China's Institute of Electrical Engineering (IEE) has successfully demonstrated a prototype superconductor-based power transformer for the first time in a power grid in China. The transformer was fabricated by IEE in collaboration with TBEA Industrial Transformer Group, the largest transformer manufacturer in China, using high temperature superconductor (HTS) wire manufactured by American Superconductor. The HTS transformer has operated since Nov. 21, 2005 in a power grid in the city of Changji, Xinjiang Province serving a TBEA manufacturing plant.

Power transformers are used in power grids to increase voltage (electrical "pressure") in power lines at generating plants so that electricity may be delivered through power lines to customers with lower energy losses. Transformers are then used again to decrease voltage to more user-friendly levels near customers. Replacing copper wire currently employed in conventional transformers with high-efficiency HTS wire reduces the waste of energy inside the transformer due to copper wire's electrical resistance. Another major advantage is the substitution of cheap, environmentally friendly liquid nitrogen (air is 79% nitrogen) in HTS transformers to provide cooling and electrical insulation for the more expensive electrical insulating oils used in conventional transformers. This reduces oil consumption and the risk of transformer fires associated with oil leaks.

The U.S. Department of Energy estimates that the worldwide market for transformers with power ratings over 10 MVA exceeds US$1 billion annually, with the fastest growth in sales of transformers occurring outside the United States. In China, the rate of power consumption increased by 9% in 2001 and continued to increase year-over-year reaching a rate of 14.8% in 2004, according to the China Electric Power Research Institute. The rate of increase of power consumption in the United States during the same period was approximately 2% to 3% per year.

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 superconductor transformers to improve the energy efficiency and reliability of power grids while reducing the amount of oil needed for use as the electrical insulation medium in large, conventional transformers.

"Demand for electric power in China continues to grow dramatically year-over-year," said Xiao. "We need to utilize innovative technologies such as superconductor transformers, fault current limiters and other devices, to guarantee the reliability and stability of our power grids because electricity is an essential ingredient in achieving sustainable economic growth."

"This demonstration project is a critical step on the path to the development of practical, commercial superconductor transformers in China -- a market we believe will be very large," said Greg Yurek, chief executive of AMSC. "China represents one of the fastest growing markets for superconductor transformers. This is because the demand for electricity continues to rise very rapidly and because energy efficiency is becoming increasingly important in China."

The superconductor transformer developed by IEE is a three-phase, 630 kVA device that transforms voltages from 10 kV to 400 V. It uses an amorphous alloy core to further reduce electrical losses over that achieved by the superconductor wires alone. The total energy efficiency of this first device was 98.3%. It is expected that more mature designs will achieve efficiencies as high as 99.9%. During its operation at the TBEA transformer plant, the HTS transformer was tested by the Shenyang Transformer Institute, which confirmed the prototype met all transformer standards. The prototype transformer 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 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.