How do you make floating ground in 100 amp sub panel Sub panel 30' from main panel and is grded to 2nd 10' rod wired to 1st 10' rod at the main panel. GFCI bkrs are nuisance tripping in bsmt location?

If the sub panel is in the same building remove the bonding screw that bonds the neutral bar to the panels enclosure. Remove the ground from the second ground rod. The sub panel is grounded by the ground wire from the sub panel's feeder.

If the panel is separate from the main building treat the sub panel as a separate service. It will need its own ground rods and ground wire from the rods to the neutral bar of the sub panel. Leave the bonding screw in. There will be no ground wire in the conduit between the two services.