Feasibility study on the application of high temperature superconducting cables in the urban power transmission system

The high temperature superconducting(HTS) cables are most likely to be used for commercial operation in the urban underground power transmission system. They are aimed mainly at retroffing the underground power system by replacing the traditional cables with HTS cables using the existing underground ducts so as to increase the transmission capacity of underground cables and transmission of high electric power(above 1 GVA) to the load centers in downtown areas by HTS cables. For normal conducting cables, the voltage needed here is generally 500 kV. But it is not possible to build 500 kV transformers in downtown areas and large length 500 kV cables and accessories have not been developed. By using HTS cables, the voltage may be reduced. It is possible to transmit high electric power above 1 GVA to the load centers in downtown areas by 220 kV HTS cables so as to meet the needs for power supply by large cities. Even 110 kV HTS cables may transmit ca. 1 GVA electric power. By design and calculation of AC HTS cables, this paper specifies a criterion to determine the suitability of 35 kV, 110 kV and 220 kV HTS cables according to transmission current(transmission capacity), transmission efficiency(ratio of loss to transmission capacity), maximum overall diameter of HTS cables and construction of superconductors. It suggests a feasibility plan for HTS cables used in urban underground power transmission/distribution systems.