High-pressure synthesis of superconducting Nb{1-x}B2 (x = 0-0.48) with the maximum Tc = 9.2 K

Superconductivity with Tc above 9 K was found in metal-deficient NbB2 prepared under 5 GPa, while no clear superconductivity was observed down to 3 K in stoichiometric NbB2. The superconductivity was observed above x = 0.04 in Nb1-xB2. and the lattice parameters also changed abruptly at x = 0.04. As x increased, the transition temperature Tc slightly rose and fell with the maximum value of 9.2 K at x = 0.24 for the samples sintered at 5 GPa and 1200 C. The Tc-value changed in the range from 7 K to 9 K, depending on the sintering pressure. A series of Ta1-xB2 (0 =< x =< 0.24) was also synthesized under high pressure to examine a special effect of high-pressure synthesis.Comment: 24 pages including 2 tables and 7 figures, accepted for publication in Physica

Use of superconducting magnetic energy storage device in a powersystem to permit delayed tripping

Use of a superconducting magnetic energy storage (SMES) device in an electric power system can extend the time margin required for clearing a fault without any loss of stability of the synchronous generators in the system. Necessary mathematical model and computer simulation results have been presented. A wider time margin would be beneficial in many ways, such as precluding unwanted line tripping following temporary earth fault or transient swings, deferring costly replacement of the existing relays and breakers by the faster ones, and making a fair decision on tripping, taking into consideration a large volume of on-line data, constraints and complicated policies likely to be encountered in operating a power system under deregulation or a competitive market environment