In this study, an experimental model is made on the basis of the Whitehead abc model and the properties of partial discharge (PD) breakdown in the micro gap are investigated. The quite unique properties of the PD breakdown in the micro gap are obtained: The voltage dependence of time to the PD breakdown and spread of residual negative charge distributions in the micro gap become discontinuous at a certain voltage amplitude. The discontinuousness in the PD breakdown properties is found to be due to the difference in surface discharge patterns in the micro gap: Polbüschel-type at lower voltage and Gleitbüschel-type at higher voltage. This paper aims at discussing the PD breakdown process at higher voltage. Time to the PD breakdown in the micro gap is analyzed using the Weibull probability distribution. The result suggests that the PD breakdown processes are classified into two different types: fatigue-failure-type and early/random-failure-type. Assuming that the PD breakdown of fatigue-failure-type is a thermally activated degradation process of Ahrenius type, the activation energy is caluculated . The value is in good accord with activation energy required for polymer bond scission caused by interaction with oxygen and ozone. The result suggests that the PD breakdown of fatigue-failure-type is caused by oxidative degradation. On the other hand, residual negative charges in the micro gap play an important role in the PD breakdown process of early/random-failure-type. In view of previous studies, it is possible that the PD breakdown process of early/random-failure-type is governed by the existing probability of structural defects where a great deal of the negative charges accumulates.