Low Voltage

You should not have any voltage drop at all in that distance.
If you are losing that much power it is going someplace.
WITHOUT touching any metal that has electricity in/on it, Feel for heat anyplace that the wires travel. feel of outlets and other stuff by putting your hand on the plastic part, You will feel warmth if the power is being used inside it.
Also, Check to be sure that the wires are tight at the connections.
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You absolutely will not have three phase.
You will not have any wire with anywhere near 200 or 220 volts either.
There are two common types of plugins for 220V.
One has only three prongs, TWO 110 'HOT' prongs, and one common/ground combination.
The other has the same Two hots and ONE each common and ground.
Common and ground are esentially the same. In lots of applications they are connected directly together, Some places they are seperate, but still the same.
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It is verry common to have less than 110 volts supplying power.
If you determine that the power is actually not being lost and you are actually only getting 90 to 100 volts. Chances are you are fine, If it is causing problems, You may request the power company to come and test the transformer, It could be bad.
I once had this problem, I told the power company I wanted a new transformer, They tested it and told me it was fine.
About a week later it blew up,
After the new unit was installed, my elec. bill went down by about 25% monthly. Go figure.

To minimize the voltage drop you need to minimize the resistance and AC impedance in the wiring and connection points. Any excess resistance in wires or connections will cause a voltage drop when current flows. Or a wiring fault somewhere could be drawing more current than expected because of partial short circuit to ground (or neutral).

From your description, it sounds like the voltage drop is somewhere between the electrical distribution box and your appliances. Here are the troubleshooting steps I recommend:

WARNING: If you do not have the knowledge and tools to make electrical measurement safely, do not do it yourself. The AC voltage is high enough to conduct through your body which means it can injure and kill you.

1. Find out which appliance is causing the voltage sag: Unplug your appliances one at a time and see when the voltage goes back to normal. This may be a no brainer (i.e. the fridge not the CD player) but it is good to make sure.

2. Connect the highest load appliance identified in step 1 directly to the electrical box with a heavy duty extension cord that can handle the rated current of your appliance. Check if there is still the same voltage sag at the appliance.
If YES (same voltage sag using extension cord), and the voltage at the electrical box is still normal, then the fault is likely in your appliance. It may be drawing too much current because of a partial short circuit. You should stop using it and get it repaired before it starts a fire or someone gets shocked.
If NO (no voltage sag with extension cord), then the problem appears to be in the wiring of your trailer. There could be bad connections between wires and terminals in your trailer or the extension cord that plugs into the electrical box. Or the wiring is just undersized for the appliances you are using. You should have the wiring inspected and repaired right away to avoid the risk of fire or shock.

If your appliances are appropriate for the electrical distribution provided, in good working order and the wiring is properly sized and installed, you should have no problem with voltage or safety. You really should confirm the source of the problem and have it corrected before continuing to use appliances in your trailer.

I look forward to hearing the results. Best of luck.

You have a short or a poor terminal connection this is a fire waiting to happen. have an electrician come and look at the phase bar lug...99% this is the problem... or a short in the wire. i would say feel to see if it is warm but don't. i promise you there is a short. fix it now.