A More Robust Grid for Manhattan

Superconducting cables could make power-grid infrastructure more secure.

Supercooled, superconducting power cables have long held the potential to deliver power efficiently, since they offer no resistance losses. Now they're being examined as a way to add redundancy in the cramped quarters of Manhattan's local power grid, potentially protecting against natural disruptions and terrorist attacks.

Cold Cables: A cross section of American Superconductor’s high-temperature superconductor cable shows liquid coolant moving through the core in blue, surrounded by a web of current-carrying wires. Such cables can carry 150 times the electrical current of copper wires of the same size, with no current losses due to resistance. These cables are at the heart of a new project designed to make Manhattan’s power grid more resistant to failures and attack. Credit: American Superconductor

Multimedia •  View an animation of a more-secure power grid in New York City.

In a city, superconducting cables offer an advantage: they are far more compact than copper wires. And some of the requisite surge protection can be engineered directly into the cables--a feat not possible with copper wires--reducing the need for bulky mechanical circuit breakers in city substations.

To develop the concept, the U.S. Department of Homeland Security and New York's major utility, Consolidated Edison (Con Ed), announced last week that they would invest $39 million over the next three years to connect two substations at undisclosed locations in Manhattan, allowing each to take over for the other in the event that one burns out. The effort will use technology from American Superconductor, of Devens, MA, which makes so-called high-temperature superconducting cables ("high temperature" means that they can operate at 90 degrees kelvin) and associated control systems.

"It's not a panacea for every system problem, but it would give us more reliability and flexibility and asset sharing," says Steve Kurtz, project engineer at Con Ed, a utility whose grid flaws became evident last summer when a power outage darkened parts of Queens for 10 days. "It would make the grid more resilient."

Part of the power grid's shortcoming in New York City--as in many other parts of the country--is the lack of Internet-like cross connections, which would add reliability. The grid's endpoints are substations that typically serve tens of thousands of customers apiece. A single lightning strike or errant squirrel can burn out a substation, leaving tens of thousands of people in darkness until the utility can get the substation back online.

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The solution is to add cross connections between substations so that others can quickly step in to supply power. Such redundancy could also prove useful during a terrorist attack. But if a city adds connections, it also needs to add more equipment to stop faults from propagating through these new connections. "It sounds pretty good, so why don't they do it?" asks Greg Yurek, CEO of American Superconductor. "The answer is that there is not enough real estate under the streets of Manhattan."

To be sure, all this is possible using tried-and-true copper wires and mechanical equipment. But in places like Manhattan, there is no room under the ground for all the extra copper cable--which has to be given some air space to dissipate heat--and no room in cramped midtown substations for new breakers.