Implementation of finite mutual impedances and its influence on earth potential rise estimation along transmission lines

As the proximity of high fault current power lines to residential areas increases, the need for accurate prediction of earth potential rise (EPR) is of crucial importance for both safety and equipment protection. To date, the most accurate methods for predicting EPR are power system modelling software tools, such as EMTP, or recursive methods that use a span by span approach to model a transmission line. These techniques are generally used in conjunction with impedances and admittances that are derived from the assumption of infinite line length. In this paper a span by span model was created to predict the EPR along a dual circuit transmission line in EMTP-RV, where the mutual impedances were considered to be between finite length conductors. A series of current injection tests were also performed on the system under study in order to establish the accuracy of both the finite and infinite methods.