You may be a homeowner considering an extension, or you may be considering developing a brownfield or greenfield site.  If it is near a substation or overhead line, what are the issues you need to consider?

First and foremost: the non-EMF issues

If you are building near an overhead line, you must preserve the voltage safety clearance distances, both for the finished development and during construction (e.g. for scaffolding or cranes).  If the development is near a substation  you must be very careful about buried cables.

The message is clear: contact the relevant electricity company at an early stage and talk to them.

The EMF issues

Your development will also need to comply with the relevant exposure limits for electric and magnetic fields (EMFs).  In most cases, this will automatically be the case:

Substations always comply with the exposure limits (there's a possible exception for substations that contain a specific piece of apparatus called a "static var compensator", but that only applies to a few of the largest substations, so is unlikely to affect you).  You can view the formal statement of compliance.

If overhead lines exceed the relevant limits at all, they do so pretty much only directly underneath the conductors.  So if your development is more than a few metres outside the outer condictors, it will be compliant.

Overhead lines at 132 kV and below are inherently compliant, even directly underneath the conductors.

Most overhead lines at greater than 132 kV - 275 kV and 400 kV - are, in fact, also compliant underneath the conductors, particularly if the clearance above ground is high enough to permit development underneath them in the first place.  But the UK's Code of Practice says that compliance with these should be demonstrated on a case-by-case basis.  Contact us if this applies to you.

You can get an idea of what voltage overhead line applies to you from our pictorial guide or in more detail in our pages that give information about specific lines.

How a planning authority should handle an application

• What is a planning authority's role?

A planning authority receiving an application need to be satisfied it complies with the safety clearance distances and with the EMF limits. 

There are no other restrictions on development near power lines, and a planning authority should not introduce restrictions - the Written Ministerial Statement of 1989 clearly sets out that this is a national decision, not one for individual local authorities.

• How can a planning authority satisfy itself about compliance?

As we set out above, the vast majority of substations, and all overhead lines at 132 kV or below, are inherently compliant.  The relevant Code of Practice sets out that the evidence for this is provided centrally - in fact, on a separate section of this website - and planning authorities should rely on this and should not require any additional information in individual cases.

For 275 kV and 400 kV lines, again, as set out above, these are nearly always compliant as well.  But in these cases, the planning authority would be entitled to ask for evidence specific to a particular application.  This basically applies only if the development is pretty much under the conductors - even just a few metres to the sides, compliance is ensured without needing specific evidence.

Broader considerations

National Grid provide a lot of help on planning a development close to overhead lines in a sensitive and safe way.