Partial discharge degradation at insulating polymer-polymer interface

Abstract

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 mechanisrri of this unsy inmetric degladarion at the solid-solid interface, we investigated effects of permittivity and mechanical stress on the tree propagation. When high-permittivity material1 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.

Interfacial aging in composite insulators as a result of partial discharge activity

“…In the geometry tested, tracks developed as trees into the epoxy resin, although this was not seen in the silicone rubber. This is consistent with reports reviewed previously [14], [15]. Figure 6 shows polished cross-sections of the epoxy resin plaques that were observed under an optical microscope.…”

“…Each sample shows the characteristics and dimensions of the trees which propagated into the bulk of the epoxy. Higher pressures appear to encourage growth of electrical trees into the epoxy resin as reported by Kobayashi et al [15]. This is likely to be due to a reduced tendency to grow within a pressurized interface.…”

“…White powder resulted on the silicone rubber surface, whereas discharge activity caused cracks on the epoxy surface. Kobayashi et al [15] investigated the effects of permittivity and interfacial pressure at epoxy/ethylene propylene rubber and ethylene propylene rubber/LDPE interfaces. Testing used two aluminum foil electrodes, separated by 5 mm in the interface.…”

Analysis of Partial Discharge Inception Voltages for the Wrong Positioning Defects in the Joint of Distribution Power Cables

“…The study for the PD in the joint interface has been mainly focused on the impurities and voids existing in the interface of HV extruded cable joints; PDIV (partial discharge inception voltage) related to interfacial pressure/ lubricants [3] and impurities/voids [4], PD at the interface of XLPE/EPR and EPR/Epoxy [5][6][7][8], etc. For the distribution power cable joints, PD inception and degradation would be occurred similar to those in transmission cable joint, even though detailed study related to distribution cables has been rarely reported.…”