Both of them asre partially correct and partially wrong.
You can run an extension cord for ever if you want to but the cost is going to be exorbitant because you will have to run huge cord. The voltage isn't he problem, it is the amperage and the line loss. For that distance it is NOT practical to run 220v through any wire. The code charts can tell you how to figure the size of wire needed but you aren't going to find that distance listed because NO one in their right mind runs much over 100 feet (approximately 30 m) with that low of a voltage, or 200' at the most.
The wire size charts start at up to 75' and then require a bigger wire size the farther you go. I'm sure you can find a metric chart somewhere, I just don't know where. I am just guessing, but I would guess 700m at any reasonable amperage would require somewhere in the neighborhood of 2-0 copper for an extension cord and that is assuming no plug-ins in the middle. For that length the most practical approach is separate wires strung in the air so they can cool better than any kind of cable.
I will contact one of my well/pump companies so see if thye can gove me that information.
I don't think it practical but I know I have seen wells nearly that far from the buildings so I'll give it a try.
Good smoking.