Cost analysis of dielectric systems for ac superconducting power transmission line

Abstract

conductor becomes unstable. At the higher rates, i.e., for t > 10' A/sec, I j increases monotonically with rate. This increased stability with rate is attributed to a heating effect since current theories of magnetic instabilities predict such an effect at higher temperatures. The simultaneous monitoring of the transport current and flux motion voltage permits one to calculate the power being dissipated at any instant. The surface power density, S, calculated from such data for the high rate regions shows that S exceeds 0.8 W /cm 2 , the value characterizing the onset of film boiling of the helium bath at the surface of a wire sample. The poorer heat transfer under these nearly adiabatic conditions raises the sample temperature, thus making it more stable against flux jumping. Thus, our results point to the possibility of some optimum temperature at which magnets or other devices employing hard superconductors should be operated to reduce flux jumping effects. In addition to this interesting result, this experiment permits one to estimate the current density and the penetration depth to which current is flowing in a wire. Also , the flux motion resistivity of superconducting materials can be studied as a function of the rate of change of current.