Almost every power plant is effectively internet connected even if it has old control equipment that predates IP as the vast majority of SCADA systems have IP connected HMIs or other core components.

There may be steps involved in getting your RDP exploit to send commands over vendor proprietary RS-485 protocols, but except for certain nuclear plants that are truly air gapped, but it's fewer than you'd sleep soundly knowing about.

I once had a network admin at a major US transmission utility tell me with a straight face that all of their SCADA was pure serial as I was telnetting into the Zhone mux doing those serial channels via a WiFi connection.