Superconductor fault current limiter successfully demonstrated in China

Westborough, MA, Dec. 20, 2005 — American Superconductor Corp., an electricity solutions company, and China’s Institute of Electrical Engineering (IEE) announced that IEE has successfully demonstrated a superconductor-based fault current limiter – essentially a high voltage surge protector – for the first time in a power grid in China.

The device was fabricated by IEE in collaboration with the Technical Institute of Physics and Chemistry and Hunan Electric Power Co. utilizing “smart” high temperature superconductor (HTS) wire manufactured by AMSC. Since August 2005, IEE’s fault current limiter device has successfully suppressed large spikes of current in the grid that were over five times the normal levels.

Superconductor wires are considered smart because they possess unique physical properties that allow them to react instantaneously to current surges, passing electricity along at normal levels while also being able to recognize and then suppress large surges of electrical current. Suppressing spikes of electrical current is important because it prevents damage to expensive electrical equipment in power grids. Fault current limiters cannot be made from conventional materials such as copper wire.

According to Dr. Liye Xiao, Deputy Director of the IEE and Director of the Applied Superconductivity Laboratory at the Chinese Academy of Science, this project is an important step in demonstrating the value of these devices in greatly improving the reliability and stability of power grids in China. “Demand for electric power in China continues to grow dramatically year-over-year,” said Dr. Xiao. “We need to utilize innovative devices, such as fault current limiters and superconductor transformers and power cables, to guarantee the reliability and stability of our power grids because electricity is the lifeblood of our rapidly growing economy.”

Fault current limiter devices utilize the unique property of superconductors to switch from a state of zero resistance to the flow of electrical current to a resistive state when the electrical current passing through a superconductor becomes too high. By switching from no resistance to a high resistance, a coil of superconductor wire placed in a power grid has the ability to sense and then suppress, or limit, electrical current spikes (technically known as “fault currents”) that are caused by short circuits.

The fault current limiter developed by IEE is installed in an electrical substation near Changsha, the capital city of Hunan Province. It has a voltage rating of 10.5 kilovolts and its normal operating current is 400 Amperes (AC). Since it was put into operation in August 2005, it has instantaneously reduced three-phase, short circuit currents in the range of 3,500 Amperes down to 635 Amperes, thereby protecting expensive electrical equipment from the current spikes. It is expected to remain in operation for a total of six months, after which it will be removed from service to undergo internal examination of all of the components in order to learn how to make improvements for commercial systems. The device will then be improved if needed and returned to operation in the power grid.

The U.S. Department of Energy estimates that the potential market for superconductor-based fault current limiters over the next 15 years is several billion dollars in the U.S. alone.

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