Résumé
Organic insulating materials are widely studied in view of their use in high voltage dc applications. This study focuses on the analysis of dielectric properties and behaviour of an epoxy resin filled with 66 wt% with alumina, used as insulating supports for ac Gas Insulated Switchgears (GIS) in order to assess their suitability for use in high DC voltage switchgear. Dielectric properties of the material at initial state with continuous temperature and electrical stress (loss factor, volume resistivity, thresholds and nonlinearity coefficients, surface resistivity, breakdown, evolution of space charge) are determined and investigated under dc fields at different temperatures. Evolutions of several electrical properties of the material submitted to long-term thermo electrical stress under various dc fields and temperatures are presented and discussed.