Electronic phenomena in solid dielectrics under high electric fields

High voltage pulses of the form of 1.2/50 μs were applied on common industrial bakelite and phenol impregnated press-board samples, through a tip-plane electrode assembly. The total electric current through the samples, during the occurrence of partial discharges, was measured. The results show an exponentially increasing current with the applied electric field or the corresponding high voltage pulse peak. In addition, an approximate estimation of the average electronic mobility and the overall conductivity in the high field regime is performed, which identifies semiconductor-like behaviour due to nonlinear phenomena such as partial discharges and negative differential resistance. An equivalent circuit of the materials under stress is also proposed. This circuit results by the combination of experimental observations with the theoretical expectations