Research On The Fault Line Selection Method For 10kV Cables In Substations Using Traveling Waves

There are many scholars study on the problem of Non-effectively earthed system grounding line selection, but they did not find a perfect solution from now on. With the progress of the socio-economic and technology, overhead lines in distribution lines replaced by cable lines is the inevitable trend of urban development, and the cable structure is more complex than the overhead lines, line selection problem is much harder. Therefore, this paper proposes a new method for cable outlet grounding line selection based on traveling wave.The main work is as follows:1. A simple analysis on traveling wave, including its generation process and the process of refraction and reflection in the lines, and on this basis, analyzed on the zero modal components of the initial transient current traveling wave, and analyzed the characteristics and properties of the fault traveling wave.2.Analyzed and compared the structure of power cables,and analyzed the kinds of grounding cable metal sheath, summarized the metal sheath grounding in three cases,and three kinds of grounding cable metal sheath were carried out modeling and simulation.3. According to the actual operation, different cable metal sheath grounding and different positions of single-phase ground fault were simulated by using PSCAD, and consider the impact of the transition resistance, analyzed the impact on transient traveling wave when cable single.phase ground fault in different circumstances, summed up the impact on line selection under the influence of different circumstances transient traveling wave similarities. The simulation results showed that different cable metal sheath grounding will influence the transient traveling wave, but no matter the cable line metal sheath grounding in which kind, when a single.phase ground fault, the polarity of the faulted phase current and zero sequence current initial traveling wave is always opponent. Different faulting positions or transition resistance has no impact on the current traveling wave polarity, but they will affect the magnitude of the initial transient current.4. Through the study of characteristics of traveling wave, and present two new method for 10 kV substation cable outlet line selection, one for the substation with three.phase CT, and another method is only for the substation with two.phase CT. According to the different situation of the cable line, you can choose a different method for line selection, and verify the two methods are accurate and reliable by simulating the 10 kV substation cable outlet circuit model.