More power trouble along Metro’s Red Line on Wednesday caused another round of hassles for commuters, including near the Friendship Heights station, where a weekend electrical fire in a tunnel frightened riders and led to a hectic evacuation.

After Red Line rail problems Monday and Tuesday caused service delays — with trains headed in opposite directions being forced to share one track near the D.C.-Montgomery County border on the western part of the line — the Wednesday morning commuter rush brought more single-tracking and more headaches.

A smoky electrical problem near Friendship Heights — a similar but less severe incident than one that prompted an evacuation Saturday night — led firefighters to briefly close the station for safety reasons shortly after 7:30 a.m., officials said.

[Metro’s 40-year history of maintenance neglect and political inertia.]

Outside the station, as riders waited to board buses, the mood was not pleasant.

“We all got off [a train], and you could see the fire in the distance, and then the platform kind of filled with smoke, and we all came out here,” one passenger told WJLA-TV. Another said, “There was a little bit of smoke coming down the tunnel, but not a lot.”

D.C. firefighters said there was light smoke in the track bed at the Friendship Heights station but no one was injured.

Metro spokesman Dan Stessel described the problem as an “arcing insulator” on outbound Red Line tracks, a short distance beyond Friendship Heights in the direction of the Bethesda station.

An “insulator” is a stubby, insulated stanchion that separates the electrified third rail from the track bed. If an insulator is damaged or worn out — as many are in Metro’s subway — electricity can flow from the third rail to the ground, generating heat and igniting flammable substances in the area. The escape of electricity is called “arcing.”

Faulty insulators in the subway — a long-standing problem that has caused numerous commuter delays in the past — are among an array of infrastructure problems that General Manager Paul J. Wiedefeld has vowed to address in a comprehensive maintenance plan, which he has said he will unveil soon.

Wiedefeld’s plan — which is likely to involve closing sections of some lines for repairs, perhaps for days at a time — stems from Metro’s long history of deferring maintenance in the 40-year-old subway.

Saturday’s incident came amid an FTA “safety blitz” that began last month and is ongoing. Federal investigators’ initial findings showed that among other shortcomings, Metro is failing to provide basic safeguards such as working fire extinguishers and clear escape routes to help riders in the event of an emergency evacuation.

Wednesday’s arcing insulator caused about an hour of single-tracking in the Friendship Heights area until the problem was resolved, Stessel said.

And commuters weren’t happy.

“This is unacceptable during rush hour,” one rider declared on Twitter, while another tweeted: “Once again sitting still on the @wmata during rush hour. Prices go up, service goes down.” And so it went, a familiar chorus on Metrorail, especially along the Red Line, the system’s oldest and most trouble-prone subway route.

“Another day=more @wmata red line delays,” griped one tweeter. Another wondered, “Can I expense a cabride ... because Metro’s RedLine decided it won’t be working today.”

[Saturday’s Red Line evacuation caused by “foreign object” falling from train.]

In Saturday’s incident, shortly before 7:30 a.m., Metro said, “a metal part of a rail car” became dislodged from a train and made contact with the third rail near the Friendship Heights station.

When the “foreign object” touched the electrified rail, “a loud noise, flash and smoke” resulted, Metro said, adding that the transit agency and Federal Transit Administration are still investigating what caused the metal piece to come loose.

The train came to a stop and, after a passenger used an emergency handle to open doors, the train was unable to back up until the doors were closed. After a delay of about 10 minutes, as smoke was wafting into some of the cars, the train was able to return to the Tenleytown-AU station, where riders were evacuated.

Earlier Wednesday, before the arcing insulator problems, a “partial power outage” at the Red Line’s Medical Center station idled escalators and left some commuters stuck in an elevator, the transit agency said. Montgomery firefighters said no one was injured.

The cause of the outage, which lasted about 50 minutes, was not immediately clear. Power at Medical Center was restored at 7:47 a.m.,Stessel said.

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