Interfacial behaviour of structured planar silicone interfaces for power cable accessories

The interfaces in cable accessories form the weakest link in the cable system and can be considered as one of the major reasons for its failure. The parameters such as surface smoothness, contact pressure and temperature in the interfaces govern the interfacial electrical withstand strength. An imperfect surface smoothness of the material creates voids at dielectric interfaces which are inevitable, initiating the partial discharges (PD). In the present work, different microstructured (rough, triangle and wrinkles) silicones are investigated with reference silicone for its interfacial discharge mechanism. The impact of structured silicone with different pressures (0.1 MPa, 0.15 MPa and 0.2 MPa) at ambient temperature and 70°C are examined. The dielectric constant of Sylgard 184 observed a deviation of only 6%, whereas the dissipation factor was 5.8 times higher from room temperature to 90°C. The wrinkle structures exhibiting a lower void area with flat reference observed a higher partial discharge inception voltage (PDIV) at different pressures compared to rough and triangular structures. In comparison to rough and triangular structures, the wrinkle structures with a flat reference and a decreased void area showed a greater PDIV at the selected pressures. The phase-resolved partial discharge pattern (PRPD) of interfaces indicates a uniform distribution of charges at positive and negative half cycles involving the presence of both voids and surface discharges. The interfacial breakdown voltage follows a similar trend in its magnitude exhibited as that of PDIV for different structures.