Could someone please explain the difference between Prospective short circuit current and prospective earth fault current when they are measured or calculated in domestic installations. Many thanks in advance Gary
Is that like 'ol beardsleys Syrup ?
Simple answer Short circuit current is calculated by the serving utility. Calculated from the serving transformers they use. Some call it let through.. It is basically how much current can be generated with bolted fault. That is why some residential services need 22k AIC rate breakers. Standard is 10k. aic = asymmetrical instantaneous current.
As for what the ...... your talking about with the "prospective earth fault current" I have not a clue.
Care to narrow the subject down?
at 11Kv it is reduced to 250 Mva
but is also measured as 13,800 amps for 3 seconds. this is the rating of all the ESi switchgear at 11Kv in the UK ( minimum as there are now 350Mva switches )
this is calculated through the impedance of the transformers they use. 33/11 Kv the impedance is (?) 23% and at 11/.415 Kv it is 4.8%
you can do the maths from there?
J
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