三相变压器剩磁在升压过程中对断路器闪络保护的影响分析及对策

Influence of Residual Magnetism in Three-phase Transformer on Breakage Flashover Protection and Precautionary Measures

介绍了某发电厂发电机在升压过程中,发变组断路器闪络保护动作造成一条500 k V线路跳闸的事故调查分析过程。通过分析,发现造成该事故的原因是该电厂在进行变压器直流电阻测试后,未采取去磁处理,主变铁心中产生剩磁,导致机组在升压过程中产生负序电流,满足断路器闪络保护动作条件,造成此次500 k V线路跳闸事故。针对该问题深入分析了负序电流的产生及剩磁对发变组保护的影响,并提出了相应的预防措施。

This paper analyzes accident reason about trip of breakage flashover protection during the stepping up from zero for a generator transformer unit,which caused the trip of a 500 kV transmission line. The reason is the residual magnetism in the transformer iron core left by measuring the DC resistance without demagnetization treatment,which caused negative sequence current during the stepping up from zero and induced the trip of breakage flashover protec- switch-in ance with appearance of negative sequence current is discussed with consideration of different three-phase initial angles and residual magnetism direction. In addition, the corresponding precautionary measures in accord- the cause of the accident are put forward.