Abstract: Most existing temperature prediction methods focus on a single cause and ignore the influence of the coupling effect of combined harmonic and overload on the temperature rise of cables, resulting in large prediction errors. This paper takes low-voltage single-core cables as the research object, and based on Fourier's law and the law of conservation of energy, constructs a transient thermal equilibrium equation under overload causes; Introduces the skin effect to correct the resistance and constructs a transient thermal equilibrium equation under harmonic causes; By coupling the equations of the two causes, determines the boundary conditions, and establishes a transient thermal equilibrium mathematical model integrating harmonics and overload. The model is numerically solved by the finite difference method, and the temperature evolution trends of overload, harmonics, and the combination of the two are deeply analyzed. The results are verified by COMSOL simulation. The results show that the steady-state temperature of the cable has a nonlinear growth relationship with the overload multiple; when the content of each harmonic is constant, as higher harmonics are superimposed, the amplitude of the cable temperature rise gradually decreases; the error between the numerical results and the simulation results is within 1 ℃, verifying the correctness of the model.

Key words: coupling, harmonic-overload, single-core cable, temperature rise