Mutual coupling between driven rods in grounding system of transmission lines

Driven rods connected by horizontal buried wire (counterpoise) is a common configuration of grounding in transmission lines. When subjected to a lightning current, the transient impedance of the grounding is prevailed by the surge impedance of the system and subsequently decreases to the steady state resistance, which is partly resulted from the distribution of currents between driven rods. Widely spaced driven rods would require longer time to reach the steady state resistance but the mutual coupling between the driven rods would be less noticeable. The transient behavior of grounding system, therefore, depends on both the surge propagation process in the system and the electrode arrangement This paper deals with the mutual coupling effects on transient behavior of grounding system in transmission lines by the Finite Element Analysis (FEA) method. Various electrode arrangements, which comprises of driven rods and a counterpoise, are investigated. Computation results suggest an effective configuration of the grounding system for a given soil condition.