David Madura

Design and test of current limiting modules using YBCO-coated conductors

Within the cooperation between American Superconductor Corporation (AMSC) and Siemens Corporate Technology we have investigated the fault current limiting performance of YBCO-coated conductors (also called second-generation or 2G HTS wires) stabilized with stainless steel laminates. Design rules for the length and width of the wire depending on utility grid requirements have been established. Bifilar coils have been manufactured and tested with a typical limitation period of 50?ms under stepwise increasing voltage loads to determine the maximum temperature the wires can withstand without degradation. Coils have been assembled into limiter modules demonstrating uniform tripping of the individual coils and recovery within seconds. At present this cooperation is proceeding within a joint project funded by the US Department of Energy (DOE) that encompasses the design, construction and testing of a 115?kV FCL for power transmission within a time frame of 4?5 years, and additional partners. Besides AMSC and Siemens, Nexans contributes the high voltage terminations and Los Alamos National Lab investigates the ac losses. Installation and testing are planned for a Southern California Edison substation. The module planned for the transmission voltage application consists of 63 horizontally arranged coils connected in parallel and series to account for a rated current of 1.2? kArms and voltage of 31?kVrms plus margins. The rated voltage of the module is considerably lower than the line to ground voltage in the 115?kV grid owing to our shunted limiter concept. The shunt reactor connected in parallel to the module outside the cryostat allows for adjustment of the limited current and reduces voltage drop across the module in case of a fault. The fault current reduction ratio is 42% for our present design. A subscale module comprising six full-size coils has been assembled and tested recently to validate the coil performance and coil winding technique. The module had a critical current of 425? ADC and a nominal power of 2.52?MV?A at 77?K. A complete series of tests with applied voltage up to 8.4? kVrms, prospective short circuit current up to 26.6? kArms and variation of phase angle at initiation of the fault has been performed. After more than 40 switching tests the critical current of the module remained unchanged, indicating that no degradation of the wire occurred.

The status of HTS motors

The status of high temperature superconducting (HTS) motor development is presented. HTS synchronous machines have been under development for over 12 years around the world. The unique characteristics for selected applications such as ship propulsion are discussed. The beneficial characteristics of air core HTS motors for ship propulsion include high power density, high efficiency and low noise production. This paper also addresses recent developments including a 5,000 HP 1800 RPM 4 pole prototype and the ongoing construction of a 5 MW 230 RPM motor. The 1800 RPM motor is a prototype constructed to validate technologies for industrial motors and generators and the 230 RPM motor is being constructed to validate technologies for ship propulsion motors in the range of 25 MW and 120 RPM.

Superconductor synchronous condenser for reactive power support in an electric grid

High Temperature Superconductor (HTS) SuperVAR dynamic synchronous condensers (DSC) developed by American Superconductor have a small foot print, are readily transportable, and are expected to be an economic option for providing peak and dynamic reactive compensation to a power system. HTS DSC machines are also inherently stable to close in faults and can provide up to twice their nominal rating for about one minute (peak rating) during depressed voltage events. Last, but not least, HTS DSC machines use less than half of the energy of a conventional synchronous condenser and about the same amount of energy as a modern Flexible AC Transmission System (FACTS) device consumes. It is expected to be highly reliable. The first HTS DSC machine is being operated at an arc furnace where it is being tested for its ability to mitigate flicker and provide dynamic power factor compensation. This location also exposes the machine to a large number of transients providing an excellent accelerated age test of the device. This paper describes features and test results of the HTS DSC.

Superconducting dynamic synchronous condenser for improved grid voltage support

Synchronous condensers are an attractive source of dynamic VARs (both inductive and capacitive) to improve system stability and maintain voltages under varying load conditions and contingencies. A synchronous condenser is a rotating machine that runs synchronized with the grid. Its field is controlled with a voltage regulator to either generate or absorb reactive power as needed by the power system. American Superconductor Corporations (AMSC) proprietary SuperVAR/spl trade/ dynamic superconducting condenser (DSC) machines upgrade existing technology by using a conventional armature mated with a field winding made from high temperature superconducting (HTS) wires. The result is a DSC that is both more efficient and has lower maintenance than conventional machines. It can provide up to 8 pu current for short periods to support transient VAR requirements. The Tennessee Valley Authority (TVA) is sponsoring the development and field testing of an 8 MVAR prototype unit to be followed by five 10 MVAR production units. Larger units are planned for the future. This paper describes features of the DSC and its performance in grid applications.

Operating Experience of Superconductor Dynamic Synchronous Condenser

High-temperature superconductor (HTS) dynamic synchronous condensers have a small footprint, are readily transportable, and are expected to be an economic option for providing peak and dynamic reactive compensation to a power system. HTS dynamic synchronous condensers are also inherently stable to close-in faults and can provide up to twice their nominal rating for about one minute (peak rating) during depressed voltage events. These machines also use less than half of the energy of conventional synchronous condensers because the HTS field windings operate at a constant cryogenic temperature. They are expected to be highly reliable. In October 2004, the first HTS dynamic synchronous condenser was installed on the Tennessee Valley Authority (TVA) grid serving an arc furnace where it is being exposed to a large number of transients, providing an excellent accelerated age test of the device. TVA has ordered five HTS dynamic synchronous condensers rated at 12 MVAR, and successful operation of the first prototype machine is expected to lead to release of these orders to production by TVA, making HTS dynamic synchronous condensers the first HTS commercial product for enhancing power grid reliability

A Pulsed Magnet System for a Field-Reversed Configuration Experiment

From a magnet engineering perspective, the field-reversed configuration (FRC) fusion concept is commercially attractive due to its cylindrical configuration. Essentially, all large coils are solenoidal, which enables efficient structural support and relative ease of manufacturing, thereby enhancing commercial viability. A design option for future experimental FRC devices, which is currently under study, would require a large number of normal conducting electromagnets to produce the required magnetic field configuration for approximately 30 ms. One of the major challenges with such a system is a requirement to achieve a magnetic field profile which evolves with time and in which both eddy currents in major components and large plasma currents are also important magnetic field contributors. This paper describes contemplated magnetic configurations and the main types of coils and the coil design choices for each. It also discusses transient analysis performed to predict fields internal to a conductive vessel, while ramping magnetic fields, and accounting for vessel eddy current and plasma contributions. An estimate of harmonic errors due to displacement of the coils is provided. The dominant error field component is found to be from the dipole contribution. Harmonic errors from eddy currents due to plasma are briefly discussed.