Optimal Design And Current Sharing Characteristics Of 110kV Cold Dielectric High Temperature Superconducting Cable

Cold dielectric high temperature superconducting (CD HTS) cable has been developed rapidly because of the small size, low losses, high capacity and non-electromagnetic pollution compared with the normal conductor power cable. Because the CD HTS cable has a multilayer structure, the non-uniform AC current distribution of the multilayer conductors will increase the AC losses and decrease the current transmission efficiency.A 1 km,110 kV/3 kA YBCO-based CD HTS AC power cable has been designed and had the uniform current distribution of the multilayer conductors. Firstly, we calculate the self and mutual inductances of the conductor layer and the shield layer in the HTS cable by using Ampere's Law and the effects of the structural parameters, such as inner diameter, winding angle and winding direction, on the electromagnetic characteristics are studied. Secondly, the equivalent circuit model of the HTS cable is constructed and the current of each conductor layer and shield layer is obtained considering the shield current influence on the current carrying characteristic of the conductor layer in the cable. Thirdly, we have optimized the cable for the current distribution equilibrium. An improved particle swarm optimization (PSO) algorithm with dynamically changing inertia weight (DCW) is presented. We apply the inner diameter, the winding angle and the winding direction of each conductor layer as the optimization variables and the current distribution among the conductors as the optimal objective in this PSO algorithm. Based on the MATLAB software, we have programmed and finished the optimal design considering the effects of the critical current under external magnetic field, mechanical strain and heat loss. After the optimization, each conductor layer current hold total current proportion is 22.9%,28.5%, 22.8%,25.7%. These results show that a uniform current distribution among each layer in a CD HTS cable is realized by optimizing the structural parameters and validate the improved PSO optimal design at the same time.A CD HTS cable optimal design software package has been completed by using the ActiveX technology to achieve the interface calling between Delphi and MATLAB. The HTS cable optimal design package realizes a 3D visualization of the optimal structure design and displayes the current distribution in each cable layers. It makes the optimal design of the CD HTS cable is more convenient and efficient. In addition, the fabrication platform of the CD HTS cable has been set up, and based on the optimal structure parameters calculation of the former, conductor layers, insulation layers and shield layers, a demo CD HTS cable with the length of 1.5 m has been efficiently fabricated by setting a single conductor layer as a winding unit and the current-carrying test has been taken to the model cable at last. The experimental results show that the current distribution of each layer in model cable is nearing to balance, and verify the proposed optimization design method is efficient.