Distance Protection Method for AC Transmission Lines Considering VSC Impact

Abstract

The integration of Voltage Source Converter (VSC) based flexible DC systems leads to the maloperation of traditional distance protection, threatening grid stability. This paper reveals how converter current-limiting and decoupling controls cause fault current phase shifts under phase-to-phase faults, forcing the operating angle to migrate and triggering protection maloperation. An adaptive distance protection method integrating transient information is proposed. A fast directional element utilizes initial transient components before control interference to achieve ultra-fast directional discrimination. An adaptive adjustment angle dynamically modifies the impedance operating boundary. PSCAD simulations verify that this method mitigates VSC controlled-source interference, demonstrating performance and adaptability.