[bobbecky]

Most people, including most electricians, believe breakers and fuses protect connected loads. That is not the case. Breakers and fuses protect the system from a fault in the connected circuit, so the rest of the system doesn't fail due to an issue on the single circuit. Then, the main breaker in the RV panel does not protect the RV, but protects the main feed from a fault in the panel that exceeds whatever the main breaker is rated at. This continues all the way up stream, even to the utility sub station, with fuses and breakers protecting the source from failures and faults on the load sides. Yes, the fuse or breaker will open when a load exceeds the amp rating, but that is a potential fault that the device is protecting the rest of the system from.

If you have an RV with a 30 amp panel plugged into a 50 amp receptacle in a pedestal, the 30 amp breaker in the RV will open if the load or a fault occurs, to protect the source side of the RV panel. If the 30 amp shore cord fails due to a cut or some other damage, the 50 amp pedestal breaker will open up to protect the rest of the RV park from the shore cord failure. If something happens inside the pedestal, the breaker that feeds the string of pedestals inside the park's main panel will open up to protect the rest of the park, and so on up stream.