"Derek *" wrote
| I don't know how in practice streetlight supplies are taken from
| the local substation - p'raps someone who does will pipe up
| real soon now ;-)
| Could it be that at various points around the town a single phase supply
| is handed over to the light dept who wire their own lampposts.

It varies. In some localities, with overhead wiring, there's a fifth
(additional to the three phases and neutral) wire on the poles, which is a
timeswitched feed for streetlights mounted on the electric supply poles.
Every 15 poles or so there'll be a rusty Venner timeswitch hanging off the
pole.

In urban areas most streetlights will be fed individually on a single-phase
tap from the local 3-phase. Illuminated bollards and traffic signs will
usually be clustered on a switched supply from a streetlight which has a
photocell switching the cluster.

If you've nothing better to do about 3.30 this afternoon watch the
streetlights come on in batches :-)

Owain