AN EXPERIMENTAL-TECHNIQUE TO STUDY SPACE-CHARGE INJECTION IN POLYMERIC MATERIALS UNDER AC VOLTAGE

Our goal is to understand the electrical aging of polymeric dielectrics in the absence of any pre-existing gaseous cavities. In such situations, charge injection from defects producing local field enhancement appears to be a necessary condition for aging. This paper describes an experimental technique for measuring the charge flow from a needle electrode into a dielectric under an ac voltage. The transition between the discharge-free electroluminescent to micro-partial discharge state (early electrical tree propagation phase) can be investigated with a sensitivity of 0.005 pC.