基于不平衡电容注入的配电网小电流接地故障定位方法

Small Current Earth Fault Location Method for Distribution Network Based on Unbalanced Capacitance Injection

为解决配电网小电流接地故障定位问题,分析了配电网小电流接地故障下母线电压异常特性,提出了一种配电网小电流接地故障甄别方法,并给出了具体步骤和公式;分析了不平衡电容负荷注入下的配电网小电流接地电流分布,通过不平衡电容注入前后故障相故障点前的稳态电流变化与故障点后及非故障相的稳态电流变化的不同,将小电流接地定位问题转换为稳态电流变化问题。同时给出了不平衡电容电流等值支路图和详细计算公式,以及故障点上游故障相电流近似计算公式及相量图;通过配电管理系统(DMS)主站对不平衡电容负荷的控制,提出了基于不平衡电容注入的小电流接地故障定位思想,并给出了详细步骤和具体判定规则。仿真实例验证了本文所述方法针对永久性接地故障或持续时间较长的间歇性接地故障具有较好的判定适应性。

In order to solve the problem of single-phase-to-earth fault location in non-solid earthed distribution, the abnormal characteristics of bus voltage under the non-solid earthed distribution fault are analyzed. A method of identifying single-phase-to-earth fault is proposed, and concrete steps and formulas are given. The power flow trend of the distribution network with unbalanced capacitance injection is analyzed in the case of the non-solid earthed fault. When the unbalanced capacitance is injected, the steady- state current change upstream of the fault point in the fault phase is different from the steady-state current change downstream of the fault point, and the steady-state current change with the non-fauh phase is also different. Based on the above analysis, the non-solid earthed fault location problem is transformed into the steady-state current comparison problem. The equivalent circuit diagram of unbalanced capacitance current and the detailed calculation formula are given, and the approximate calculation formula and phasor diagram of the fault phase current are given. By controlling the unbalanced capacitance with distribution management system （DMS）, the method of locating the non-solid earthed distribution fault based on the unbalanced capacitance injection is proposed, and detailed steps and specific rules are given. The simulation results show that the proposed method has good judgment adaptability to permanent non-solid earthed fault and intermittent non-solid earthed fault with longer duration.