PJM Interconnection Inc., the regional grid operator, has approved $4.6 billion in upgrades to the high-voltage electric transmission system that serves 61 million people in 13 states and the District of Columbia.

More than $3 billion of the changes are upgrades to connect new gas-generating facilities that are replacing old coal-fired plants.

The plan also includes a $1.2 billion project in northern New Jersey to address short-circuit and overheating problems in that area.

- Andrew Maykuth