Study of the ageing of impregnated paper of high power capacitors using the thermal step method and the thermally stimulated currents

The Thermal Step Method (TSM) allows to determine and to localise the charge density in solid dielectrics. The Thermally Stimulated Currents (TSC) technique allows one to obtain the activation energies of the different processes of depolarisation, but cannot give the spatial distribution of charges. The information given by these two methods are therefore complementary, and the necessity to combine them is very important. In this study, this technique of coupling used on thick films of impregnated paper coming from two different high power capacitors permits us to show the ageing of one of them