Partial discharges measurements in industrial dielectrics

摘要

In the high field regime, dielectrics exhibit an increased conductivity due to non-linear phenomena, which take place in the prebreakdown stages. Current instabilities are observed and high mobility states are stimulated. The initiation and growth of partial discharge channels is related to these phenomena and plays a very important role in the dielectric aging procedure. The experimental procedure of this work is based upon the simultaneous recording of the charge flow through a MIM structure and the voltage profile of the applied pulse. The obtained results show an exponential increase of the number of free electrons and it's concluded that the outbreak of partial discharges above a threshold electric field may come as a result of the avalanche mechanism (impact ionization effect). Focusing in a single partial discharge the average number and energy of electrons are estimated. Analysis of the above experimental results is performed and the physical processes involved are discussed.