PD degradation process of fatigue failure type in a micro gap under the surface discharge pattern of Gleitbüschel type

In this study, we have discussed the partial discharge (PD) degradation process of fatigue-failure-type in a micro gap under the surface discharge pattern of Gleitbuschel-type. An artificial void model was made based on the Whitehead abc model. AC voltage of 60 Hz at which PD degradation process of fatigue-failure-type under the surface discharge pattern of Gleitblischel-type was dominant was applied to this model. The number of PD pulses was measured using a PD detector until PD breakdown occurred in a micro gap. The number of PD pulses increases with the spread of PD degradation area. The reason for this phenomenon is considered as follows: PD becomes easy to occur in the micro gap because the PD degradation area promotes injection of initial electrons for PD generation. To investigate this conjecture, Laue plots of PD time lag was performed and statistical time lag of PD was estimated. The result shows that the statistical time lag of PD becomes short according to the passage of the application time and its time dependence correlates to the spread property of the PD degradation area. Therefore, injection of initial electrons from PD degradation area probably plays an important role in PD degradation process of fatigue-failure-type