Design and construction of a high temperature superconducting power cable cryostat for use in railway system applications

Abstract

The primary objective of the current effort was to design and test a cryostat using a prototype five-meter long high temperature Bi 2 Sr 2 Ca 2 Cu 3 O y (Bi-2223) superconducting dc power cable for railway systems. To satisfy the safety regulations of the Govt of Japan a mill sheet covered by super-insulation was used inside the walls of the cryostat. The thicknesses of various walls in the cryostat were obtained from a numerical analysis. A non-destructive inspection was utilized to find leaks under vacuum or pressure. The cryostat target temperature range was around 50 K, which is well below liquid nitrogen temperature, the operating temperature of the superconducting cable. The qualification testing was carried out from 77 down to 66 K. When using only the inner sheet wire, the maximum current at 77.3 K was 10 kA. The critical current (I c ) value increased with decreasing temperature and reached 11.79 kA at 73.7 K. This is the largest dc current reported in a Bi 2 Sr 2 Ca 2 Cu 3 O y or YBa 2 Cu 3 O y (Y-123) superconducting prototype cable so far. These results verify that the developed DC superconducting cable is reliable and fulfils all the requirements necessary for successful use in various power applications including railway systems. The key issues for the design of a reliable cryogenic system for superconducting power cables for railway systems are discussed.

H-formulation for simulating levitation forces acting on HTS bulks and stacks of 2G coated conductors

“…However, some applications that use high temperature superconducting materials are able to overcome these obstacles and have been realized. These applications include machines [2], cables [3], fault current limiters [4], and superconducting magnetic bearings (SMBs) [5,6], which are the subject of this work. In this context, in order to make superconductors competitive with other technologies, it is important to develop a simulation tool able to predict the behavior of these materials with high accuracy.…”

Fault current analysis of DC electric railway feeding systems using superconducting power cables

“…In Japan, the Railway Technical Research Institute has designed, developed, and tested prototype DC superconducting power cables and peripheral equipment for cooling, etc. [3] [4]. The highest critical current of the DC superconducting cables that the RTRI developed was 10 kA class at 77 K. According to the results of various tests and demonstration, the performance and reliability of the developed DC superconducting power cable systems has been successfully verified.…”

“…The superconducting wire was assumed to have a uniform temperature over the entire conductor with no lengthwise heat transfer. The thermal equation is as follows: (4) where h is the convection heat transfer coefficient, A is the contact area with LN 2 , m is the mass of the conductor, and C is the heat capacity of the conductor.…”

<b>Superconducting Feeder Cable Laying and Stress Relaxation Method for Cooling</b>

“…It is assumed that superconducting cable can also be used in railway feeder systems. We therefore produced a prototype cable by using superconducting tapes and performing characteristic evaluation tests [2][3][4][5]. A superconducting cable has zero electrical resistance.…”