Split phase is indeed common in rural set ups (voltages presenting as 230-0-230). It has the advantage (for the farm) over simple single phase of allowing longer runs or more power for the same run because to some extent neutral currents cancel, so voltage drop is lower. 3 phase is nicer for machines, to use bog machines on split phase often involves  inverters to re-create the phases.

It is done, because it can be, for the transformer at the far end of the 11kV overheads, there is some cost saving in bringing 2 wires rather than 3 potentially for several km. Usually the poles and cross-bars are sized so the 3rd phase could be reinstated easily, just the wire and insulators are missing.


To use a board and breakers rated for 400V 3 phase with really 460 between lives is a bit naughty, though often seen and rarely a problem, there is not enough of it about to warrant certifying a special range of double pole switches or enclosures, so a neater way to do it is often as 2 single phase installations side-by side.

Not just Norfolk, seen in Essex and Hampshire too.

We have this down in the more rural parts in my area of South Wales also.

Mike is right, strictly speaking normal 400V equipment is operating above its design voltage, and, if you ask the equipment manufacturers they will confirm if it is OK for 460/480 V.

Some is some isn't.

Most of the big brand OEM's do have equipment suitable for this system, though the wholesaler may not stock it, or in some cases even know it exists.