Thanks for that link Scooterman.
I was wondering if there was a short in a piece of equipment, the GFCI would have tripped prior to any power outage. And that is its main purpose as a GFCI to recognize a diversion of current and cut it off.
However, since it was only tripping at the time power came back on it seemed to me it had to be starting load.
There is more info on that here
How Does a Ground Fault Circuit Interrupter Work? | DoItYourself.com
quote from this link "In the United States, GFCI outlets are rated for 125 volts on either 15- or 20-amp circuits. This means that in most household and business applications, a GFCI outlet will trip if the current exceeds 15 or 20 amps, depending on the individual outlet rating."
Most of our equipment, particularly metal halides and pumps and heaters, if they are all plugged into the same outlet, will exceed that, particularly on start up.
Thinking about how many things we have plugged in on our tanks, its a wonder there are not more issues for any one of us.