Woland wrote:

I had read that and I was expecting a serious voltage drop (no load
reading doesn't count, obviously).
So I set up the usual easy measurement with a 2 KW load (circular saw
+ lights + other resistive loads) and... strange but true no drop!

A saw's not much good as a test load because the current drawn will vary
wildly with the mechanical load. Use a 3 kW fan heater or similar.

Experiment repeated several time... same result. I am actually curious
to find out why I'm not withnessing any voltage drop... maybe the load
is too small?

How are you measuring? Is the cable perhaps bigger than you think?

The resistance of a 40 m run of 2.5 2-core will be about 0.6 ohm. If
you were to allocate the whole 3% permitted drop (for lighting) to the
submain on the assumption that there'll be little more in the short
wiring in the summerhouse, the max load will be 6.9 V / 0.6 ohm which is
only 11.5 amps.

What equipment do you propose to use in the summerhouse? For a 32 A
supply you really need a 10 mm^2 cable, or 6 mm^2 (4 at a pinch) for a
16 A feed.

--
Andy