Research On Some Problems Of Stator Ground Fault Protection With Outside Sources

With the generator capacity increasing,the requirement of the stator earth-fault protection is becoming more and more high for the generator.The injection stator earth fault protection will be widely used for its predominant highlighted.In order to solve the issues in practical applications of this protection,the theoretical analysis and simulation test were carried out in this paper.The first,this paper analyzed the principle of the 20Hz injection protection.The protection logic was presented based on the admittance criterion and power frequency zero sequence voltage criterion.The setting principles were studied.The performance of this protection was verified by simulation test.In order to shorten the data window of the stator ground fault protection with 20 Hz voltage injection,the least square algorithm was used to extract the 20 Hz component instead of the full-wave Fourier algorithm in this paper.The research contents of this paper also including the precision of the admittance criterion with the generators grounded via Petersen-coil,the influence of the stator capacity increasing, the protection measures during startup and shutdown,the influence of the components parameters on the 20Hz band-pass filter properties.The simulation tests verified the analysis. The improvement measures were presented.