Diagnosis Of Grounding Grid In Substations Based On CDEGS

The substation grounding grid is the most important approach for guaranteeing power system safety. The faults in substations grounding grid will bring great hidden trouble to the safe and stable operation of the power system, when serious it will cause huge economic losses to the society. Monitoring the state of grounding grid is essential for maintaining substation operation. Since the grounding grid is buried under earth, it is very difficult to diagnose grounding grid defects and determine defect position without excavation. We used the method of excavation a large area to check and detect the corrosion of the ground grid. This approach is not only inaccurate, but also a lot of blindness workloads, and it may affect the normal operation of the power system.For a practical substation, network topology structure and spatial position has been established after completion of the design and construction. When some conductors appeared corrosion or break points, the branch resistance change, so you get two same topological structure, but the resistance network is different. The field source must be changed when the grounding grid happens corrosion or break points, the spatial domain of magnetic induction intensity will change too. Therefore, the change of the magnetic induction intensity can reflect that the change of the field source. Because the magnetic induction intensity is easy to get in the field test relatively, so this article choose magnetic induction intensity on the surface of the ground grid as the research object, the main work involving is as follows:The paper analyzes in detail the research achievements on defect diagnosis for ground grids, and introduces the development and the status of ground grids’defect diagnosis method at the same time. How to diagnosis the faults condition of grounding grids is a very important problem remained to be resolved in our country. A practical and effective diagnosis method and technology without opening grids and stopping operation is needed. The paper briefly introduces the function and characteristics of the ground simulation software CDEGS, and computes the grounding grid model by using the RESAP module and the MALZ module. Measure magnetic induction intensity on the surface of the ground grid after the excitation current source injected into the grounding grid. A new diagnosis method of faults of the substation grounding grid is presented by analyzing the distribution characteristics and comparing with the results of the normal simulation computations. The method does not need large area for excavation of grounding gird, saves a lot of manpower and material resources, financial resources, but also it can guarantee the normal operation of the power system, does not affect people’s normal life.Combined with the simulation calculation results and complex electromagnetic environment in substations, the magnetic induction intensity which diagnose grounding grids’ defect status is designed and developed. Based on the design of the induction coil and power frequency notch, band-pass filter, and so on, signal acquisition and processing system is developed. And through the simulation experiments verify the effectiveness of the diagnosis system, the experimental results show that the availability of the measuring system is tested by experiments and its immunity ability, distinguish rate and precision satisfy the diagnosis demands.On the basis of above work, the diagnosis method and diagnostic system are applied in a few practical substations, the substation can come true testing diagnosis and safety evaluation without opening grids and stopping operation. The testing results show that this diagnosis idea is feasible, this diagnosis method is effective and this diagnosis technology is dependable.