Quench protection in high-temperature superconducting magnets

Patent metadata

Field	Value
Publication number	US-2019252104-A1
Application number	US-201716346030-A
Country	US
Kind code	A1
Filing date	Oct 10, 2017
Priority date	Oct 31, 2016
Publication date	Aug 15, 2019
Grant date	—

Abstract

A superconducting magnet comprising: a field coil comprising high temperature superconducting material and having a joint; a bypass resistance comprising a non-superconducting conductive material, wherein the bypass resistance is electrically connected to the field coil on both sides of the joint; wherein the joint is openable to break the field coil such that current flowing in the superconductor flows though the bypass resistance in order to dump energy from the field coil, and wherein the superconducting magnet is configured to open the joint in response to detection of a quench in the magnet.

First claim

1 . A method of detecting quenches in a superconducting magnet comprising a plurality of jointed cable sections comprising HTS material in a coil, the method comprising:
providing a plurality of optical fibres, wherein each cable of the coil of the superconducting magnet is in thermal contact with at least one of the optical fibres; monitoring backscattered light from each of the optical fibres; comparing changes in wavelength of backscattered light from each optical fibre; detecting a change in temperature of a cable of the coil on the basis of a change in wavelength observed in one or more first optical fibres of the plurality of optical fibres which are in thermal contact with the cable, but not observed in second optical fibres of the plurality of optical fibres which are not in thermal contact with the cable; and in response to said detection, determining that the cable has quenched.

2 . A method according to claim 1 , where each optical fibre is in thermal contact with a single section of cable between joints.

3 . A method according to claim 1 , wherein each of the cables comprises one of the optical fibres.

4 . A method according to any claim 1 , and further comprising monitoring strain of the superconducting magnet by analysing changes in wavelength of backscattered light which are observed in substantially all of the optical fibres.

5 . A method according to any claim 1 , further including analysing said changes in wavelength in said first optical fibres to determine a magnitude of the change in temperature; and
determining that the cable has quenched if said change in temperature exceeds a threshold in a subset of the fibres.

6 . A method of detecting quenches in a superconducting magnet comprising a plurality of cables comprising HTS material in a coil, comprising:
providing a plurality of optical fibres, wherein each cable of a coil of the superconducting magnet is in thermal contact with at least one of the optical fibres; monitoring backscattered light from each of the optical fibres; comparing changes in wavelength of backscattered light from each optical fibre; detecting a change in temperature of one or more cables of the coil on the basis of a change in wavelength observed only a subset of the plurality of optical fibres, but not observed in the rest of the optical fibres; and in response to said detection, determining that the cable has quenched.

7 . A superconducting magnet comprising:
a plurality of turns comprising cables comprising HTS superconducting material; a plurality of optical fibres, wherein each cable is in thermal contact with at least one of the optical fibres; a control unit configured to:
monitor backscattered light from each of the optical fibres;
compare changes in wavelength of backscattered light from each optical fibre;
detect a change in temperature of a cable of the coil on the basis of a change in wavelength observed in one or more first optical fibres of the plurality of optical fibres which are in thermal contact with the cable, but not observed in second optical fibres of the plurality of optical fibres which are not in thermal contact with the cable; and
on the basis of said detection, determine that the cable has quenched.

8 . A superconducting magnet according to claim 7 , where each optical fibre is in thermal contact with a plurality of the cables.

9 . A superconducting magnet according to claim 7 , wherein each of the cables comprises one of the optical fibres.

10 . A superconducting magnet according to claim 7 , wherein the controller is further configured to monitoring strain of the superconducting magnet by analysing changes in wavelength of backscattered light which are observed in substantially all of the optical fibres.

11 . A toroidal field coil assembly for use in a nuclear fusion reactor, the assembly comprising:
a toroidal field coil comprising high temperature superconductor; neutron shielding configured to shield the high temperature superconductor from neutrons emitted by a nuclear fusion reaction; wherein the neutron shielding is conductive and is configured to operate as a shorted inductive coil magnetically coupled to the toroidal field coil.

12 . A toroidal field coil assembly according to claim 11 , wherein the neutron shielding comprises tungsten carbide.

13 . A cable comprising:
high temperature superconductor, a first copper stabiliser in electrical contact with the high temperature superconductor, and a second copper stabiliser electrically insulated from the high temperature superconductor and the first copper stabiliser, such that when the cable is wound so that the high temperature superconductor forms a magnetic field coil the second copper stabiliser forms a shorted inductive coil magnetically coupled to the magnetic field coil.

14 . A magnetic field coil comprising cable according to claim 13 .

15 . A superconducting magnet comprising:
a field coil comprising high temperature superconducting material and having a joint; a bypass resistance comprising a non-superconducting conductive material, wherein the bypass resistance is electrically connected to the field coil on both sides of the joint; wherein the joint is openable to break the field coil such that current flowing in the superconductor flows though the bypass resistance in order to dump energy from the field coil, and wherein the superconducting magnet is configured to open the joint in response to detection of a quench in the magnet.

16 . A superconducting magnet according to claim 15 , wherein the joint is closeable by the application of pressure, and comprising releasable means for applying pressure to the joint.

17 . A superconducting magnet according to claim 16 , wherein said means for applying pressure is a hydraulic ram.

18 . A superconducting magnet according to claim 15 , wherein the field coil is a non-insulated or metal-insulated field coil.

Assignees

• Tokamak Energy Ltd

Inventors

• Slade Robert

Classifications

• G21B1/23

  Optical systems, e.g. for irradiating targets, for heating plasma or for plasma diagnostics · CPC title

• H01F6/065

  Feed-through bushings, terminals and joints (leading of conductors or axles through casings of transformers H01F27/04) · CPC title

• G21B1/21

  Electric power supply systems, e.g. for magnet systems, switching devices, storage devices, circuit arrangements {(methods or means for discharging superconducting storage windings H01F6/003)} · CPC title

• H02H7/001

  for superconducting apparatus, e.g. coils, lines, machines · CPC title

• G01K11/32

  using changes in transmittance, scattering or luminescence in optical fibres · CPC title