Space charge measurements by the thermal step method in filled epoxyde systems

We study the appearance and evolution of space charge in epoxyde systems filled with alumina, silica or Wollastonite. The thermal step characterization allows us to compare different insulating structures, in order to optimize reliability and life time. We investigate the space charge distributions in 3 samples tested before and after the application of electrical and thermal stresses. The results show fundamental differences between different materials and give information about the presence of space charges from the manufacturing process of these materials. We can therefore classify the tested materials. We also try to reveal the part played by space charge in the phenomenon of aging