转子一点接地保护双重化配置研究

Dual-configuration of rotor one-point grounding protection

提出了转子一点接地保护双重化配置方案,保护配置由注入直流转子一点接地保护和注入交流转子一点接地保护构成。这2套保护可同时配合使用,也可以独立使用。阐述了2套保护的基本原理和计算接地电阻的方法。对所提保护方案的进行测试,测试结果表明:对于注入交流转子一点接地保护而言,当接地位置位于励磁绕组中间时,接地电阻测量误差较小,一般情况下,励磁绕组电感对保护接地电阻测量的影响可以忽略不计;接地电阻小于1 kΩ时,直流回路对于接地电阻测量的影响不大;当接地电阻大于1 kΩ时,需考虑直流回路电阻对接地电阻的补偿;注入交流转子一点接地保护受励磁绕组对地电容的影响较大,当接地电容大于5μF时,能准确测量小接地电阻;但是当接地电阻大于10 kΩ时,受保护装置AD分辨率影响,测量电阻不稳定,波动较大。可见,注入交流转子保护对小电阻接地的测量相对更为精确;注入直流转子保护对大电阻接地的测量更为稳定。

A dual-configuration scheme is proposed for rotor one-point grounding protection,which is composed of the rotor one-point grounding protection with DC-injection and the rotor one-point grounding protection with AC-injection. Each protection can operate independently or cooperatively with the other one. Its basic operating principle and the calculation of grounding resistance are introduced. The test results show that,for the rotor one-point grounding protection with AC-injection,the error of its grounding resistance measurement is small when the grounding point is located in the middle of excitation winding;the influence of excitation winding inductance on the measurement can normally be ignored;the influence of DC loop on the measurement is little when the grounding resistance is less than 1 kΩ,otherwise it should be compensated; the grounding capacitance of excitation winding has great influence on the measurement,and only the grounding resistance less than 10 kΩ can be accurately measured when the grounding capacitance is greater than 5 μF,otherwise it fluctuates obviously due to the AD resolution of protection. Conclusion ：the grounding resistance less than 10 kΩ can be more accurately measured by the rotor one-point grounding protection with AC-injection while the grounding resistance greater than 10 kΩ can be more stably measured by the rotor one-point grounding protection with DC-injection.