Analysis on influence of long vertical grounding electrodes on grounding system for substation

Three dimensional grounding system is introduced to decrease the grounding resistance, step and touch voltages of grounding system in areas with high soil resistivity or with limited areas for grounding system. The relationship between the number of vertical grounding rods and the grounding resistance is discussed. The new means to add grounding rods to the grounding system with explosion grounding technique, have efficiently decreased the grounding resistance in the actual grounding engineering. Reasons why vertical grounding rods can efficiently decrease the maximum touch and step voltages of the earth surface above the grounding system are analyzed. Calculated results shows the vertical grounding rods can also effectively decrease the influence of seasonal factor on safety of grounding system. This paper provides the rule to choose the vertical grounding rods in multi-layer soil based on the relationship analysis between the number and the length of the vertical grounding rods.