Swelling Crosslinkable Monomers to Improve Electrical and Mechanical Performance of SiR–XLPE Interfaces

Cable joints are the weak links in cable lines, and prone to frequent failures. A decreased breakdown strength (BDS) of composite insulation composed of silicone rubber (SiR) and cross-linked polyethylene (XLPE) is a main reason of these failures. This study proposes a prematurely-swelling (PS) method where monomers with cross-linkable groups are first permeated within SiR, and then interconnected using a crosslinker at the interface. To assess the bonding strength at this junction, the authors employed an interfacial BDS test to evaluate and study interfacial BDS performance, along with optical microscopy (OM) and polarization-depolarization current (PDC) devices. By applying a crosslinked coating that penetrates the interface, significant improvements in interfacial electrical performance were achieved. The results indicate that this practical and straightforward approach greatly diminishes interface polarization, enhancing the sample's interfacial BDS performance by 124% compared to uncoated samples. Both the insulation performance and the mechanical performance were significantly enhanced.