There is more information about what happened that caused Metro to close part of the Red Line for several days last month.
Rail service was suspended from Saturday night July 30 until Monday morning between the Van Ness and Farragut North stations.
Smoke that began wafting into the Dupont Circle station appears to have been caused by a circuit breaker failing to trip, which could have stopped what was happening, according to a preliminary report from the Washington Metrorail Safety Commission.
“Some of Metrorail’s initial response appears to have assumed that the event was an arcing third rail insulator,” safety commission Executive Officer David Mayer said during a meeting Tuesday.
But it wasn’t, and workers who had been waiting for power to be cut to the third rail allowed the problem that affected other electrical systems to continue.
“The source appears to be what Metro terms low-voltage electrical systems because the systems are not used to power the third rail but instead power other Wayside equipment,” Mayer said. “This was a prolonged event, and it resulted in damage requiring extensive repairs.”
The investigation continues into the cause of the initial electrical problem and overall response, which includes when and how it was decided for the train to be moved out of the tunnel where sparks were observed on the wall.
“Areas of investigation include implementation and quality of fire alarm response processes, Metrorail’s incident management and emergency response, Metrorail’s interdepartmental coordination and communication, and other factors that may arise as the investigation progresses,” Mayer said.