Assessment of Compact High-Tc Superconducting AC Power Cable and Its Application

We present the possible application of a compact high-Tc superconducting AC power cable for transmitting electric power in urban areas, reflecting its novel features such as extreme compactness for installation in underground ducts and considerably large-capacity rating comparable to present high-voltage cables. These new aspects are expected to bring a great cost benefit in the expansion of underground power transmission systems, primarily due to the fact there is no need to construct additional underground tunnels. We set up a model system using 66kV high-Tc superconducting cables with a 350-700MW capacity based on the typical skeleton of a present 275kV system. We investigated the stability of the model system, and found that stable power transmission is possible using a parallel capacitor within a rating capacity of a tertiary coil of transformers even though the high-Tc superconducting cable operates at a fairly low voltage and carrries large electric power. It was pointed out that the effective reactance of high-Tc superconducting cable is roughly an order of magnitude lower than that of present-day 66kV cable to the existence of a perfect shielding layer, which greatly contributes to the stability of the system.