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Has anybody mentioned 'isolation' transformers; particularly as one
understands are used on UK construction sites?

Agree that having to drag around a heavy transformer or have longer
extension cords can be a chore; having done it since 1956 in order to
use my 230 volt British Wolf drill (purchased in 1953 and still going
strong) here in North America on 115 volts 60 hertz!

Also have now added some carefully grounded 230 volt outlets above a
work bench to avoid having to use the transformer, which also acts as
an extension cord when not at a fixed location. Also bench saw etc.
are 230 volts.

With the North American 3 wire 115-0-115 volt system the maximum
voltage to ground is 115 RMS.

The UK construction site system appears to combine, for the use of
hand tools, the best of two worlds?

It allows the use of generally cheaper and more universally available
115 volt tools on European mains voltage of 230 volts 50 hertz.

As understood, the construction site isolation transformer has a 230
volt input. The isolated secondary winding is half that at 115 volts
and since it is closer to where the tool is used voltage drop not a
concern.

But, particularly, the 115 volt secondary is centre tapped and THAT is
grounded/earthed. So the maximum voltage to ground/earth, at the tool
itself, is 115/2 = 57.5 volts RMS.

So the maximum 'peak' voltage, per cycle, to ground, at the tool, is
around 81 volts!

Compared to 230 x 1.41 = 263 peak volts for a hand held 230 volt
tool, that's a lot safer?

Thinking of a possible variation of that system to use on our North
American 115/230 volt domestic wiring. And or use a lighter weight
auto-transformer to be able to plug my 230 volt drill into 115 volts
more easily, anywhere.