I was thinking the actual ground wire to the big 8 foot rods either with or without a surge protector. either way. I think you would have to monitor for a while to get any real spikes if any. I would think they would be fairly uncommon or whole house surge protectors would be much more common.
I will move the CT to the ground wire coming from my Sycom 120/240 whole house surge protector. As you mentioned this may take a very long time to capture and report back to. It goes with out saying I hope not to capture any power readings on this particular circuit.
The last time I had to deal with this Sycom unit. My entire house was zapped by a two week long thunder boomer which wouldn't go away!
The saving grace was that it protected the home during the first lightning strike and surrendered itself and died.
The next several strikes took out my secondary point of use surge protectors, again sacrificing themselves to protect the devices attached.
During the final last surge event during the two week episode, one of the boomers took out my $1500.00 dishwasher!
So, I do wish I had this GEM prior to see what the recorded values would have been for that period.
Teken . . .