Current limiter debuts with record HTS coils

San Diego

The Fault Current Limiter (FCL) II device, built under a U.S. Department of Energy (DOE) Superconductivity Partnership Initiative (SPI) program for the design, fabrication and testing of a pre-commercial 15 kV-class superconducting current controller, has completed its first phase of testing in Norwalk, Calif. The innovative FCL device incorporates three world record-size high temperature superconducting (HTS) coils, each measuring more than one meter in diameter and three-quarters of a meter in height and weighing more than 1,500 pounds.

The project team was led by General Atomics (GA), with Intermagnetics General Corp., DOE`s Los Alamos National Laboratory (LANL) and Southern California Edison (SCE) as partners. The California Energy Commission and EPRI also supported this project financially.

The FCL II device was shipped from GA`s San Diego plant in June to SCE`s Central Test Substation in Norwalk, where the test program was carried out. Subsequently, the project was named as the “Best Project” in the Annual Peer Review of the DOE Superconductivity Program. This is one of a number of DOE SPI cost-sharing projects in which teams consisting of a system integrator (GA), a wire manufacturer (Intermagnetics), a utility end-user (SCE) and a national laboratory (LANL) were tasked to develop HTS power applications. The FCL II is a second-phase, three-and-a-half-year, $9.8-million program in which the industrial partners contributed half of the funding.

Fault current management is always an important and difficult task for power utilities. A fault condition is created when there is a system short to ground, caused by lightning, downed trees from storms, strayed metallic balloons or unwary animals. The resulting fault current can be up to 100 times what is normally flowing in the power lines. If uncontrolled, it would damage equipment, cause system instability and eventually blackouts affecting the public. The fault current limiting function of the FCL II device is designed to reduce fault current by 50 percent to 80 percent, as required by the utility. In addition, while most of the existing electromechanical breakers can operate only in three to five cycles, the FCL II device can double as a super-fast 3/4 cycle (12 millisecond) opening switch. As a result, the system can be shut down before the fault becomes a problem.

Likening the current controller to a gigantic version of the surge protector for home personal computers, Eddie Leung, team leader and senior program manager from GA, said: “Our current controller concept combines cutting-edge power electronics and high temperature superconducting magnet technologies. It is one of the several HTS power applications that should benefit the nation`s deregulated power industry significantly in the 21st century. The device`s main benefits for the utilities are equipment upgrade deferral, power quality enhancement, system flexibility and reliability improvement.”

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