Code of Practice for the Electricity (Wiring) Regulations - 2009 Edition

(b) Where an entrance or exit of a switchroom/substation is provided
with locked doors or gates, the arrangement of the lock should be
such that it requires a key to open the door or gate from outside.
(c) Every high voltage (H.V.) switchroom/substation, except when
manned, should be kept locked. A duplicate key for each H.V.
switchroom/substation should be available, for emergency purposes,
in a key box at a designated location. All other keys for use in the
H.V. switchroom/substation should be kept under the control of a
responsible person.
(d ) Exceptionally, a key may be held by a person whose duties require
him to have frequent access to an H.V. switchroom/substation. In
such a case, that person should obtain a written authorisation from
the responsible person stating the duties for which the person is
required to hold the key.
(2) Arrangement of entrance/exit
(a) At least one exit of a switchroom/substation should open outwards
and this emergency exit should be identified clearly.
(b) Conductors near the entrance/exit of a switchroom/substation must
be so arranged or protected that there is no risk of accidental
contact of any live metal by any person entering or leaving.
(c) In order to provide free and ready access at all times for the
maintenance and operation of the electrical equipment contained in
a switchroom/substation, every entrance/exit of a switchroom/
substation should be kept free of any obstruction including—
(i) locking facilities other than those in accordance with paragraph
(1);
(ii) structures/goods/materials and
(iii) litter or waste,
which impedes the access to the switchroom/substation from a
public area.
(3) Illumination and ventilation
(a) Suitable lighting giving a minimum illumination level of 150 lux
measured at floor level in each switchroom/substation and an
average vertical illumination level of 120 lux minimum should be
provided to allow for the proper operation of electrical equipment.
Where electrical equipment in the switchroom/substation is required
to be operated in case of mains power failure, adequate emergency
electric lighting independent of the mains supply and capable of
operation for a minimum period of 30 minutes should be provided.
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