Practility Study For Erosion Optimized Diagnosis Of Large Or Medium-scale Grounding Grid

The safe operation of transformer substation is important safeguard for safe and reliable movement of the electrical power system, but the grounding grid conductor buried in underground, the performance often goes badly because of year by year corrosion of the soil. It threatens the safe operation of the electrical power system,the safe of the staff and the electrical equipment. If discovering the resistance unqualified or occurring the accident, then we excavate the earth. The work load is enormous; it also has blindness, and affects the normal operation of the electrical power system. Some experts only research the diagnosis principle,mathematical model and so on; It can find the breakdown of the grounding grid in a certain degree. But it does not have the project usability.The corrosion optimization diagnosis practical application method for large and middle-scale grounding grid of this paper researching, solve breakdown diagnosis equation according to the breakdown diagnosis principle and electrical network, utilizing resistance value of between the grounding grid and it's lead wire. It is able to judge the corrosion situation of grounding grid based on the change value of branch resistance in accordance to fuzziness order. Based on C++ and MATLAB, diagnosis software for erosion of grounding grid was coded. Simulative platform was established using ATPDraw. The parameters of the grounding grid in practice were simulated on this simulative platform. Lots of summative experiments were done. The method for erosion optimized mearsurement and diagnosis of medium or large-scale grounding grid was concluded. The feasibility and accuracy of this method were proved by emulation computations for single leg, double legs, as well as the partial legs actual breakdown types of grounding grid network. 220 kV Nanjiao, 220 kV Hailong and 500 kV Yaxi substation grounding grid erosion optimized diagnosis experiments were done in practice. The grounding grid corrosion situations were more accurately judged which had provided the basis for transformation. The excavation indicated that this diagnosis method has already met the project practical requirements. Main conclusions were below:â‘ The diagnosis equation was solved with quasi-Newton method and digital approximation, it increased equation solution speed.â‘¡Elementary diagnosis integrating with supplementary diagnosis was efficient. During the elementary diagnosis, long span measurement integrating with standing node was suitable to medium-scale grid. Big separated scales integrating with standing node when elementary diagnosis does was a good method to large-scale grounding grid. The piecemeal survey simultaneously use the piecemeal diagnosis, the diagnosis correctly rate quite was high.â‘¢To partial double-deck grounding grid, if only the upper network was diagnosed neglecting lower level network, the corrosion diagnosis result error of double-deck region was very large;The corrosion diagnosis of single-layer region may be ignoredâ‘£The survery lead wire displacement had certain influence to the corrosion diagnosis result, connected position was exacely judged between down lead wires and grounding grid before selecting mearsead points.