Influence Analysis of Secondary Circuit Disconnection of Potential Transformer on Protection

This article analyzes the secondary disconnection of potential transformer,and it is found out that the secondary voltage amplitude and phase will vary during the disconnection and that the interphase protection will be influenced differently by the different connection modes of secondary load.The terminal voltage characteristics of the added protection device during the disconnection are obtained by the analysis of value and phase.Through the study of action behavior of interphase directional element and impedance element of 90° connection,it can be concluded that both of the protection false action and malfunction probably appear,which should be taken into consideration.