electrical services minimum requirement - NSW Public Works

Part 1 - Installation
Where switchboards are fitted with cable-entry plates, one or more plates shall be neatly
adapted to accept the incoming cable(s). Only the minimum number of plates shall be
used thereby leaving spare cable entry plates for future cable entries.
Cables entering a switchboard or control panel shall be glanded using non-ferrous
metallic or plastic glands with neoprene compression seals conduit with suitable adaptor
and locknut may be used where circuit is enclosed in conduit for its entire length. Cable
entry shall only be through the detachable gland plate supplied with the switchboard.
Where the sheath of a multicore cable enters either a switchboard or an electrical
equipment enclosure, the sheath shall be:
(i) Continued unstripped up to within less than 350 of either its lug terminations if a
power cable or its connecting terminal block if a control cable.
(ii) Continued unstripped after either the related conduit entry or the related cable
gland by at least 100 to allow for cable identification marking.
(iii) Identification marked as indicated within 100 of the end of the sheath.
Where multicore cables with numbered cores are installed, the same numbers shall be
continued from the switchboard to the final connections. This may require stripping of the
outer sheath and continuation of the cores. This may also require the use of extra earth
cables where more than one final connection is made.
The unused cores of a multicore cable shall be terminated in the terminals provided in a
switchboard and in an insulated screwed connector in the field. The length of the unused
cores shall be at least as long as the longest used cores. The unused cores shall be
looped and tied so as to be easily accessible.
Terminations of multicore cables shall be such as to minimise the length of the
unsheathed cores, but sufficient core length in the form of a neat loop shall be left to
ensure that no termination is under tension and to allow for connectors to be relocated.
Cores with the same insulation colours or numbers shall not be run together.
There shall be no more than one conductor per terminal and all field cables shall enter
switchboards via terminals (except instrument cables where indicated).
Cables enclosures shall continue to the switchboard, but each cable shall be separately
glanded at the gland plate.
Cable and cable cores shall be identified in accordance with Clause 205 of this
document.
Where more than five separate surface run cables or cable enclosures are to enter a
switchboard through the top or bottom, enclose all this wiring within U-shaped metal
covers or ducts run from ceiling or floor to within 150 of the switchboard. Gland all cables
when they enter the switchboard. Covers shall be earthed to switchboard cubicle, fixed to
walls generally in accordance with Clause 112, painted to match switchboard and shall
maintain the switchboard IP rating. The metal cover or duct shall have minimum 50%
spare capacity for future wiring.
Cables shall not enter through the top of externally mounted switchboards.
To minimise eddy current effects, where single core cables rated over 300 A pass
separately through a steel cable entry plate, the entry holes shall be joined with slots and
the slots brazed or epoxy filled. In addition, metal cable saddles shall not be fitted over
these cables.
All mains and submains shall be supported or tied within 200 of the terminations. This
support or tie shall be substantial due to the stresses under short circuit conditions.
Where a busway is brought into a switchboard, the insulated cable entry plate shall have
a close tolerance cut-out to fit the busbars. The busway enclosure shall be flanged at the
switchboard and shall be bolted and sealed to the switchboard enclosure. The busway
enclosure shall be earthed to the switchboard cubicle. Busbar clearances entering the
switchboard shall comply with Clause 204.8.
Page 24 MEW E101