Analysis of interfacial pressure changes of thermally cycled cold shrinkable joints

This study is conducted to compare and evaluate thermomechanical stresses of four different types of interfaces in power cable accessories. This study proposes a numerical method designed to effectively integrate material characteristics and their temperature-dependent variations. Finite element method is used to validate the analytical approach. The analytical method enables the calculation of thermally induced stresses with a precision near 10%. A two-dimensional thermomechanical model for a 110 kV cable accessory is developed to calculate the variations in radial and hoop stresses for four types of interfaces: cross-linked polyethylene–cross-linked polyethylene (XLPE–XLPE), silicon rubber–silicon rubber (SiR–SiR), (XLPE–SiR), and XLPE–ethylene propylene rubber (XLPE–EPR). SiR–SiR interfaces exhibited the lowest pressure variations, while XLPE–XLPE interfaces demonstrated the highest. The XLPE–EPR interface showed greater changes in radial thermal stresses than the XLPE–SiR interfaces. It is found that at a conductor temperature of 90 °C, the change in radial thermal stress is − 9.335 × 10⁴ Pa at the XLPE–EPR interface and − 1.587 × 10⁴ Pa at the XLPE–SiR interface. Conversely, the XLPE–SiR interface experienced higher changes in hoop thermal stresses than the XLPE–EPR interface. The change in hoop thermal stress at a conductor temperature of 90 °C is 7.142 × 10⁴ Pa for XLPE–SiR and 3.449 × 10⁴ Pa for XLPE–EPR. The sensitivity analysis conducted in this study indicated that changes in radial thermal stress are positively influenced by the cable insulation’s thermal expansion, the joint insulation’s elastic modulus, and ambient temperature. These factors, however, negatively impacted the changes in hoop thermal stresses.