Embodiments include a system, control process, and method for improving the reliability of mineral insulated electrical cables for use in oil and gas industry applications. The embodiments may include a PWM variable speed drive having an optimized operating frequency, a sine wave filter connected to an output of the drive and designed to mitigate reflective voltage wave spikes from the drive's PWM voltage pulses, a mineral insulated electrical heater cable connected to the filter, and an external controller for receiving voltage, current, and temperature feedback to create a voltage set point at which the drive operates. The embodiments may (i) mitigate common failure mechanisms of mineral insulated cables operating at a medium voltage level and in a temperature range of from 200° C. to 700° C.; (ii) extend the range of application of mineral insulated cables; and (iii) prevent high voltage spikes from causing damage to the insulant material of heater cables.