An arc fault happens in a flash when a high-power discharge of electricity between electrical conductors explodes in a superheated blast of air and ionized gas, destroying equipment and putting anyone nearby in serious harm’s way. In only a few seconds, a several-hundred-pound electrical switchboard the size of a midsize car can be reduced to a smoldering heap of twisted metal.

More than two decades ago, The Johns Hopkins University Applied Physics Laboratory leveraged internal research funds and Navy sponsorship to create a system of sensors for the Navy to quickly detect and stop arc faults on submarines. These systems, since deployed on all classes of subs and aircraft carriers, have helped avert disaster on 10 Navy ships.

Now, with the nation’s demand for electricity on the rise, APL is expanding this protection to the commercial sector, where arc faults also cause significant injuries and damage. Earlier this year, the Lab licensed the rights to its arc fault detection tools to the Training and Control Systems Unit of DRS Technologies, Fort Walton Beach, Fla. While the Navy is still the primary consumer, DRS officials say additional development will broaden the system’s appeal in other markets, such as hospitals or computer processing centers.

“This is an excellent example of dual-use technology,” says Ms. S. Furney, of APL’s Office of Technology Transfer, which arranged the licensing deal. “We have transitioned this technology to a commercial company so industry and the rest of the nation can benefit from the research done at APL for the Navy. With DRS’s added resources, this technology is likely to reach more people and have an even greater impact.”

A Shocking Problem

Arc faults—and the explosive flashes that can result from them—are a major electrical industry hazard, sending more than 2,000 people to U.S. emergency rooms with severe burns each year. A decade-long French Power Corporation study found that arcing caused 77 percent of all recorded electrical injuries; a widely cited National Institute for Occupational Safety and Health study found that arc flash burns accounted for nearly 40 percent of the 44,000-plus electrical-related, lost-workday injury cases in the United States from 1992 to 2001. Department of Labor research showed that nearly 2,300 workers died in arc fault accidents from 1992 to 1999.

And those numbers don’t account for less-serious unreported injuries or millions of dollars in damaged and destroyed property. Government regulations mandate that workers protect themselves when working on electrical equipment, mostly by wearing special helmets, gloves and other gear. But Bruce Land, a researcher from the Lab’s Research and Technology Development Center, equates those requirements to seatbelt laws; people don’t always follow them, for reasons ranging from comfort to convenience.

“Imagine you’re working on energized equipment at a substation, and you’re supposed to be wearing a full suit that closely resembles what a fireman wears,” says Land, a developer of the Lab’s arc fault technology. “On a 100-degree day, with the sun beating down on you, you’re lucky if you don’t pass out from the heat. So people take shortcuts and they get hurt.”

Even if they wore the suits properly, Land says, that’s no help against the deafening boom or shock wave from an arc flash, which can pack enough punch to knock technicians through walls or into adjacent rooms.

Invented by an APL team that includes Land, Christopher Eddins, Leo Gauthier Jr. and John Klimek, the arc fault detection technology combines a conventional smoke detector’s radioactive ionization chamber with custom electronics, allowing it to sense pyrolytic products that indicate overheated electrical insulation. Before the connection can reach temperatures necessary to melt copper and create an arc that leads to an electrical fire, the detector sends an “alert” that allows operators to proactively diffuse the impending problem while maintaining uninterrupted power.

“People are sometimes protected by newly designed high-powered electrical switchboards that release hot arc gases away from where an operator may be standing—at the sacrifice of the equipment,” says Land. “However, conventional power systems don’t offer even this limited protection, and it will be many years before older boards are replaced with safer designs. The beauty of the APL technology is that it can upgrade older equipment, making it possible to protect both personnel and property by warning of an impending arc or stopping an arc should
it occur.”

Miniaturized through 20-plus years of development for Navy ships and submarines, the APL system is small enough to fit inside most enclosures. It can also detect insulation temperature with a single non-contact sensor, route signals through a “network” of detectors to protect several electrical enclosures at the same time, continually monitor susceptible units and alert personnel when it detects a high-risk situation, and immediately extinguish inadvertent arcs before serious damage occurs.

“Its detector senses when pressure rises inside an enclosure and, within milliseconds, interrupts the arc’s intended rogue pathway before the release of pressurized hot plasma [ionized gas],” Land says.

Evolving Technology

Gary Thurston, business development manager for Naval Control Systems in the DRS Training and Control Systems unit, says Navy ship-modernization plans are driving further upgrades to the arc fault system his company has licensed. Working with APL’s Land, DRS engineers seek to shrink the system’s controller to nearly half its current size, reduce its cost and tie its sensors into high-speed, advanced data-acquisition networks that offer a complete, real-time picture of a ship’s operating status.

“Arc fault detection is a key piece of technology for DRS,” Thurston says, adding that the demand for arc fault protection should increase as the Navy continues to develop all-electrically powered ships.
Increasing demand for electricity in the United States will also strain electrical generation and distribution systems, Land says, fueling the need for technology to make these systems safer and more reliable. Arc fault detection systems such as APL’s could have prevented or at least minimized the impact of recent, costly power outages in the business districts of New York and Chicago, he said, perhaps saving millions of dollars in lost transactions and productivity.

“Our technology can do for others what it continues to do for the Navy,” Land says. “That is, protect people and other valuable, critical resources.”