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 Post subject: Realistic maximum incident energy or theoretical maximum inc
PostPosted: Thu Mar 13, 2014 6:01 am 
Sparks Level

Joined: Fri Jan 03, 2014 6:57 am
Posts: 66
Location: the Netherlands
Hello guy’s,

I was wondering the following: Do you put the realistic maximum incident energy on the label or the theoretical maximum incident energy on the label?

Let me give you the situation;
There are 6 generators in parallel, 2 big engines that contribute to the short circuit current distributed over 2 main switchboards normally connected with a tie breaker.

Those engines are only online in 1 specific situation, in that same situation a maximum of 3 generators is online.

In the situation that all 6 generators are online those engines are always off.

Now to repeat the question with the example: for the label on a MSB cabinet do you put the realistic incident energy (6 generators on and some small motors online that are actually online at that time) OR the incident energy with 6 generators online and both the 2 large engines online?

Bear in mind that the word ‘theoretical’ is a bad choice off words but I could not think off another word. This is a bad choice because in reality it can happen that 6 generators are online and the 2 engines because there is nothing locking these engines when 6 generators are online nor is there anything blocking 3 generators coming online when those engines are online.

So it can happen but it’s like riding in your car when its not raining and then knowingly turn on you windscreen wipers, you just don't do itbecause it doesn’t do anything besides use energy.

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PostPosted: Thu Mar 13, 2014 7:50 am 
Arc Level

Joined: Mon Jan 18, 2010 11:35 am
Posts: 544
Location: Wisconsin
I have customers that label based on the anticipated operating conditions.

For example:
A data center does not perform maintenance while running on generators, so their labels are based on the utility, Their Work Practices program address the more 'dangerous' non-routine condition.

A different facility has a manual Main-Tie-Main closed transition transfer scheme, they have one set of labels based on the worst case condition (all breakers closed) and their Live Work Permit process allows them to select PPE, from the report, based on one source being locked out.

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PostPosted: Thu Mar 13, 2014 7:56 am 
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Joined: Tue Nov 12, 2013 6:31 am
Posts: 238
Location: Port Huron, Michigan
I would put the worst case scenario on the label. If that changes things significantly from what you would otherwise have calculated, I would possibly place multiple labels, with a detailed explanation included telling people what scenario(s) would trigger more stringent PPE requirements.

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