Available MVA rating
Available MVA rating
(OP)
Gents,
Could you advise please if its normal to assume that parameters of positive phase sequence is equal to negative phase sequence at single line to ground fault? Is it possible to derive from positive and zero phase sequences reactive MVA ratings the source available MVA ? Grateful if you could show simple calcs.
Regards,
Danilo
Could you advise please if its normal to assume that parameters of positive phase sequence is equal to negative phase sequence at single line to ground fault? Is it possible to derive from positive and zero phase sequences reactive MVA ratings the source available MVA ? Grateful if you could show simple calcs.
Regards,
Danilo






RE: Available MVA rating
"Negative sequence components for overhead lines are always equal to the positive sequence components."
2) If with "available MVA" you meant "initial symmetrical three-phase short-circuit apparent power" then, in my opinion, you could derive from zero phase [single phase-to-ground fault] short-circuit current if you would know the positive and zero system impedance-considering negative sequence equal to positive sequence. But you have to check the rest of the circuit-transformers and generators. Usually if generators are far from the fault location the positive
and negative impedance are close.
3)For simple calculations see ABB above mentioned handbook [or IEC 60909-0 standard].
RE: Available MVA rating
A transmission system is largely interconnected so we don't see that difference when we deal with distribution faults, for example. I'm sure that's what 7anoter4 had in mind with his comments and I agree with his conclusion too.
RE: Available MVA rating