Novel protection scheme against turn-to-turn fault of magnetically controlled shunt reactor based on equivalent leakage inductance

Abstract

Magnetically controlled shunt reactors (MCSRs) are key elements of extra-high voltage/ultra-high voltage (EHV/UHV) transmission systems for reactive power compensation and overvoltage suppression. Owing to the special core structure and winding connection mode, there is a complex electromagnetic relationship between faulty and non-faulty windings, which makes it challenging to accurately identify a turn-to-turn fault, which is the most common type of MCSR fault. To overcome this problem, a novel protection scheme is proposed by combining a start-up criterion with a fault discrimination criterion. The start-up criterion is based on the fundamental component of the total control current (itc) and the fault discrimination criterion is based on the identification of the equivalent leakage inductance (ELI). Firstly, based on the equivalent circuit of the power, control, and compensation windings, the corresponding ELI identification model is derived and solved using the recursive least squares (RLS) method. Subsequently, a fault discrimination scheme is derived based on the difference among three-phase ELIs. Finally, the proposed protection scheme is verified through simulations in MATLAB/Simulink and experiments on a physical model. The proposed scheme overcomes the limited sensitivity and reliability of conventional protection methods and can locate faulty windings, which is of great significance for the promotion of MCSRs and their applications in engineering.