Effects of the Local Soil Nonuniformity Upon Performances of Ground Grids

The effects are studied of the material for leveling spread over and of installation channels led through substation site upon the safety risk associated with grounding. The main ground grid performances in case of ground faults are analyzed for various ratios of overlaid material and surrounding soil resistivities and horizontal dimensions and thickness of the overlaid material. Also, the effects of the installation channels dug along various routes upon the potential distribution on the ground surface and step voltages are considered. It was shown that the mentioned local nonuniformities can substantially affect the safety performances of the ground grid and that they should be carefully taken into consideration. The local soil irregularities considered have been modeled by applying the method of finite elements.