Fault Diagnosis For Grounding Grids Based On Electric Network Theory

Grounding grid in substation is vital for preserving the safety and reliablity of power system, protecting the operator and electrical equipment. However, the corrosion caused by earth's acidity and alkalinity may result in thinness even break of the grounding down-lead and horizontal equal-voltage conductors. When grounding fault occurs, it will bring out huge lost, not only leads to fault spread, but also will be dangerous to human and facilities. The common way to detect the grounding grid is to dig widely to see the corrosion directly. This way is diseconomy and blindness, and it also needs lots of work and affects the running of power system.In this paper,the writer researchs the theory of fault diagnosis for grounding girds in substation. The grounding grid is treated as a pure resistance network. The corrosion diagnosis equations are built by application of the electric network theory and then solved by using of the topology of real grounding grid and measured data of the voltage between down-leads. Using the lowest power loss theory, mathematic function is established as well as being solved by optimal method. We can obtain the change of the grounding grid branch resistance which determine the level of the diagnosis. Primary simulation calculations and experiments proved its practicability.