Estimating voltage surges on buried coaxial cables struck by lightening

The protective devices incorporated in the repeaters of transistor coaxial systems afford no protection to the cable itself. In this paper expressions for the voltage surges to be expected in cables containing up to 8 coaxial pairs of 1.2/4.4 mm and associated service pairs are derived. Three types of surge are discussed, between the metallic cable sheath and coaxial outer conductor or interstice conductor or between the coaxial inner and outer conductors, the latter only occurs if the dielectric between the sheath and outer conductor breaks down. For each of these three cases the surge voltage at the point of entry is derived in terms of cable and lightning characteristics and soil resistivity.