Interface resistivity and interfacial DC breakdown voltage of double-layer dielectrics

Double-layer dielectrics are widely used as insulation in electrical equipment, such as cable accessories. The interface between dielectrics is the weakest part of the insulation, which is critical to the overall insulation system. In this paper, the interface resistivity is studied as a parameter for evaluating the interface insulation performance. The interface resistivities of XLPE/SiR interfaces with different levels of roughness and pressures, as well as other interface types (XLPE/SiR, XLPE/EPDM, LDPE/SiR, LDPE/EPDM, HDPE/SiR, and HDPE/EPDM), were measured using an annular four-terminal electrode system. Moreover, interfacial ramped DC breakdown tests of XLPE/SiR interfaces with different levels of roughness and interface pressures were performed. As the roughness of the XLPE/SiR interface decreased, the interface resistivity increased from 5.10×10
¹²
to 1.15×10
¹³
Ω and the interfacial ramped DC breakdown voltage (U
_63.2%
) increased from 20.48 to 36.80 kV. As the interface pressure of XLPE/SiR increased from 0.1 to 0.5 MPa, the interface resistivity increased from 9.72×10
¹²
to 1.73×10
¹³
Ω, and U
_63.2%
increased from 26.49 to 53.61 kV. Interface resistivity is closely related to the contact morphology and surface resistivity, and an interface resistivity model is proposed to analyze the mechanism of the relationship between these factors. The interfacial ramped DC breakdown voltage has an obvious positive correlation with interface resistivity. Adopting interface resistivity as the characteristic parameter of interface insulation performance is beneficial for improving the reliability of interface insulation.