The Johns Hopkins University Applied Physics Laboratory (APL), Laurel, Md., has licensed technology to prevent dangerous and destructive electrical fires to DRS Technologies' Training and Control Systems unit in Fort Walton Beach, Fla.
The license gives DRS exclusive rights to market APL's patented arc fault and arc flash detection system, designed to prevent electrical fires caused by "arcing." An arc fault is a high-power discharge of electricity between two or more conductors; an arc flash is the pressurized blast of plasma and hot air that occurs when the arc strikes the conductors. The APL system quickly detects and quenches an electrical arc before it can damage an electrical distribution system.
"Conventional high-powered electrical switchboards protect personnel by releasing the hot gases from the arc from the top of the switchboard rather than from the sides, where an operator may be standing," says APL researcher Bruce Land, one of the system's inventors. "However, conventional power systems can not warn of an impending arc or quench an arc should it occur. The fielded APL technology can predict many types of arcs and quench all arcs. Fielded systems are credited with saving the electrical systems of 10 Navy ships. Conventional systems try to protect the personnel, but the APL technology protects both the personnel and the equipment."
Invented by an APL team that includes Land, Christopher Eddins, Leo Gauthier Jr. and John Klimek, the system combines a conventional smoke detector's radioactive ionization chamber with custom electronics, allowing it to sense pyrolysis products that indicate overheated electrical insulation. Before the connection can reach temperatures necessary to melt copper (1,981 degrees Fahrenheit) and create an arc or electrical fire (36,000 degrees F) the detector sends an "alert" that allows operators to maintain uninterrupted power while addressing the problem.
"This is an excellent example of how technology transfer should work," says Susan Furney, technology associate in the APL Office of Technology Transfer. "We have transitioned this technology to a commercial company so that our sponsors and the nation can benefit from the research done at APL."
Evolving from nearly three decades of development for Navy ships and submarines, the APL system is small enough to fit inside existing enclosures. It can also detect insulation temperature without consumables such as tracer gases; "network" signals from multiple 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 arc flash detector senses when pressure rises inside an enclosure, quenching the arc before there is a release of pressurized hot plasma. The plasma can escape through vents and cracks in a switchboard — or though uncovered switchboards during routine maintenance — potentially injuring or killing people nearby and damaging equipment and property.