American Superconductor Corporation and Siemens AG have announced commercial-grade performance levels for a medium-voltage superconductor surge protection device known as a fault current limiter (FCL). The device was based on Siemens' proprietary superconductor switching module technology, which uses coils fabricated with AMSC's proprietary 344S superconductors. Fault current limiters act as high-voltage surge protectors for power grids to increase grid reliability. The United States Department of Energy has estimated that the potential market for fault current limiters is several billion dollars over the next 15 years.
AMSC and Siemens also announced the extension for a third year of their strategic alliance, which is focused on the development and commercialization of fault current limiters for power transmission and distribution grids.
"We have made tremendous progress during the past two years through our collaboration with AMSC in developing a dynamic fault current limiter solution for utilities," commented Heinz-Werner Neumueller, department head of Siemens Corporate Technology. "Based on our new test results, our combined efforts have created an excellent prospect to develop a commercial fault current limiter that is able to suppress fault currents, enabling reliable expansion of power grids to meet the ever-increasing demand for electricity in cities around the world."
The successful test by AMSC and Siemens was conducted on a 2 mega-volt-ampere (2 MVA) FCL. The single-phase laboratory test was based on a superconductor switching module fabricated by Siemens from 344S superconductors. The system operated at a voltage of 7.5 kV, which corresponds to a 13-kV class of three-phase power equipment, widely used in utility distribution grids. It suppressed, or limited, the current during a fault by up to 25 times. Such limitation is increasingly important in urban grids where large fault currents, or current surges, arising from accidental, but common, short circuits can destroy power equipment if they are not adequately suppressed. The test results are a critical step on the pathway to the development of commercially viable superconductor fault current limiters.
"Our new results show that fault current limiters are now able to achieve commercial performance levels needed for urban power grids," said Alex Malozemoff, executive vice president and chief technical officer of AMSC. "Aging power infrastructures are facing rapidly increasing demands for more electricity to meet customers' needs in our digital, plug-in economy. As new electricity generation sources are added to meet this demand, fault currents arising from short circuits are becoming dangerously large. Fault current limiters based on Siemens superconductor switching modules and AMSC's 344S superconductors will help utilities safely meet these growing electricity demands."
344S superconductors are smart materials because they possess unique physical properties that allow them to conduct electricity with no resistance under normal operating conditions, while also being able to recognize and then instantaneously suppress large surges of electrical current by switching to the resistive state. Suppressing spikes of electrical current is important because it prevents damage to expensive electrical equipment in power grids.