不接地系统同名相两点接地故障工频特征及选线

Power Frequency Characteristics and Line Selection under Two Point Grounding Faults Occurring in Same Phase in Isolated Neutral System

针对不接地系统偶发两出线相继接地故障处理难题,利用故障前后工频电气量信息,提出了一种适应于不接地系统同名相两点接地故障的选线方法。通过建立不接地系统同名相两点接地故障复合序网,推导出母线零序电压、接地点故障电流、各出线零序电流和无功功率等工频电气量随两个接地点过渡电阻的变化规律。在此基础上,分析了原有选线方法的适应性问题,并提出了基于两阶段无功功率方向的选线方法。最后,通过仿真验证了同名相两点接地故障特征与所提方法的可行性。

Aimed at the difficult problem in dealing with the consecutive grounding faults of two outgoing lines in an isolated neutral system,based on the information about the power frequency electrical quantity before and after fault,a line selection method suitable for two point grounding faults occurring in the same phase in the isolated neutral system is proposed.The composite sequence network under the two point grounding faults occurring in the same phase in the isolated neutral system is established,and the changes in power frequency electrical quantities(e.g.,zero-sequence bus voltage,fault current at the grounding point,zero-sequence current of each outgoing line,and reactive power)with the transition resistance at two grounding points are deduced.On this basis,the adaptability of the original line selection method is analyzed,and a novel line selection method based on the two-stage reactive power direction is proposed.Finally,the feasibility of characteristics under two point grounding faults occurring in the same phase and the proposed method is verified through simulations.