We have an enquiry for a project which involves transporting an item under a 33kV overhead line. I can't find a reference that specifies the safe air gap from the conductor/line/wire. Can anyone advise? From a leaflet I have, "National Grid, Working Safely on Substations - A Guide for Competent Persons working with the NGC" it specifies the following: 132kV 1.4m 275kV 2.4m 400kV 3.1m but nothing for system voltages less than 132kV. I don't know if it makes any difference but we are also carrying out this work in the Middle East and not the Uk. Thanks in advance.

The distances you quote for higher voltages are the 'safety distances' as defined in (UK) "Operational Safety Rules" and used universally within the industry here in UK. The corresponding number for up to and including 33kV is 0.8m. (33-66kV, 1.0m, 66-132kV 1.4m, 132-275kV 2.4m, 275-400kV 3.1m). Please note that these numbers are NOT the same thing as safe working and access clearances which are generally defined in terms of safety distance plus a margin known as an 'application factor' (which depends on the type of work being done and may vary slightly from one utility to another....). If the power lines are slung from towers ('pylons') then generally you should be OK if you can maintain the safety distance... there wouldn't normally be an additional application factor - unless your equipment has a crane or other rising element that could cause interference... If you are going to be anywhere near these numbers, then you must contact the utility supply company and discuss your requirements. And note that if you are very close to the line, it may be possible to get more clearance by routing traffic closer to the towers - but the actual sag (and hence the clearance availabe) will depend on a lot of factors - and the Utility Co. is the only one that can advise... Steve