what is the difrence between short circut level and earth fault in electrical system, i can calculate SC level in a system,but how can i calculate erath fualt level??
an 'earth fault' is just a special case of 'short circuit'. A short circuit can be phase - neutral, phas e- phase, phase - phase to neutral etc - any combination of the 3 phases (and neutral where there is one). Neutral and earth may or may not be the same thing.
As Bung suggested, neutral and earth may not be connected directly. Low earth fault current occurs if the system neutral is connected to earth through a high impedance. Is this the case for your system?
Tanks alehman
yes,in my case an impedance exist. but what is the advantage of using this ampedance ?
and you mean for reaching to 450A i should 31.5KA/R ???
The impedance is usually installed to reduce damage when an earth fault occurs. I=V/Z. Neglecting the impedance of your circuit and the source, Zg = 33,000 / sqrt(3) / 450.
If this is a real system, perhaps you should consult a licensed engineer to perform this analysis correctly.