Research of optimal distance of external grounding grid

External grounding grid is an effective measure to reduce grounding resistance of grounding grid. In order to meet the requirements of the grounding resistance in the most economical way, it is important to determine the distance and the area of the external grounding grid. Generally speaking, when the area is larger, the grounding resistance is smaller. When the distance of the external grounding grid increases, the grounding resistance decreases firstly and then increases. Therefore, there is a minimum of the external grounding grid area and the optimal distance to meet the requirements of the grounding resistance within the constraints. Also means to get the best economic design scheme that minimum material consumption and construction of the external grounding grid. In this paper, we establish the objective function of the minimum grounding resistance based on the area and the distance of the external grounding grid using the method of grounding grid unequal potential model. Through optimization theory and genetic algorithm optimization, the optimum parameters of the distance and the area size of the grounding grid are obtained. Provide important basis for the design of the grounding grid economically.