A kalibr only have only 500kg warhead... that explosion was huge. Maybe a first strike created aerosol from the fuel and gaz on the plant and a second ignited it all together ? If it's what happened it's a lucky shot. If it's a thermobaric, it's a giant one.I can't imagine ways for a similar explosion at that power plant.
There are three oil tanks at the power station, but those should simply burn.
At there is looks like a thermobaric bomb - or something hit a gas storage, or liquid gas storage.
Very strange.