含分布式电源的小电阻接地方式配电网单相接地故障分析

摘要

The distributed generator (DG) with different grounding modes will affect the characteristics of single-phase earth fault current.For a low resistance grounded distribution network,the grounding mode selection of DG is rather flexible and its influence on earth fault current is particularly complicated.Based on a low resistance grounded distribution network,a single-phase earth fault analysis model of distribution network containing rotary DG is established.Earth fault point current,sequence fault current and three phase fault current are analyzed respectively when DG adopts different grounding modes.Research results show that DG with the non-grounding mode has little influence on the characteristics of earth fault current and that when DG adopts the direct grounding mode or low resistance grounding mode,fault current will obviously increase or decrease, even reaching several hundred amperes from nil,which will affect the performance of existing earth fault protection and three-phase over-current protection.Research results can provide theoretical basis to configurations of earth fault protection and the neutral grounding mode selection of DG in low resistance grounded distribution network containing DG.%不同接地方式分布式电源(DG)并网将影响系统单相接地故障电流特征,对于小电阻接地方式配电网,DG 接地方式选择较为灵活,对接地故障电流的影响尤为复杂。针对小电阻接地方式配电网,建立了旋转型 DG 并网后的接地故障分析模型,分析了并网 DG 采用不同接地方式时接地故障点电流、线路三相故障电流与线路正序、负序、零序电流的特征。结果表明,不接地方式 DG 对接地故障电流基本无影响；但 DG 采用直接接地、小电阻接地方式时,各故障电流将明显增大或减小,甚至从无到数百安培,将会影响系统原有接地保护与三相保护性能。研究成果可为含 DG 小电阻接地方式配电网的保护配置与 DG 接地方式选择提供理论依据。