The study of semiconductor layer effect on underground cables with Time Domain Reflectometry (TDR)

Abstract

Time Domain Reflectometry is a technique used for fault location and partial discharge analysis in underground electric distribution cables. The technique is based on the analysis of the propagation of short electric pulses. In underground cables, semiconductor layer properties and degradation cause perturbations in the signal wave shape. These perturbations complicate the interpretation of reflectograms and, as a consequence, fault location. This work presents a circuit model of distributed elements that includes the electrical resistance of the semiconductor layers. The results of computer simulations using the proposed model are compared with measurements in new and aged XLPE cables. This comparison shows that the proposed model can represent the phenomena satisfactorily.