A fast full-line tripping distance protection method for HVDC transmission line

Though distance protection has been successfully used for AC transmission line, there is no practical application of it for HVDC transmission line. For distance protection, it is essential to measure accurately at the zone boundary to distinguish internal fault from external correctly, and high measurement accuracy at any part of the full line is unnecessary. Besides, HVDC transmission line is generally connected with smoothing reactor at two ends and it can be regarded as the operating boundary of distance protection. Considering these features, a fast full-line tripping distance protection method for HVDC transmission line is introduced in this paper. Based on distributed parameter model, the voltage and current at the end-point are calculated accurately using those at the relay point. After that, the line between the end-point and fault point is simplified as lumped parameter RL model and the fault distance is obtained with differential equations. In this way, high calculation accuracy at the zone boundary is attained and which contributes greatly to the improvement of protection performance. Simulation results show that this method is capable of protecting the whole line with high rapidity, and can be used as primary protection for HVDC transmission.