This is a typical wiring diagram of the camp ground pedestal...
The "GREEN" wiring makes it straight your trailer frame ground through the large pin on both the 30A and 50A shore power cable hook up. This is the only ground you need to be safe.
I also carry the same adapters and circuit tester discussed above...
I want to know the 120VAC level as well as correct wiring as established by the circuit tester lights that are on when plugged in.
If they are not within specs i will not hook my trailer up to them and make it know to management. Either they fix it right away or I want to move to anther site location. I also make sure they hang a sign on the bad pedestal.
A few time the problem was only with the 30AMP connection and I was able to plug into the 50A connection with the proper dogbone adapter.
Good reason to carry the various adapter laong with you on your camping trips...
Roy Ken