一种组合式原理的发电机转子接地保护建模及分析

摘要

This paper analyzes several generator rotor grounding protecting methods and the existed problems. Theoretic analysis shows that the measurement accuracy of the first grounding resistance is very important for the calculation of the second point grounding resistance. In this paper, a new combined principle for generator rotor grounding is presented from the practical debugging and operating experience of generator-transformer protection. The new principle measures and calculates three times for the rotor grounding resistance and position combining the ping-pong method and the injected square-wave method. Theoretical analysis and the MATLAB simulation results based on the ALSTOM unit model of Three Gorges prove that the reliability and accuracy of the rotor one-point grounding protection is improved compared with conventional single measurement methods. The sampling circuit can also be monitored at the meantime.%　　分析了在实际工程中几种的发电机转子接地保护及其存在的问题，通过计算第两点接地的阻值和位置，从理论上分析出一点接地阻值的测量准确性对于第二点接地阻值有重要的影响。根据几年来现场机组保护调试和投运的工程经验提出了一种新的组合式的转子接地计算方案，即将乒乓式和注入式原理相结合，对于转子接地阻值及位置三次独立的测量并综合计算。通过理论分析和以三峡ALSTOM机组为模型的Matlab仿真数据结果表明，和常规单一测量方式的转子接地保护相比较，组合式原理的保护能提高发电机一点接地的可靠性和准确性，同时也能起到监视采样回路的功能。