A novel protection scheme against turn-to-turn fault of MCSR based on equivalent magnetizing inductance

Abstract

Magnetically controlled shunt reactor (MCSR) is one of the key equipments applied in EHV/UHV transmission systems for reactive power compensation and voltage control. Due to its special core structure and winding connection mode, the probability of occurrence of turn-to-turn faults is high and the detection is still a challenge. The existing protection schemes have problems of low reliability and sensitivity—the maloperation may happen when MCSR is pre-excited energized, and the fault with less short-circuited turns is difficult to detect. To solve these problems, a novel protection scheme based on equivalent magnetizing inductance (EMI) is proposed. The definition and calculation of EMIs of MCSR are introduced. Based on the parameters of 750 kV MCSR applied in Northwest China, a simulation model in MATLAB/Simulink is built. The variation of EMIs in different scenarios is analyzed through theoretical and simulation and an EMI-based protection is proposed through calculating unbalance level of EMIs of limb p and q (ULEMI) and average values of EMIs. The novel protection scheme provides an effective method for turn-to-turn fault detection and will not be affected by energization, which is of great significance for practical engineering application.