Posted By Ken Urquhart Denis. I am not from the Electricity Supply Industry and cannot give you chapter and verse on Safe distances from live Overhead Power lines. Your dimensions ex CITB source that you quote worry me. Although my copy of GE700 is not bang up to date I think the distances that you are quoting relate to the minimum clearance height of the Conductor Lines at the lowest point of the line between 2 poles or pylons and the ground. If you are involved in work at, near or associated with Overhead Power lines contact the Supply/Distribution Company before you do anything. Also if the work is adjacent to Overhead Rail power Lines check with the Rail operator. The Rail Overhead Voltages are different to normal overland transmission lines. A for instance: A scaffolder handling a 7m Scaffold tube on a construction type operation where the site is near to a Rail system could quite unintentionally when handling the tube in a horizontal position on his work area, which is remote from and has nothing to do with the Rail operation, induce a power Arc from the Rail Overhead conductor to the tube that he is carrying, with of course horrendous results. Similarly, in open country, over fields etc, remember Engineers and Surveyors are vulnerable. They may open a levelling siting staff and stand it up in the air and get close enough to 11000volt lines to Fry and Die. I know of a case near Lincoln some years ago where the Surveyor questioned his boss about Overhead Lines and was told not to worry, they were Telephone wires. He carried on with his work and a short time later on raising his surveying staff in the air was electrocuted when the power arced from the OH 11000volt lines and he earthed it out through his body. If works or design take you or your personnel near any overhead Lines, consider them all as LIVE ELECTRIC untill you have checked and know for sure that they are not electric. If they are Electric consult the Supply/Distribution operator before any work takes place and preferably before any equipment or plant is moved into or near to the area/work zone. In my experience over some 40 years of Construction Safety there is no safe distance when working around Live Overhead power lines. By that I mean the distances vary according to the type of Conductor or line, its voltage and the weather conditions prevalent at the time. (Also be wary of Night work, looking up in the dark, you don't tend to see Overhead lines of any sort). The electrical energy can jump and arc across considerable distances, and the distance varies with the conditions. Ideally Get the Power Companies/Transmission supply operators to make the lines dead or isolate some of the conductors. On High Voltage Pylon lines it is sometimes possible to isolate and de-energise one circuit, usually the lower conductors and the ones nearest your work operation. (There is of course the issue of convincing everyone once these sections are re-energisd of the dangers after having allowed close safe working because they were dead or isolated). With CDM of course The Planning Superviser and the Design Team should be looking at their duties. The design should re position the structure or the method of Construction, or maintainence should be reviewed so that there is no need to go near the OH Lines. The client and the related parties may have to share the time and cost of diverting the Lines or placing them underground or otherwise safe by position. Again check with HSE and HSE Films. There is a Training Film on Overhead Power Line Electrical saftey that includes the story of a young man who was a Trainee Scaffolder, (Work Experience). He was handling Scaffold tubes, taking them off the back of a truck, standing them upright and placing them across his shoulder to balance as he was instructed to by his supervisers and work colleagues with whom he was working.He then carried them off across the site to where they were needed. He drew a tube off the back of the truck and proceeded to stand it up, No one had identified the Live Overhead 11000Volt Power Lines. He earthed out the powr and fried. His work and site colleagues attempted to help. They resuscitated him and he survived. When I met him at the Institution of Civil Engineers in London some years ago at the launch of the safety Video, he was there with his Mother and his 2 artificial Legs and his 2 artificial arms. Yes he is now a quadriplegic. His quality of life and his disabilities are not what he expected out of life. He at that time was beginning to get his life together again but most of all did not want what had happened to him to EVER happen again to anyone else.(Sadly it does). So, keep as far away as possible from any Overhead Lines, especially Power lines and keep Plant, Cranes, Tipping Trucks,Agricultural Machines, Scaffolders with Tubes over their shoulders,Operative carrying metal ladders or lengths of pipe or conduit over their shoulders, Engineers/Surveyors with elevating Staffs, and Siting targets fom looking up before they raise anything up in the air. Watchout if you are working at on or alongside Railway Tracks with overhead Electrical power lines. Remember the social/domestic/hobbies Safety aspect as well, especially Fishermen/Anglers and families with children wanting to fly kites etc. If you are involved in Agriculture, work in open fields with Machinery, Tractors with Fork trucks etc etc always a risk of overhead Power Lines. Sorry to have lectured on about this but as I said at the outset I personally do not blieve that there is any set safe distance to work around Live Overhead power lines. Every situation MUST be assessed and contact Must be made with the Line Operators so that clear guidance and safe procedures are agreed, communicated and actioned. The outcome of disregarding the risk of Overhead power lines is predictable and preventable. I hope some of this information is of help and in general of informative interest for others who might just be browsing. Regards. Ken Urquhart