"Simon Avery" wrote in message
...
"Dave Liquorice" wrote:

snip

DL| Ours sing, I can't quite make up my mind if it's some
DL| curious midfrequency oscilation in the single phase pole
DL| transformer or just wind induced wire whistle that is
DL| amplified by the pole.

I'd guess wind - never noticed any hum (except from 240vac
transformers under heavy load), and I spent several years working next
to 'em. (Contract tree trimming to maintain the 4m safety zone)

Aeolian (sp?) vibration! I knew of a section of 33/11kv dual circuit that
was in an exposed location on the edge of Salisbury Plain that had the
problem. Even some barbed wire fencing nailed to the 'H' pole sang if the
wind was in the right quarter! As a generalisation, however, I've never come
across it on lv systems.