Background.
Two (2) identical transformer 90MVA 132/33kV, Z%=14.2, OLTC +6 and -9 with 1.67% step. These transformer connected at 132kV grid supply.
1 transformer (TxA) tap position at 16 (145.2kV) and the other (TxB) tap position at 5 (121kV) due to controller malfunction(broken communication between master-slave). Both transformer are connected to the same 33kV bus to distribution system, both operate in parallel.
Impact - Low Power factor 0.3 is recorded at grid supply point. Oil temperature increase.
Known Issue - Circulating current between transformer due to tap mismatch.
Question -
1-How circulating current between transformer cause system to absorb/import more MVAR from grid?
2- What aspect of transformer that absorb the MVAR? (eddy current, iron core, copper losses)?
Increased circulating primaries current flowing from primary the inductive loading, reflects in secondary caused reduction of load power factor of secondary sides…..
transformer is in the no load case or with less load,
and is about a net reactive load
the circulation current can increase the magnetic flows and increase inductivity
and transformer be more inductive.
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