@Greg, I've worked in electricity power distribution monitoring, but it was monitoring and not control, so I know nothing of standards or indeed best practice in your area - what I have to say here is impressions as an informed but not expert reviewer.
- Having controls around the edge of the panel is good (Fitts law). If the 'Stop' control is like an emergency shutdown it should be larger than the start control. I would look at using more space for all the controls. I am assuming this as being for use both on touch screen and not.
- What color do you use to indicate problem? At the moment you are using red for closed and off, are those actually problems that an operator needs to be alerted to in this image? Would a neutral gray be better if it is just a perfectly OK operational state?
- Context. It would be an improvement to show a thumbnail overview of the plant, or relevant area of plant, inset at bottom right, with this unit highlighted. You can afford to reduce the size of the diagram for this unit a bit to help make the space.
History - should there be some indication of recent operational status, e.g. duration of operation? On the motor protection controllers I worked on the number of recent restart attempts was vital information.
Communication Status - how is communication status shown? Here we know that the cooling water valve is open. How do we know when communication with the valve is lost and we are guessing based on last known state?