ABSTRACT This paper primarily investigates the patterns of overvoltage changes during an interruption of oil‐immersed iron‐core reactors by circuit breakers and their distribution along the axial winding of the reactor, which optimises the winding structure. A test platform was established to measure the frequency response curves of the reactor core. Based on the operating frequency parameters of a specific model of a 500 kV oil‐immersed iron‐core reactor, the variation of the reactor parameters with frequency was studied and a simulation model was constructed. A simulation model of the SF 6 circuit breaker was developed using the Fortran language and a three‐phase distributed parameter simulation circuit was constructed for the interruption of oil‐immersed iron‐core reactors by the SF 6 circuit breaker. The obtained amplitudes and types of overvoltages from the simulations were analysed to determine the patterns of overvoltage variation. Overvoltages of higher amplitude from various types were selected, their distribution on the axial winding of the reactor was analysed and the winding structure of the reactor was optimised to reduce the maximum distribution of interruption overvoltages. The results show that the overvoltages generated by the interruption of the oil‐immersed iron‐core reactor by the SF 6 circuit breaker are related to the chopping current and operation time lag of the breaker. The largest voltage drop occurs at the “internal shield‐continuous transition” along the axial winding of the reactor and adding a small amount of shielding wire at this position can effectively reduce the maximum distribution of overvoltages.
Nie et al. (Thu,) studied this question.