灵活接地系统中配电网接地保护的适应性分析

Analysis on Adaptability of Grounding Protection for Distribution Network in Flexible Grounded System

目前,灵活接地(消弧线圈并联小电阻接地)系统的接地保护多沿用小电阻接地系统的定时限零序过电流保护,仍存在高阻接地故障时保护灵敏度不足等问题,应用已有的配电网高阻接地保护方法作为后备保护是较合理的解决方案。对灵活接地系统单相接地故障时并联小电阻投入前后各电气量特征进行了分析。首先给出了灵活接地系统中接地保护所面临的问题,进一步对定时限零序过电流保护、零序功率方向保护、反时限零序电流保护等配电网接地保护方法在灵活接地方式下的适应性进行分析,给出提高保护性能的思路。

At present, the grounding protection of flexible grounded(grounded via arc-suppression coil and low resistor in parallel)systems mostly uses the definite-time zero-sequence overcurrent protection of low-resistance grounded systems. There are still some problems such as insufficient protection sensitivity in the case of high-resistance grounding fault. It is a reasonable solution to use the existing high-resistance grounding protection methods of distribution network as backup protection. The characteristics of each electrical quantity before and after connecting parallel small resistor in the case of single-phase grounding fault in flexible grounded system are analyzed. First, the problems faced by grounding protection in flexible grounded systems are given. The adaptability of distribution network grounding protection methods such as definite-time zero-sequence overcurrent protection, zerosequence power direction protection and inverse-time zero-sequence current protection in the flexible grounded mode is further analyzed, and the ideas to improve the protection performance are given.