Analysis And Optimization Design Of Grounding Grid Impact Characteristics

Study on the lightning impulse characteristics of grounding grid is the basis for lightning protection of power system. When the substation is struck by lightning, the grounding system will be affected by the high frequency of lightning current, and the substation grounding grids presents complex impulse characteristics, and which has very little consideration in the traditional safety design for the grounding system. At the same time, the optimization design for the impulse characteristics of grounding system could improve the effect of lightning current on the impulse of grounding system. This is very important to ensure performance of the grounding system that in the design of grounding system should consider the influence of the impact characteristics and carried on the qualitative and quantitative analysis, seeking to deal with the performance of this method. Based on the impulse characteristics of grounding grid as the object of study, this paper make the research of the impact characteristics of rectangular and circular grounding grid. In the consideration of the impulse characteristics for the conventional rectangular grounding grid, an optimal design method for grounding grid is proposed based on the Fruit Fly Algorithm, it could get the optimal form of grounding conductor when the lightning transient effect is considered, and the reliability of grounding grid could be improved.In the basis of the existing research, the double PI equivalent model of the grounding conductor which is based on EMTP is established in this paper, and the simulation results of the impulse characteristics proved the feasibility of the model. Further, analysis of the impulse characteristics of rectangular grounding grid systematic, according to plenty of simulation analysis, the influence rules of some factors of impulse characteristics of grounding grid such as the lightning current waveform, the lightning current immit different position, soil resistivity, vertical grounding conductor and grounding grid structure are obtained.The general layout of grounding grid with rectangular, rarely consider the effect of grid shape on the impulse characteristics. This paper presents a layout method of two kinds of ring grounding grid which shielding coefficient is lower than rectangular grounding grid. According to make the research on the impulse characteristics of ring grounding grid found out that the current flow effects of ring grounding grid is better than the traditional rectangular grounding grid, and compared with the rectangular grounding grid, the impulse characteristics of ring grounding grid has been improved greatly.Based on the analysis of the impulse characteristics of the rectangular grounding grid, the advantages of unequal spacing layout of rectangular grounding conductors are analyzed. An optimal design method for grounding grid is proposed based on the Fruit fly algorithm, this method is based on using the exponential rule to layout grounding conductor, and it could get the optimal layout form of grounding conductors under the lightning transient effect. The method can overcome the error by using mathematical fitting formula, and have the characteristics of fast convergence and high accuracy. The superiority of the proposed method is verified by practical examples.