Study on the Closing Protection Accounting for Breakers Asynchronous Closure

摘要

While a faults at the terminal of a line, the reflection of travelling wave is complex and the polarity of forward and backward current travelling wave may be different. In this condition, the fault location results of faulted lines and fault-free lines are same. Therefore, the protections based on polarity comparison and travelling wave fault location will mal-operate. According to the theory of travelling wave reflection and refraction, if the transmission line is fault-free, the forward travelling wave will be reflected only at the terminal of lines, and the reflect coefficient of current travelling wave is -1. Whereas the forward travelling wave will be reflected at the fault points when switching onto faulted line, and the reflect coefficient of current travelling wave is not equal to -1 whether the faults at the middle or at the terminal of lines. Based on the theory described above, a new closing protection is presented. The principle of proposed protection can ensure that the relays will operate correctly in any case, and the results of tests show that this method is reliable and effective.