As is customary in winter, squirrels have begun their seasonal storing of nuts. But recently an alarming number in the Washington area have chosen to stockpile their nuts in the electric transformers at the top of power poles. The result, according to Potomac Electric Power Co. officials: Squirrels are getting zapped and electrical blackouts are increasing.

Seven squirrel-related blackouts occurred last Monday alone.

These blackouts usually affect from 50 to 100 homes and occur more frequently on holidays and weekends because there is less traffic to frighten the squirrels away from roadside power poles, according to Pepco officials. Repairs usually take between 45 minutes and three hours.

Pepco has established an Animal Outage Task Force to investigate the problem. So far Pepco officials have documented 579 blackouts caused by squirrels since July 1983 and believe there may be as many undocumented cases.

The power company has yet to find a solution.

Montgomery County has been hardest hit, with 87 squirrel outages recorded in Rockville alone. Silver Spring has had 79, followed by Bethesda with 63 and College Park trailing with 22.

Carol Lippincott, a Pepco spokesman, said the squirrel-induced power failures have cost the company about $50,000 annually. "This is a low estimate," Lippincott said. "It doesn't include the outages we list as 'unknown' because we don't find a squirrel body"

The power lines are charged with 8,000 volts of electricity, enough to cause instant heart failure in a human being.

What happens to a squirrel in the same situation is best left to the imagination.

"The squirrel does not survive the experience," said up Nancy Moses, another Pepco spokeman. "It shorts the equipment out. Sometimes it can go up to the primary lines and flip a breaker in the substation."

Pepco transformers have bushings to protect the wires from squirrels. But Moses said the squirrels not only like to chew on the bushings, but have been using them to stash nuts, as well as leaves and assorted litter.

"It doesn't surprise me at all," said National Park Service biologist John Mansky of Pepco's squirrel problems. Mansky said that, apart from the damage caused by the nut caches, there are simply more squirrels around to make trouble during this season. While winter's cold has not yet killed many of the squirrels off, those born during the spring and summer are now independent enough to roam up and down the power poles.

Mansky has been studying squirrels in Lafayette Square for four years. The square, with 120 squirrels an acre, has the highest density of gray squirrels ever reported. Pepco's power lines run underground in that area.