Dozens of staff will stay on the site during the planned protest
An energy firm is planning a major security operation to stop protesters carrying out a threat to shut down a Nottinghamshire power station.
Five different climate change groups plan to demonstrate at the Ratcliffe-on-Soar site in what they call "the great climate swoop" later this month.
The station supplies power to around three million East Midlands homes.
E.ON said it would step up security and planned to enforce a High Court injunction against trespassers.
Temporary security fences will create an inner cordon and a new perimeter fence has been put in place.
During the planned protest, dozens of staff will stay on the site and sleep there instead of going home. Security guards will back up the police, E.ON said.
Spokesman Andrew Barrow said: "We appreciate that the protesters have a right to come and hold their demonstration.
"We have no problem at all with reasonable, responsible protests and demonstrations.
"What we don't want to see is anybody putting themselves at risk by trying to break into the station or by trying to shut it down.
"It's just idiotic, it's not a playground, it's a power station."
The protesting groups include Climate Camp and Plane Stupid.
Campaigners said they had chosen Ratcliffe because of its central location and its size.
They said they wanted to end all coal fired power stations because they believe they are not sustainable and there are greener ways to raise electricity.
Protesters want coal-fired power stations closed down