Transient fault identification method for bipolar short-circuit fault on MMC-HVDC overhead lines based on hybrid HVDC breaker

A bipolar short-circuit transient fault identification method for overhead transmission lines in modular multi-level converter-based high voltage direct current (MMC-HVDC) grid based on the hybrid HVDC breaker is proposed. The circuit breakers on both sides of the positive and negative overhead transmission lines will trip after a bipolar short-circuit fault in the MMC-HVDC grid. In order to identify whether the fault is a transient fault, the isolating switch of the DC breaker on one line side is reclosed first, and the voltage change on this line side in the case of transient and permanent faults is analysed. By comparing the electrical characteristics of the voltage on the line side under transient and permanent faults, a transient fault identification method is proposed, and the calculation method of the setting value of the criterion is obtained. Finally, by building the MMC-HVDC system model for simulation in power systems computer aided design, the accuracy and effectiveness of the proposed method for transient fault identification are verified.