一种基于拖尾电流识别的失灵保护实现

摘要

When the fault current is successfully interrupted by the CB open, it always contains a subsidence current in the secondary side of the current transformer (CT), and this current extends the reset time of the breaker failure current, which may lead to breaker failure protection's maloperation. Now, it used to increase the delay time of breaker failure protection to avoid maloperation. In this way, when the CB is real failure, breaker failure protection will take much more time to open the CB, and this does not meet the fast feature of protection relay. In this paper, based on difference characteristic between subsidence current and other current, it presents a method to identify subsidence current fast. In this method, it effectively avoids breaker failure protection's maloperation by the recognition of subsidence current without increase the time delay. In the last, the RTDS is used to test the breaker failure protection integrated with the subsidence current blocking function. The result shows that the improved breaker failure protection takes good operation behavior in both fault current condition and subsidence current condition. No maloperation on the subsidence current condition, no non-action on the fault current condition.%当断路器跳开后,电流互感器(CT)二次侧产生的拖尾电流延长了失灵电流元件的返回时间,有可能造成断路器失灵保护误动作.目前工程上多采用增加失灵保护动作延时来躲避拖尾电流影响,但这会增加断路器真正失灵时失灵保护的动作时间,偏离了继电保护的快速性特点.基于拖尾电流和非拖尾电流在波形特点上的差异性,对拖尾电流进行快速有效的识别.一经识别出拖尾电流,立即闭锁失灵保护,消除拖尾电流对失灵保护产生的不利影响.利用实时数字仿真系统(RTDS)对基于拖尾电流闭锁的失灵保护进行仿真实验.实验结果表明,基于拖尾电流闭锁的失灵保护能准确识别断路器跳开后的拖尾电流,在故障电流条件下不拒动,在拖尾电流条件下不误动,动作行为可靠.