马莲台电厂1号、2号机组主变比率差动保护动作分析

The action analysis on the main transformer ratio differential protection device in Maliantai Power Plant

针对马莲台电厂1号、2号机组主变比率差动保护在区外连续多次故障的动作行为,通过理论分析,得出结论:马莲台电厂1号、2号机组在连续2次区外故障冲击后,尤其是在第1次出现故障电流时,对侧330 kV徐家庄徐铝I线断路器故障跳开,主变电流互感器(CT)有剩磁,且在线路保护重合闸750 ms动作后,对侧断路器又重合于永久性故障,此时的故障电流与2种CT剩磁衰减的时间不一致,导致2种CT感应到的电流不一致,且三相差流中的谐波含量很低,造成差流,导致主变比率差动保护动作。通过仿真实验对结论进行验证,并根据实际情况提出了相应的整改措施。

Aiming at the main transformer ratio differential protection device many times continuous actions happened outside the zone in Unit 1 and Unit 2 of Maliantai Power Plant,through theoretical analysis,draws the conclusion： after two times continuous faults impact happened outside the zone in Unit 1 and Unit 2 of Maliantai Power Plant,especially when the fault current appeared for the first time,the line opposite side breaker brings on the trip fault in Xulv No.1 bus bar of 330 kV Xujiazhang substation,the current transformer（CT） of main transformer has remanent magnetism,after the line protection reclose for 750 ms,the line opposite side breaker reclose for permanent fault,the fault current differs with remanent magnetism of the two kinds of CT in attenuation time,brings on the induced current of two kinds of CT disagree,and that the contents of harmonic wave in three-phase differential current are very low,leads to the main transformer ratio differential protection device action.Through the simulation test proves the conclusion,and puts forward the relevant solutions according to the practical situation.