The effect of frequency on the dielectric breakdown of insulation materials in HV cable systems

In this study, the effect of frequency on the breakdown strength of polymeric insulating materials is investigated. Two types of polymeric insulating materials that are used in extruded high voltage (HV) cable systems have been investigated: cross-linked polyethylene (XLPE) and epoxy resin. Breakdown tests are performed under DC voltage and AC voltage with frequencies ranging from 50 Hz to 2500 Hz. Weibull statistical techniques are applied to analyse the breakdown results. The results show that, for both materials, the breakdown strength is significantly higher under DC voltage than AC voltage. For AC voltage, there is a statistically significant dependency between breakdown strength and frequency: the higher the frequency, the lower the breakdown strength.