P.W. Fisher

Installation and operation of the Southwire 30-meter high-temperature superconducting power cable

Southwire Company has installed, tested and is operating the first real-world application of a high-temperature superconducting cable system at its headquarters in Carrollton, GA, USA. The cable is powering three Southwire manufacturing plants, marking the first time a company has successfully made the difficult transition front laboratory to practical field application of an HTS cable. The cables are rated at 12.4-kV, 1250-A, 60 Hz and are cooled with pressurized liquid nitrogen at temperatures from 70-80 K. Before placing the cables into service, extensive offline electrical testing was performed including voltage withstand, measurement of DC critical current, extended load current testing, rated voltage testing and partial discharge measurement. The cables were energized on Jan. 5, 2000 for online testing and operation, and by the end of August 2000, had provided 100% of the customer load for 2164 hours.

Tests of tri-axial HTS cables

The Ultera/ORNL team have built and tested 3-m and 5-m triaxial cables rated at 3 and 1.3 kA-rms, respectively. The three concentric superconducting phases are made of BSCCO-2223 HTS tapes, separated by layers of cold-dielectric tapes. A copper braid is added as the grounding shield on the outside of the three active phases. Tests of these cables were performed at temperatures ranging from 70 to 84 K. AC loss data reconfirmed the previous result on a 1.5-m prototype cable that the total 3-phase ac loss is about the sum of the calculated ac losses of the three concentric phases. These and other test results of the 1.3 and 3 kA cables will be used to construct a second 5-m triaxial cable rated at 3 kA-rms, 15 kV. Preliminary test results supporting this new cable and the associated termination are summarized.

Design, analysis, and fabrication of a tri-axial cable system

Encouraged by the positive test results of a /spl sim/1.5-m long prototype tri-axial cable, the Southwire Company/Oak Ridge National Laboratory (ORNL) team has conceived, designed, and built a 5-m tri-axial cable with three-phase terminations. The three concentric superconducting phases are made of BSCCO-2223 high-temperature superconducting (HTS) tapes, separated by layers of cold-dielectric (CD) tape. A copper braid is added as the grounding shield. The completed tri-axial cable is enclosed in a flexible cryostat. Cooling of the cable and terminations is achieved by liquid nitrogen flowing through the annulus between the cable and the cryostat. A challenging analysis and design problem was development and implementation of an insulator material between the concentric phases with high enough thermal conductivity to meet temperature gradient requirements and acceptable mechanical performance (strength and contraction on cool down). The resulting three-phase, CD cable and termination design is nearly as compact as the single-phase, co-axial design developed previously by Southwire/ORNL and represents the highest cable current density achievable in an electric alternating-current power cable.

Development and testing of HTS cables and terminations at ORNL

The Oak Ridge National Laboratory (ORNL) and the Southwire Company have used the ORNL 5 m cable test facility to develop high-temperature superconducting (HTS) cables and terminations to support the first industrial demonstration of an HTS cable at the Southwire manufacturing complex. Two 5 m, cold dielectric cables have been tested for direct current (DC) voltage, alternating current (AC) losses, AC withstand at 18 kV, thermal-hydraulic performance, heat load, and long-term operation at rated voltage (7.2 kV) and current (1250 A). Two separate termination concepts, one operating at 10/sup -4/-10/sup -5/ mbar vacuum and the other operating with pressurized nitrogen gas at <10 bar, have been developed and tested with the 5-m cables. A 5-m cable has been removed from the facility and bent in a test rig to simulate transport in a spool. A testing program for a third 5-m cable with a splice is in progress. The test program at ORNL has validated the basic design of the cables and terminations and indicated areas for further R&D to optimize this technology for electric utility applications.

Eight‐shot pneumatic pellet injection system for the tokamak fusion test reactor

An eight‐shot pneumatic pellet injection system has been developed for plasma fueling of the tokamak fusion test reactor (TFTR). The active cryogenic mechanisms consist of a solid hydrogen extruder and a rotating pellet wheel that are cooled by flowing liquid‐helium refrigerant. The extruder provides solid hydrogen for stepwise loading of eight holes located circumferentially around the pellet wheel. This design allows for three different pellet diameters: 3.0 mm (three pellets), 3.5 mm (three pellets), and 4.0 mm (two pellets) in the present configuration. Each of the eight pellets can be shot independently. Deuterium pellets are accelerated in 1.0‐m‐long gun barrels with compressed hydrogen gas (at pressures from 70 to 105 bar) to velocities in the range 1.0–1.5 km/s. The pellets are transported to the plasma in an injection line that incorporates two stages of guide tubes with intermediate vacuum pumping stations. A remote, stand‐alone control and data‐acquisition system is used for injector and vacuum...

Design considerations for single‐stage and two‐stage pneumatic pellet injectors

Performance of single‐stage pneumatic pellet injectors is compared with several models for one‐dimensional, compressible fluid flow. Agreement is quite good for models that reflect actual breech chamber geometry and incorporate nonideal effects such as gas friction. Several methods of improving the performance of single‐stage pneumatic pellet injectors to muzzle velocities ranging from 2 to 2.25 km/s in the near term are outlined. Two‐stage pneumatic injectors have the potential for much higher muzzle velocities (4–6 km/s) because of the higher gas pressures and temperatures achievable with the second‐stage compression. The design and performance of two‐stage pneumatic pellet injectors are discussed, and initial data from the two‐stage pneumatic pellet injector test facility at Oak Ridge National Laboratory are presented. Finally, a concept for a repeating two‐stage pneumatic pellet injector is described.

Tritium proof-of-principle injector experiment

The Tritium Proof-of-Principle (TPOP) pellet injector was designed and built by Oak Ridge National Laboratory (ORNL) to evaluate the production and acceleration of tritium pellets for fueling future fision reactors. The injector uses the pipe-gun concept to form pellets directly in a short liquid-helium-cooled section of the barrel. Pellets are accelerated by using high-pressure hydrogen supplied from a fast solenoid valve. A versatile, tritium-compatible gas-handling system provides all of the functions needed to operate the gun, including feed gas pressure control and flow control, plus helium separation and preparation of mixtures. These systems are contained in a glovebox for secondary containment of tritium Systems Test Assembly (TSTA) at Los Alamos National Laboratory (LANL). 18 refs., 3 figs.

A cryogenic xenon droplet generator for use in a compact laser plasma x-ray source

A research instrument has been designed, fabricated, and tested that produces ∼25–100 μm diameter, liquid xenon droplets on demand at variable repetition rates of 1–100 Hz. Drops have been produced with low spatial dispersion which allows consistent interception by a high power laser beam to produce x-rays for advanced lithography systems. Experimental sequences of up to 42 min in length have been conducted at 30 Hz, producing over 75 000 xenon drops. This technology allows significant debris reduction from the laser-target interaction. The mass-limited, cryogenic droplets are vaporized, producing no fragments, and the resulting gas can be collected preferentially on a cold surface for later recycling.

High-temperature superconducting tri-axial power cable

Abstract Encouraged by the positive test results of a 1.5-m long prototype tri-axial cable, the Southwire/ORNL team has conceived, designed and built a 5-m tri-axial cable with three-phase terminations. The three concentric superconducting phases are made of BSCCO-2223 HTS tapes, separated by layers of cold-dielectric tape. A copper braid is added as the grounding shield. The completed tri-axial cable is enclosed in a flexible cryostat. Cooling of the cable and terminations is achieved by liquid nitrogen flowing through the annulus between the cable and the cryostat. The terminations used in the cable tests are cooled by a separate liquid nitrogen stream. The resulting three-phase, cold dielectric, cable and termination design is nearly as compact as the single-phase, co-axial design developed previously by Southwire/ORNL and represents the highest known cable current density achievable in an electric AC power cable. DC testing of the 5-m cable includes V–I curves for each of the concentric HTS phases, cable heat loads at varying DC currents, liquid nitrogen flow-pressure measurements, and over-current tests. AC testing of the cable includes ac loss measurements, induced-current in the Cu-shield measurements and operation at the line voltage test. The ac losses are measured calorimetrically by measuring the temperature differential of the coolant across the cable length due to the ac loss in the superconductors. Both balanced and un-balanced currents among the three phases are used in ac loss and induced current measurements.

Testing of a Liquid Nitrogen Cooled 5‐meter, 3000 A Tri‐Axial High Temperature Superconducting Cable System

The tri‐axial HTS cable design uses three concentric superconducting layers for the phase conductors separated by a cold dielectric material. It offers an efficient HTS cable configuration by reducing the amount of superconductor needed, and placing all three phases in a single cryostat. Ultera and ORNL tested a 5‐meter long tri‐axial HTS cable and terminations designed to operate at 3 kA ac and 13.2 kV. Test results, including the thermal loads on the system, will be reported. An existing liquid nitrogen skid that circulates subcooled liquid nitrogen through the cable was initially designed for the heat loads on single phase cables at lower current ratings. The refrigeration needed for the 3 kA tri‐axial cable configuration made it necessary to upgrade the nitrogen system to increase the cooling capacity. A description of the upgrades and performance of the system is provided.