I think it depends if its an operational powerstation and not an old out of service one like Battersea Powerstaion.
If its a proper powerstaion, then no, i dont think so.
Why not get your safety passport anyway? - Its cheap, only a 2 day course and last 3 years... once you get it, you can work in a number of places with no worries and it'll pay for its-self straight away.