AC Loss Reduction of Coaxial Multi-Layer HTS Cable

Abstract

Reducing AC losses, cable size and cost of HTS tapes are required for the practical application of HTS power transmission line. We have theoretically investigated the relationship between AC losses and cable parameters such as layer radius and twisting pitch and direction in coaxial multi-layer HTS cable using our developed simulation method and revealed that the larger number of HTS tapes and twisting pitch are desirable for reduction of AC losses. In this paper we investigated influence of twisting pitch and direction on cable size and total amount of HTS tapes under a condition of constant AC losses. The diameter of each layer and total amount of HTS tapes in the cable with the same twisting direction are much smaller than those of alternate twisting direction. The cable with the same tape current would be better than that of the same layer current because of the smaller difference of the number of tapes per layer. In the cable with the same tape current, cable size decreases with the number of layers in spite of almost the same amount of total HTS tapes in the whole cable. In cable design, we cannot handle the restrictions of AC loss and load factor individually; it would be difficult to satisfy both the conditions of low AC loss and high load factor. AC losses could be reduced by increasing critical current of HTS tape without the restriction of load factor, while AC losses increases with the critical current with the restriction of load factor.

A Simple and Fast Computation Equivalent Circuit Model to Investigate the Effect of Tape Twisting on the AC Loss of HTS Cables

“…If the mechanical limits surpass the threshold value, the critical current abruptly becomes zero. The correlation between the strain and the critical current of tapes is expressed in (15)(16)(17)(18)(19) [34]:…”

“…The AC current and the generated fields induce losses in HTS cables which are known as transport current loss and hysteresis loss respectively [16]. These losses increase the heat load of the cooling system and consequently, the efficiency of the cable is reduced [17,18]. To avoid such consequences, numerous attempts were conducted to reduce the AC loss of cables.…”

Performance Analysis of Real-Scale 23 kV/60 MVA Class Tri-Axial HTS Power Cable for Real-Grid Application in Korea

“…The governing equation for the tri-axial HTS power cable AC loss analysis applies Maxwell's equations, including Faraday's law and Ampere's circuital law, as shown in Equations (4) and (5). In addition, E-J characteristics with superconducting nonlinear characteristics, as shown in Equation (6), are reflected in each phase's superconducting wire [17,18].…”