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 A tale of two pulsars' tails: Plumes offer geometry lessons to astronomers
18.01.2017 | Penn State

nachricht Studying fundamental particles in materials
17.01.2017 | Max-Planck-Institut für Struktur und Dynamik der Materie

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: How gut bacteria can make us ill

HZI researchers decipher infection mechanisms of Yersinia and immune responses of the host

Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...

Im Focus: Interfacial Superconductivity: Magnetic and superconducting order revealed simultaneously

Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.

While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...

Im Focus: Studying fundamental particles in materials

Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales

Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...

Im Focus: Designing Architecture with Solar Building Envelopes

Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.

As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...

Im Focus: How to inflate a hardened concrete shell with a weight of 80 t

At TU Wien, an alternative for resource intensive formwork for the construction of concrete domes was developed. It is now used in a test dome for the Austrian Federal Railways Infrastructure (ÖBB Infrastruktur).

Concrete shells are efficient structures, but not very resource efficient. The formwork for the construction of concrete domes alone requires a high amount of...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

12V, 48V, high-voltage – trends in E/E automotive architecture

10.01.2017 | Event News

2nd Conference on Non-Textual Information on 10 and 11 May 2017 in Hannover

09.01.2017 | Event News

Nothing will happen without batteries making it happen!

05.01.2017 | Event News

 
Latest News

A big nano boost for solar cells

18.01.2017 | Power and Electrical Engineering

Glass's off-kilter harmonies

18.01.2017 | Materials Sciences

Toward a 'smart' patch that automatically delivers insulin when needed

18.01.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>