Quench currents of AC superconductor in supercritical helium

Abstract

A bstra ct-Supercritical helium is proposed as a coolant for a.c. superconducting fault current limiters, because it provides better electrical insulation than conventional pool-boiling helium. However, the effect of SHE cooling on the current carrying capacity of a x . devices is presently unknown. Quench currents were measured for two single-strand NbTi conductors and a tightly-wound two-layer coil at 0-200 Hz frequency and 0-1 T d.c. background magnetic induction in boiling atmospheric helium (LHE) and 6-atm, 4.2-K pressurized helium (SHE).The a.c. quench currents for the Cu30%Ni matrix wire were 2 0~3 0 % lower in SHE, while the CulO%Ni matrix composite showed almost identical quench currents in both coolants. Transient thermal analysis suggests that higher internal temperatures resulting from the Cu30 %Ni matrix's smaller thermal diffusivity may be responsible for its reduced current capacity in SHE.

Single-phase resistive superconductor electrical current limiter

“…Many papers have been reported the developments on this type of electrical equipment, among them [2] and [3] can be mentioned. In this paper it is presented additional details of single-phase RSCL design.…”

Fast Single Layer Cylindrical and Helicoidal Coil With Voids Between Turns Electromagnetic Field Calculation to Be Used in Superconducting Current Limiter Simulator for Design Purpose

“…The resistive superconducting electrical current limiter (RSCL) is an effective solution to solve this problem [1], [2] because it presents all that mentioned desired characteristics to perform as a very fast switch introducing an electrical resistance in series with the circuit in less than 1 ms limiting the short-circuit current to a required value. When the electrical current quickly increases due to an overload or short-circuit occurrence exceeding a critical current at a given temperature of the cryogenic coolant fluid, the superconducting material transits from the superconducting state to the conducting state (quench) due to the increase of the magnitude of the magnetic flux density vector (B) on the material surface above the critical magnetic field Bc.…”