基于故障相接地的配电网单相接地故障自动处理

针对中性点非有效接地配电网单相接地故障处理难题,提出一种基于故障相接地的配电网单相接地故障自动处理方案。自动化系统由变电站内的故障相接地熄弧选线装置和配置于馈线开关的故障相接地启动保护装置构成。通过采用故障相接地手段实现单相接地故障的可靠熄弧,利用故障相接地断开前后的零序电压和零序电流变化特征实现永久性单相接地故障选线、选段、隔离和健全区域供电恢复。通过对故障相接地断开前后系统零序电压和零序电流的变化规律分析,构造了基于故障相接地断开前后基波零序电流比值的单相接地选线和选段判据。讨论了单相接地故障处理启动判据、故障相接地断开时刻感知、故障相接地断开前中性点中电阻投入必要性等关键技术问题。结合实例对所提出的单相接地故障处理过程进行了说明,并开展了实验验证,结果表明了所提出方法的可行性和有效性。

Automatic Processing of Single-phase Grounding Fault in Distribution Network Based on Fault Phase Grounding

To solve the problem of single-phase grounding fault processing for neutral point non-effective grounding in distribution network, an automatic processing scheme for single-phase grounding faults in distribution network based on fault-phase grounding approach is proposed. The automation system consists of a fault-phase grounding arc-extinguishing line selection device in the substation and fault-phase grounding start-up protection devices deployed to the feeder switches. By adopting the fault-phase grounding method to achieve the reliable arc-extinguishing of single-phase grounding faults, the characteristics of zero-sequence voltage and zero-sequence current variations before and after the fault-phase grounding disconnection are used to achieve the line selection, location and isolation of permanent single-phase grounding fault and power restoration of sound district. By analyzing the variations of zero-sequence voltage and zero-sequence current of the system before and after the fault-phase grounding disconnection, a single-phase grounding line selection and location criterion based on the fundamental zero-sequence current ratio before and after the fault-phase grounding disconnection is constructed. The key technical problems, such as the start-up criterion for single-phase grounding fault processing, the detecting of the fault-phase grounding disconnection moment, and the necessity of throwing in a resistance to the neutral point before the fault-phase grounding disconnection are discussed in detail. Combined with an example, the proposed processing process for single-phase grounding fault is explained and experimental verification is carried out. The results show the feasibility and effectiveness of the proposed method