American Superconductor and Siemens Achieve Commercial-Grade Performance Levels for Superconductor Surge Protection Device for Power Grids
American Superconductor Corp. and Siemens AG 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 utilizes 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.
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 7.5kV, which corresponds to a 13kV class of three-phase power equipment, widely used in utility distribution grids. It suppressed, or limited, the current during a fault by up to twenty-five 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 reported today 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 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. The 344 superconductors, which have the architecture of what are generically known as second generation (2G) high temperature superconductor (HTS) wires, are designed as a drop-in replacement for customers who are currently using first generation (1G) HTS wire. The 344 superconductors comprise the basic 2G HTS wire architecture clad with ultra-thin strips of copper. When laminated with stainless steel, the product is known as 344S superconductors. Applications for HTS wire include power transmission and distribution cables, propulsion motors and generators, degaussing cable systems, synchronous condensers and fault current limiters.
