The effect of extreme ambient temperatures on interface pressure of different interfaces in cable accessories under thermal cycling

My research addresses the critical need for accurate stress analysis in power cable joints, a topic that has significant implications for the mechanical design of power cable joints. The paper presents an innovative 2D model, employing the finite element method to calculate mechanical pressure and stresses within a power cable joint. This study is important as it demonstrates that the common assumption of a constant elastic modulus for insulation can lead to significant miscalculations of stresses, potentially impacting the reliability and safety of the joint tubes. The major contributions of our research are: • A comprehensive analysis of radial and circumferential stresses in a power cable joint at different type of interfaces, highlighting the implications of varying ambient temperature. • Evidence that using materials with constant elastic modulus and thermal expansion amplifies both radial and hoop stresses within the joint. • Insights into the critical stress factors at the interface of cable and joint insulations, emphasizing the importance of material choice in ensuring mechanical stability. Climate change introduces formidable challenges to power system infrastructure. Extreme weather and temperature changes are increasing the risk of limiting the withstanding capability of transmission and distribution equipment to stresses. This study employs a 2D thermomechanical model for a 110 kV cable joint, investigating the impact of extreme ambient temperatures on thermally induced stresses at solid-solid interfaces. The model incorporates temperature-dependent thermal expansion and elastic modulus. The changes in radial and hoop stresses are calculated for four types of interfaces; cross-linked polyethylene-silicone rubber (XLPE-SiR), XLPE-EPR Ethylene Propylene Rubber, (XLPE-XLPE), and (SiR-SiR). It is found that at extremely low ambient temperatures, the risk of a drop in radial pressure is higher. Moreover, the change in hoop stress at extremely low ambient temperatures elevates the initial tensile stresses at the interface. SiR-SiR interfaces experienced the lowest variations in pressure while XLPE-XLPE interfaces demonstrated the highest variations. A sensitivity analysis is performed to highlight the significant influence of material properties and ambient temperature. The ambient temperature has a positive impact on radial thermal stress and a negative influence on thermal hoop stress. The model proposed in this research can be used to explain pressure fluctuations that could lead to failures at extreme ambient temperatures. This research offers critical insights into the performance of cable joint materials under extreme conditions, contributing to the design of more resilient power infrastructure.