The impact of interfaces and space charge formation on breakdown strength of epoxy resin

The re-emergence of HVDC necessitates re-evaluation of dielectric materials. Epoxy resin is employed as a dielectric material for joints and terminations in HV electrical systems up to about 75 kV, and higher ratings are required. Under DC however, space charge accumulation is a problem especially where interfaces are encountered. In this study, epoxy-epoxy laminates were fabricated and tested for space charge formation, using the PEA method, and breakdown strength under AC and DC were investigated. It was found that negative charges are accumulated at the layer interface and the breakdown strength under DC conditions is about 39% and 35% higher than that under AC condition for single and double layer samples respectively.