500kV主变低抗保护误动案例分析及解决策略提出

Case Analysis and Solution Proposal of Protection Misoperation of Low Voltage Shunt Reactor in 500kV Transformer

基于500kV主变低抗保护在启动过程中发生误动的案例,通过对低抗保护配置方式、动作条件及闭锁条件进行分析,结合电抗器动作时电流特性,总结该案例中低抗保护误动作的原因。针对CT异步饱和造成保护误动问题,提出一种基于并联电抗器首末端电流幅值特征及末端电流2次谐波为故障特征量的低抗保护动作策略,区分电抗器工作的正常态和故障态,可有效降低低抗保护的误动率。

Based on a misoperation case of low-voltage shunt reactor protection of a 500 kV transformer during its startup,the analysis and solution proposal are put forward in this paper.The protection configuration,operation condition and blocking conditionof this low-voltage shunt reactor are illustrated.Combining with the current characteristics of this reactor in action,the reason of mis-operation is summarized.Due to CT asynchronous saturation,the mis-operation may happen.Based on the characteristics of the current amplitude at the head and end of the shunt reactor and the second harmonic of the terminal current,which can be used as the fault features,the protection strategy of low-voltage shunt reactor is proposed to distinguish the normal state and fault state.It can reduce the mis-operation rate of protection of low-voltage shunt reactor effectively.