The dangers of working underneath overhead power lines

We know visits to the circus can be hair-raising but a trip to the one pictured above, sat underneath overhead power lines, might have led to more than that.

Building control surveyors are often involved with Public Entertainment Licences at their authorities and these are granted once public safety can be ensured.

This particular company had moved onto the site and erected the big top before permission had been granted and seemed oblivious to the electricity cables overhead.

How much space should you leave beneath overhead lines?

The National Grid has strict guidance on the use of space beneath power lines and needs at least 7.6m to the ground, 5.3m to any object on which a person can stand and 3.1m to an object where a person can’t stand or access isn’t required.

Making contact or near contact with overhead lines is extremely dangerous.

Overhead electric conductors are normally bare (uninsulated) and if an object approaches too closely (like a high wire or trapeze act) it’s possible that a flashover will occur and an electric current will flow with the likelihood of fatal or severe shock and burns to any person nearby.

High voltage equipment produces electric fields which can cause nearby conductive objects to acquire a static charge. For instance, a large elephant or the clown’s car parked under an overhead line can pick up a voltage and when a person touches it, a small spark may occur. Although the car is designed to fall apart, who knows what the elephant might do! 

Metal-clad or framed buildings can similarly pick up a voltage and should be earthed to reduce the effect of such voltages. There’s also the possibility of static spark discharge at the petrol generators used to light the premises, which could have been explosive.

What happened next?

Needless to say, the big top was taken down and moved to another part of the site to allow everyone including trapeze artists, clowns and the elephant to enjoy the fun of the fair in safety.

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