A Montgomery County jury has decided that the Potomac Edison Co. must pay $420,000 to a Gaithersburg dairy farmer whose cows produced less milk after they were shocked by electricity leaking from the company's electrical cables on his farm.

Edward M. Burdette, 43, who owns a dairy farm on Damascus Road with his stepmother Juanita T. Burdette, was awarded the money by a Circuit Court jury after a four-day trial that ended Thursday night.

"We were extremely pleased that the jury found the evidence proved that the power company was negligent in causing high levels of stray voltage on the Burdette dairy farm," said Cynthia B. Malament, the attorney for the Burdettes.

"The stray voltage had an adverse effect on the Burdettes' cows, which in turn caused the Burdettes to lose substantial profits due to lower milk production and also to suffer substantial damage due to loss of herd value."

John H. Bolgiano, the attorney for Potomac Edison, could not be reached to determine whether the company intends to appeal the decision.

The Burdettes filed suit against Potomac Edison last summer after learning that electricity had escaped from the power company's cables at 6520 Damascus Rd. in Gaithersburg in 1979 and shocked the Burdettes' Holstein cows when they entered the milking parlor.

Edward Burdette testified that he first suspected problems at the time because he felt a "tingle" when he touched equipment in his milking parlor.

He said he became even more concerned when he continued to feel that sensation after turning off the power.

The electricity put the cows under stress and their milk production decreased, Burdette testified. He said the cows became reluctant to enter the milking barn and were nervous and jumpy when they were inside.

As a result, the dairy farmer told the jury, he suffered substantial losses in milk production from 1979 to 1982, when he installed equipment that isolated the stray voltage from his milking parlor.