Power frequency transmission and installations in the UK

The basic theory is used to demonstrate the orders of magnitude of the magnetic fields generated by the transmission and distribution of electricity. For 400 kV circuits, peak fields at ground level beneath the conductors are of the order of 20 mu T per kilo amp carried. For a double circuit line carrying 1 kA on each circuit, this field falls to around 0.1 mu T at 100 m. In most homes, the background field is generated by the 415 V distribution cables under the pavement outside the house and is less than 0.1 mu T. If there are lines with a voltage of 132 kV or greater within 100 m of the house, they are likely to dominate the background magnetic field.