110 kV电阻接地系统零序方向电流保护的整定研究

中性点经合适阻值的电阻接地，能有效抑制单相接地故障造成的负荷侧电压暂降，明显提高供电质量。但中性点电阻的接入改变了系统的零序阻抗，导致零序电流、电压的大小和分布以及它们之间的相位差与中性点直接接地系统有很大的不同。通过对其零序电流电压特点的分析，推导出110 kV中性点经电阻接地系统零序电流保护的整定计算方法，修正了中性点经电阻接地系统零序方向元件的动作条件。据此对一个改造的110 kV系统进行了整定计算，并通过现场试验和试运行证明了其正确性。

Research on setting calculation of zero sequence directional overcurrent protection for 110 kV neutral point grounding via resistance system

An appropriate parameter of the grounding resistance at the neutral point can effectively suppress the load-side voltage sag caused by the single phase earth fault, and accordingly is favorable for the development of power quality. However the grounding resistance changes the zero sequence impedance of the system and will cause it fairly different from the directly grounded system in the value and distribution of the zero sequence current and voltage and in their phase difference. Through analyzing characteristics of the zero sequence current and voltage, this paper proposes a setting calculation of zero sequence current protection in 110 kV systems grounded via resistances at neutral points. And the operating condition of the zero sequence directional element is modified. For an enhanced 110 kV system, correctness of the proposed setting calculation is proved through field experiments and trial operation.