One of the advantages of the power protection unit such as the Progressive Industries model is not only both over and under current is shown, but missing grounds and mis-wired pedestals can be determined by the readout. I pulled into one place and it had about 95 volts. Pulled into another one in the middle of nowhere, and it was putting out 140AC! Another place had no ground, another wired backwards. These units do is at least warn you before you hook up. The ungrounded plug was near a redwood tree national park in southern California, under dripping wet leaves with standing water on the ground.
Another place near Waco, Texas, after arriving after dark, I heard a loud explosion near the bath house, and all the RV's that had been lit up went dark. A 6 foot flame of fire was shooting out of the ground and a loud noise could be heard every time the flame shot out of the ground. Turned out the main circuit had shorted out underground and was surging on and off. Fortunately for me, I had just arrived so I was not yet connected. But I'd venture to guess I would have got my money's worth out of the device that night.
A shady park (and I don't mean with trees) put me in a slot late one evening. The 30 amp was mis-wired both with no ground and in some other way I can't recall, but the 20amp was fine. So I went with that with an adapter. A lady parked down the road came up and asked me how I was able to use the electrical because it wouldn't work in her rig when they put her there earlier in the week. She didn't try the 20amp. Even though she notified the park owner of the mis-wired plug, they still put me in the spot completely unconcerned that the pedastal was mis-wired.
I gave the park on RVPark Reviews an appropriate review for the lack of concern that could get someone killed.
It's really shocking just how poor some parks are wired.
2011 Interstate WD/Lounge