Voltages Induced by Lightning Strokes and Ground-Faults on a Coaxial Telecom Circuit Enclosed in a Composite Earthwire Part I: General Approach and Earth Faults Induced Voltages

This paper presents the first part of a comprehensive research program about the problem of maximum induced voltages inside a composite coaxial earthwire for overhead transmission lines (the coaxial pair being used as a private telecommunication circuit). Based on the concept of transfer impedance, one can derive a general four steps calculation procedure valid for both cases of lightning strokes and earth faults. The problem of voltage induced by phase to earth faults is dealt with in Part I where unpublished experimental results on saturation effects in composite earthwire at 50 Hz and a parametric analysis of induced voltages are presented. Practical values of maximum induced voltages are given.