The Corrosion Break-point Diagnosis Method Of Grounding Grid Based On The Principle Of Uniting Magnet Field And Electric Circuit

The grounding system of power station and substation is an important measure for maintaining power system reliable operation and protecting the safety of operating personnel and electrical equipment. Grounding conductors and lead wires are easy to corrode, even break up due to poor welding, soil corrosion and the affection of short circuit current making worse electrical connection performance of grounding network and larger resistance value of grounding conductor. The methods usually used for determining grounding network corrosion is to detect the resistance value of grounding conductors or check the integrity of grounding network by evacuating the soil in a large area. But these methods lacked of necessary scientific basis and needed greater work load will affect the grounding network operation. Recently, the researches for detecting grounding network corrosion without soil evacuation have made some process. But in some literatures, grounding networks are equivalent to a simple resistor network and the grounding network corrosion is detected by using the method of combining grounding network topology and theory of error diagnosis. In the process of diagnosis, conductors self inductance, mutual inductance and soil resistivity are not taken account. So the grounding network corrosion model compared to the actual network has high margin of error and could not reflect corrosion situation correctly.This paper establishes unequal potential model of grounding network considering conductor resistance, self inductance, mutual inductance and conductor leakage current based on the principle of magnetic field and electrical circuit combination. The corrosion diagnosis equation established by using the corrosion diagnosis theory and measuring the voltage level of grounding lead wires, can be solved by using the simulation software of MATLAB and the result is verified. While establishing the equivalent model of grounding network based on the ATPDraw software and analyzing the influence of node voltage measurement plan to the corrosion diagnosis result, at the same time calculating the performance parameters of grounding network corrosion. Finally the effectiveness of corrosion diagnosis method is verified and the error is less than 10%. And the proper node voltage measurement plan had practical value in engineering is given, that is large span length measurement plan should be used in the middle or small scale grounding network and block measurement plan should be used in the large scale grounding network.