检修的共用接地极线路分流电流实测分析

Analysis on Shunt Current Measured of Sharing Earth Electrode Lines Maintained in HVDC System

共用接地极在土地占用、建设投资等方面具有很好的经济性和使用价值。但共用接地极在检修和运行过程中可能会存在一些问题,特别是在接地极线路检修时,运行直流系统可能会出现不平衡运行或单极大地回线运行方式;检修接地极线路会有电流流过,对检修人员的安全造成威胁。为充分掌握检修的接地极线路电流分流水平,对3个共用接地极的6个换流站的接地极线路分别进行试验测量。通过统计比较的方法对测量数据进行分析,得到了接地极线路和换流变中性点的分流百分比以及分流电流的变化趋势;同时分析得出影响检修接地极线路分流电流的因素主要包括:挂接的检修接地的位置、接地极电阻、入地电流水平等。依据实测数据计算分析得到的结果,为共用接地极的直流系统检修时的运行方式安排提供了工程数据参考,对保障检修人员的安全具有重要意义。

In many respects, such as land use and construction investment, sharing earth electrode has perfect advantages in economy and in use value. But there may be some problems in maintenance and operation. Specially, when earth electrode line of a HVDC system is maintaining, another HVDC system will probably run in unbalance operation or monopole ground return mode. So, grounding current may be produced and personal security of maintainers may be kept in a threat. In order to prevent known security threats and fully grasp shunt current level of earth electrode line, currents of earth electrode line were respectively measured for 6 converter stations of 3 sharing earth electrodes. Through measurements analysis by the method of statistical comparison, current distribution percentages for earth electrode line and converter transformer neutral and trend of shunt current were obtained. Based on study on distribution law of current of earth electrode line, main factors of influencing shunt current of earth electrode line include maintenance grounding location, earth electrode resistance and grounding current provided by running HVDC system. According to analysis result, engineering reference is provided for maintenance and operation arrangement of some HVDC systems with sharing earth electrode. Meanwhile, it is important significance for personal security of maintainers.