Crowds are seen at the Stadium-Armory Metro station in this file photo. (Kevin Clark/The Washington Post)

Daily rush-hour slowdowns on Metro’s Orange, Silver and Blue lines could be over by the end of the year, instead of lasting at least six months, because engineers have come up with a possible temporary solution for the subway power shortage that is causing the problem, the transit agency said Thursday.

Thousands of riders have suffered more aggravation than usual since Sept. 21, when fire damaged a rail power substation, forcing Metro to reduce the frequency of Silver and Orange trains during peak commuting hours and impose lower speed limits near the Stadium-Armory passenger station, where those lines and the Blue Line share tracks.

Although Metro initially said the diminished service would last at least six months, while the substation is being rebuilt, the agency Thursday offered a less gloomy estimate.

“We believe we can accelerate that timeline to less than six months,” said Andrew Off, Metro’s assistant general manager for engineering. Because damage at the substation turned out to be less severe than originally thought, he said, some equipment might be temporarily usable while the rebuilding is underway.

“The challenge is defining exactly how much less than six months,” Off said, adding that, in the best case, the three lines would be running at full capacity by year’s end.

However, he cautioned, “If tests prove that the equipment is not sufficient, it’s at that point that we’ll continue to unfortunately grow” the timeline. In the worst case, he said, the rush-hour slowdowns would continue until late spring.

The fire apparently resulted from an electrical malfunction, Off said, but the exact cause has not been determined.

The blaze in the underground substation heavily damaged the facility’s three large transformers, which convert commercial electricity into the kind of current that propels subway trains. The transformers had a combined output of 9 megawatts, supplying power to long sections of the Silver, Orange and Blue lines near Stadium-Armory.

Because trains in that area are now relying on power from smaller substations located farther away, officials said, Metro has imposed speed restrictions in the area, to avoid overtaxing the smaller substations.

To prevent the lower speeds from causing huge traffic backups in the rail system, Metro has been running fewer Orange and Silver trains during the morning and evening rush hours, which has led to more crowding on trains. Even with fewer trains on the two lines, rush-hour commuters from Northern Virginia to Prince George’s County have been experiencing more stop-and-go rides, including “holds” in tunnels.

Metro has not cut back on the number of rush-hour Blue Line trains, because those trains already were running less frequently than trains on the Orange and Silver lines. However, because the three lines share tracks along a 13-station stretch, from Rosslyn to Stadium-Armory, Blue Line commuters also have been enduring more sluggish rides.

Immediately after the fire, Off said, “our damage assessment was quite devastating.” He said engineers thought all three transformers were destroyed.

However, Off said, with two of the transformers, “the damage was primarily dirt, residue, some minor damage to control cables and other things. But the guts of the equipment, unless testing proves otherwise, we believe it will be able to be put back in service.”

If the two transformers can be made to work again, he said, their combined 6 megawatts of output will be enough to restore full service in the Stadium-Armory area.

“This is a temporary solution,” he said, adding that the two transformers, like the ruined third transformer, eventually will be replaced. He said the transformers have to be built from scratch by a manufacturer, which will take months.

He said repair work on the two damaged transformers will begin in early November.

“What we will do is clean the equipment and put it through the same exact test requirements that we would do if we were buying it new,” Off said. “If it tests properly, we will continue the process and commission it” by the end of the year.

But if the testing shows that the two transformers are too damaged even for temporary use, the commuting headaches will last through winter and into spring.