Virginia's two democratic candidates for governor met last night in what was their first - and probably will be their only - debate in Northern Virginia.

Although newspaper accounts typically described such encounters as "clashes," last night's meeting between former Lt. Gov. Henry E. Howell and former Attorney Generral Andrew P. Miller was probably no more intense than a cordian bump.

It was the sixth or seventh such debate between the two men, depending on whose count you follow, and the confrontation before about 100 persons at a Reston Community Center building produced none of the sharp exchanges that had been present in some of their previous encounters elsewhere in the state.

It did produce its share of gaffes, both mechanical and human. As in the Presidential campaign debates there was a microphone failure that sent a technician for Reston's cable television system scrambling twice to get new microphones for Miller.

And each candidate produced at least one gaffe. Miller when he told the audience he was delighted to be in the town of "Reston," and Howell when he praised the residents of the area for fighting the "Concordia," a reference to the fight of Reston area residents against landings of the British-French supersonic transport Concorde.

Howell, a Norfolk lawyer who has carried Reston in his previous statewide races, attempted to focus on his record of fighting against the state's utilities in his remarks. He predicted that both the Virginia Electric and Power Co. and the Washington [WORD ILLEGIBLE] Light Company two of the area's utilities, will have to make refunds to area customers for excessive profits they earned during the January and February cold snap.

Miller immediately attacked Howell, saying his proposal for abolishing the fuel-adjustment clause would penalize the state's Vepco customers later this year when the utility's atomic-powered North Anna power station begins operation.

Without continuing the adjustment clause. Vepco customers would not be able to benefit from the cost savings created by the operation of the new plant, Miller said.

But for the most part last night's debate was polite. Howell, more subdued than in other debate appearances, twice deferred to Miller, saying that neither his nor Miller's administrations would do anything to decrease Northern Virginia influence in the state government. He also said that both he and Miller recognize that diminishing water resources pose a major problem for the future growth of the state.

Not unexpectedly, the two men challenged each other's position on Howell's proposal to legalize collective bargaining for state employees by executive directive.

Howell contended that under current state law he would be authorized as governor to establish "a meaningful line of communication" between state workers and state employees and that he could therefore, acting as "director of personnel" for the state, direct that collective bargaining be begun between state workers and employee groups.

Miller challenged that position, saying such an executive order would, without question, be declared "unconstitutional" under a state Supreme Court ruling that earlier this year held that local governments had no power to enter collective gargaining agreements on their own.

According to Fairfax Del. Raymond E. Vickery (D-Fairfax), who attended the debate, it will be essential for Howell to carry areas like Reston by large margins if he is to offset in roads that Miller has made in other areas of the state among more conservative voters. However, Vickery said last night he was surprised at the "very defensive" nature of the debate and that the two candidates had not been more aggressive in attacking each other's positions.

Last night's debate was sponsored by the Reston Democratic Club.