Analysis on strategies of suppressing secondary arc current in UHV system with controllable shunt reactors

To solve the contradiction between UHV transmission line's over-voltage limitation strategy and its reactive power compensation strategy, China plans to apply controllable shunt reactors in its UHV system. The paper briefly introduces the UHV power transmission system using controllable shunt reactors. The structure and basic operating principle of the controllable shunt reactors is described. Through analyzing the characteristic of controllable shun reactors and the mechanism of secondary arc current, two strategies are proposed to suppress secondary arc current in the system with controllable shunt reactors. Their applicability is analyzed by simulation on China's planned UHV transmission project with controllable shunt reactors. The result shows that, when the neutral point of the controllable shunt reactors connects to the ground through a fixed reactor, by switching the capacity of controllable shunt reactors to the maximum capacity when a single phase to ground fault happens, the secondary arc current can be suppressed effectively.