The article presents the results of modeling the temperature regime of the electric cable under conditions of a pulse load with high current pulse duty cycle. In these conditions, the IEC and CIGRE standards are not applicable. Therefore, a numerical model for calculating the electrical thermal regime in the COMSOL Multiphysics environment has been proposed. The current pulses are characterized by the pulse front of 10 ms and exponential decrease over several tens of seconds, with a maximum value of 1.5 kA, followed by a 1200-second period, which corresponds to operating modes of the ITER thermonuclear reactor. After approximately 18000 seconds, the core temperature reaches a steady-state periodicity. At the same time, the estimated time required for the task is about 40 hours and depends on the cooling conditions and the pulse period. Based on the calculation of the initial transient temperature function for a single pulse, we propose a numerical and analytical approach to calculate the steady-state electrothermal mode. This significantly reduces the calculation time to 2 hours.