Fault current through generator cables
Fault current through generator cables
(OP)
If you have 4 generators in parallel each capable of supplying 10kA fault current, could you able the argument:-
With all generators running and for a fault on the cables of one generator, would the maximum fault current seen by that cable be 3 x 10kA, rather than 4 x 10kA? (obviously approx. 4 x 10kA flows into the fault with 3 parts being supplied by 3 sets and 1 part being supplied by the faulted generator). This argument is being put forward to me as part of a protection study which includes I2t protection of the cables.
All sounds good in terms of Kirchoffs but I've always worked on the basis that the switchboards and cables would all be rated on maximum fault level.
With all generators running and for a fault on the cables of one generator, would the maximum fault current seen by that cable be 3 x 10kA, rather than 4 x 10kA? (obviously approx. 4 x 10kA flows into the fault with 3 parts being supplied by 3 sets and 1 part being supplied by the faulted generator). This argument is being put forward to me as part of a protection study which includes I2t protection of the cables.
All sounds good in terms of Kirchoffs but I've always worked on the basis that the switchboards and cables would all be rated on maximum fault level.






RE: Fault current through generator cables
If this is an isolated system from the utility and the cable runs is short, probably the dampening may be neglected. There is a possibility that the fault is larger than the 4 generators contribution if there are large motor load.
RE: Fault current through generator cables
RE: Fault current through generator cables
Technically the argument you stated can be made and is correct "only if" there is no motor contribution and the generators are not paralleled with the utility source. It is also only true for the cable between the generator and the paralleling swithgear.
RE: Fault current through generator cables
Obviously, if you use maximum bus fault current, you will always be safe.
The analysis software we use actually caculates the maximum fault current through each breaker (in either direction) and uses that value to compare to the equipment rating.
RE: Fault current through generator cables
GO PLACIDLY, AMIDST THE NOISE AND HASTE-Desiderata