Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Ames laboratory physicist develops 'electrifying' theory

19.08.2008
Analysis will improve superconducting fault-current limiters

John R. Clem, a physicist at the U.S. Department of Energy’s Ames Laboratory, has developed a theory that will help build future superconducting alternating-current fault-current limiters for electricity transmission and distribution systems.

Clem’s work identifies design strategies that can reduce costs and improve efficiency in a bifilar fault-current limiter, a new and promising type of superconducting fault-current limiter.

“I was able to theoretically confirm that planned design changes to the current bifilar fault-current limiter being developed by Siemens and American Superconductor would decrease AC losses in the system,” said Clem. “My calculations are good news for the future of the device.”

Fault-current limiters protect power grids from sudden spikes in power, much like household surge protectors are used to save televisions and computers from damage during a lightning strike. Limiting fault currents is becoming an increasingly critical issue for large urban utilities, since these currents grow along with growing electric power loads. Superconductors enable a novel and very promising type of fault current limiter — or “firewall” — that rapidly switches to a resistive state when current exceeds the superconductors critical current. At the same time, in normal operation, the superconductors’ near-zero AC resistance minimizes power loss and makes the fault current limiter effectively “invisible” in the electric grid.

Clem analyzed a type of fault-current limiter, called a bifilar fault-current limiter, developed by Siemens and American Superconductor Corporation, who are now under contract with the DOE to demonstrate the technology at transmission voltages in the power grid of Southern California Edison. The team also includes Nexans, which is developing the terminations for the transmission fault-current limiter, and Air Liquide, which is providing the cryogenic cooling system.

Bifilar fault-current limiters are made from many turns of insulated superconducting tape wound into a coil shaped like a disk or a pancake. The tape consists of a thin, flat strip of superconducting material sandwiched between two strips of stainless steel. In the bifilar fault-current limiter design, adjacent tapes in the pancake coil carry current in opposite directions to effectively cancel out each tape’s magnetic fields, thereby limiting electrical losses.

Siemens and American Superconductor were seeking to optimize the performance of their bifilar design. They asked Clem to predict how AC losses would change as the width of the tape is increased. Clem reported his findings, "Field and current distributions and ac losses in a bifilar stack of superconducting strips," in a recent issue of Physical Review B.

“I modeled the bifilar design as an infinite stack of superconducting tapes, in which adjacent tapes carry current in opposite directions,” said Clem. “I was able to find an exact solution for the magnetic fields and currents that are generated in such a stack of tapes. Once I calculated how the magnetic flux penetrates into the tape, I then could calculate how much energy is lost in each current cycle for different tape widths and spacings between adjacent tapes.”

“Clem’s result was not obvious since there are competing mechanisms for AC loss in the bifilar configuration. It turns out that for typical parameters, when the spacing between adjacent tapes is small enough, the result is very simple: AC losses decrease as the tape width increases and the spacing decreases,” said Alex Malozemoff, chief technical officer of American Superconductor. “This result is helping to guide us and our partner Siemens in an optimized design for a fault- current limiter in a major DOE-sponsored program, and it is expected to open a path to a commercial product in the future.”

Clem’s research was funded by the DOE Office of Science, Basic Energy Sciences Office.

Ames Laboratory is a U.S. Department of Energy Office of Science laboratory operated for the DOE by Iowa State University. The Lab conducts research into various areas of national concern, including the synthesis and study of new materials, energy resources, high-speed computer design, and environmental cleanup and restoration .

Breehan G Lucchesi | EurekAlert!
Further information:
http://ww.ameslab.gov

More articles from Physics and Astronomy:

nachricht CCNY physicists master unexplored electron property
26.07.2017 | City College of New York

nachricht Large, distant comets more common than previously thought
26.07.2017 | University of Maryland

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Carbon Nanotubes Turn Electrical Current into Light-emitting Quasi-particles

Strong light-matter coupling in these semiconducting tubes may hold the key to electrically pumped lasers

Light-matter quasi-particles can be generated electrically in semiconducting carbon nanotubes. Material scientists and physicists from Heidelberg University...

Im Focus: Flexible proximity sensor creates smart surfaces

Fraunhofer IPA has developed a proximity sensor made from silicone and carbon nanotubes (CNT) which detects objects and determines their position. The materials and printing process used mean that the sensor is extremely flexible, economical and can be used for large surfaces. Industry and research partners can use and further develop this innovation straight away.

At first glance, the proximity sensor appears to be nothing special: a thin, elastic layer of silicone onto which black square surfaces are printed, but these...

Im Focus: 3-D scanning with water

3-D shape acquisition using water displacement as the shape sensor for the reconstruction of complex objects

A global team of computer scientists and engineers have developed an innovative technique that more completely reconstructs challenging 3D objects. An ancient...

Im Focus: Manipulating Electron Spins Without Loss of Information

Physicists have developed a new technique that uses electrical voltages to control the electron spin on a chip. The newly-developed method provides protection from spin decay, meaning that the contained information can be maintained and transmitted over comparatively large distances, as has been demonstrated by a team from the University of Basel’s Department of Physics and the Swiss Nanoscience Institute. The results have been published in Physical Review X.

For several years, researchers have been trying to use the spin of an electron to store and transmit information. The spin of each electron is always coupled...

Im Focus: The proton precisely weighted

What is the mass of a proton? Scientists from Germany and Japan successfully did an important step towards the most exact knowledge of this fundamental constant. By means of precision measurements on a single proton, they could improve the precision by a factor of three and also correct the existing value.

To determine the mass of a single proton still more accurate – a group of physicists led by Klaus Blaum and Sven Sturm of the Max Planck Institute for Nuclear...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Clash of Realities 2017: Registration now open. International Conference at TH Köln

26.07.2017 | Event News

Closing the Sustainability Circle: Protection of Food with Biobased Materials

21.07.2017 | Event News

»We are bringing Additive Manufacturing to SMEs«

19.07.2017 | Event News

 
Latest News

CCNY physicists master unexplored electron property

26.07.2017 | Physics and Astronomy

Molecular microscopy illuminates molecular motor motion

26.07.2017 | Life Sciences

Large-Mouthed Fish Was Top Predator After Mass Extinction

26.07.2017 | Earth Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>