to less than 4cal/cm^2.
This is my question: I know that the labels are supposed to be worst case, but can I create a method within our company for our techs to wear a lower amount of PPE when working on or interacting with equipment that is on Normal Power, and then put the higher level of PPE on when working on or interacting with the equipment when on Emergency Power? All of our generators are very close to the electrical rooms, some are inside and others are outside. You hear the generators start and come on line at most locations but not all. I am curious to hear if anyone has had success with this at their locations.
We have had the thought of putting a flashing light into the center of our electrical rooms that is only on when the generator is running. The generator would only run about 2 or 3% of the time that stations are in operation, mainly when the monthly tests are being run.
Thanks!

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 Post subject: Re: Normal vs Emergency PowerPosted: Mon Jun 29, 2015 8:29 am
 Sparks Level

Joined: Mon Jun 07, 2010 9:40 am
Posts: 119
Realistically I would say, no.
Even in those subs where you can hear the generator start, doesn't mean you pay attention to the fact that it did.
Evenwith the flashing red light, how do you cover the situation, where you are in the "correct" PPE, but due to an issue else where, the generator starts. Now you are wearing the wrong PPE. [Actually you were always wearing the wrong PPE]

And for that matter just because you can see the flashing light when you enter the room,
doesn't mean you can see it when you are in the switchgear.

I think it is fairly clear, that if you want to be wearing the "normal power PPE", you have to make it impossible for the system to transfer you to emergency.

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 Post subject: Re: Normal vs Emergency PowerPosted: Mon Jun 29, 2015 9:15 am
 Sparks Level

Joined: Fri Apr 15, 2011 7:43 am
Posts: 177
I agree with JK. Depending the the breaker - is there a way to put a maintenance setting/switch in? We always use worst case because problems usually occur when things are different - such as when emergency generation is needed.

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