基于反行波差值的特高压直流线路纵联保护方案

纵差保护作为高压直流线路后备保护,需设置较长延时躲过区外故障时分布电容电流的影响。为提高纵联保护性能,提出一种基于反行波差值的纵联保护原理。区内故障时,远离故障侧的反行波与近故障侧的前行波不满足线路的传输函数;区外故障时,远离故障侧的反行波与近故障侧的前行波满足线路的传输函数。因此根据传输函数与近故障侧前行波计算远故障侧反行波,并将计算所得的反行波与实际反行波比较,识别区内、外故障。在PSCAD/EMTDC中对所提方案进行了验证,仿真结果表明,不同故障情况下保护方案均能快速、可靠地识别故障,并具有良好的耐受高阻能力。

A pilot protection scheme for UHVDC lines based on backward traveling-wave difference

As a backup protection for HVDC lines, the current differential protection needs long time delay to avoid the influence of distributed capacitor current under external faults. To improve the performance of pilot protection, a novel protection principle based on backward traveling wave difference is proposed. Under internal faults, the backward traveling wave at the side away from the fault point and the forward traveling wave at the side near the fault point will not satisfy the transmission function of the DC line. In the case of external faults, the backward traveling wave at the side away from the fault point and the forward traveling wave at the side near the fault point satisfy the transmission function of the DC line. Therefore, according to the transmission function and the forward traveling wave at the side near the fault point, the backward traveling wave at the side away from the fault point can be calculated to compare with the actual/sampled backward traveling wave to discriminate internal and external faults. The proposed principle is verified in PSCAD/EMTDC, and simulation results show that, it can identify the fault reliably and rapidly under different fault scenarios, while having better tolerance to high fault resistance. This work is supported by National Natural Science Foundation of China (No. 51877084), Natural Science Foundation of Hebei Province (No. E2018502063), and the Fundamental Research Funds for the Central Universities (No. 2017MS096).