Calculation of the response of unshielded distribution lines to direct lightning strikes Part I. Multiconductor travelling wave analysis

Abstract

This paper describes a comprehensive computer program to calculate the response to lightning strikes of a single-phase or three-phase unshielded distribution line with an earthed neutral conductor. The program uses a new implementation of a multiconductor travelling wave technique so that voltage and current waves on all phase conductors and the neutral are calculated. This new method is an improvement over previous methods which involved a modified single-conductor travelling wave calculation. In this new multiconductor travelling wave analysis, a set of equations describing the relationship between the incident and reflected waves for each node type is derived. The distribution system is made up of a series of node types classified according to their respective modes of earthing and function. The function equations derived are then solved on a time iterative basis to include non-linearities necessary for the accurate modelling of the problem. This paper describes the formulation of the technique and features of the program. A companion paper (Electr. Power Syst. Res., 22 (1991) 97 - 103) shows the validation by comparison of calculated results with some actual field measurements of the surge currents on a single-phase distribution line which has been specially instrumented. © 1991.