Posted By Stephanie Could anyone point me in the direction of information regarding overhead line clearances please. The situation is that we have football pitches underneath 11kv power lines, and some worried footballers. These pitches are also going to be installed with a rain gun for irrigation. Thanks in advance.

Posted By George Wedgwood National Grid Transco have a helpful free leaflet (at http://www.nationalgrid....rid_planning_and_amm.pdf) on "Development Near Lines" and the Appendix gived advice on clearances: Safety clearances Making contact or near contact with overhead lines is dangerous. Overhead electric conductors are normally bare(uninsulated) and if an object approaches too closely it is possible that a flashover will occur and an electric current flow with the likelihood of fatal or severe shock and burns to any person nearby. In order to prevent such incidents minimum safety clearance for overhead lines are prescribed. Overhead transmission lines must conform to the specifications contained in the Electricity Supply Regulations 1988. The minimum heights at which the conductors are strung between pylons are given for lines operating at specified voltages. Overhead lines are also constructed to conform with the Electricity Supply Idustry’s own engineering standards which govern the minimum clearance to be maintained between the conductors, ground, roads, trees and objects on which a person may stand. A summary of ESI Standard 43-8 “Overhead Line Clearances” is given in table 1, the application of safety clearances are illustrated in figures 4, 5, 6 and 7 respectively. The minimum clearance to ground for a 400,000 volt line is 7.6m and for a 275,000 volt line is 7.0m. It is important to note that the information in table 1, giving the minimum safety clearances is for illustrative purposes only. The necessary clearance at a specific location will be dependent on several factors including the location the line is passing over, the line’s construction, design, and its operating voltage. It is herefore important to contact National Grid where it is intended to construct or alter the ground levels within the vicinity of an National Grid overhead line so that detailed advice on safety clearances and other relevant information may be given. In order that safety clearances are not infringed where works are planned near to overhead lines, National Grid can provide profiles of the overhead line crossing specific sites which detail the height above ground of the lowest conductor. Line profiles are drawn at the time of construction to illustrate the position of the conductors at maximum sag. The position of the conductors at maximum swing should also be taken into account. Developments adjacent to overhead lines should be designed to facilitate their construction without infringing electrical safety clearances. Care should be taken by personnel involved in the unloading, stacking or moving material under conductors. Developers and personnel should be acquainted with the Health and Safety Executive Guidance Note GS6 which advises on the avoidance of danger from overhead electric lines. References a) Electricity Supply Regulations 1988 (S.I. 1988 No 1057 as amended by S.I. 1990 No. 390). b) Electricity Association - Technical Specification 43-8 Issue 2: 1988 - Overhead Line Clearances. c) Health & Safety Executive Guidance Note GS 6 - Avoidance of danger from overhead electric lines. d) Health & Safety Executive Guidance Note HS(G) 47 - Avoiding danger from underground services. 23 MAXIMUM LOAD HEIGHT MINIMUM CLEARANCE TO ROAD TABLE 1: OVERHEAD LINE CONDUCTOR CLEARANCES item Description of Clearance Clearance (metres) Clearance (metres) at 400,000 volts at 275,000 volts 1 To ground 7.6 7.0 2 To normal road surface 8.1 7.4 3 To road surface of designated “6.1 metres high load” routes 9.2 8.5 4 To motorway or other road surface where “Skycradle” can be used 10.5 9.8 5 To motorway road surface where scaffolding is to be used on: (i) Normal 3 lane motorways 16.3 15.6 (ii) Elevated 2 lane motorways 13.3 12.6 6 To any object on which a person may stand including ladders, access platform, etc 5.3 4.6 7 To any object to which access is not required AND on which a person cannot stand or lean a ladder 3.1 2.4 8 To trees under or adjacent to line and: (i) Unable to support ladder/climber 3.1 2.4 (ii) Capable of supporting ladder/climber 5.3 4.6 (iii) Trees falling towards line with line conductors hanging vertically only 3.1 2.4 9 To trees in orchards and hop gardens 5.3 4.6 10 To irrigators, slurry guns and high pressure hoses 30.0 30.0 11 To street lighting standards with: (i) Standard in normal upright position 4.0 3.3 (ii) Standard falling towards line with line conductors hanging vertically only 4.0 3.3 (iii) Standard falling towards line 1.9 1.4