RESPONSE OF MULTICONDUCTOR POWER-LINES TO NEARBY LIGHTNING RETURN STROKE ELECTROMAGNETIC-FIELDS

The calculation of voltages induced by indirect lightning on multicond uctor lines has been the subject of several studies, The reported conc lusions are not always in agreement with each other, In this paper, us ing a modeling procedure presented in a previous work, we study the sh ielding effect due to mutual coupling among the conductors of a three- phase line and between the ground wires and the line conductors. The r esults are compared with those published by other authors, and explana tions of the disagreements are given, Additionally, a simplified metho d to evaluate lightning-induced voltages on a multiconductor line from the values obtained for the single conductor case is presented, and a simple formula which gives the magnitude reduction of the induced vol tages due to the presence of other conductors is derived. It is shown that, for the examined case, the derived simple formula gives practica lly the same results as those obtained using the rigorous procedure. W e have also compared results obtained using the simplified formula pro posed by Rusck to evaluate the protective ratio of a ground wire with our results, and we have found that the values predicted by the Rusck formula are about 6% lower than ours.