Well, I've done the CDM Regs/MEWP Training/Various others and as per their guidance, its 9m horizontal from the pole for cables on normal wooden poles or 15m on steel pylons. This goes for people, cherrypicker baskets and anything else conductive!!
This is a wee bit contradictory as the minimum heights for respective cables above the ground, taking into account the droop between poles are 7.2m for 400kV, 7m for 235kV, 6.7m for 132kV and 5.2m for 33kV and lower. Considering a telehandler's reach, or the height of a fully stacked bale trailer, the propensity for a f@@k up can be considered high!!
In practice, just keep the hell away, minimum 10m, 20m better......
Just one of the fires I have to fight on a regular basis, don't even mention earth bonding of scaffolding :argh:
Mind you, that's only guidance (but try arguing it in a court of law..... :angel:)
Just wear rubber boots and a pair of marigolds and you'll be fine :cool2:
Alec.
http://www.hse.gov.uk/electricity/information/overhead.htm