基于不平衡过电压动态抑制的谐振接地配电网单相接地故障保护新方法

现有配电网单相接地故障保护技术在高阻接地故障时无法可靠启动,选相与选线结果易受三相不对称的影响。针对这一问题,提出了基于不平衡过电压动态抑制的谐振接地配电网单相接地故障保护新方法。在三相不平衡过电压动态抑制的基础上,分析了故障前后注入电流与馈线零序电流特征。根据故障发生后注入电流变化量特点构建了接地故障动态感知判据,利用注入电流变化量的相角与幅值分别进行故障相识别与过渡电阻计算,通过比较各馈线零序电流变化量有效值进行故障选线。通过PSCAD/EMTDC仿真软件对所提方法进行验证,结果表明所提方法能够准确识别高阻接地故障,选相与选线结果不受三相不平衡与系统对地电容大小影响。

A new method of single-phase grounding fault protection for a resonant grounding distribution network based on unbalanced overvoltage dynamic suppression

The existing single-phase grounding fault protection method for distribution network cannot be reliably started when a high resistance grounding fault occurs. The results of fault phase selection and fault line selection are greatly affected by three-phase imbalance. To solve the above problem, a new method of single-phase grounding fault protection for a resonant grounding distribution network based on unbalanced overvoltage dynamic suppression is proposed. Based on the dynamic suppression of a three-phase unbalanced overvoltage, the characteristics of injection current and feeder zero sequence current before and after the phase-to-ground fault are analyzed. Given the characteristics of the injection current variation, the dynamic perception criterion of grounding fault is constructed. The fault phase selection and the transition resistance calculation are carried out by adopting the phase and root-mean-square value of the variation respectively and the fault line selection is carried out by comparing the amplitude of the zero-sequence current variation for each feeder. The PSCAD/EMTDC simulation results show that the proposed method can be started accurately for a high resistance ground fault, and the results of phase selection and line selection are not affected by the three-phase imbalance and the capacitance to ground. This work is supported by the Key Program of the National Natural Science Foundation of China (No. 51737002 and No. 51807012).