具备故障选极能力的高压直流输电线路差动保护新原理

A Novel Differential Protection Scheme With Fault Line Selection Capability for HVDC Transmission Line

为解决传统高压直流输电线路差动保护无法快速响应区内故障的难题,该文提出一种具备故障选极能力的新型差动保护方案。直流线路两端测量电压、电流经过合适截止频率的低通滤波器处理后,沿线电压可近似视为线性分布。利用线性分布电压计算沿线分布电容电流并对其补偿后,提出一种新型直流线路差动保护方案;进一步降低滤波器截止频率,分布电容电流将减小至可被忽略,因而可通过比较滤波后两极差流选出故障极。采用云广±800kV高压直流输电系统仿真模型对保护新原理进行验证,大量仿真结果表明,在不同故障情况下,新保护方案均能快速、准确地区分区内外故障并选出故障极,并且在高阻接地故障时仍具有较高的灵敏度。

In order to solve the problem that the conventional differential protection for high voltage direct current（HVDC） transmission lines can＇t respond to internal faults quickly, a novel differential protection scheme was proposed in this paper. After voltage and current signals at both line ends are processed by the same low-pass filter the cut-off frequency of which is low enough, then the voltage distribution along the line can be regarded as linear distribution. The distributed capacitive current can be calculated by integrating the linear distributed voltage. After compensating for this current, the new differential criterion can be implemented. If the cut-off frequency is set lower, the distributed capacitive current can be ignored. In this case, the fault line can be selected by comparing the filtered differential current of both lines. A ±800 kV Yun-Guang HVDC transmission system was built to test the performance of the new protection scheme. Comprehensive simulation results show that the proposed method not only can detect internal faults and select the fault lines correctly and quickly, but also can respond to internal faults with high ground resistance.