US3214637A - Device for indicating the ceasing of super-conductivity - Google Patents

Device for indicating the ceasing of super-conductivity Download PDF

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US3214637A
US3214637A US270698A US27069863A US3214637A US 3214637 A US3214637 A US 3214637A US 270698 A US270698 A US 270698A US 27069863 A US27069863 A US 27069863A US 3214637 A US3214637 A US 3214637A
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super
conductor
voltage
conducting
sensing means
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Persson Erik
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ABB Norden Holding AB
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
    • H02H7/001—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for superconducting apparatus, e.g. coils, lines, machines
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N60/00—Superconducting devices
    • H10N60/01—Manufacture or treatment
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
    • Y02E40/60—Superconducting electric elements or equipment; Power systems integrating superconducting elements or equipment
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S505/00—Superconductor technology: apparatus, material, process
    • Y10S505/825—Apparatus per se, device per se, or process of making or operating same
    • Y10S505/85—Protective circuit

Definitions

  • the present invention relates to a protective device sensing the cessation of super-conductivity in a superconductor which encloses a flux generated by a current through the super-conductor.
  • a non-super-conducting'conductor is electrically connected to one end of the super-conductor to follow the superconductor closely but is electrically insulated therefrom and between the non-connected end points of the two conductors a voltage-sensing means is connected, said voltage sensing means being so arranged that at a predetermined voltage diiference between the last-mentioned end points it initiates protective action by first connecting together the end points of the non-super-conducting conductor, possibly across a suitable discharge resistor, and
  • the voltage difference normally sensed by the voltagesensing means is zero. If the super-conductivity ceases at some point of the super-conductor, a voltage drop is obtained across the super-conductor which gives a voltage difference e between the non-connected end points of the two conductors. The presence of this voltage difference e thus means that a fault exists in the super-conductor and the voltage-sensing means is arranged to break the super-conductor current circuit.
  • the non-super-conductor is suitably arranged to enclose wholly or partly the superconductor.
  • FIGURE 1 is a circuit diagram of a device in accordance with the invention and FIGURES 2 and 3 show how the non-super-conducting conductor may be arranged around the super-conductor.
  • the numeral 1 indicates a super-conducting conductor and 2 a non-super-conducting conductor which have been wound to form a coil.
  • the conductors 1 and 2 are electrically connected at 4 and between their ends 5 and 6 a voltage-sensing means is connected.
  • the coil is enclosed by a cooling system 7 filled with e.g. liquid helium.
  • the super-conductor is fed from a voltage source 8.
  • the voltage-sensing means includes, inter alia, a time delay relay 10 and is operatively connected to a switching device in the form of a contactor 11.
  • the contactor 11 receives its operating voltage from a voltage source 9.
  • the time delay relay includes a coil 12 and a closing contact 13, and the contactor consists of a coil 16, a breaking contact 17 and a closing contact 18.
  • the device functions in the following manner. On the occasion of a fault in the super-conductor 1 a voltage difference e arises between the points 5 and 6.
  • the contact 13 then closes with a certain delay determined by the dimensions of a capacitor 14 and a resistance 15.
  • a current flows through the coil, whereupon first the contact 18 is closed and thereafter the contact 17 is opened.
  • the current in the super-conductor may be broken very quickly since it may be transferred to conductor 2. It may however be necessary to insert a damping resistor 20 in order to take care of the little energy which remains in the leakage field between the conductors 1 and 2.
  • FIGURES 2 and 3 show possible ways of enclosing the super-conductor 1 within the non-super-conducting conductor 2, there being a layer 3 of electrical insulation between the conductors. Having regard to the very large dynamic forces which act on a conductor in a magnet coil of the magnitude mentioned above, the embodiment according to FIGURE 3 is perhaps mechanically the more suitable.
  • a circuit including a super-conductor, means for protecting said super-conductor in case of cessation of super-conductivity, said super-conductor having a first and second end terminals and enclosing a magnetic flux generated by a current through said super-conductor, said device including a non-super-conducting conductor arranged to follow said super-conductor closely but electrically insulated therefrom between said terminals, said non-super-conducting conductor having first and second end points, said first terminal being electrically connected to said first end point, a voltage sensing means connected between said second end terminal and said second end point, a switching device in said super-conductor circuit,
  • said voltage sensing means being operatively connected to said switching device to initiate protective action in response to a predetermined voltage difference between said second terminal and said second end point, said switching device thereupon first connecting together said end points of said non-super-conducting conductor and thereafter breaking said current in said super-conductor.

Description

E. PERSSON 3,214,637
DEVICE FOR INDICATING THE GEASING OF SUPER-CONDUCTIVITY Filed April 4, 1965 Fig 2 United States Patent 3,214,637 DEVICE FOR INDICATING THE CEASING 0F SUPER-CONDUCTIVITY Erik Persson, Vasteras, Sweden, assignor to Allmanna Svenska Elektriska Aktiebolaget, Vasteras, Sweden, a corporation of Sweden Filed Apr. 4, 1963, Ser. No. 270,698 Claims priority, application Sweden, Apr. 9, 1962,
3 Claims. (Cl. 317-9) Certain materials have the property, at low temperatures in the neighbourhood of the absolute zero point, of becoming super-conducting, implying that the resistivity at a certain critical temperature suddenly sinks to zero. The critical temperature for lead is about 7 K and for mercury 4 K. In recent times this property has been utilised by using super-conductors in the magnetising winding of very large magnets with large field strength. Such magnets are suitably built without an iron circuit. The necessary magnetising power becomes equal to zero since the super-conductor has no resistance, but of course a certain amount of power is consumed in keeping the super-conductor at the necessary temperature. As a rule the cooling is performed by means of liquid helium.
Problems arise, however, if for some reason an increased temperature occurs at some point on the superconductor and the super-conductivity as a result ceases to exist at this point. If steps are not taken to disconnect the super-conductor quickly, it will melt at the fault point. The process becomes explosive since the very large magnetic energy of the magnet coil (of the order of 100 mws.) will be discharged in a short time in the nonsuper-conducting zone, which will be very short as the heat generated by current losses in the zone will not have time to spread to other parts of the coil.
The present invention relates to a protective device sensing the cessation of super-conductivity in a superconductor which encloses a flux generated by a current through the super-conductor. According to the invention, a non-super-conducting'conductor is electrically connected to one end of the super-conductor to follow the superconductor closely but is electrically insulated therefrom and between the non-connected end points of the two conductors a voltage-sensing means is connected, said voltage sensing means being so arranged that at a predetermined voltage diiference between the last-mentioned end points it initiates protective action by first connecting together the end points of the non-super-conducting conductor, possibly across a suitable discharge resistor, and
thereafter breaking the super-conductor current circuit.
Since the super-conductor, when it is super-conducting, has no resistance and the other conductor carries no current and both conductors are influenced by the same flux, the voltage difference normally sensed by the voltagesensing means is zero. If the super-conductivity ceases at some point of the super-conductor, a voltage drop is obtained across the super-conductor which gives a voltage difference e between the non-connected end points of the two conductors. The presence of this voltage difference e thus means that a fault exists in the super-conductor and the voltage-sensing means is arranged to break the super-conductor current circuit.
It is important that the conductors follow each other as intimately as possible so that due to a great many different leakage fluxes the voltage e will not be generated on the occasion of faults other than a fault in the superconductor. For this reason the non-super-conductor is suitably arranged to enclose wholly or partly the superconductor.
In spite of this arrangement of the two conductors it 'ice is impossible to eliminate the circular flux between the conductors, which, on the occasion of changes in the current through the super-conductor, may induce a voltage of the magnitude e across the voltage sensing means. It is therefore advisable to provide the device with a delaying means, which is intended to obstruct the protective action when the voltage-sensing means senses a predetermined voltage difference e of only short duration. The time delay chosen is so long that the voltage-sensing means does not initiate action for the diiferent irrelevant disturbances which may occur, but not so long that the voltage-sensing means cannot initiate action before a fault in the super-conductor causes its destruction.
The invention will now be described in greater detail, by way of example with reference to the accompanying drawings, in which FIGURE 1 is a circuit diagram of a device in accordance with the invention and FIGURES 2 and 3 show how the non-super-conducting conductor may be arranged around the super-conductor.
In FIGURE 1, the numeral 1 indicates a super-conducting conductor and 2 a non-super-conducting conductor which have been wound to form a coil. The conductors 1 and 2 are electrically connected at 4 and between their ends 5 and 6 a voltage-sensing means is connected. The coil is enclosed by a cooling system 7 filled with e.g. liquid helium. The super-conductor is fed from a voltage source 8. The voltage-sensing means includes, inter alia, a time delay relay 10 and is operatively connected to a switching device in the form of a contactor 11. The contactor 11 receives its operating voltage from a voltage source 9. The time delay relay includes a coil 12 and a closing contact 13, and the contactor consists of a coil 16, a breaking contact 17 and a closing contact 18.
The device functions in the following manner. On the occasion of a fault in the super-conductor 1 a voltage difference e arises between the points 5 and 6. The contact 13 then closes with a certain delay determined by the dimensions of a capacitor 14 and a resistance 15. When the contact 13 is closed a current flows through the coil, whereupon first the contact 18 is closed and thereafter the contact 17 is opened. This means that the end points of the non-super-conducting conductor 2 are first connected across a resistor 19 and that the current circuit of the super-conductor is thereafter broken. The current in the super-conductor may be broken very quickly since it may be transferred to conductor 2. It may however be necessary to insert a damping resistor 20 in order to take care of the little energy which remains in the leakage field between the conductors 1 and 2.
FIGURES 2 and 3, show possible ways of enclosing the super-conductor 1 within the non-super-conducting conductor 2, there being a layer 3 of electrical insulation between the conductors. Having regard to the very large dynamic forces which act on a conductor in a magnet coil of the magnitude mentioned above, the embodiment according to FIGURE 3 is perhaps mechanically the more suitable.
I claim:
1. In a circuit including a super-conductor, means for protecting said super-conductor in case of cessation of super-conductivity, said super-conductor having a first and second end terminals and enclosing a magnetic flux generated by a current through said super-conductor, said device including a non-super-conducting conductor arranged to follow said super-conductor closely but electrically insulated therefrom between said terminals, said non-super-conducting conductor having first and second end points, said first terminal being electrically connected to said first end point, a voltage sensing means connected between said second end terminal and said second end point, a switching device in said super-conductor circuit,
said voltage sensing means being operatively connected to said switching device to initiate protective action in response to a predetermined voltage difference between said second terminal and said second end point, said switching device thereupon first connecting together said end points of said non-super-conducting conductor and thereafter breaking said current in said super-conductor.
2. In a circuit according to claim 1, said non-superconducting conductor being arranged to enclose said super-conductor at least partly. l
3. In a circuit according to claim 1, delaying means for preventing protective action when said voltage sensing means senses a predetermined voltage difierence of short duration.
References Cited by the Examiner UNITED STATES PATENTS SAMUEL BERNSTEIN, Primary Examiner.

Claims (1)

1. IN A CIRCUIT INCLUDING A SUPER-CONDUCTOR, MEANS FOR PROTECTING SAID SUPER-CONDUCTOR IN CAE OF CESSATION OF SUPER-CONDUCTIVELY, SAID SUPER-CONDUCTOR HAVING A FIRST AND SECOND END TERMINALS AND ENCLOSING A MAGNETIC FLUX GENERATED BY A CURRENT THROUGH SAID SUPER-CONDUCTOR, SAID DEVICE INCLUDING A NON-SUPER-CONDUCTOR CONDUCTOR ARRANGED TO FOLLOW SAID SUPER-CONDUCTOR CLOSELY BUT ELECTRICALLY INSULATED THEREFROM BETWEEN SAID TERMINALS, SAID NON-SUPER-CONDUCTING CONDUCTOR HVING FIRST AND SECOND END POINTS, SAID FIRST TERMINAL BEING ELECTRICALLY CONNECTED TO SAID FIRST END POINT, A VOLTAGE SENSING MEANS CONNECTED BETWEEN SAID SECOND END TERMINAL AND SAID SECOND END POINT, A SWITCHING DEVICE IN SAID SUPER-CONDUCTOR CIRCUIT, SAID VOLTAGE SENSING MEANS BEING OPERATIVELY CONNECTED TO SAID SWITCHING DEVICE TO INITIATE PROTECTIVE ACTION IN RESPONSE TO A PREDETERMINED VOLTAGE DIFFERENCE BETWEEN SAID SECOND TERMINAL AND SAID SECOND END POINT, SAID SWITCHING DEVICE THEREUPON FIRST CONNECTING TOGETHER SAID END POINTS OF SAID NON-SUPER-CONDUCTING CONDUCTOR AND THEREAFTER BREAKING SAID CURRENT IN SAID SUPER-CONDUCTOR.
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Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3270247A (en) * 1964-10-01 1966-08-30 Gen Electric Protective circuit for removing energy from superconducting coils
US3336526A (en) * 1963-12-30 1967-08-15 Varian Associates Superconducting magnet
US3360692A (en) * 1963-12-24 1967-12-26 Siemens Ag Device for producing high-intensity magnetic fields of short duration
US3414660A (en) * 1964-12-16 1968-12-03 Asea Ab Means for protection against and/or indication of faults in coreless induction furnaces, heating furnaces and the like
US3579035A (en) * 1967-09-29 1971-05-18 Alsthom Cgee System for detection of transition between superconductive and resistant state in superconductive coils
US3629690A (en) * 1969-06-26 1971-12-21 Siemens Ag Current limiting device for limiting short circuit current in energy transfer systems
US4140021A (en) * 1976-10-08 1979-02-20 Agency Of Industrial Science & Technology Method and device for monitoring superconducting system
US4375659A (en) * 1981-09-21 1983-03-01 General Dynamics Corporation/Convair Div. Electronic circuit for the detection and analysis of normal zones in a superconducting coil
US4467384A (en) * 1982-02-10 1984-08-21 Mitsubishi Denki Kabushiki Kaisha Protective device for DC regulated power supplies for superconducting magnet coils
US4978922A (en) * 1989-08-31 1990-12-18 Westinghouse Electric Corp. Superconducting sensor for quench detection in a superconductor

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3056889A (en) * 1958-05-19 1962-10-02 Thompson Ramo Wooldridge Inc Heat-responsive superconductive devices
US3109963A (en) * 1960-08-29 1963-11-05 Bell Telephone Labor Inc Insulated superconducting wire
US3148308A (en) * 1961-12-27 1964-09-08 Westinghouse Electric Corp Transformer
US3176195A (en) * 1962-04-02 1965-03-30 Roger W Boom Superconducting solenoid
US3177408A (en) * 1961-09-18 1965-04-06 Robert G Mills Superconductor solenoid with overheat protective structure and circuitry

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3056889A (en) * 1958-05-19 1962-10-02 Thompson Ramo Wooldridge Inc Heat-responsive superconductive devices
US3109963A (en) * 1960-08-29 1963-11-05 Bell Telephone Labor Inc Insulated superconducting wire
US3177408A (en) * 1961-09-18 1965-04-06 Robert G Mills Superconductor solenoid with overheat protective structure and circuitry
US3148308A (en) * 1961-12-27 1964-09-08 Westinghouse Electric Corp Transformer
US3176195A (en) * 1962-04-02 1965-03-30 Roger W Boom Superconducting solenoid

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3360692A (en) * 1963-12-24 1967-12-26 Siemens Ag Device for producing high-intensity magnetic fields of short duration
US3336526A (en) * 1963-12-30 1967-08-15 Varian Associates Superconducting magnet
US3270247A (en) * 1964-10-01 1966-08-30 Gen Electric Protective circuit for removing energy from superconducting coils
US3414660A (en) * 1964-12-16 1968-12-03 Asea Ab Means for protection against and/or indication of faults in coreless induction furnaces, heating furnaces and the like
US3579035A (en) * 1967-09-29 1971-05-18 Alsthom Cgee System for detection of transition between superconductive and resistant state in superconductive coils
US3629690A (en) * 1969-06-26 1971-12-21 Siemens Ag Current limiting device for limiting short circuit current in energy transfer systems
US4140021A (en) * 1976-10-08 1979-02-20 Agency Of Industrial Science & Technology Method and device for monitoring superconducting system
US4375659A (en) * 1981-09-21 1983-03-01 General Dynamics Corporation/Convair Div. Electronic circuit for the detection and analysis of normal zones in a superconducting coil
US4467384A (en) * 1982-02-10 1984-08-21 Mitsubishi Denki Kabushiki Kaisha Protective device for DC regulated power supplies for superconducting magnet coils
US4978922A (en) * 1989-08-31 1990-12-18 Westinghouse Electric Corp. Superconducting sensor for quench detection in a superconductor

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