OK, Some things I have learned about Shore Power:
1) NEVER hook up "hot". Arcing at the socket will occur (and is unavoidable be cause the power converter will always try to draw several amps immediately to charge the battery. This burns the tips on the shore power cord and burns the blades on the socket you plug into. Eventually, the resistance in the burned blades and tips will start causing breaker trips in the house or power pedestal.
2) NEVER plug a shore power cord into a GFCI controlled outlet. Most newer campers have GFCI circuits that control all outlets in the camper. This includes the outlets your water heater and Fridge are plugged into. Double GFCI protection makes them unstable and can trip off for no apparent reason. Some off the GFCI control outlets are hard to find. Like the one that controls the Fridge (
3) 30 AMP extension cords drop voltage. There are places I camp that require a 150 foot run (1 100 foot extension cord and 1 25 foot extension cord and the 30 foot shore power cord). I use a Franks Auto Transformer to kick the voltage back up to 110-120, but at the expense of AMPS. That means no AC if I need much of any other power. The AC must be off to use the microwave for example as it will trip a 30 amp breaker. On a long run like that, even a 20 amp breaker means no microwave, AC, or DW's hair curler.
4) DO NOT count on the campground's power being "good." The absolute worst power at the pedestal, in my limited travels, was at a very expensive RV resort in Miami (104 volts AC) it was a hot day and everyone had their air on. My voltage dropped below 100 every time the AC cycled.
I was lucky I had the Franks unit in the camper as I was not planning on using the extension cords (the reason I bought it). I have used it at two KOAs and a Good Sam park, since. I always check voltage and polarity before I hook up now. I keep the tester and a 30 amp adapter with the shore power cord.