HTS materials for ac current transport and fault current limitation

The European SUPERPOLI project aims to define a MV fault current limiting power link, and to demonstrate its feasibility by a functional model. It includes the development of two alternative low-ac-loss conductor designs suitable for current limitation: a low-cost composite tubular Bi-2212 conductor with moderate Jc; and a coated tubular Y-123 conductor, presenting a very high J_c. BSCCO tubes are developed by Alcatel HTS (length : 650 mm and diameter : 50 mm) with silver contacts on both ends. These tubes have an effective thickness of the superconducting layer of 1.5 mm. This layer is reinforced by an additional non superconducting layer in order to increase mechanical stability. Based on theoretical simulations, Alcatel HTS seeks to develop tubes with a Jc scattering lower than 2%. The main issue with Y-123 films is to find a way for producing them in long reproducible lengths. A novel high rate PLD technique with a repetition rate of 300 Hz has been recently developed and used for manufacturing films on large-area substrates, made of flexible stainless steel foils buffered by IBAD. The largest samples prepared are in size of 34 mm × 1 m, and present a Jc of 4000 A/mm² (77 K, self-field). For a sample with dimensions of 10 mm × 0.5 m, Jc exceeds 6000 A/mm².