by Melissae Fellet
High energy arcing faults are high-power electrical discharges between two or more conductors that can release tens of thousands of amps of current. They can result in explosions that reach about 35,000 degrees Celsius — about the temperature of lightning strikes — and vaporize steel and spew hot metal particles into the air.
In a power plant, such a fault can quickly spread, which is just the thing Sandia National Laboratories researchers are trying to prevent by finding a new way to peer into the flames. Those flames are filled with useful information that can help keep power plants operating safely.
Sandia fire protection and optical engineers are using high-speed cameras and advanced algorithms, imaging and analytic methods to understand these dangerous arc faults between two conductors, such as the high-voltage bus bars in a switchgear at a power plant.
Power plants evaluate risks from arc faults by knowing their zone of influence — the distance that neighboring cables and equipment would be damaged beyond functionality. In a nuclear power plant, this helps engineers evaluate the potential of damaging the reactor core if the neighboring equipment plays a role in safely shutting down the reactor.
But precise data about a rapid arc fault is hard to collect. Bright flames and smoke obscure the view, and the high heat destroys many diagnostic instruments. The electromagnetic interference associated with the flash also impairs the ability to collect data.
Sandia optical engineers have a way around those challenges. They often train high-speed cameras on fiery tests at Sandia’s blast tube and rocket-sled track. Now they’ve turned their lenses toward arc faults at power plants.
Working with Sandia fire protection engineers and colleagues at the National Institute of Standards and Technology, the group recently participated in large-scale tests at an independent lab in Pennsylvania. The project is funded by the Nuclear Regulatory Commission.
Data from the tests will enable a computer model to be developed that will predict an arc fault’s zone of influence. The results could be applied to low or medium voltage cabinets at any facility, said Chris LaFleur, a fire protection engineer who led the Sandia effort.