This post may not make much sense unless you have some knowledge as to how electrical distribution systems are wired, at least here in the US.
Here’s what I came across:
From the main service a three conductor direct burial type cable was used to feed the RV type power pedestals. So, two ‘hot’ conductors and a neutral.
Each RV pedestal had a ground rod driven which was connected to the ground bar in the pedestal.
Although the (US) National Electrical Code now requires that a grounding conductor be installed along with the feeders it wasn’t required when this park was originally wired so long as each pedestal was considered its own ‘service’. That requires that neutral and ground are bonded together. Or in other words electrically connected with either a screw or bonding jumper from the neutral bar to the cabinet or ground bar.
None of the bonding jumpers had been installed in any of park RV pedestals. Curiously enough, the factory-supplied jumpers and screws were still in their packages, neatly tucked under the neutral bars.
So what happens in this case if there is a short between hot and ground in an RV where the circuit isn’t protected by GFCI? Answer: Nothing. The trailer frame becomes energized. – No breakers trip.
I took some ohm readings between ground and neutral at various points around the park and was getting anywhere between 12 Ω and 75 Ω.
If we do the math: 120V / 12 Ω = 10 Amps. So a 20 Amp breaker just sees a 10 Amp load – Not a short circuit.
Interesting to note that RV voltage testers/protectors aren’t looking for resistance/impedance issues.