Shocking! AC power tingle between frame and (real) ground

Harvard: There are lots of what if here. The diagram in your last post although could work, it is probably not the way the Power Company has connected it physically. If you have a voltage drop that can be read with a meter, then you will get current flow through a resistive and/or impedance electrical path.
If an over head bare high voltage power line had broke and is lying on the ground, you can’t assume the earth is a pure conductor (0 resistances to current flow). This is the reason why grounding and bonding methods are so important. The powers that make the Electrical Codes can’t make it 100% safe.

The OP trailer could have a bonding or grounding problem that is causing him to feel a shock. I say “could” because what if the wet ground was providing the 18 volts from the power cord sitting in the water and the chassis of his trailer is a less resistance path to the source’s safety ground, meaning his trailer chassis is wired properly? At some time or another you’re going to read a voltage from chassis to earth ground, the code’s wiring methods are there to hopefully reduce that voltage so the no harm comes to us. From a keyboard, I can’t assume were the OP’s problem is, but he knows he had a problem and is taking steps to correct it.

FYI:
The power company use meters to detect ground fault currents and they are not volt meters from a hardware store. A GFI receptacle doesn’t monitor voltage to ground. 18 volts I wouldn’t think a human would feel a strong tingle, at least I don’t? There is a good reason why the power’s to be picked no more then 120 volts to ground and not a subject that can be taught on a RV Forum.

Eddy currents.

What is your objective?

Here is a sketch of the Bigger Picture. There is a steady approx 0.4 VAC between the GROUNDS and surrounding EARTH even at the power meter pole.

BUT, why would the Earth Current NOT take the path of least resistance through the Ground Wire instead of going through Earth? Still puzzled about that! The AC wiring at the Bonding Point and the Ground Rod wire combo may be serving as a small scale step down auto transformer.

EDIT 1:
Just as we have stray capacitance in the RV wiring, we may have stray inductive coupling in the Breaker Box where the N/G Bonding takes place causing a small voltage to develop (ie 0.4 and 2.2 VAC) in the wire to the ground rod..

EDIT 2:
To really get to the bottom of this we would probably need to consider all stray inductance and capacitance all the way to/from and including the Power Transformer on the power pole.

End of story for me.

I have an opinion on what we are observing. Wayne, I think in your 0.4 VAC case we are measuring the VAC drop on the Neutral Wire as I have shown in the Top Circuit.

The 0.4 and 2.2 VAC Joe and I are measuring is the voltage drop in the bottom circuit and is developed by the small current (~ 1.5 AC mA) flowing through the Earth path. The Earth Resistance on my 0.4 VAC is in the magnitude of 165 OHMS. In Joes case (2.2 VAC) there is either a bit more current and/or higher resistance. It might mean that Joes RV is located further away from his Ground Rod then my RV is from my Ground Rod.

Then there is also possible soil conductivity differences.

Wayne, I guessing your 0.4 VAC test setup would have a much smaller source impedance then my 165R. Be careful, I do not want to blow your meter. Better still, get a couple of shunt resistors and measure VAC instead of mA as I did.

The things we don't do for science? :)

I have an outbuilding that's fed from the main panel in the house but has its own independent grounding electrode. There's a neutral-ground bond at the main service entrance, and another at the outbuilding. The grounding points are maybe 200 feet apart. I ran a wire between the 2 buildings and measured the voltage between the building grounds which was in the 0.4 volt ballpark. Switching on a big 240 volt load in the house changed nothing. 120 volt loads cause a change. Specifically, a 1/2 HP air compressor changes the ground potential difference between the buildings by 0.2 volts, higher or lower depending on which 120 volt leg it's powered by. The load on the neutral is eventually carried through to the grounding electrode via the neutral-ground bond, causing its voltage to be pulled up a bit from the actual ground potential. Back to the rv situation, I'm suggesting that the shore power's safety ground could legitimately be at a higher potential than the actual no-load ground potential. How much depends on the neutral current, resistance from the bonding point to the grounding electrode, effectiveness of the grounding electrode, and potential differences at different points on the ground. All theory and speculation, none of which establishes that the OP's rig is now correctly grounded.

FWIW dept, the source impedance of the 0.4 VAC is about 165 Ohms based on the shunt resistance on the 2 Ma range was 100 Ohms and measured 1.5 AC milliAmp current. So, the 100 ohm load resistance brought the 0.4 voltage down to 0.15 VAC. So its never going to start any fires is it? :)

When I connect to earth, I make sure the connection is good enough to blow open a 50 amp breaker leaving 0.000 potential between chassis and earth.

We are suggesting the maximum current through the 3rd wire Ground Conductor is 10 milliAmps. If we had 1000 feet of 14 AWG Ground Wire (from the Neutral/Ground/Earth bonding) it would be about 2.5 Ohms of wire which would only produce a 0.025 VAC drop. Joe has 2.2 VAC and I have 0.4 VAC. So the question, where is this unexpected voltage coming from? It seems to have something to do with EARTH currents and not just the current in the wire.