小电阻接地有源配电网比幅比相式接地保护

Grounding Fault Protection Based on Amplitude and Phase Comparison for Low-resistance Grounding Active Distribution Network

针对小电阻接地有源配电网单相接地短路,提出一种零序电流比幅比相式保护方案。根据逆变型分布式电源控制策略、并网接地方式及约束条件,建立逆变型分布式电源并网等效模型。考虑多逆变型分布式电源分散接入的网络结构、不同出线长度和过渡电阻等场景,分析有源配电网单相接地短路特征,并考虑现场应用情况和测量误差,提出利用各出线及中性线零序电流的高灵敏度接地保护判据。保护按躲过正常运行时不平衡电流启动,整定值低,灵敏度高,不受分布式电源灵活投切影响,过渡电阻高达1000Ω时依然可靠。仿真结果证明了所提接地保护方案的有效性。

Aimed at the single-phase grounding fault of low-resistance grounding active distribution network,a protec⁃tion scheme based on amplitude and phase comparison of zero-sequence currents is proposed.According to the control strategy for inverter-interfaced distributed generator(IIDG),grid-connected grounding mode and constraints,the equivalent model of grid-connected IIDG is established.The characteristics of single-phase grounding fault in active dis⁃tribution network are analyzed considering the network structure with multiple IIDGs connected,different feeder lengths and the existence of transition resistor.Then,a high-sensitivity grounding fault protection criteria based on the zero-sequence currents of each feeder and neutral line is proposed,which also considers field application and measure⁃ment errors.The protection is started while one of the zero-sequence currents is greater than the unbalanced current in normal operation,so the setting value is low and the sensitivity is high.In addition,it is not influenced by flexible DGs switching and still reliable when the transition resistance reaches 1000Ω.Simulation results show the effectiveness of the proposed grounding fault protection scheme.