Partial discharge degradation at insulating polymer-polymer interface

In order to investigate partial discharge (PD) degradation in composite insulating systems such as a prefabricated cable joint (PJ), we proposed an electrode system to simulate PD degradation at a solid-solid interface. It was observed that the tree at the EPR-epoxy resin interface tended to propagate into the epoxy resin bulk, even though the breakdown strength of epoxy resin was higher than that of EPR. To clarify the mechanism of this unsymmetric degradation at the solid-solid interface, we investigated effects of permittivity and mechanical stress on the tree propagation. When high-permittivity material was put behind the electrode, the tree tended to propagate to the high-permittivity-material side under voltages higher than the tree-inception voltage. This suggests that unsymmetry of the electric field or polarization charge has an effect on the tree propagation. At the interface of EPR and LDPE with about the same permittivities, the tree along the interface tended to propagate into the LDPE bulk as high voltage is applied. This suggests that factors other than permittivity also influence the tree propagation. When a high pressure was applied to the EPR-epoxy resin interface, the tree tended to propagate into the epoxy resin bulk. Mechanical properties and conditions also contribute to the unsymmetric tree propagation