Research On Travelling Wave Distance Protection On Transmission Lines

In order to increase the stability and transmission capacity of the HV line, fast operation is needed for line protection. Because of filtering, operation speed of traditional protection based on power frequency is not fast enough and also hard to improve. In the opposite, transient protection based on fault transient component can meet the operation speed demand. Thus more and more transient protection research has been carried out.The distance protection based on travelling wave is kind of transient protection. Its stability has nothing to do with transition resistance and system oscillations compared with traditional distance protection. But there are some problems occurred on travelling-wave-based distance protection, such as distance measuring inaccurate while fault occurred near the opposite bus bar and misoperation while fault is located outside the region. The main work of this paper is to solve these two problems. For the first problem, a method using polarity relationship of the initial and the second reverse traveling wave to identify inflection travelling wave from fault point is involved. For the second problem, a comparison between travelling time and time that calculated from the initial and second travelling wave is introduced. Meanwhile, simulation is carried out to prove these two theories.Although there is more and more research on transient protection, its stability needs further study. So at the end of this paper, the feasibility of the transient protection in digital sampling system and distance protection based on main frequency are briefly introduced.