Design, Fabrication and Testing of a Superconducting Fault Current Limiter (SFCL)

The purpose of this project was to conduct R&D on specified components and provide technical design support to a SuperPower team developing a high temperature superconducting Fault Current Limiter (SFCL). ORNL teamed with SuperPower, Inc. on a Superconductivity Partnerships with Industry (SPI) proposal for the SFCL that was submitted to DOE and approved in FY 2003. A contract between DOE and SuperPower, Inc. was signed on July 14, 2003 to design, fabricate and test the SFCL. This device employs high temperature superconducting (HTS) elements and SuperPower's proprietary technology. The program goal was to demonstrate a device that will address a broad range of the utility applications and meet utility industry requirements. This DOE-sponsored Superconductivity Partnership with Industry project would positively impact electric power transmission reliability and security by introducing a new element in the grid that can significantly mitigate fault currents and provide lower cost solutions for grid protection. The project will conduct R&D on specified components and provide technical design support to a SuperPower-led team developing a SFCL as detailed in tasks 1-5 below. Note the SuperPower scope over the broad SPI project is much larger than that shown below which indicates only the SuperPower tasks that are complementary to the ORNL tasks. SuperPower is the Project Manager for the SFCL program, and is responsible for completion of the project on schedule and budget. The scope of work for ORNL is to provide R&D support for the SFCL in the following four broad areas: (1) Assist with high voltage subsystem R&D, design, fabrication and testing including characterization of the general dielectric performance of LN2 and component materials; (2) Consult on cryogenic subsystem R&D, design, fabrication and testing; (3) Participate in project conceptual and detailed design reviews; and (4) Guide commercialization by participation on the Technical Advisory Board (TAB). SuperPower's in-kind work for the SFCL will be provided in the following areas: (1) Work with ORNL to develop suitable test platforms for the evaluation of subsystems and components; (2) Provide cryogenic and high voltage subsystem designs for evaluation; (3) Lead the development of the test plans associated with the subsystem and components and participate in test programs at ORNL; and (4) Based on the test results, finalize the subsystem and component designs and incorporate into the respective SFCL prototypes

Laser-induced fluorescence of phosphors for remote cryogenic thermometry

Remote cryogenic temperature measurements can be made by inducing fluorescence in phosphors with temperature-dependent emissions and measuring the emission lifetimes. The thermographic phosphor technique can be used for making precision, noncontact, cryogenic-temperature measurements in electrically hostile environments, such as high dc electric or magnetic fields. The National Aeronautics and Space Administration is interested in using these thermographic phosphors for mapping hot spots on cryogenic tank walls. Europium-doped lanthanum oxysulfide (La2O2S:Eu) and magnesium fluorogermanate doped with manganese (Mg4FGeO6:Mn) are suitable for low-temperature surface thermometry. Several emission lines, excited by a 337-nm ultraviolet laser, provide fluorescence lifetimes having logarithmic dependence with temperature from 4 to above 125 K. A calibration curve for both La2O2S:Eu and Mg4FGeO6:Mn is presented, as well as emission spectra taken at room temperature and 11 K

Influence of dump voltage and allowable temperature rise on stabilizer requirements in superconducting coils

A superconducting winding must have enough stabilizer to satisfy two sets of criteria. During normal operation, the amount of stabilizer must be large enough either to make the coil unconditionally stable or to give a certain desired stability margin. Once a dump occurs, the amount of stabilizer must be large enough to carry the current without generating excessive dump voltages or allowing the winding to exceed a certain maximum temperature (and maximum pressure, in the case of force-cooled coils). The voltage criterion often dominates for very large coil systems, but it is frequently ignored in initial design studies. This paper gives some simple relations between the dump voltage and the stored energy, temperature rise, and coil geometry that are useful in scooping the required amount of stabilizer. Comparison with some recently proposed fusion magnet system designs indicates that excessive dump voltages could result in some cases. High-temperature superconductors may require more stabilizer than the conventional alloys. Calculations with simple model coil systems indicate how trade-offs between various coil parameters affect the dump voltage. 12 refs., 1 fig., 1 tab

Cryogenic pressure testing of demountable seals for large-coil program applications

A total of four sample K seals was used in the tests. Two were 57 mm in outside diameter and coated with lead, and two were 48 mm in outside diameter and coated with teflon. (MOW

HTS Magnets for Advanced Magnetoplasma Space Propulsion Applications

Plasma rockets are being considered for both Earth-orbit and interplanetary missions because their extremely high exhaust velocity and ability to modulate thrust allow very efficient use of propellant mass. In such rockets, a hydrogen or helium plasma is RF-heated and confined by axial magnetic fields produced by coils around the plasma chamber. HTS coils cooled by the propellant are desirable to increase the energy efficiency of the system. We describe a set of prototype high-temperature superconducting (HTS) coils that are being considered for the VASIMR ( Variable Specific Impulse Magnetoplasma Rocket) thruster proposed for testing on the Radiation Technology Demonstration (RTD) satellite. Since this satellite will be launched by the Space Shuttle, for safety reasons liquid helium will be used as propellant and coolant. The coils must be designed to operate in the space environment at field levels of 1 T. This generates a unique set of requirements. Details of the overall winding geometry and current density, as well as the challenging thermal control aspects associated with a compact, minimum weight design will be discussed

Stability measurements on a 1-T high temperature superconducting magnet

A high temperature superconducting magnet based on Bi-2223 conductor was built at the American Superconductor Corporation. The magnet was constructed by a react and wind technique using conductors made from a metallic precursor process. It was a winding ID of 25.4 mm, OD of 87.6 mm, and height of 107.3 mm. A heater, two thermometers, and several voltage taps were built into the high field region of the magnet for stability measurements. The magnet generates 1.1 T central field at 4.2 K when operating at 1 {mu}V/cm over the entire conductor length, including all the joints. Stability measurements were performed in background fields up to 2.5 T from 4.2 K to 77 K. Stability margins more than 2 orders of magnitude higher than a low temperature superconductor were observed

Experience with operation of a large magnet system in the international fusion superconducting magnet test facility

Superconducting toroidal field systems, including coils and ancillaries, are being developed through international collaboration in the Large Coil Task. Focal point is a test facility in Oak Ridge where six coils will be tested in a toroidal array. Shakedown of the facility and preliminary tests of the first three coils (from Japan, Switzerland, and the US) were accomplished in 1984. Useful data were obtained on performance of the helium refrigerator and distribution system, power supplies, control and data acquisition systems and voltages, currents, strains, and acoustic emission in the coils. Performance was generally gratifying except for the helium system, where improvements are being made

Performance of pancake coils of parallel co-wound Ag/BSCCO tape conductors in static and ramped magnetic fields

Critical Currents are reported for several Ag/BSCCO single-pancake coils in static magnetic fields ranging from 0 to 5 T and temperatures from 4.2 K to 105 K. The sample coils were co-wound of one to six tape conductors in parallel. Since the closed loops formed in such an arrangement could lead to eddy current heating or instability in changing fields, one of the coils was also tested in helium gas, in fields ramped at rates of up to 1.5 T/s. For these quasi-adiabatic tests, at each temperature the transport current was set just below the critical value for a preset static field of 3.3 or 4.9 T. The field was then rapidly ramped down to zero, held for 20 sec, and then ramped back up to the original value. The maximum observed temperature transient of about 1.7 K occurred at 9 K, for a field change of 4.75 T. The temperature transients became negligible when the sample was immersed in liquid helium. Above 30 K, the transients were below 1 K. These results give confidence that parallel co-wound HTSC coils are stable in a rapidly-ramped magnetic field, without undue eddy current heating

Drift tube beam blocking experiments performed on the ORNL/PLT neutral beam line at the ORNL medium energy test facility

The Fusion Energy Division of the Oak Ridge National Laboratory (ORNL) in cooperation with the Princeton Plasma Physics Laboratory (PPPL) designed, constructed, and tested four high power neutral beam injectors for application on the Princeton Large Torus (PLT). This system employs a modified duoPIGatron ion source which has produced ion beams with parameters up to 70 A, 45 keV, and 500 msec. Nominal extraction parameters were 60-A, 40-keV, and 300-msec pulses, simultaneously. Neutral power up to 750 kW for 100 msec was calorimetrically measured on a simulated PLT target behind a PLT-sized aperture of 20 x 25 cm located at 4.10 m. Initial performance of these beam lines on PLT was near these parameters. Calorimetric measurements of beam power delivered to the PLT torus with a 3.65-m beam line length and with 100-msec full power pulses indicate a 10 to 15% reionization loss when the beam line pulse is synchronized to the pulsed torus magnetic fields. Data taken at ORNL are presented to show that this power loss is approximately equal to that calculated on drift tube pressure measurements taken without drift tube magnetic fields