Virginia’s two largest utilities are upgrading a transmission line that runs through central and western Virginia. The 500-kilovolt Lexington-Cloverdale line was built in 1966. It stretches from north of Roanoke to just outside Lexington. Appalachian Power says it plans to replace the wire on the transmission line by 2016 at a cost of $40 million. It will replace seven towers and add four new ones. Dominion Virginia Power says construction is under way for its portion of the line at a cost of about $20 million. It is scheduled for completion by May 2014. The upgrades will allow the line to carry more current. Appalachian Power serves about 500,000 customers in Virginia and Dominion serves about 2.3 million customers in the state.