Fundamental Analysis of Electrothermal Coordination of Underground Cables toward High-Penetration Renewable Generation

As the penetration level of intermittent renewable generation increases, transmission line current exhibits more fluctuations and uncertainty compared to conventional power systems. Assuming that intermittent renewable generation is sinusoidal line current based on root-mean-square (RMS), this study evaluates the conductor temperature of a single-core cross-linked polyethylene (XLPE) underground cable. To analyze the increase in the temperature of the cable, the multistage Cauer-type thermal equivalent circuit model for XLPE cables consisting of several parts of thermal resistance and thermal capacitance is applied. Considering various periods of RMS-based sinusoidal line current signals, the appropriate number of stages of the thermal equivalent circuit components is determined such that cable conductor temperature can be estimated accurately. The external surface temperature of the cable is evaluated considering the temperature distribution inside the cable. Owing to thermal capacity, the cable itself can reduce the temperature rise by absorbing the heat generated by the sinusoidal input current.