Current distribution on tower lines under fault and surge conditions

In this paper, an investigation of current distribution on tower lines under lightning and power frequency fault conditions is carried out. An equivalent circuit model of a 400 kV double-circuit transmission line was established using EMTP and two models of differing complexity were developed. The power-frequency earth fault was simulated by short circuiting one phase conductor to the earth wire while lightning conditions were simulated by injecting an impulse-type current onto the earthwire and also onto to one phase conductor. The current and potential distribution through the tower line was examined for different fault locations and the effects of soil resistivity and tower footing resistance variations were quantified.