基于零序电流-电压微分特性的小电阻接地系统单相接地故障保护原理

中性点经小电阻接地的系统适用于电缆居多的配电网,然而由于配网馈线所处环境复杂,造成了现有的基于零序电流阶段式的保护方案无法满足单相高阻接地故障快速、灵敏地检测需求.针对此现象,文中通过分析故障线路和非故障线路零序电流-零序电压的关系,寻求两者不同的故障特征,由此提出一种基于线路零序电流与母线零序电压微分值波形相似度的保护算法.所提保护算法通过对线路的零序电流和零序电压进行采样,并根据线路零序电流与母线零序电压微分值的波形相似度来判断线路是否发生单相接地故障,可大大提高单相高阻接地故障保护的灵敏度.通过PSCAD仿真测试验证了该算法的有效性.

Grounding faults protection in low-resistance grounded systems based on zero-sequence current-voltage differential characteristics

The neutral point through the low-resistance grounding system is applicable to the distribution network with majority of cables. However, due to the complicated environment of the distribution feeder, single-phase high-impedance ground faults cannot be detected rapidly and sensitively by existing zero-sequence overcurrent protection. To solve this problem, this paper analyzes the relationship between the zero-sequence current and the zero-sequence voltage of faulty line and healthy line, and seeks different fault characteristics between them. A protection algorithm based on the waveform similarity between the line zero-sequence current and the bus zero-sequence voltage differential is proposed. Sampling the zero-sequence current and the zero-sequence voltage of the line, the proposed method judge whether a single-phase ground fault occurs on the line by comparing the waveform similarity between the line zero-sequence current and the bus zero-sequence voltage differential value, which can greatly improve the sensitivity of ground fault protection. Finally, the effectiveness of the algorithm is verified by PSCAD simulation.