I once watched two engineers/technicians argue for two hours about what power definitions should be displayed on a HMI interface. One of them argued that VARs were being EXPORTED during lagging conditions, so a lagging current should be shown as POSITIVE VARS and Power Factor! The other argued that VARs were IMPORTED during lagging conditions, so a lagging current should be shown as NEGATIVE VARs and Power Factor!

I was fairly new to the business and had no skin in the game, so I couldn’t contribute at the time, but I did find both arguments compelling and the whole scene was hilarious. Now that I’ve had some experience, I realize that they were both correct… from their perspectives.

Here’s an excerpt from The Relay Testing Handbook: Generator Relay Protection Testing that should help clarify how Phasor Diagrams can be interpreted differently by electrical workers with different backgrounds, and why you should NEVER plot a phasor on a Power (P-Q) Diagram: