The Study And Calculation Of Grounding Grid Surface Potential Distribution And The Gradient

As the extra-high voltage and ultra-high voltage electricity grid with high capacity for long-distance power transmission comes into appearance, the voltage class used by the electric power system becomes higher and higher, as well as the short circuit current flowing to the ground during the fault of the electric power system. All of these lead to better and newer demand of the design and test for the electric power system ground. In the past, for a large ground grid the ground grid safety is evaluated by the measurement of the ground resistance for the most, however, it is the distribution of ground potential, the number of touch and step potential that matter for the risk during the fault. In this paper, it is is mainly focused on the ground potential distribution, and the analysis and calculation simulation for the potential gradient distribution are also studied.In this paper, all kinds of faults resulted from ground and the endurance of human beings for electric shock are introduced and analyzed. And the endurable voltage for humans during various faults is calculated through equivalent model, therefore, the importance of the calculation of ground potential distribution is proved.The calculation with ground parameters proposed in this paper can be used by arbitrarily distributed ground grids, whose results can be more useful and valuable for various ground grids in various circumstances after analyzed by the calculation software. In this paper, the potential distribution at the circumstance of uniform grids in different numbers is calculated, as well as non-uniform grids in the same number at different scaling interval, and the effects of the increase of the number of grids and the decrease of the scaling interval is also studied, and what is more, these results are proved to be efficient by comparison with others.In the end of this paper, through the calculation of a large substation's ground grid by the ground parameters software, and the analysis of the calculation software, with both the drawing of 3D and grey-scale images, an evaluation for safety of this ground gird can be given at the moment of electric shock on step voltage and touch voltage. The results from the experiment shows its efficiency in analysis of ground grids'safety design, and guidance role of evaluation of ground grids'safety.