张北柔直电网金属回线故障监测研究

±500 kV张北柔直电网金属回线正常时无压,有单回、双回同杆并架2种线路形式,在单、双回线连接处波阻抗存在不连续问题,常规方法难以满足金属回线故障监测的需求。文中分析了张北柔直电网金属回线的波阻抗及行波折反射特点,提出了基于差模时域反射法的故障监测系统方案和波形比较分析方法,通过施加差模量脉冲信号实现故障监测,通过波形比较法消除线路波阻抗不连续引起的行波反射,并凸显故障点特征。仿真和现场试验表明,该系统及方法能适应张北柔直电网金属回线的工况,可以克服线路波阻抗不连续的问题,故障监测具有较高的可靠性和灵敏度,测距精度优于300 m。

Fault monitoring research of the metallic return line in Zhangbei VSC-HVDC grid

The metallic return lines of ±500 kV Zhangbei VSC-HVDC grid have no voltage during normal situation, and there are two kinds of line forms, including single-loop line and double-loop line. At the connection point of single-loop line and double-loop lines, the wave impedance is discontinuous, thus traditional methods are not suitable for the fault monitoring of the metallic return lines. The wave impedance and traveling wave characteristics are analyzed, and a fault monitoring system and waveform comparison analysis method are presented, which are based on differential mode Time Domain Reflection (TDR) method. The system applies differential mode pulse to monitor the fault, and uses waveform comparison method to eliminate the wave reflection caused by inherent impedance discontinuity of the line and highlight the fault characteristics. The simulation and field tests show that the system and method can adapt to the operating condition and wave impedance discontinuity of the metallic return lines of Zhangbei VSC-HVDC grid. The method has high reliability and sensitivity for fault monitoring, and the location accuracy is better than 300 m.