Termination for superconducting power transmission systems

• US 3,902,000 A
• Filed: 11/12/1974
• Issued: 08/26/1975
• Est. Priority Date: 11/12/1974
• Status: Expired due to Term

• Current Assignee: Eric B. Forsyth, Jack E. Jensen
• Original Assignee: Eric B. Forsyth, Jack E. Jensen
• Inventors: Forsyth, Eric B., Jensen, Jack E.
• Primary Examiner(s): Grimley, Arthur T.
• Application Number:
  US05/523,182
• Time in Patent Office: 287 Days
• Field of Search: 174/15BH,16BH,12BH,14BH,15C,15R,DIG.6,19,20,73R,11BH,11R
• US Class Current: 174/15.3
• CPC Class Codes: H02G 15/34 Cable fittings for cryogenic cables superconductive cables per se H01B12/00
• CPC Class Codes: Y02E 40/60 Superconducting electric elements or equipment; Power systems integrating superconducting elements or equipment
• CPC Class Codes: Y10S 174/32 having means for cooling
• CPC Class Codes: Y10S 505/886 Cable

Abstract

Cold, electrical gradient, terminal section for a superconductor cable for alternating current power transmission for making an electrical connection between room-temperature components and a cable that is operating in the superconducting mode and is carrying electrical power. In one embodiment, this invention has a cold electrical gradient section in series with a separate thermal gradient section, the former having an electrical stress cone of increasing diameter filled with a flowing, pressurized, gaseous, He, cryogenic coolant, which acts as an electrical insulator and longitudinally separates spaced-apart, solid, oppositively tapered, electrical insulators axially arranged between co-axial, cylindrical superconductors forming composite structures in a containment for the cryogenic coolant for providing control of the electrical field intensity and current density in a cold electrical gradient terminal section that is in series with a thermal gradient section having a room temperature portion containing high pressure seals. The cable may be rigid or flexible.

Claims

1. Cold, electrical gradient, terminal apparatus for use with a source of cryogenic cooling fluid under pressure in a gas pressure insulated, superconducting transmission line having electrical and thermal gradient sections in series comprising:

a. first, stabilized, cylindrical superconducting means;

b. second, stabilized, cylindrical superconducting means that is co-axial with the first superconducting means and forms an annulus of increasing diameter therebetween; and

c. first, pressurized, terminal, thermal gradient, electrical insulating means in said annulus forming a tapered, terminal, electrical gradient, stress cone that extends longitudinally in the annulus between the first and second superconducting means having d. flowing cryogenic cooling fluid under pressure in the annulus between the first and second superconducting means along the electrical gradient stress cone for providing a terminal cold electrical insulator between the first and second superconducting means;

e. the thermal gradient electrical insulation means having outlet means for the cryogenic cooling fluid for circulating the same through the annulus and along the stress cone at a substantially constant pressure and at a temperature below the critical temperature of the first and second superconducting means so that the stress cone provides a cold electrical gradient terminal in series with the thermal gradient electrical insulation means.

2. The apparatus of claim 1 in which the first and second, flexible, cylindrical superconducting means are flexible, helicallywound, flux-jump stabilized, composite superconductors forming spaces between the windings for receiving and transporting the cryogenic cooling fluid therethrough while the superconducting means receive and transmit opposite adjacent, balanced ac currents therein.

3. The apparatus of claim 2 having a containment for immersing the first and second flexible, cylindrical, superconducting means in the cryogenic cooling fluid.

4. The apparatus of claim 3 having a helically wound, lapped, flexible, insulating tape that is permeable to the cryogenic cooling fluid and extends longitudinally in the annulus between the superconducting means to a point adjacent the first terminal, thermal gradient, electrical insulating means so as to form a space for communicating the cryogenic cooling fluid with the tapered, Terminal, electrical gradient, stress cone therebetween.

5. The apparatus of claim 1 in which the co-axial superconducting means are bent to form an L-shaped annulus therebetween having labrynth means therein for communicating the cryogenic cooling fluid to the annulus and circulating the same therein in a serpentine-shaped flow pattern.

6. The apparatus of claim 4 in which the first super-conducting means forms a tube along an axis that extends longitudinally through the tapered, terminal, electrical gradient, stress cone for transporting cryogenic coolant longitudinally along and radially through the first and second superconducting means and the lapped, flexible insulating tape at 10-20 atmospheres.

7. The apparatus of claim 6 in which the superconducting means, comprise at least one Nb3Sn superconductor ribbon forming a composite interleaved with tapes of stainless steel, copper, aluminum, and normal resistance insulating tapes that are lapped in opposite directions for producing a balanced torque effect.

8. The apparatus of claim 7 in which the first, flexible, terminal, thermal gradient, electrical insulating means, comprises an electrical insulating matrix having imbeded therein co-axial capacitive grading cylinders forming ends that are graduated according to a log log radius function.

9. The method of terminating a superconducting transmission line having co-axial, cylindrical, inner and outer high and low tension, gas pressure insulated superconductors forming an annular space therebetween and having electrical and thermal gradient sections in series, comprising the steps of:

a. circulating in stages a cryogenic cooling fluid under pressure along the transmission line in a superconducting section in the annulus between both superconductors;

b. releasing a portion of pressure of the cooling fluid in a thermal gradient section; and

c. electrically insulating the superconductors with the cryogenic fluid under pressure in a portion of the annulus forming a stress cone section of increasing diameter at a temperature below the critical temperature Tc of the super-conductors so as to form a cold electrical gradient section in series with the thermal gradient section and interposed longitudinally between the superconducting and thermal gradient sections of the transmission line.

10. The method of claim 9 in which a major amount of the cryogenic cooling fluid is circulated at a first rate in two outer concentric annuli, a minor amount of the cooling fluid is circulated in an inner central channel at a second rate, the annuli and channel communicate the fluid through a stress cone, and the fluid is released selectively from the outer annulus and from inside the central channel for maintaining a balance between the aforementioned rates, a first temperature and pressure in the superconducting and stress cone sections, first electrical breakdown characteristics in the superconducting and stress cone sections, and second lower electrical breakdown characteristics in the thermal gradient section.