Study on the Induced Voltage of Concentric High Temperature Superconducting Cable

High temperature superconducting (HTS) cable, with advantages such as high current density, low transmission loss and low corridor occupation, has been a cutting-edge research field for electric power transmission. The concentric HTS cable does not need a superconducting shielding layer as the leakage magnetic field is very small. Therefore, concentric HTS cable saves the amount of HTS tapes and is more compact. However, in reality, the three phases in a concentric core could not be absolutely balanced both in physically and in electrically and the induced voltage outside the cable core would exist inevitably. In practice, the grounding methods of the shielding layer and cryogenic pipes are closely related to the induced voltage characteristics as well. In this paper, an analytical electromagnetic model of concentric HTS cable is established based on the Maxwell relations and the 2D axisymmetric model. The characteristics of three-phase imbalance and its induced voltage characteristics generated on the shielding layer and the cryogenic pipes are studied. Since the cryogenic pipes are consisted of two pipe and electrical connected parallelly, the related circulation current and its additional heat load to the cryogenic cooling system are considered. The analysis approach and research result in this paper is not only for designing concentric HTS cable system, but also for referring of other types of HTS cable systems.