基于三次谐波电流的并列运行发电机定子单相接地保护

针对中小型水电站并列运行的多台发电机,提出一种具有选择性的发电机定子单相接地保护方法,测量发电机中性点侧和机端侧各相的三次谐波电流,计算定子绕组对地泄漏电流三次谐波分量的相间差,检测故障发电机,实现选择性定子接地保护.理论分析和EMTP仿真结果表明,该保护方法具有良好的选择性,能有效检测中性点侧及机端侧故障,具有鲁棒性强、精度高等优点.

Stator winding ground faults protection with the third harmonic current for multi-generator systems

Most small or medium waterpower generation stations are Multi-Generator-Systems(MGS) with more than one generator directly connecting a bus.A novel selectivity protection for generator stator grounding faults in the MGS is proposed in this paper.The third harmonic currents of each phase are measured in generator neutral points and generator terminals respectively.The third harmonic leaking current differences between phases from the stator to earth are calculated.The fault phase and the ground fault generator with the current difference larger than its threshold are thus detected,and the selectivity protection scheme is also presented.Theory analysis and EMTP simulation results show that the protection can detect the ground fault generator with selectivity,it can detect the faults on or near the generator neutral point and the generator terminal with high precision.