High Voltage Cable Fault Traveling Wave Based On Wavelet Transform Ranging Study

With the accelerating reconstruction of urban and rural power grids, the adoptive proportion of power cable in electricity transmission and distribution lines is also growing. For its unique advantages, such as no power transmission corridor, city beautified, high reliability, the application of power cable in engineering works has become an increasingly widespread. Especially, when the overhead lines can not be adopted or very difficult to achieve the power transmission, the high voltage power cable would become the primary choice. In addition, if rivers, straits, detached islands and mainland have to be crossed, as well as urban and industrial load centers are directly interconnected by the high voltage transmission line, and the like, then the high voltage power cable is the best option for power transmission and distribution.Once fault occurred in high-voltage or ultra high-voltage power cable lines, the users and regions connected will inevitably suffer serious losses. As against, kinds of faults occur on high-voltage or ultra high-voltage power cable are covered, thus a lot of limitations are subjected by external test conditions. As a result, fault locating on high-voltage or ultra high-voltage power cable lines are much more difficult than on overhead lines. Therefore, to choose reasonable fault test equipment and algorithms, as well as to accurately and reliably locate fault in order to shorten the outage time, are common concerns for both of power suppliers and users. Because the high-voltage cables are single-line spacing of the sub-phase emissions, single-phase failure has become the most common fault of power cable. Therefore, the research on location of single-phase fault of high-voltage power cable has very important theoretical and practical significance.The main research content and results are as follows:1. The application background of high voltage power cable and the significance of high voltage cable fault location are introduced. The fault type of power cable, basic requirements of fault location, and commonly used algorithm for fault location, together with the latest research results are stated.2. By comparing the common time-frequency analysis tool, wavelet analysis method is selected in this paper to process signal transform and analysis. Through the analysis of traveling-wave signal, a suitable wavelet analyzing method is chosen to process the location analysis. Analysis focused on thrice B-spline wavelet analysis theory, and the effectiveness of which is proved through the actual analysis of traveling-wave signal.3. Through wave process analysis of power cable lines, the attenuation and distortion are verified. Several common wave velocities, such as phase velocity, group velocity, apparent wave velocity, front velocity and the signal velocity are discussed. Theoretical analysis and simulation show that at various speeds during transmission there are varying degrees of distortion and attenuation. Based on this, a wave velocity with correct value, combined of attenuation, is given. First of all, the wave velocity is based on actual measurement on the cable to be measured, and then it would be corrected combining with the attenuation according to power transmission length.4. Simulations are conducted to the faults of single-phase low resistance grounded, single-phase high resistance grounded and single-phase line breakage on different locations, based on the two-terminal transmission power cable model established. And then the locations are verified with combination of the wave velocity access approach. Considering the accuracy requests of fault location on power cable lines, two-terminal locating approach is adapted in this article. Simulations show that the wave velocity chosen under such mode has lower theoretical error, so that it could meet the requirements of the cable fault location.5. Through analysis of mode features of high voltage power cables-overhead power transmission lines, a locating method for hybrid lines based on normalized wave velocity is given. The normalized wave velocity is based on practical measurement. With combination of four common wiring models, digital simulations are conducted, whose results show that it has a certain of fault locating accuracy.