The Research On The Numeric Algorithm Of Grounding Grids And The Development Of Its Software

The research on the numeric algorithm of grounding grids began at 1970's. Traditional numeric algorithm of grounding parameter calls for making some assumptions, so parcel dealt of parameter is not rigorous enough, which has the problems such as computational inefficiency, weak precision and so on. Along with the development of electric industry, the grounding systems become larger increasingly, and the structure is much more complicated than before, thereby, it is urgent and necessary to realize new efficient simulation numerical calculation of grounding grids. In order to enhance the level of design for grounding system, this paper concentrates on the numerical algorithmic research of grounding parameter, and proposes improved algorithm of two-layer grounding grids along with software for two-layer grounding system.Firstly, the method for calculating the Green's functions is discussed in this paper, which is the key to calculate the model of two-layer soil efficiently. After analyzing stationary current field produced by a point current source in detail, the classical image method is introduced as well as the complex image method, on the basis of which the close-form Green's functions of a point current source in two-layer horizontal or vertical stratification soil are derived.This paper researches deeply on the basic algorithm of two-layer grounding grids. In order to resolve the difficulty of dual-integral brought by Galerkin's moment method in the numeric algorithm of grounding grids, analytical formulas for resistance between arbitrary two conductors are derived, which are able to increase the efficiency and the precision of the simulation calculation greatly.The complex image method melt into the concept of symmetry is combined with the direct matrix method organicly in this paper, on the basis of which optimized algorithm of the resistance is derived. It is unnecessary to suppose the tatal fault current, but through transforming the resistance coefficient matrix to acquire the resistance of ground grids directly. Simulation confesses: the method has high calculation precision, the computing time can also be improved.As another work in this paper, the close-form numeric algorithm software of grounding parameter is developed based on the algorithm of two-layer grounding grids which is derived in this paper. The software has well interface and can be used flexibly. It can not only accomplish the calculation of the grounding parameter exactly, but also give 3D figure of surface potential, which authorizes project design and enhances the level of the design for grounding grids. Meanwhile, through calculating two actual grounding grids——baojing and gaoxi electric substation, it confesses: the software has high efficiency and precision of the simulation calculation.