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NEC - Mass Photo courtesy of Washington Metropolitan Area Transit Authority (WMATA)

Risky Rail Ride

Plagued by growing and potentially dangerous electrical arcing incidents, the Washington, D.C. commuter rail line mobilizes an ambitious insulation resistance and stray current testing program.

Unlike wine and cheese, complex electrical systems rarely improve with age. Instead, they only grow more unreliable and potentially unsafe, if only incrementally. But left unattended, performance can suffer and risks can multiply. That reality has come into sharp focus over the last two years at the offices of the Washington Metropolitan Area Transit Authority (WMATA).

An uptick in track electrical arcing incidents — traceable to aging and worn rail components and less-than-ideal trackbed conditions — has intermittently disrupted the agency’s busy Metrorail network, a traction-power electrification (TPE) commuter rail system serving the Washington, D.C. metro area.

Arcing has been occurring more regularly on the line, which dates to 1976. Like other TPE systems, it utilizes a so-called “third rail” that delivers electric power to trains running on twin-rail track. Arcing is growing more acute because it can spawn combustion that ignites flammable debris and dirt-covered cables and track parts. In the worst instances, dangerous right-of-way fires and smoke can result, increasing the potential for service interruptions and safety risks.

Photo courtesy of Washington Metropolitan Area Transit Authority (WMATA)

Washington Metropolitan Area Transit Authority (WMATA) crews are busy replacing insulators, securing power cables, eliminating third-rail joints, and addressing standing water in an effort to reduce unwanted arcing events throughout its system.

One incident produced a perfect, course-altering storm: dense smoke in one of the system’s numerous tunnels that forced a packed train’s evacuation mid-afternoon on a winter Monday, leaving one rider dead and 90 injured (see “Up in Smoke” from the November 2015 edition of EC&M). In other less-dramatic cases, arcing-induced fires and smoke have been bad enough to force temporary service shutdowns. 

Turning point

But it was the fatality incident in January 2015 that proved the wake-up call for WMATA and its federal safety overseers. Within months, on the heels of a National Transportation Safety Board investigation of the incident that concluded it was the equivalent of an iceberg’s tip, the Department of Transportation’s Federal Transit Administration (FTA) seized temporary oversight of Metrorail safety operations.

Since then, safety and maintenance operations on Metrorail’s 118 miles of track have been put under a microscope, leading to a flurry of efforts to address multiple and varied deficiencies that jeopardize operations and public safety. Central to that mission have been efforts to bring the arcing situation under control. By first identifying where it’s occurring, where it’s likely to happen, and its ultimate sources, WMATA has been performing repairs and improvements at known arcing locations or those with suspected vulnerability.

The bid to address the problem quickly, but thoroughly, has strained WMATA’s resources. The agency had to pursue fixes with increased vigor following the fatal incident, and also because records showed consequential arcing incidents had been on the increase.

In the course of its work, WMATA has grown more aware of the risks of de-emphasizing preventive maintenance. The situation has illustrated the susceptibility of rail electrical systems to both neglect and environmental conditions.

“Problems like this are quite prevalent throughout this industry,” says Andy Off, WMATA’s assistant general manager of rail services. “Third-rail systems are challenged with keeping track beds clean, the integrity of the system intact and TPE components insulated to standards so high voltage doesn’t go places it shouldn’t.”

But WMATA probably should have seen it coming, and better understood that mounting arcing problems were inevitable and would demand attention, says Gus Ubaldi, a rail expert with Robson Forensic, a consulting engineer in Lancaster, Pa. He acknowledges WMATA’s primary need to stay operational, but questions the apparent decision to delay critical work.

“The sense I’m getting is that someone woke up from a Rip Van Winkle sleep and said, ‘this needs to be repaired,’” he says. “So now they have a decision to make: Do the repairs or run trains on a full schedule.” 

Testing’s role

WMATA’s predicament is serving to reinforce the value of electrical testing, measurement, and inspection. It highlights the essential role that procedures used to locate, isolate, and better anticipate electrical system failures — notably cable insulation resistance and stray current testing — must play in comprehensive electrical system maintenance and effective incident response. Challenging and time-consuming under the best conditions, these tests have proven especially difficult to carry out in an active and demanding transit environment.

Yet in spite of logistical challenges, the testing has produced results. And it’s now poised to play an even bigger role.

In July 2017, WMATA was to have kicked off a new long-term dedicated preventive maintenance program. It will subject one-quarter of the system to tests and inspections for electrical current leaks each year. The agency’s goal is to identify and address areas vulnerable to arcing on the entire length of the system in four years or less, and then to start the entire process again.

“We’ve done intermittent cable insulation resistance and stray current testing, primarily in response to known failures, but not in a methodical and comprehensive way,” says Off. “The shift taking place now is one of moving from carrying these out in a reactive fashion to one of being proactive, finding potential failures before they occur.”

Photo courtesy of Washington Metropolitan Area Transit Authority (WMATA)

A maze of conduit, often wedged into a cramped urban right-of-way, feeds the traction power electrification system of the Washington Metrorail system.

Ahead of the new preventive maintenance program, and concurrent with a year-long push to pour resources into a concentrated and multi-faceted track improvement program called SafeTrack, WMATA in 2016 began targeting segments of the line where arcing was known to have occurred.

According to an FTA report issued in December 2016 detailing its investigation of the TPE system, WMATA logged 70 arcing incidents in the year that elapsed after October 2015. And in the period between March 2016 and the drafting of the report, WMATA documented 58 arcing events that required emergency response because of smoke and/or fire.

Deploying maintenance crews to areas of documented arcing, WMATA replaced insulators, secured power cables, eliminated third-rail joints, and addressed standing water — all conditions that, among others, can contribute to arcing. That appeared to produce results; a trouble-prone section that had four “major” and 14 less-serious arcing incidents over three months pre-maintenance, experienced eight minor incidents over the ensuing six months.

Targeted work to address arcing continued into 2017. A WMATA report issued in late April appeared to show mixed results.

On the one hand, the system logged 26% fewer fire incidents in the year’s first quarter, 20 compared with 27 a year earlier. WMATA attributed the decrease largely to a general track cleanup effort that reduced the availability of combustible material. Yet there was little evident progress on arcing-incident reduction; 12 were documented in the year’s first three months, compared with 11 in the first quarter of 2016.

At that rate, Metrorail arcing incidents for 2017 would project to come in well under recent-year totals, and might suggest more aggressive efforts to curb them is paying off. But WMATA and FTA appear to want set an even higher bar for success going forward, and the new preventive maintenance program starting this summer is a clear step in that direction. 

FTA mandates

The program will be ambitious and crafted to begin complying with a host of specific safety directives issued by FTA in December 2016. Detailing multiple deficiencies in Metrorail’s TPE system that have brought arcing to a critical-concern stage, FTA has instructed WMATA to begin addressing four categories of concern — one of which is its testing and inspection program.

In its December 2016 TPE system report, FTA found that the agency’s testing and inspection process was lacking in rigor and that corrective and preventive maintenance was inadequate. It concluded that, “Without dedicated implementation of such a program (of ongoing inspection, testing, maintenance and replacement of aging or damaged components), TPE systems will continue to experience fires and system shutdowns and be prone to potential injuries and fatalities and a loss of public trust.”

To remedy that, FTA is ordering WMATA to undertake specific actions, among them development of plans to: insulation resistance test the integrity of cross-bonded cables, especially those in tunnel areas where water and muck can collect; test jumper and transition cables in tunnels ahead of upgrading or replacement; and to greatly expand regular testing for stray current and corrosion, especially in components like track fastening systems that have deteriorated to the point where electrical isolation is jeopardized. FTA also wants WMATA to establish a system to grade TPE system defects, and better utilize the results of thermal imaging and automated inspections of other rail system conditions to assess TPE system integrity.

Photo courtesy of Washington Metropolitan Area Transit Authority (WMATA)

A megohmmeter readout during a Washington Metrorail test reveals information about anomalies in high voltage circuits.

So WMATA’s testing and inspection menu was full as it began quickly transitioning in late June 2017 from SafeTrack to the new preventive maintenance program. That initiative marks a rebirth of sorts for WMATA operations. Years ago, before the agency prioritized correcting documented, observable problems on the system, it maintained a more robust proactive maintenance stance.

“There were ideas and programs in place to do some of this, but ultimately, as the system ages, you start becoming overburdened with doing corrective work, and the first thing to go is preventive maintenance,” Off says.

Now, with arcing clearly identified as a threat, and ample evidence that system safety and reliability is becoming compromised, prevention and proactiveness are making a comeback.

“This preventive maintenance program is the antithesis of SafeTrack, which was all about replacing failed components like ties, fasteners, insulators, and the like,” Off says. “This is about testing the infrastructure we have and finding weaknesses before systems fail, and it’s driven by the need to improve the safety and integrity of the system. We need to get in front of it.” 

Testing obstacles

But WMATA faces a formidable task in hunting down and fixing the conditions that lead to electrical arcing. Despite the plan to take it in small bites, inspection and testing is tedious and time-consuming — even more so on a busy and vital commuter rail line.

Since insulation resistance and stray current testing require complete de-energization, and can’t be done in a way that cuts power to only one track in the two-track system, work will have to be compressed into off-peak hours. Late-night service will be cut back to open a bigger window for the work, but crews will still be under pressure to move methodically but determinedly through the process of cutting power, setting up and performing tests, collecting data, and restoring service. Plans call for all sections of the line — cables feeding the third rail that powers the trains and the negative, return side that carries electricity on a circuit back to substations — to be analyzed.

“There are a lot of places where we don’t have a visual on the cables, so pursuing a visual inspection plan won’t give us a full picture,” Off says.

Photo courtesy of Washington Metropolitan Area Transit Authority (WMATA)

A Washington Metrorail maintenance crew employee performs an insulation resistance test in early July 2017.

The testing itself can be done rather quickly, Off says, but setup and repeating the process for each section is time-consuming.

“The technique itself hasn’t changed much in 40 years, and there’s not much to it in terms of equipment,” he says. “The act of using the instrumentation represents a fractional minority of the total time needed to carry out the activity, which involves scheduling the work, disconnecting the rails, making sure it’s performed safely, collecting results, and producing a report on what actions we need to take.”

Follow-up action on the test results will depend on a number of factors, most importantly how extensive the leakage is and how likely it is to produce arcing. Off says WMATA will generally be guided by a set threshold for insulation resistance; if there’s failure, corrective actions up to and including replacement will be made. 

Marshaling resources

New FTA mandates will likely exert even more pressure on the agency to take remedial action. In addition to funding the tests, the agency has budgeted for upgrades and improvements to fix the arcing problem. The goal will be to make smoke and fire incidents due to arcing as unlikely as other zero-tolerance events that plague rail lines.

“Our goal is to limit these to the greatest extent possible,” he says. “That’s a high bar, but it’s similar to the one we have for derailments.”

While WMATA has an extensive in-house staff and crews to address all aspects of the arcing problem, it does rely on outside help. Engineering consultants, including HNTB Corporation and Mott McDonald, have a long history of involvement with WMATA. They’re presumably among those Off says have been helping the agency craft a comprehensive plan to address the arcing problem, a task made more difficult by the need to comply with nearly 50 FTA mandates related to the TPE system.

“Consultants have helped build a program in terms of prioritizing what we do, how the tests are constructed and creating the documentation needed to track the program’s progress,” says Off.

WMATA is also using outside help to perform the actual work of remedying the conditions that create arcing. One provider is C3M Power Systems, a Capitol Heights, Md. company that, through its parent company, Clark Construction Group, has a long relationship with the agency.

Some of the roughly 90 workers engaged in numerous projects, which include substation and tie breaker station upgrades, are set to transition into roles in the new preventive maintenance program, says Chuck Hinton, C3M vice president. They’ll come in behind crews performing insulation resistance and stray current testing and do the work that close inspections have deemed critical to prevent future arcing incidents.

“WMATA will note the deficiencies, and if the results are out of acceptable range, we’ll repair and document it and check the item off the list,” he says.

While all TPE rail system work is uniquely pressured by the need to serve and protect the public, work in this new preventive maintenance surge will raise the challenge bar, says C3M General Superintendent Donald Schwier.

“WMATA goes to great lengths to ensure that things are done correctly, and every task we perform has to be laid out to protect workers and the system,” says Schwier. “These measures combined with the sheer magnitude of what has to be accomplished in tight time windows here makes this different. The agency may only be able to get in two to four hours of actual repair work each night.”

That work is likely to be challenging, too, because of the prevailing Metrorail system environment, says Kivins Beecher, C3M senior project manager.

“What makes the WMATA situation difficult is that so much of the system is underground, and a lot of the cable that will have to be removed has been subject to water and insulation breakdown over 20 or 30 years,” he says. “All of that water seeping in over time goes hand-in-hand with the arcing and fire problem.”

WMATA clearly faces a daunting task in getting a handle on its arcing problem. But with the problem clearly identified, resources mobilized, a preventive maintenance plan in place, and proven electrical testing ready to deploy, the Metrorail TPE system can be hardened to the point that any arcing that occurs has only benign consequences.

“We’re going to get after this, and it’s a positive that in the past six months we’ve already seen a significant reduction in the number of smoke and fire events,” Off says.                    

Zind is a freelance writer based in Lees Summit, Mo. He can be reached at [email protected].

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