发电机励磁绕组一点接地保护改进方案研究

Study on improvement plans of ping-pong type ground protection for generator field winding

针对乒乓式一点接地保护无法解决励磁电压变化对保护精度和灵敏度的影响问题,采用了在励磁回路的双端注入一个直流电压,并将开关切换回路接在该电压两端的改进方案,给出了该方案的原理和动作判据,并对接地电阻的计算方法进行分析。仿真实验结果表明改进方案能满足实际运行需要的精度和灵敏度。

Current ping-pong type field winding ground protections cannot detect the accuracy and sensitivity of winding affected by voltage change. To remedy this defect, this paper uses an improved scheme for ping-pong type field winding ground protection, i.e. a DC voltage is injected into field winding and switching-over circuit is connected in parallel with the injected voltage. Principle of this improving scheme and the criterion for protection action are given, and several problems such as the calculation method of grounding resistance are analyzed. Simulation results show that the accuracy and sensitivity of the improved scheme can meet the requirement of practical operation.