Study On Impulse Characteristics Of Grounding System In Substation

When lightning strike occurs in or around the substation, or the short-circuit failure occurs in the gas insulation substation, the grounding system under the substation will be injected into impulse current with high frequency and large magnitude, therefore, the safety performance of large grounding system is further complex. The experimental research show that when electric-field intensity around the electric rod exceeds the critical breakdown field strength, the area around the conductor will emerge spark-discharge zone. The relationship between current intensity and field density in the spark zone is nonlinear. At present, no literature propose effective method to successfully measure the distribution regulation of leakage current, while this regulation is of great meaning to theoretical analysis of impulse characteristics of large grounding grid. The mainly influence factors to the impulse characteristics of grounding grid are depth of burial, dimension of grounding grid, soil resistivity and parameter of lightning current. The relationship between these factors are extremely complex, it is difficult to build up general function to analyze their performance. Therefore, it is necessary to built up accurate simulation model and carry out experimental research for the safety operation of the power system and the personal safety of the staff.The mainly content of this paper can be divided into four sections.â‘ Combining circuit theory with electric-magnetic theory to propose new method to analyze the frequency-domain property of grounding grid when considering the non-liner property of the spark domain. Combining this method with FFT method, a theoretical model for the research of impulse characteristics of grounding grid is built up;â‘¡Analyzing a simple square grid with this method and compare with the experimental data. The simulation experiment is based on principle of dimension similarity, and mainly carried out in uniform soil and two-layer soil.â‘¢Analyzing the influence of burial depth, dimension of grounding grid, soil resistivity and parameter of lightning current to the impulse characteristics of the grid by quantity of calculation using this method.â‘£Measuring the axial current value of grounding grid at several points by using pearson current sensor and finding the flow regulation of leakage current. The above achievements are of important instructive meaning to the research on impulse characteristics of large grounding grid in future both in aspect of theory and experiment.