Influence of DC Component on Partial Discharge Activity

The purpose of this work is to analyze how the presence of combined AC-DC voltages can influence the partial discharge (PD) activity. A DC offset can be introduced by power electronics components affecting the partial discharge inception voltage (PDIV). If the PD phenomenon is the main cause of the electrical insulation degradation, the lifetime can be influenced by the presence of a DC component in the voltage waveform. In this work a simplified configuration has been considered in order to analyze the influence of the DC offset on the PD behavior. Twisted Pair samples have been taken into account representing surface PD activity conditions. The enameled wires have been subjected to PD activity after a conditioning in oven at 150 °C. The effect introduced by the DC continuous component offset is considerable. The number of discharges increases and the level of inception voltage decreases proportionally with the decrease of the continuous component, consequently the lifetime values vary since they are influenced by the PD activity. It has been possible to observe how the DC component influences the PD activity and the relevant degradation processes. This preliminary work suggests to perform exhaustive studies to better understand how the presence of a AC-DC voltage waveform can influence the PD behavior in case in different types of defects.