I am not sure if you like to draw the power over time or in dependence of another variable i.e. the rounds per minute or voltage.
The first case would be a classic PI Batch theme. The reference could be a "golden" batch. PI Batch is supposed to be replaced by PI Event Frames but PI ProcessBook does not yet support PI Event Frames.
If your intention is to show the dependency of power from another variable, this would be a classic use case for an XY Plot.
Andreas has created 2 blog posts you might be interested in:
I think that the characteristic curve one is what I need - I will reasd his post = thank you