More than 3,300 employes of Potomac Electric Power Co. went on strike yesterday for the first time in the utility's 89-year history. Pepco said it handled the walkout with minimal disruption, while union officials predicted breakdowns in the event of heat waves, thunderstorms or a prolonged strike.

Pepco officials said the strike by about two-thirds of its work force could force the company to suspend new electrical hookups, curtail some repair services, and stop most meter-reading and instead send estimated bills to its 570,000 residential and commercial customers in the District, Maryland and part of Arlington.

Coming at the peak of air-conditioning season, the strike by the International Brotherhood of Electrical Workers could cause prolonged problems in the event of outages, when 1,800 supervisory and clerical personnel would attempt to restore a system usually manned by 5,000 workers, Pepco officials acknowledged at a news conference.

"If there are power outages due to severe storms or equipment failures, it may take longer to get your lights back on, because restoration work -- except life-threatening emergencies -- will not be conducted at night or in hazardous conditions when it would not be safe for our employes," said Paul Dragoumis, Pepco's senior vice president.

Power plant operators, repair workers, linemen, meter readers and customer service representatives walked off their jobs starting at 1 a.m. yesterday and picketed more than a dozen Pepco plants and offices in a dispute focused primarily on health benefits, wages and work rules.

"We are very disappointed that the new union leadership has taken such an uncalled-for strike action," Dragoumis said. "Pepco has presented what we consider to be a fair and reasonable proposal for a new contract, and we remain willing to meet with the union at any time."

Dragoumis and Pepco's chief negotiator, William Torgerson, said the union has misrepresented the company's contract proposal by labeling it a demand for concessions.

Pepco is offering salary increases of 4.5 percent to 4.75 percent per year, plus improvements in benefits -- with the only concession a demand for higher deductibles in health insurance, they said.

But Terry Cross, president of IBEW Local 1900, said that the union membership is angered by what they see as a "nickel and dime" offer from a company that is earning record profits for stockholders but offering a combination of minimal improvements and concessions.

"They have record profits and we want a fair share. We are not being greedy. We are not asking exorbitant stuff, but we don't want our medical plan pillaged and we want improvements" in other benefits, Cross said.

Neither side would release figures on the total costs of the contract proposals, but Dragoumis said the changes in health plans are necessary to control "skyrocketing" insurance costs.

The union said those changes could prove costly to employes who would have to pay up to $175 more in deductibles annually and possibly more in out-of-pocket expenses for illnesses.

On the picket lines, Pepco employes said they believe they deserve a greater share of the profit they help generate through work that is often hot, dirty and dangerous.

Some described working on utility poles and in steamy, water-filled manholes, and handling 13,000-volt cables that can, and occasionally do, deliver fatal shocks.

"When you wake up at midnight and you have to go to the bathroom, you flick on the lights and you don't think of us. You take us for granted, but we are the people who keep this system working. Last night, Bruce Springsteen played here because we keep that big system running," said Neal Spitzer, a 17-year veteran power plant operator at the District's Benning Road power plant.

Veteran employes such as Terry White, who earns $15 an hour as a plant operator, are losing $120 a day or more by striking. But White said, "If we don't strike now, we'll just keep losing. If they do this to us in good times, what'll they do in bad times?"

"We are the backbone of this company," said Gail Brooks, 31, a bilingual customer service representative who assists Hispanic clients. "It's an excellent company, and we do good work. All we want is a fair shake . . . . I think Pepco underestimated us."

Strikers said they doubted many supervisors could handle hazardous work in emergencies. A company spokesman said Pepco would confine some emergency repairs to daylight hours because the supervisors "may know what they are doing, but may not be able to do it in the dark."