Study On Fault Diagnosis And Optimization Of Grounding Grid In 500kV Substation

The 500 k V substation is an important node of the main power grid of the domestic power system,which connects the power grids of various cities and provinces to form a stable power grid architecture.Its safe and stable operation is of great significance to the stability of the power supply of the whole system.For substation,good grounding has very important engineering significance.However,it is difficult to detect the horizontal grounding electrode directly because it is buried underground.At present,in engineering practice,the grounding wire conduction test and grounding impedance test are often used to infer the state of the horizontal grounding pole or to conduct excavation inspection directly.In these two ways,the indirect test is inaccurate and the direct excavation inspection is blind.In order to better diagnose the condition of the underground horizontal grounding pole,many scholars at home and abroad have put forward a variety of diagnostic theories and scheme designs,but most of the research is aimed at the small and medium-sized network of 220 k V and below,and the actual situation is fully integrated in the engineering site.This paper focuses on the grounding diagnosis optimization of 500 k V substation.Based on the theory of electrical network,the diagnosis method will be developed and the actual substation grounding network will be approximated to a pure resistive network.Based on the fault diagnosis principle and telegen’s theorem,the corrosion diagnosis equation is constructed,the initial value required for diagnosis is obtained by using the ground grid design Drawing and technical documents,the actual value is obtained by using the ground conduction test,and the branch state of the ground grid is judged by comparing the difference of the initial value.The method of least square method is used to solve the problem that the number of equations is far less than the number of variables in engineering practice.The above calculation process is relatively complex,will use MATLAB to complete.In order to make the whole diagnosis process more operable and applicable to the project site,the fault diagnosis software was compiled by using the GUI in MATLAB,and the visual operation interface was built to realize a simpler topology construction,correlation matrix generation and fault diagnosis analysis.The accuracy of the diagnostic software is verified by simulation test based on the actual substation grounding grid.ATPDraw program in ATP was used to build the actual substation grounding grid structure diagram,set fault parameters,and use the current source and voltage probe in the program to obtain the actual resistance value of the grounding grid after the fault,which was simulated in the diagnosis software.Model to explore the diagnostic approaches,in the diagnosis for large span diagnosis scheme,natural block,diagnosis and diagnosis according to the voltage grade,compare the different approaches to influence on diagnosis accuracy and efficiency,and connecting with the engineering site,the diagnosis could be operated suggestions: according to a preliminary analysis of grounding systems located in soil,diagnostic localization diagnosis for local grounding network,using the natural block or are rated according to the voltage value diagnosis method combined with large span,gradually close to the real failure.Combines diagnostic software and grounding conduction testing at present stage,summarizes the specific test methods,formed the standardized operation process,to the west of Zhengzhou 500 k V substation and the south of Pingdingshan 500 k V substation field measurement,accurate discovered,proved the practicability of diagnostic methods and accuracy,improve the 500 k V substation ground network efficiency and accuracy of fault diagnosis,reach the standard of the engineering practical application.