Protection scheme for turn-to-turn faults of magnetically controlled shunt reactor based on waveform similarity comparison

Magnetically controlled shunt reactor (MCSR) is one of the key elements applied in EHV/UHV transmission systems for reactive power compensation and overvoltage suppression. Due to its complex core structure and winding connection mode, the accurate identification of turn-to-turn faults in MCSRs becomes challenging. In addition, the existing protection scheme of MCSR is liable to mal-operate under energization due to the similar features of internal fault. In order to solve this problem, a novel protection scheme is proposed by analyzing the waveform similarity and frequency spectrum of three-phase control winding currents. The waveform similarity is measured by the Euclidean distance (ED) between any two of three-phase control winding currents after phase shift. The EDs approach to zero under normal operation but increase under internal faults or pre-excited energization. Internal faults can be further distinguished from the pre-excited energization according to frequency spectrum differences of control winding currents. Finally, simulations in MATLAB/Simulink verify the proposed algorithm, which helps to promote the application of MCSRs in engineering.