Mechanical Characteristics Of HTS Quasi-Isotropic Strands

With the development of high temperature superconducting (HTS) technology, significant progress has been made on HTS coated conductors (CCs). The critical current has been increased and anisotropy has been also improved. The superconductor can be used in electric power equipments such as superconducting transformers, superconducting cables, superconducting fault current limiters and superconducting generators. In addition, the study on HTS strands with high current capacity is also growing vigorously. Several kinds of structure of strands such as TSTC, CORC, Roebel Cable have been put forward.In this paper, a new structure of HTS strand based on 2G HTS CCs was put forward. The structure of the strand is presented firstly. The inner parts of the HTS strands are composed of 4 sub-square superconductors which are composed of stacked ReBCO CCs in parallel. The aluminum foil wound on the superconducting core and filling materials are made between the aluminum foil and the metal sheath is tightened by drawing technique. The fabricating process is described in detail.The samples of HTS strands are established with magnetic field simulation software according to the structure of the strand, and the inductance distribution of the strands is calculated. The critical current is calculated based on the simulation results. The E-I curves of the sample HTS strands are also tested in liquid nitrogen.The tensile characteristics and bending characteristics of the superconducting strand are experimentally studied. The critical current of the strand under different tensile stress are tested to get the critical tensile stress. And the ReBCO CCs inside the bended strands are analyzed theoretically. The critical in-plane-bending radius of the CC is tested at 77 K, self-filed. And the HTS strand is bended with different bending radii to obtain the influence of the bending radius on critical current and get the critical bending radius of the HTS strand.Twisting technique is an effective method to reduce AC loss. However, the critical current would be decreased if the twist pitch is too small. The twisted CC is theoretically analyzed and the twist strain of the ReBCO CCs is calculated. A type of twisting apparatus is designed and fabricated to perform measurement for twisting ReBCO CCs and strands. The twisting experiments were carried out at room temperature and the critical currents were tested at 77 K and self-field. The results are predicted that the strand has significance to the application of power transmission and current leads.