An Enhanced Double-Ended Current Accumulation Protection Method Considering the Effects of Mutual Inductance for HVDC Transmission Lines

Traditional high-voltage direct current (HVDC) transmission line protection is susceptible to issues such as false tripping due to inter-polar mutual inductance and non-fault pole protection. This paper analyzes the current characteristics, taking into account the influence of inter-polar mutual inductance, and further verifies it using the equivalent network of the DC system through Faraday’s law of electromagnetic induction. It is discovered that when there is a single-polar fault at the end of the line, the induced current in the non-fault pole line is maximized. In the case of a bipolar fault, the fault current exceeds that of a single-pole fault at the same position. On the basis of consideration, a pole selection criterion is established by comparing the amplitudes of the accumulated sudden change currents. Additionally, a bipolar fault protection criterion is developed using the accumulated sudden change currents at both ends. The inclusion of the opposite-end quantity effectively addresses transient faults. While maintaining the original main protection criterion, the pole selection criterion and bipolar fault protection criterion form a double-ended current accumulation protection system through an OR gate logic. Simulation demonstrates that the dual-end current accumulation protection accurately identifies the faulty pole in the case of a single-polar fault, exhibits a fast response time in the case of a bipolar fault, and is unaffected by different power transmission levels.