Protection Configuration Scheme of Static Excitation System

Based on the available protection configuration schemes of generator-transformer unit and basic composition of static excitation system, this paper analyzes the disadvantages of protection configuration schemes of excitation system. It is concluded that the single phase grounding faults occurred in low voltage sides of excitation transformer can't be effectively protected by existing protection scheme and may cause improper operation of rotor grounding relay. Arms breaking and trigger pulse losing of controlled rectifier bridge can directly lead to the variation of amplitude and waveform of excitation voltage, which maybe result in improper operation of loss-of-excitation protection based on excitation voltage. Therefore, this paper suggests that the influence of excitation system faults on existing protection principles must be carefully studied and some measures must be taken to improve the performance of existing protection schemes.