160MVA transformer will be able to pass about 1600MVA through it in case of a fault on 132kV side, assuming the 220kV side to be infinite bus and the transformer %Z of 10%.
Vice versa also is true.
The fault MVA you mentioned, I guess includes contributions from other grid transformers, Grid connected generators and transmission lines.
I would expect the transformer to only have an impedance %Z of 4% maximum for a transformer of this size. Is the 10%Z read from the nameplate or just an inferred value? When we tested transformers of that size and found a 10% impedance for copper and iron loss it would be rejected as having too high a loss.
One can only suppose that the fault level at 220kV is 18000 MVA and this is the source side, with greater power.
At the 132 kV level, a single 160MVA transfo would have to have only 2% impedance to get 8000 MVA N.B. 160/8000 = 0.02 per unit or 0.02 x 100 = 2% impedance on 160 MVA base level. Transfo impedances are usually given as % on their rating plates.
This is not practical, since transfo of this size will be about 10% impedance - so several of the 160 MVA transfo, about 5 must be in parallel.
Or maybe there are generators feeding in at 132 kV.
Without a "single line" diagram of the whole system, with a rating and impedance for each transfo & generator and transmission line, there can be no explanation of the fault MVA calculation.
Yes, there are generators feeding at 132 kV. We intend to keep it as pooling substation, where power is brought from powerhouses at 132 kV, step them up and feed in a 220 kV transmission line.
Around 168 MW of power is brought for which we intend to keep 53.33*6 single phase autotransformers.
With your original statement of a 160 MVA total transfo capacity & addition that groups are made up of individual single phase transfo of 53.33 MVA each, I suppose your original transfo were 9 x 53.33 MVA, that is 160 MVA per phase, but 480 MVA total.
So reduction to 6 transfo means 2 x 53.3 = 106 MVA per phase, 318 MVA total for 168 MW at ?? power factor [0.85 P.F. would be 198 MVA].
However, to compute the fault level for short at 220 kV level, you need to sum the current from other sources at 220kV with the current from the transfos.
To get the current from 132 kV you need the impedance of each generator/step-up transfo set - for that you need MVA/impedance for generator and transfo in each set.
Similarly, for S/C fault current at 132 kV. The transfer through the transformer will not be the same for 220 kV as for 132 kV short circuit.
Fault MVA
Re: Fault mva
