difreence between earth fault an short circuit level

[far243]

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??


regards ,

 

[Bung]

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.

Bung
Life is non-linear...

 

[far243]

for example in my project SC level of main busbar 33Kv is 31.5 KA and earth fault level is 450 A??!!! I have confused!

 

[alehman]

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?

 

[far243]

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 ???

 

[alehman]

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.