Study And Improvement On The Positioning Method Of Grounding Grid Fracture Failures

Grounding grid in substation is very important to maintain the security and reliability of power system. But, for the conductors which constitute the grounding grid is buried in the ground, it is very easy to be eroded by soil, and during the construction of the grounding grid some place is badly soldered, these reasons may lead to grounding grid’s property can’t reach the standard. A earth short circuit current may take serious loss to economics even threatens the people’s safety when grounding grid malfunction, and grounding resistance increase heavily. So, the study of the grounding grid fault diagnosis is of great significance.This thesis studies the fault diagnosis of substation grounding grid. Currently, many experts studied for this problem, the most common method is electric network method. Through the change of the resistances between ground leads after branch eroded and electric network theory, matrix theory, optimization technique, establish fault diagnosis equation and solve it, after that fault branches can be find. But, for the measurement of the port resistance is eyeless, a large amount port resistances need to be measure, for this reason, a new method which can easily select the useful ports between ground leads is proposed. By this means, both accuracy and rapidity are guaranteed.In order to validate the diagnosis method in this thesis, using ATP-Draw establish a small network, setting fault branches, and then through the method in this thesis find the fault branches. And then, establish a 100 nodes model, select a few ports, and measure the port resistance, then choose the areas where branch corrosion may exist, and measure more port resistances in these areas to supply more fault information. Through this method, the times of diagnosis can be decrease, it’s very useful in engineering application. In this thesis, using flat steel establish a real grounding grid, and make an experiment upon it. Through measure port resistances of this grounding grid, find the fault branch, validated the diagnosis method in this thesis.At last, using CDEGS software to analyze the model of grounding grid under AC source, study the relationship between port impedance and frequency, leaking out current and frequency. propose a diagnosis method based on frequency-domain approximate, and then proved it’s practicability by simulation.