Summary version
All the parts of the electricity system in the UK - pylons, overhead lines, substations etc - are required to comply with the relevant exposure limits for the general public - and they always do so. On a separate page, we provide the formal statement of this. On this page, we provide a summary.
High-voltage transmission
"Transmission" is the highest voltage overhead lines and substations used to transmit electricity long distances in bulk. All transmission equipment does in fact comply. Sometimes this is inherent in the design, but sometimes it needs demonstrating on a case-by-case basis.
Transmission - the details for different voltages (400 kV and 275 kV)
Transmission | Compliant – can be demonstrated on a case-by-case basis | Always compliant in populated areas where the exposure limits apply, but can exceed the limits in other areas e.g. farmers’ fields. | ||
Is always compliant, but for reassurance, this can be demonstrated | ||||
400/275 kV (where they include high-field items of equipment*) | Compliant – can be demonstrated on a case-by-case basis | Is always compliant, but for reassurance, this can be demonstrated | ||
400/275 kV (normal substations without any high-field equipment*) | Automatically compliant | The design means it is not possible for these substations to exceed |
* The high-field equipment in question is anything involving a large air-cored coil - static var compensators are the commonest example. These can produce high fields, but usually only inside the substation, not outside it. Most substations do not have these and are automatically compliant. Substations that do have one of these are always compliant in practice too, but, because of the presence of high fields inside, where necessary, compliance can be demonstrated on a case-by-case basis.
Lower-voltage distribution
"Distribution" covers everything below the high-voltage transmission networks - from 132 kV down to the final distribution wires into your home. All this equipment is inherently compliant.
Distribution - the details for different voltages (132 kV and below)
Distribution | Inherently compliant | The design means it is not possible for these lines to exceed the | ||
132 kV | Inherently compliant | The design means it is not possible for these substations to exceed | ||
66 kV | ||||
33 kV | ||||
Working out what is what
If you need help in working out what is transmission and what is distribution, and what the different voltages look like, see our pictorial guide
Compliance and Safety
The question most people want answered is "is it safe?" The exposure limits exist in order to ensure that people are not exposed to unsafe levels of EMFs. So on this page, we interpret "is it safe?" in terms of "is it compliant with the exposure limits?". For full details of the evidence on health, safety, etc, see the pages on "known effects" and "evidence on health".