Effect of graphene oxide-based nano-coatings on electrical ageing

In previous works, we have shown that partial discharge activity in a cavity can deplete oxygen, thus leading to partial discharge suppression. In order to suppress as much as possible partial discharge activity, it is thus essential to improve the oxygen impermeability. In this study, sandwich-like samples of cross-linked polyethylene (XLPE) have been coated with organic-inorganic hybrid coatings containing graphene oxide (GO) in order to hinder the oxygen permeability. The samples containing a cavity having fixed geometry were subjected to electrical ageing above partial discharge inception voltage, while partial discharges were monitored. The electrical aging test was carried out in two cycles. Between cycles, the samples were extracted from the test vessel (full of silicone oil, to prevent surface discharges) and exposed to air, to investigate whether the coating could effectively prevent oxygen ingress in the cavity. Next, aging tests were carried out till breakdown. The effect of GO is thus evaluated indirectly through PD activity behavior, and by statistics of the breakdown times. Experimental results show the effectiveness of the coating and highlight the dependence of partial discharge degradation rates on coating composition.