By Tim McLaughlin

July 3 (Reuters) - Largest U.S. power grid operator PJM said ‌on Friday it was under ‌a federal alert to cut electricity consumption across ​its territory as it battled generator outages, massive overloading on its transmission lines and a surge in air conditioning use ‌from prolonged ⁠sweltering heat.

PJM said it told utilities to reduce electricity to customers ⁠who are under contract to reduce consumption during emergencies. PJM serves 67 ​million people ​in the Mid-Atlantic, ​South and Washington, ‌D.C., area.

Spot wholesale electricity prices in northern Virginia, home to the largest collection of data centers in the world, have surged beyond $2,000 per megawatt hour this ‌week. That compares to ​about $40 per MWh ​when PJM is ​not in distress.

The surge ‌in prices is mostly because ​it has ​become expensive to provide power across congested high-voltage power lines, according ​to industry ‌analysts and PJM's operations data.

(Reporting by ​Tim McLaughlin and Bhargav Acharya; Editing ​by Bill Berkrot)