A contribution to the improvement of ASTM-D2303 polymer covered cable testing

Abstract

The use of polymers covered cables for medium voltage electricity distribution grids is an attractive option in Brazil thanks to their low cost and simplicity in installation. Owing to the fact that there are no controlling electric fields in these cables, they present surface currents in their polymeric covers which are responsible for electric tracking and erosion. This paper describes a methodology of electric tracking test of polymeric material covers of cables using actual cables in contrast with the methodology which uses slat, shaped test bodies. The advantage of this new method is that it makes possible, working with the cylindrical shaped samples, a more realistic evaluation of the cable, in comparison with the former method which gives only information about the polymeric material without taking into consideration all the stresses and possible contamination due to the cable fabrication processing. The starting procedures were taken from the ASTM-D2303 standard for testing slab shaped polymer test bodies. The influences of the test related parameters like contaminant solution flow, sample preparation, electrode shape and others were studied. This method permits one to correlate the events with the degradation of the polymeric material through the analysis of the electrical current waveshape.