All extraneous conductive
parts the installation, gas pipes, water pipes and any lightning protec-
tive system are then connected the main earthing terminals. 14. 14.
NO EARTH PROVIDED SUPPLIES (TT SYSTEM)
This the type supply more often found when the installation fed
from overhead cables.3 show the layout typical domestic service
position for these three supply systems. The
arrangement shown Fig. The arrangement shown Fig. There are two other systems of
supply, the TN-C and systems but they not comply with the supply
Main switch
Main protective
earthing
terminal
16mm2
L L
Label Safety electrical
connection (do not remove)
Protective equipotential
bonding conductors
Label Safety
electrical connection
(do not remove)
10mm2
100A
10mm2
Water
service
pipe
Electricity supply
Gas
service
pipe
Gas meter
Metal gas
pipe
Lights,
cooker
water
heating
CPC
Socket
outlets
25mm2 tails
kwh
30mA
RCD
16mm2
FIGURE 14.2 and Fig. 2.Basic Electrical Installation Work
282
protective earth and neutral conductor (PEN conductor). The supply authorities not provide earth ter-
minal and the installation’s circuit protective conductors (CPCs) must be
connected earth via earth electrode provided the consumer.4 the IEE Regulations.1
Cable Sheath Earth Supplies (TN-S system): showing earthing and bonding arrangements. Thus phase
to earth faults are effectively converted into phase neutral faults.2 and 14.
Figures 14.3.1, 14. the supply
intake point consumer’s main earthing terminal formed connecting
the earthing terminal the neutral conductor. An
effective earth connection sometimes difficult obtain and most
cases residual current device (RCD) provided when this type supply
is used.
