Method for Debugging the Polarity of the Mutual Inductor for 1,000 kV EHV Regulating and Compensating Transformer

For the polarity test of the CT for 1, 000kV ultra-high voltage(UHV) infrastructure projects, the polarity layout method and test program of a main transformer, etc. were discussed under 3/2 complete serial connection mode in an all-round manner. The protection of 1, 000kV bus difference, circuit breakers, lines and high resistance, the polarity of a metering device CT and the receiving method of a secondary circuit were discussed; and a reasonable point polarity method was provided before actual production. The polarity configuration of CTs at the low-voltage side of an ultra-high voltage transformer body bushing, common windings, a voltage regulation-compensation transformer, a house transformer and a main transformer, and the calculation logic of protective devices were studied. The effect of essential factors such as actual wring, equivalent impedance, etc. on polarity were analyzed, and the adverse factor of voltage regulation position was pointed out. When the polarity at the high-voltage side of the housing transformer was being studied, it is strongly interfered by electromagnetic coupling. The selection scheme of CT secondary circuit was studied according to the requirements of different ultra-high voltage protective devices, and the point polarity measures of the voltage regulation-compensation transformer were explored according to protection calculation logic. When the polarity of the main transformer and the auxiliary transformer for a compensation transformer were being tested, the cause of interference among three phases due to the Y/Δ wiring method at HV and low sides of the main transformer was mainly discussed.