±800 kV宾金直流接地极线路电流不平衡异常分析

Analysis on Abnormal Unbalanced Current of ±800 kV Binjin DC Earthed Electrode Line

接地极线路是直流输电系统的重要组成部分,其安全稳定运行对整个系统的可靠性至关重要。然而,近年来国内接地极线路多次发生故障,成为薄弱环节。2016年4月16日±800 kV宾金直流输电工程的极Ⅱ线路遭受雷击后绝缘击穿。极Ⅱ线路在直流控保的作用下全压再启动两次成功。在极Ⅱ线路第2次再启动过程中,接地极引线不平衡保护动作。通过故障录波分析和登塔检查,发现宜宾换流站接地极线路一侧导线绝缘在极Ⅱ线路接地故障后发生过电压击穿,在重启过程中持续流过直流续流。基于此次故障,详细分析了目前接地极线路多次故障的原因,提出通过改进接地极建立绝缘配合解决此类问题。

Safe and stable operation of electrode line is important to the reliability of UHVDC transmission system. However, electrode line fails repeatedly in recent years, which made it a weak part. On April 16, 2016, the pole Ⅱ line of Ⅰ 800 kV UHVDC Binjin transmission project failed because of lightning stroke. Under the control of protection system, pole Ⅱ restarted successfully in the second time. During the restart procedure, unbalanced protection of electrode line was triggered. Fault records were analyzed and fault tower was checked. It is found that one of the two electrode lines was breakdown under overvoltage. DC on the fault place continued during the whole restart procedure. Based on this fault analysis, the causes of most electrode line faults are analyzed in detail, and solutions based on insulation coordination are presented.