Defect position locator for cable insulation monitoring

Abstract

A device for detecting insulation defects in a cable having a conductor while an electrical signal is impressed on the cable conductor, the device being composed of an ion source for generating an ion cloud and arranged for causing the ion cloud to be displaced along, and to envelop, the cable, a sense conductor arranged to be disposed along, and in proximity to, the cable and to be in communication with the ion cloud, and a plurality of coded position conductors arranged to be disposed along, and in proximity to, the sense conductor and to be in communication with the ion cloud, each position conductor having at least one discrete region covered with insulation arranged in a pattern which differs from one position conductor to another. An alternating signal having a respectively different frequency is applied to each position conductor, the frequency of the signal impressed on each position conductor being different from the frequency of the signal impressed on the cable conductor. When the ion cloud envelops the conductors and a region of the cable insulation which contains a defect, signals present in the cable conductor and the position conductors are coupled into the sense conductor. The signals impressed on the cable ocnductor and on each position conductor are synchronously detected with respect to the signals coupled into the sense conductor to provide an indication of the existence and location of cable insulation defects.