External Temperature Response of a 154 kV Gas-Insulated Cable Termination for Submarine Cable Systems under Dielectric-Loss Variation

This study investigates whether variations in dielectric loss inside a gas-insulated cable termination can be detected through temperature changes at the lower copper tube and PVC band. A three-dimensional model of a 154 kV, 2500 mm² XLPE cable termination was developed for the grid connection of a submarine cable system. Conductor heating was applied equally to all cases, while dielectric heat generation in the XLPE insulation and stress cone was calculated using the electric field, relative permittivity, and loss tangent. Three cases with different dielectric properties were evaluated. Electric field distributions were obtained using ANSYS Maxwell 3D, and the calculated volumetric heat sources were applied to a transient thermal model. Under identical load and ambient conditions, Case 3 showed temperature increases of approximately 1.0 °C at the lower copper tube and 1.4 °C at the PVC band compared with Case 1. These results provide a physical basis for detecting changes in internal insulation conditions through continuous external temperature monitoring.