中性点不接地系统对距离保护的影响分析

Influence analysis of ungrounded neutral system on distance protection

距离保护受电力系统运行方式和结构变化的影响较小,保护范围相对稳定,在电力系统输电线路的继电保护中得到广泛应用。主要阐述了中性点不接地系统对距离保护的影响,首先从中性点不接地系统距离保护的基本原理出发,分析正序方向元件的判别直接影响距离保护的动作,然后对不接地系统的故障特点进行分析,并结合距离保护继电器的四边形特性,提出了一种闭锁正序电压方向元件判别的改进距离保护方案,最终通过实时数字仿真仪(RTDS)的仿真试验验证本方案的正确性。

Operation mode and structural changes of power systems have little influence on distance protection whose protection range is relatively stable.It is widely used in the relay protection of power transmission lines.The influence of the ungrounded neutral system on the distance protection is mainly described.Firstly,based on the basic principle of the distance protection of the ungrounded neutral system,it is found out that the discrimination of positive sequence component directly affects the action of distance protection,and then the failure of the ungrounded system.The characteristics of ungrounded system faults are analyzed,and combined with the quadrilateral characteristics of the distance protection relay,an improved distance protection scheme for blocking the discrimination of positive-sequence voltage direction component is proposed.Finally,the correctness of the scheme is verified by the simulation test of the real-time digital simulator(RTDS).