Insulating polysiloxane coating for XLPE‐Si‐rubber interfaces with high long‐term stability

Abstract Cable joints play an important role in the power supply systems, but at the same time, they greatly contribute to the majority of direct failures. Weak parts of the cable lines, especially for the solid‐solid interfaces in joints, attract much attention and are investigated by researchers worldwide. High‐voltage power transmission in electrical grids requires reliable and durable dielectric coatings for the interface insulation. The breakdown caused by local electric field enhancement is a gradual damaging process that leads to structural degradation and an increase of electrical conduction of dielectric materials, and ultimately, it results in catastrophic failure of the cable joints. Here, we demonstrate that the coating of silicone gel instead of silicone grease enables the improvements of tangential AC (alternating current) BDS (breakdown strength) and long‐term stability in the interfaces of joints. Under the pressure of Si‐rubber (silicone rubber) cold‐shrinkable cable accessories, the silicone gel almost did not lose, which improved the insulating stability of the interfaces. Our method allows us to fill the XLPE‐Si‐rubber (cross‐linked polyethylene and silicone rubber interfaces with silicone gel instead of silicone grease), which could reduce the risks of the power outage caused by cable joint faults.