High Performance 2G Wires: From R&D to Pilot-Scale Manufacturing

Tremendous progress has been accomplished in 2008 in key metrics of YBa₂Cu₃O_x (YBCO) second-generation (2G) HTS wires at SuperPower. Using improved precursor chemistry in our metal organic chemical vapor deposition (MOCVD) process, critical currents (I_c) as high as 813 A/cm were reached over meter-long lengths, representing the highest reported I_c in meter long 2G HTS. By use of Zr doping of (Gd,Y)Ba₂Cu₃O_x, strong enhancements were achieved in in-field performance over a wide angular range. A I_c of 229 A/cm was achieved at 77 K and 1 T perpendicular to the wire which is about a factor of 2.5 times better than that of standard MOCVD-derived films. At 65 K and 3 T, a I_c of 340 A/cm was demonstrated perpendicular to the wire. Kilometer lengths of 2G HTS have been demonstrated for the first time. Over 35 tapes 1,000 to 1,500 m in length with a complete 5-layer buffer stack have been routinely produced in our pilot-scale manufacturing facilities. An excellent in-plane texture of 6 to 7 degrees with a uniformity of about 2% was reproducibly achieved in the kilometer-long fully-buffered tapes. Using these high-quality buffers, the longest 2G wire length to date of 1,311 m was produced with a minimum Ic of 153 A/cm corresponding to a I_c times length value of 200,580 m. Also, an 1,030 m long complete 2G HTS wire has been demonstrated with a minimum Ic of 227 A/cm corresponding to a record I_c times length value of 233,810 A-m. Further, a 630 m long segment of the wire sustained a minimum I_c of 302 A/cm, the longest 2G wire reported to date with a I_c over 300 A/cm. Also, a I_c of 337 A/cm was achieved over a 540 m long segment. All these values represent a 2 to 3 fold improvement in length and I_c of 2G wires compared to our achievements in 2007. In 2008, a 30 m long 2G cable made with nearly 10,000 m of 2- - G wire previously delivered by SuperPower was successfully installed and energized in the grid of National Grid in downtown Albany, marking the world´s first of 2G HTS device in the power grid.