Interface Charge Characteristics of XLPE-EPDM Double Layers with Different Silicone Grease Coated

Space charge measurements were conducted on double-layer dielectric materials of XLPE and EPDM with common-used silicone grease (CSG) and fluorosilicone grease (FSG) coated at the interface. The conductivities and dielectric constants of the four materials were also tested. The study found that the interfacial charges increase with the applied electric field for both coated XLPE/EPDM samples. Bipolar charges appear at both coated XLPE/EPDM interfaces under low electric field strength, with a polarity opposite to the adjacent dielectric. These bipolar charges gradually disappear as the field strength increases. When the interface is coated with common-used silicone grease, the polarity transition of the interfacial charge at the XLPE/EPDM interface aligns with the Maxwell-Wagner-Sillars polarization model. However, this alignment does not occur when the interface is coated with FSG. With the application of FSG, there is a significant increase in the accumulation of negative charges at the interface, and the rate of interfacial charge establishment and dissipation at the beginning of the voltage on and off is faster compared to the interface coated with CSG.