Optimisation of partial discharge testing techniques

The authors consider the behavior of dielectric films subjected to surface partial discharges (PDs) under AC voltage (power frequency) in cells containing a gas gap in a series with a film. The recurrent formation of PDs in the gap creates damage which can lead to breakdown. It had been suggested previously that the damage to thin polymer films during tests of this kind can be related to synergic factors: the action on the film surface of the discharges and the effect of electrical aging in the bulk of the film present during the discharge time windows. In order to clarify the effect of the electrical aging factor on the duration of the films during PD testing it was necessary to devise a way to separate the contribution of the two factors, maintaining the conditions driving the first factor and changing the stress present on the film during discharge periods, when the air gap is short-circuited. The initial assumption that the damage to thin dielectric films during surface PD tests can be related to the two above-mentioned synergic factors was confirmed