The most embarrassing part of the telephone company's power failure that blacked out the first half of the Bullets' playoff game Wednesday night was the WDCA station announcer initially calling them the Baltimore Bullets.

Nevertheless, despite 66 minutes of reruns and apologies, the Bullets-San Antonio game drew the biggest audience in the history of the independent UHF station.

"We're No. 1 in the marketplace.We doubled our nearest competitor, and that's extraordinary," gushed Milt Grant, WDCA's chief executive, after a "coincidental rating" Wednesday night showed Channel 20 with a 20 rating and a 37 share.

The closest competition was WJLA, Channel 7, with the second hour of an "Eight is Enough" special and a Vegas rerun drawing a 10 rating and an 18 share.

The sixth game of the Atlanta series drew a 15 rating and 27 share and tied Channel 7 for No. 1 in the local market. The WJLA fare included toprated Mork and Mindy. For WDCA, it was the first time one of its telecasts drew a million viewers, Grant said.

"It's been an economic boon to the station. The Bullets have been a bonanza not only from their point of view, but the station's point of view and the advertisers'."

It remains to be seen whether the Bullets will provide for their sponsors. In 1969 the New York Mets' baseball team made its spectacular National League pennant drive and its beer sponsor's sales "jumped like hell," according to one TV industry source.

The power failure, Grant said, was a result of a "power outlet, just not functioning." A C&P telephone company spokesman said his firm took full responsibility for the failure.

Grant said no immediate announcement was made at 8:30 "because we expected it back any moment." However, he said, the phone company could not immediately locate the source of its power failure.

WDCA receives its line feed from a C&P substation in upper Northwest Washington. That relay station did not receive the signal. The problem finally was tracked to another relay station at 14th Street and Columbia Road, NW.

When the picture from San Antonio finally got on the air at 9:06, play-by-play announcer Jim Karvellas was interviewing Bullet owner Abe Pollin during halftime. After a commercial, Karvellas explained the "problem was with AT&T . . . but it doesn't matter who the problem was with.We're sorry you missed it."

Grant said yesterday he would meet with C&P officials to make sure a backup system is available for tonight's fourth game of the Eastern Conference finals in San Antonio. Although not perfect, WDCA's effort at television Bullet basketball games this season was admirable.

The standard for comparison is not the networks, but other independent and locally produced games, since these stations should not be expected to have the same resources as the networks.

In this respect, Channel 20 productions rate higher than most, both at the microphone and in the control room. Compare its own telecast to its pickup last week of the seventh game of the Philadelphia-San Antonio series from the 76er's home-town outlet.

Unlike some other area announcing teams. Karvellas and color commentator Mike Riordan, the former Bullet forward, are acceptable.

Karvellas leaves all the insight to Riordan, who does a good technical job of explaining what happened and why.

And how can anyone not like a chap who tells a halftime guest, with a straight face, "And for being our halftime guest you'll receive two free dinners from Riordan's Saloon in Annapolis?"