A practical method for evaluation of ground fault current distribution on double circuit parallel lines

The paper presents an original analytical procedure for quick and, for practical purposes sufficiently accurate evaluation of the principal components of the ground fault current. The procedure is valid for faults at any of the towers of a double 3-phase circuit line with an arbitrary number of spans. The method is obtained by application of relatively simple and exact equations for uniform ladder circuits of any size (for any number of pis, from one to infinity) and for any terminal conditions. The method can be applied to solve several practical problems: the evaluation of the maximum substation grounding system fault current, the selection of a ground wire capable of withstanding the fault currents and the prediction of step and touch voltages near the transmission towers. In the case of a double circuit 3-phase line, the solution of these problems is additionally complicated by the mutual inductive coupling between the two parallel lines.