Fault Calculations

[steve66]

I have a Excel spreadsheet that I use to do fault calculations. The POCO normally gives me a 3 phase transformer size, and the impedence of the transformer. However, this time they are pole mounting 3 transformers in a delta-wye configuration. If each transformer is 50KVA, and 2.2%Z, how do I convert that to a single transformer size and Z?

Do I enter 150KVA at 2.2% Z? Or should I enter 50 KVA at 2.2%? Or 150KVA at 6.6% Z?

Steve

 

[LarryFine]

Do I enter 150KVA at 2.2% Z? Or should I enter 50 KVA at 2.2%? Or 150KVA at 6.6% Z?

Yes, no, and no.

 

[ron]

And to further expand ...
150kVA @ 2.2%

 

[infinity]

I'm a little rusty at fault calculations. Does anyone have a link to a good article regarding fault calc's?

 

[al hildenbrand]

Trevor,

Over the years, I've made good use of the Bussman SPD Electrical Protection Handbook. This link is to a 3 megabyte PDF file.

 

[infinity]

Trevor,

Over the years, I've made good use of the Bussman SPD Electrical Protection Handbook. This link is to a 3 megabyte PDF file.

Thanks for the link. I dug through some old books that I had and found a Buss SPD based on the 1984 NEC. Tells you why I'm a little rusty.:smile:

 

[al hildenbrand]

I've still got my 1984 SPD. . .must be why I'm rusty, too.

 

[mikehughes8]

I've still got my 1984 SPD. . .must be why I'm rusty, too.

I don't have the 1984 SPD....then again I can't imagine why I would be doing short-circuit calculations at age 9:grin:

 

[al hildenbrand]

I don't have the 1984 SPD....

And I'll just bet you're not rusty at short circuit analysis. :smile:
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No, wait. This is a logical fallacy.
:wink: