Partial discharge testing using CIGRE method II upon nanocomposite Epoxy resins

Nanocomposite polymers are becoming a new family of dielectric materials with promising insulating properties. In order to apply this technology to insulation systems, a study about the material longterm endurance (life) is needed. In this paper results from comparative life tests performed upon base and nanostructured epoxy resin samples are presented. The nanofiller is a organophillic-modified ultra-clean montmorillonite. Specimens were subjected to ageing under surface discharge phenomena using a standard electrode configuration, that is the CIGRE method II. Life data and partial discharge phase resolved patterns, acquired during time under stress, are presented and commented, in order to characterize the ageing processes that leads to the specimen breakdown and to explain the longer life of the nanocomposite materials. A further insight on the breakdown mechanism is obtained through microscopic observations (using optical and SEM techniques) of the surfaces of the samples before and after ageing and breakdown. A different morphology of the discharge channel walls is observable for base and nanostructured resins.