直流配电系统故障特征及对继电保护的影响

Fault characteristics of DC distribution system and its influence on protective relaying

分析了采用单极接地方式的双端直流配电系统中直流侧单极接地故障特征,将故障过程分为直流电容放电、自然换向至稳态两个阶段,并基于DIgSILENT/PowerFactory搭建双端直流配电系统模型进行了仿真分析.通过理论分析故障回路特性并结合仿真结果,总结出线路越长、滤波电抗器越大、电源内阻越大,越容易引起交流侧保护误动的规律.在交直流配电网交流侧进行保护整定时,为避免保护误动,可靠系数选取应尽量大一些.

In this paper,the features of pole-to-ground fault on the DC side are analyzed in the double-terminal DC distribution system which adopts the pole-to-ground mode.As for the fault process,it is divided into two stages:the DC capacitor discharging stage and the natural commutation to the steady state.In order to simulate the fault process,a double-terminal DC distribution system is built based on DIgSILENT/PowerFactory.Based on the theoretical analysis of fault circuit and simulation results,several conclusions are obtained:the longer the line is,the greater the filtering reactor is,and the larger the internal resistance of the power supply is,the higher the rate of protection malfunction is.Therefore,in order to avoid protection malfunction,the reliability coefficient should be selected as large as possible when configuring the protection settings on the AC side.