电流互感器拖尾电流对断路器失灵保护的影响

Impact of Tail Current of CT on Breaker Failure Protection

为了探讨电流互感器(current transformer,CT)拖尾电流的特征及其对继电保护设备的影响,基于理论分析和实际系统中CT电流拖尾的波形对CT电流拖尾现象进行分析,探讨了该现象对断路器失灵保护的影响。实际波形分析表明,CT拖尾电流的大小和持续时间有可能达到一定的量值,如果失灵保护算法设置不当或者保护定值整定不当,有可能影响失灵保护的正确动作。建议在保护逻辑计算前,应先通过软件算法、滤波等方法消除其对失灵电流判据带来的不利影响;另外,拖尾电流呈现指数衰减的特征,适当的保护动作定值和延时整定可有效消除拖尾电流造成的失灵保护误动作等。

For discussion on characteristics of tail current of current transformer （CT） and the impact on relay protection e- quipment, the paper analyzes current tailing of CT on the basis of theoretical analysis and waveform of current tailing in real system and discusses impact of this phenomenon on breaker failure protection. The analysis on the waveform indicates that the tail current and duration may reach a value of quantity, which may influence correct operation for failure protection if failure protection algorithm is improperly set or the protection setting is inappropriate. It is suggested that negative influence on criteria for fault current should be eliminated by software algorithm, filtering and etc~ besides, there appears the attenuating index of tail current, and appropriate protection setting value and delayed setting can get rid of misoperation of failure protection resulted from tail current.