Influence of titanium dioxide and carbon black on the high density polyethylene DC breakdown strength evaluated by Weibull distribution

In this work, we present results of the short-time dielectric breakdown test in high-density polyethylene with different pigment levels (titanium and carbon black). These pigments are commonly added in polyolefines used as insulation in medium voltage cables. The specimen thin films, were obtained by hot-compression from extruded material. For the dielectric breakdown test an automated system developed in this department was used. A voltage ramp of 500 V/sec was applied to specimens immersed in a silicon oil bath at room temperature. The results were analysed by the Weibull distribution. The shape and scale parameters of the Weibull distribution were calculated by Graphical and Maximum Likelihood methods and their values showed that titanium dioxide does not affect the breakdown voltage of HDPE and in order to obtain high dielectric strength insulation the carbon black level must be as low as possible.