2 September 2009

Superconducting cable ensures power distribution

Most Americans take electric current for granted and assume power will always be there when they fire up a TV, computer, or vacuum cleaner.

However, with more energy intensive products hitting the market, little do most know the strain on our electric grid will only intensify in coming years.

The annual cost of power outages is approximately $80 billion, according to the U.S. Department of Energy. Now add the risk of terrorists that want to cripple the U.S. economy.

There is now a product in development that may help end those problems: A superconductor cable that would link electrical substations and allow the sharing of excess capacity during emergencies, according to researchers at the Science and Technology Directorate (S&T) of the U.S. Department of Homeland Security.

This idea is not in play right now, so the flexibility strengthens the resiliency of the overall grid, reducing the likelihood of major power failures. The superconducting cable is the “inherently fault current limiting (IFCL)” superconductor cable.

Engineers are putting decades of existing electrical research into practice. S&T managers and scientists just wrapped up a test of the new superconducting technology at the Oak Ridge National Laboratory in Tennessee.

These cables can deliver more power, prevent power failures, and take up less physical space. A single superconductor cable can replace 12 copper cable bundles, freeing up more space underground for other utility needs such as water, natural gas, or phone service. The technology is capable of carrying 10 times as much power as copper wires of the same size, while also being able to adapt automatically to power surges and disruptions from lightning strikes, heat waves, and traffic accidents, even sabotage.

“The IFCL superconducting cable being tested could well revolutionize power distribution to the country’s critical infrastructure,” said Dr. Roger McGinnis, director of the Homeland Security Advanced Research Project Agency at S&T. “Eventually, these technologies will help incorporate localized clean, green electricity generation into the power grid.”

As for the science, the cables work by transmitting electricity with near zero resistance at higher temperatures than usual. The cables conduct electricity at -320°F instead of -460°F for traditional superconductor cables.

Holding and conducting energy better than traditional copper means these cables take up a fraction of the space. Manhattan’s electrical workers may be able to eventually clear out the subterranean congestion beneath Wall Street that looks much the same today as it did a century ago.

Since the cables themselves better prevent extremely high currents from cascading through the system, they will help eliminate the power surges that can permanently damage electrical equipment, similar to a breaker switch in a home, McGinnis said. The cable switches off during a surge or failure, but automatically resets when conditions return to normal.

For some context, electrical substations take electricity delivered over transmission and distribution lines and lower the voltage so homes and businesses can use it. Even if power is lost to an individual substation, by creating multiple, redundant paths for the electric current, the cables allow quick power restoration to all the surrounding power loads. Ultimately, these cables may allow substations that companies had intentionally isolated from one another in the past, for fear of cascading failures, to now interconnect in order to share power and assets.

For related information, go to www.isa.org/manufacturing_automation.