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I have never seen a Phase-Phase service transformer for single phase service.
.classicsat

Very common in rural New Zealand.
The primary HT side is taken of any 2 phases from the 3Ø line.
The secondary is either 230 - 0 - 230 Volts, so 460 Volts is available at the outer 2 terminals at 180° phaseshift , or both secondary windings are parallelled up to have 230 volts at double amperage.

for Wolfgang.
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As I see just four wires, does this mean HV and LV share the neutral (grounded) wire or is it just not visible?
at the primary there is one insulator visible in this case, photo from MartinX
and the return is via the earthed transformer tank. HT current return through earth only.
at the secondary 120 - 0 - 120 is available, in case of MEN the neutral is earthed. The secondary current loop is completed within the secondary windings from the transformer.

To feed a 1Ø SWER line an isolating transformer is required at the start of the SWER line e.g. 2Ø 11 kV to 1Ø 11 kV SWER and return path through a very good earth otherwise the feeder would trip on earthfault all the time.

The product of rotation, excitation and flux produces electricty.