Research On Optimum Design And Resistance Reducing Measure Of UHV Grounding System

The substation grounding system is an important method to ensure power system running safely, protect the safe of staff and instructions, the design of grounding system is one of the most important electric design. With the development of electric power system capacity, the value of failure current flowing into ground increased greatly. Particularly, after start operating converter station, the earth-fault current is even 30kA or more and the area of the grid is over 100000m~2. The gradient of earth surface potential above the large equidistant substation is large, and the leakage current of theirs conductors are not uniform. On the other hand, how to decrease the grounding resistance economically and effectively in the complex soil structure with high soil resistivity becomes an important question of power system for discussion. It is very essential that the grounding grids of large substation using variable spacing and the methods to minimize resistance should be researched.Aiming at question of equal space grounding grid, optimization method at home and abroad is introduced and optimization method of UHV grounding grid is introduced. The influence of vertical grounding rods on the grounding resistance in uniform soil is discussed. The influence of top-layer soil resistivity, the reflective coefficient, top-layer soil thickness and other factors on the grounding resistance of the grounding grid in two-layer soil is analyzed. The influence of resistance reducing effect of vertical grounding rods is studied and selection rule of vertical grounding rods is given. Some advices are provided for the ground grid design about vertical grounding rods.The method of designing the grounding system and the application of vertical grounding rods in UHV grounding system is introduced, The article researches the conductor unequal space distributing linking converter station grounding grid, gets the optimal scheme through lots of design calculations using CDEGS software. By using unequal space scheme, the tough voltage, step voltage are decreased, the conductor and cost are economized.