发电机机端PT熔断器慢熔引起断线的故障检测方法研究

Detection Method for PT Disconnection Caused by High-voltage Fuse Melting Fault at Generator Terminal

为解决发电机组机端PT(电压互感器)一次熔断器慢熔不能被PT断线判据所检测的问题,对目前基于电压平衡式原理的PT断线检测方法进行改进,提出了一种基于一次熔断器电流、励磁电压突变量、零序电压及其二次谐波电压含有故障特征量的PT断线判别方法。改进后的判据可同时适用于PT一次侧和二次侧断线的检测,能有效避免因熔断器慢熔而导致机组误强励和匝间保护动作。

Melting fuse of PT （potential transformer） at generator terminal cannot be detected by current PT breaking criterion. Therefore, the existing PT breaking detection method based on balancing voltage is improved, and a method based on fuse current, excitation voltage mutation, zero-sequence voltage and its second harmonic voltage content as fault characteristic quantity is proposed. The improved criterion can be applied to the detection of the primary and secondary sides of PT breaking and it can effectively avoid faulty forced excitation and inter-turn protection due to melting fuse.