HOUSTON (Reuters) - Two new utilities have joined a group of existing Texas transmission owners seeking state approval to build more than $5 billion in new power lines needed to tap the state's abundant wind generation.

The group will file a detailed proposal of its construction plan with the Texas Public Utility Commission on Friday, according to a press release.

New lines are needed to move electricity from the state's windiest areas in the west to power-hungry cities.

The commission wants to see enough new transmission to accommodate about 18,500 megawatts of wind generation by 2012.

The existing transmission operator group includes Dallas-based Oncor, the state's largest power delivery company, Electric Transmission Texas (ETT), units of American Electric Power Co, the Lower Colorado River Authority Transmission Service Corp (LCRA) and Sharyland Utilities LP.

Joining this group will be the South Texas Electric Cooperative and Texas-New Mexico Power Co, a unit of PNM Resources, according to the release.

The utility commission will weigh the consortium's proposal along with competing plans to construct about 2,400 miles

of high-voltage power lines at a cost exceeding $5 billion.

Texas leads the country in wind capacity with more than 5,500 MW. But a paucity of transmission prevents wind power from moving to the state's largest cities.

The filing will describe the group's "extensive support networks available to plan, design, finance and construct the needed facilities in the most cost-effective manner," the release said.

The companies said that because they are existing transmission operators, they would be able to begin developing the lines as soon as the commission gives approval.

But at least a dozen other entities, including new players, also want the opportunity to invest in transmission expansion.

They include units of FPL Group, Babcock and Brown and ITC Holdings, along with existing electric cooperatives and CenterPoint Energy.

Electric Transmission Texas is a joint venture formed by AEP, the nation's largest transmission operator, and MidAmerican Energy Holdings, a unit of Warren Buffett's Berkshire Hathaway Inc.

The Texas commission, which has two new members, will decide which companies build the new lines.

(Reporting by Eileen O'Grady; Editing by David Gregorio)