Electro-Thermal Coupling Simulation and Fiber Optic Temperature Measurement of Partial Discharge Thermal Effect in XLPE Cable Joints

Aiming at the problem that the existing studies on the thermal effects of partial discharges mainly focus on the steady-state analysis and lack the satisfactory resolution of transient processes, this paper proposes a thermal degradation assessment method based on the coupling of multiple time scales. By constructing a coupled electric-thermal multi-physical field model and adopting a 0.01-mm-level boundary layer grid with an adaptive time discretization algorithm, the simultaneous analysis of the whole process from the microsecond discharge pulse to the hourly thermal diffusion is realized. Numerical simulations show that the air-gap thermal resistance effect increases the local temperature rise by 10°C., and the temperature evolution is characterized by three stages: the initial rapid warming stage, the mid-period thermal diffusion dominated stage, and the late quasi-steady state stage. Distributed validation experiments based on the Brillouin optical time-domain analysis confirm that the temperature responds linearly with the frequency shift to 1.16 MHz/ °C and achieves the accuracy of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">${\pm 0.2}^{\circ}\mathbf{C}$</tex> within the 34 km sensing distance. The method establishes a quantitative model of the time-space evolution of the discharge thermal effect for the first time, which provides a multiscale analytical framework for the state diagnosis of cable joints.