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 Post subject: Utility data, 40% rule etc.....
PostPosted: Fri Oct 31, 2014 12:07 pm 

Joined: Mon Jul 21, 2014 11:53 am
Posts: 2
All,

I've been away from arc flash analysis for a good little while, but am having the opportunity to get re-engaged with it. I seem to recall, and I can't put my finger on where, but a general rule regarding utility data. I want to say that it's an IEEE 1584 topic, but I may be mis-remembering.

What I remember is the assertion that in cases where utility specifics can't be found that 40% of the infinite bus calculation could be applied. As I said, I can't remember where I heard/read that tidbit, and again I may be foggy on it, but that 40% figure sticks out in my mind for whatever reason. If anyone out there knows what I'm referring to, and more importantly can point me in the direction of where I can substantiate this point, I would greatly appreciate it. On the other side of the coin, if I'm all wet and what's true is something differen, by all means throw that in here too.

Thank you in advance.


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 Post subject: Re: Utility data, 40% rule etc.....
PostPosted: Fri Oct 31, 2014 12:41 pm 
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There was a IEEE paper published in IEEE Transactions On Industry Applications, V46, No. 5, Sept/Oct 2010, titled Impact of Available Fault Current Variations on Arc-Flash Calculations by I. Balasubramanian & A. Graham, which discussed when utility fault current is unavailable.

The conclusion of the paper seemed to be that 50% of the maximum secondary fault current would provide worst case incident energy in the absence of actual utility data.

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 Post subject: Re: Utility data, 40% rule etc.....
PostPosted: Fri Oct 31, 2014 12:52 pm 

Joined: Mon Jul 21, 2014 11:53 am
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I just found the paper you mentioned online, downloaded a copy and was reading it when you posted your reply. I found the mention of this method, and the paper even says that the 1584 recommends minimum and maximum, but the paper doesn't specify where the 50% and 100% figures are referenced in the 1584, or even if they are. Any further guidance anyone has would help me out.

Thanks again.


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 Post subject: Re: Utility data, 40% rule etc.....
PostPosted: Fri Oct 31, 2014 1:13 pm 
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I think IEEE is referring to obtaining the min and max available fault current from the utility. I have had mixed success with that in that some will only give one value and say the maximum should be considered an infinite bus.

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