At the height of Friday afternoon rush, an insulator caught fire at Metro Center, kicking off a meltdown on the Orange, Silver, and Blue lines. A smaller but similar incident hit the Red Line Sunday evening as well. The day before, the WMATA board received a briefing on the power system that both issues were related to and how problems with it continue to plague the system.
Photo by John Grant.
Friday’s fire right around 5 pm at Metro Center on the Orange/Silver/Blue lines caused trains to halt service for around 40 minutes and then single-track until the system closed, delaying thousands and adding an hour or more to some commutes. Sunday’s issue happened at a time where delays were an inconvenience for fewer people, but it was certainly a problem nonetheless.
Issues can crop up at various points in any power system, which makes routine maintenance so important. Substations that receive power from the supplier (Dominion and PEPCO, primarily) have cables that run to the third rail, which runs alongside the tracks that trains run on and which supplies power to the trains. Trains use this power, which is then fed back through the rails through the “negative return” back to the substation.
The likely culprit in both incidents is what’s called stray electrical current, which can happen when a power circuit is created through a path that isn’t the one intended. Instead of making a circuit from the power substation through cabling to the train then back out through the rails, an alternate circuit path could be created across insulators or through the stud bolts that help secure the tracks.
This unexpected path can create arcing, smoke, and fires, which cause harm to the equipment and are dangerous for passengers. Dirt, dust, and other contaminants, all of which aren’t exactly uncommon in Metro tunnels, can increase the severity of stray currents.
When these mixtures stick to the third rail insulators, the insulator’s function starts to break down. Instead of preventing the current from “escaping” the third rail through the trackbed, the debris lets the current travel to unintended portions of the system not meant for it. These stray paths can case bolts to heat up and glow, smoke, or spark, or cause the insulators to arc or even catch fire if they’ve broken down far enough. These side-effects are just a few reasons why proper maintenance of a power system and making sure insulators, supply and return cables, transformers and other components is important.
The stray current and other power issues aren’t new to Metro; a current issue across an insulator led to an explosion at Federal Center in May, and arcing insulators are almost a common occurrence, especially on the Red Line.
Metro’s General Manager, Paul Wiedefeld, requested an American Public Transportation Association (APTA) peer-review of portions of its third-rail power system back in June, and the report was made available after WMATA’s September 22nd board meetings. The peer review request was part of Metro’s safety department’s larger holistic review of the power system to try and help pinpoint and solve its various power issues once and for all.
The APTA review provided a list of observations about Metro’s third rail system that could potentially cause issues. One of the primary ones (which isn’t a new idea, or even new to Metro) is that the reviewers found “insulators seemed to be excessively contaminated” both in the rail yard they visited as well as on open track. This contamination, a combination including brake dust from train brake pads, oils, and various other types of dust and debris, can stick to the insulators that hold up the third rail which provides power to the trains.
APTA gave Metro two recommendations for the contamination. One, Metro should analyze what the deposits on the third rail insulators are to figure out where they come from, and determine how to cut down on how much is generated. Second, they suggest Metro develop and maintain an insulator cleaning program. A tunnel cleaning program did exist at Metro up through the early 90’s, but was terminated.
APTA reviewers also found that Metro staff are “constantly in a catch-up mode” when it comes to the power system, so they don’t have much time for preventative maintenance that might also help cut down on smoke/fire incidents.
Metro’s Board of Directors has heard about many of these issues before
The lack of an active cleaning program was one issue the NTSB found that contributed to the January 2015 smoke incident that killed one passenger and injured dozens others. Metro’s deputy general manager in May of 2015 told the Board that the agency was to reinstate this program, and wanted to become “so proactive that these incidents don’t happen.”
Smoke and fire incidents, many caused by stray or imbalanced current, continue to occur in the system— more have happened in 2016 than had up to this point and last year.
Metro is certainly more active now than it has been in the past regarding tunnel cleaning (said to be part of SafeTrack and partially restarted after the L’Enfant incident) and insulator replacement from ceramic to fiberglass within underground station limits is complete (but still needs to be done for above-ground stations and in tunnels), and many power cables and equipment have been replaced in the meantime as well.
But becoming a proactive organization requires hard analysis to detect issues and get to the root causes before they become larger problems, not simply when an outside organization finds them or when somebody gets hurt. It’s a long road to walk down, but with the proper management it’s an achievable goal and results in a safer and more reliable transit system for riders to use.