【摘要】 变压器的差动保护因受到铁芯饱和引起的虚假差流的影响,其正确动作率较低,动作速度也较慢。研究表明,由于变压器的铁芯进入饱和需要一定的时间,励磁涌流引起的虚假差流突变量出现时刻要比相电压突变量的出现时刻滞后一个时间差。基于该现象,提出了一种基于相电压突变量和差流突变量出现时差的变压器差动保护新判据,设计了合适的滤波器保证变化出现时刻的快速准确捕捉,并运用该判据对各种变压器故障状态的响应和逻辑判断进行了分析。基于EMTDC进行了大量的仿真试验,实验结果验证了该判据的可行性和有效性。更多还原

【Abstract】 The differential protection for power transformers features less ratio of proper actuation and slow response,because it severely suffers from false differential current caused by core saturation.Investigation shows that transformer core saturation needs certain time,so emergence time of abrupt differential current of inrush is lager than the time of abrupt change phase voltage.And it can be utilized to distinguish internal faults from external faults.A new criterion for transformer differential protections based on abovementioned time difference is proposed.Furthermore,a novel filter algorithm is designed in order to ensure fast and accurate detecting,effective noise-repressing as well as high-speed response during the instant of variation emergence.The EMTDC-based simulation,which covers various fault situations,is analyzed,and the test results confirm that the criterion can effectively prevent the differential protection from mal-operating and guarantee the high-speed response to the internal fault as well.更多还原