Behavior of surface partial discharge on aluminum oxide dielectrics

Partial discharge (PD) was generated with alternating voltage applied to a point electrode touching the surfaces of aluminum oxide (Al ₂O₃) dielectrics of different purity in air. The amplitudes and phases of all pulsating PD events that occurred during voltage application periods up to 35 minutes were recorded and the results were analyzed to reveal details of the time- and voltage-dependent stochastic behavior of the discharge. It was discovered that the characteristics of PD exhibit rapid changes with time that depend significantly on voltage and the purity of the Al₂ O₃ sample. Examples are shown of statistical data for individual positive and negative pulses in a voltage cycle that are much more refined than data that can be obtained from conventional PD measurement systems. The results presented here illustrate the advantages of using continuous data records in the investigation and characterization of pulsating PD phenomena