Alexandria last night became the second major Washington area jurisdiction to approve a cable television franchise as the City Council selected a firm that includes former Virginia House Majority Leader James M. Thomson.

The Alexandria Cablevision Co. was the council's choice over two other firms, including one that is half-owned by the firm that runs a successful cable TV franchise in Arlington.

The development of cable TV in the Washington area has concentrated so far in the Virginia suburbs. The Fairfax County Board of Supervisors will hold a public hearing July 9 on regulations that will provide for awarding a cable TV franchise in that county.

Last night's selection of Alexandria Cablevision clears the way for formal award of a potentially lucrative 15-year franchise to the firm next Tuesday.

The company estimates it can begin hooking up individual television sets to its cable in 16 months and that subscriptions will cost $17 a month.

The 190-mile cable network will provide a wide variety of commercial and educational television stations unavailable through ordinary antenna reception.

The cable service could also open up a wide range of consumeroriented services, such as a home security system or the ability to obtain stock quotations or certain library services on demand, if a subscriber elects to add two-way equipment.

The city government will receive 3 percent of the firm's revenues in taxes. Consultans have said that could amounts to as much as $1 million over the 15-year life of the franchise.

The motion to select Alexandria Cablevision was made last night by council member Donald C. Casey (D) and seconded by council member Robert L. Calhoun (R), both of whom were authors of the city ordinance that formed the basis for franchise applications from three rival firms.

Calhoun called the Alexandria Cablevision proposal superior "both on a pragmatic and technical side." He also said, 'I would like us to do something on our own in this city rather than be a part of an empire." He was referring to the application of the Alexandria Telecommunications Corp. (ALTEC), which is half owned by the Arlington Telecommunications Corp. (ARTEC), which operates the Arlington franchise.

The third firm in the competition was the Alexom group.

All three of the companies had affiliations with prominent local figures.

Thomson, the former Democratic House majority leader, is on the Alexandria Cablevision board of directors along with well-known local investment broker Charles Henry Smith. The company's president is former city council member James W. Carroll.

Alexandria Cablevision will be managed by a Pennsylvania-based company - Metz-Jarvis - and it will get most of its capitalization - $4.1 million - from a bank in Boston. But it has told city consultants it will receive $1.4 million from Old Port, a local investment firm that includes Harry S. Flemming, who was in charge of White House patronage in the Nixon administration.

Former Attorney General Richard Kleindienst, who also served in that administration, is affiliated with Old Port, although his name does not appear on documents submitted in connect with the cable TV negotiations.

Council member Beverly Beilder (D) criticized the reasoning that Alexandria Cablevision deserved the award because of its local ties. "I would like to express my regrets over the debate as to which is the most local company," she said. "No one is going to get all his money from inside Alexandria, regardless of what they say. The issue has been vastly overstated."

ALTEC, which got a major boost from several reports submitted to the council a wekk ago, is headed by politically influential developer William L. Vosbeck Jr. and retired Democratic State Sen. Armistead L. Boothe.

The Alexcom group is headed by Bernard Corbett and local investor Bruce G. Duncan.

Initially, Casey, Calhoun, council member Nicholas A. Colasanto (D) and Vice Mayor Nora O. Lamborne (D) voted for the motion to pick Alexandria Cablevision while Mayor Frank E. Mann (I) and council members Beidler and Ellen Pickering (I) voted no. Mann then changed his vote to "aye," making the final vote 5 to 2.