If there are faults at the terminal of the lines, the reflection of traveling wave is complex and the polarity of forward and backward current traveling wave is different. Under this condition, the fault location results of faulted lines and fault-free lines are the same. Therefore, the protections based on polarity comparison and traveling wave fault location will mal-operate. According to the theory of traveling wave reflection and refraction, if a transmission line is fault-free, the forward traveling wave will be reflected only at the terminal of line and the reflect coefficient of current traveling wave is -1. Whereas the forward traveling wave will be reflected at the fault point when switching onto the faulted line, and the reflect coefficient of current traveling wave is not equal to -1 no matter whether the fault is at the middle or the terminal of the line. 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.
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Related Author
ZHANG Guangbin
SHU Banggui
SHU Hongchun
SI Dajun
XUE Yusheng
CHANG Kang
YU Chen
XUE Feng
Related Institution
Yunnan Grid Research Construction and Planning Center of Yunnan Power Grid Co., Ltd.
Faculty of Electric Power Engineering, Kunming University of Science and Technology
State Grid Electric Power Research Institute (NARI Group Corporation)
School of Electrical Engineering and Automation, Harbin Institute of Technology
State Key Laboratory of Power Transmission Equipment & System Security and New Technology(Chongqing University)