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3 phase xfmr fault calculation

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insprian

Electrical
Joined
Jan 11, 2003
Messages
1
Location
CA
help...I can't remember the calaculation for fault current at the secondary of a 3 phase transformer.
 
Try the following simplified short cut method:

Isc = Ifl/Zt

Were:
Ifl=KVAtransf/1.73xKV (Transf full load current)
Zt = Z%/100 (Transformer impedance)

Be ware that this method consider an infinte source on the primary side and do not include motor short circuit contribution from the secondary side.

If you should be interested in more detail calc. consuly the IEEE Std 141 and 142.
 
Suggestion: Reference:
1. ANSI/IEEE Std 242-2001 Buff Book
 

Administrative aside: There’s that upstart IEEE Draft Std P551 Calculating AC Short-Circuit Currents in Industrial and Commercial Power Systems An excerpt of the text is: standards.ieee.org/colorbooks/sampler/VioletBook.pdf
 
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