PJM Interconnections, which oversees the power grid in Ohio and a dozen other East Coast states, reviewed plans for closing the FirstEnergy plants and told the company it needed to upgrade its transmission lines before shuttering the coal-burning units in northeast Ohio, Durbin said. PJM wanted the three Ohio plants to stay online as a backup to ensure enough power generation during the upgrades.

The company provided a copy PJM’s analysis of reliability effects as an exhibit in an April 30 filing with the Public Service Commission of West Virginia.

“Deactivation of these generating units will adversely affect the reliability of the PJM transmission absent upgrades to the transmission system,” PJM wrote in its analysis, adding a long list of anticipated line overloads and voltage violations. Although PJM did not identify the needed transmission upgrades that are under way, FirstEnergy said in the filing, “The necessary upgrades will be made by FirstEnergy subsidiary Potomac Edison at an estimated cost of approximately $75,000…and are expected to be completed prior to June 1, 2013.”