Research on fault detection method of grounding grids based on surface potential distribution

Abstract

Grounding grids play a very important role for the safe operation of the substation. When grounding grids fault occurred, resulted in abnormal surface potential or uneven distribution, and that will be a serious threat to personnel and equipment. Considering the influences of leakage current and displacement current in the soil, establish mathematical model of transient electric field. Combining with the grounding grids of 800kV GIS substation, I established three dimensional electric field model of grounding grids using finite element method and obtained surface potential distribution of three-dimensional figure. And then I analyze the buried depth, soil resistivity, and other factors of grounding grids on the surface potential distribution, using the method of transient wave injection. At last, I calculated the surface potential distribution of the grounding grids in the case of fault and non-fault, proposed a method of grounding grids fault detection based on surface potential distribution features. Research shows that: the influence rule of the buried depth of grounding grids to the surface potential distribution of conductor and grids center are different. The surface potential increased gradually with the increase of soil resistivity. It is possible to detect grounding grids fault according to the characteristics of the surface potential distribution.