The Electricity Supply Regulations 1988

General requirements for connection with earth

5.—(1) The supplier shall, in respect of his works, ensure that—

(a) every high voltage system shall be connected with earth at or as near as is reasonably practicable to the source of voltage in the System:

Provided that where there is more than one source of voltage in the System the connection with earth need only be made at one such point;

(b) every low voltage supply system shall be connected with earth in accordance with paragraphs (2), (3) and (4);

(c) so far as is reasonably practicable, no system shall become disconnected from earth in the event of a fault;

(d) no conductors which respectively connect a supply neutral conductor with earth, and any apparatus used in a high voltage system with earth—

(i) shall be interconnected unless the combined resistance to earth does not exceed 1 ohm; or,

(ii) shall be connected to separate earth electrodes unless any overlap between the resistance areas of those electrodes is not sufficient to cause danger;

and

(e) where the high voltage System is connected with earth through a continuously rated arc Suppression coil, an automatic warning shall be given to the supplier of any fault which causes the arc suppression coil to operate.

(2) The supply neutral conductor shall be connected with earth at or as near as is reasonably practicable to the source of voltage and, subject to regulations 6 and 7, no other such connection shall be made:

Provided that where only one consumer is connected to the source of voltage that connection may be at some other point.

(3) Except as required by any arrangements made pursuant to regulation 26, no impedance shall be inserted in any connection with earth of a low voltage system other than that required for the operation of switching devices, instruments, control or telemetering equipment.

(4) The external conductor of any electric line comprising concentric conductors shall be connected with earth.