线路接地故障对源端变电站接地系统的影响

The Influence of Line Ground Fault on the Source-Side Grounding System of Substation

输电线路接地故障的短路电流回流将在源端变电站接地网产生较高的暂态电位差和内部转移电位差,可能引发接地系统问题,对接地网均压、电气完整性和绝缘提出较高的要求。本文以接地运行变压器引发转移电位差而导致油色谱装置输油管放电烧蚀漏油、变电站内部参考电位引发转移电位差而导致火花放电草地起火,以及暂态电位升高风险点引发接地系统故障等典型事件为案例,对暂态地电位升不均匀性分布进行计算分析,指出线路故障期间的源端变电站网内暂态转移电位差可达到数千伏的水平,具备触发火花放电或绝缘击穿的条件,给站内绝缘薄弱点带来运行风险,提出对站内转移电位危害的高风险点加强与主接地网连接的电气导通性和做好隔离的有针对性的防范措施。

The short-circuit current backflow of the the transmission line grounding fault will generate high transient potential difference and internal transfer potential difference in the grounding grid of the source substation,which may cause problems in the grounding system,and put forward higher requirements for the voltage equalization,electrical integrity and insulation of the grounding grid.In this paper,the typical accidents are discussed,such as that the grounded operation transformer causes the transfer potential difference,which leads to the discharge,ablation and oil leakage of the oil pipeline of the oil chromatography unit;the transfer potential difference caused by the internal reference potential of the substation,which leads to the spark discharge and the grass to catch fire;and the transient potential rise risk point causes the grounding system fault.The non-uniform distribution of transient ground potential rise is calculated and analyzed.And it is pointed out that the transient transfer potential difference in the source substation network during the line fault may reach to thousand of volts,which has the conditions to trigger spark discharge or insulation breakdown,bringing operation risks to the weak points of insulation in the station.The preventive measures are put forward to strengthen the electrical continuity and isolation of the high-risk points of transfer potential hazards in the station.