Hi. I'm working with this, so I should actually know this already, but... :P I'm just not sure how this actually works. Googled a little and found this forum with a good thread https://www.physicsforums.com/showthread.php?p=3973084 But for me, this is too much math. Can someone explain this a little easier for me? Almost i laymen term? In the switchboard I have DEIF protections (PPU3/GPU3), which I set up the protections for high voltage, var import, var export, reverse power etc.. I would really like to have a better understanding of what I do instead of doing it the way I do now. I have a "recipe" on how to set up the protections for this, but this is not telling me what I actually do :P Since the drawings I work with is copyrighted, I can't upload this, but I guess it is the same more or less all over the world...? The generators are energized (excitation), I got voltage, and I connect it to the switchboard.... Setting up a PPU3 og GPU3 is not so difficult, but it would be nice to know some more when I get specific problems with for example loss of sensing to the AVR... We use mostly DECS-100 for AVR with either, PPU3 (paralell protection unit) or GPU3 (generator protection unit)..