The arrangement shown Fig.
A system consists electrical installation connected supply. The limiting values earth fault loop impedance are
given inTables 41.
Five systems are described the definitions but only the TN-S, TN-C-S
and systems are suitable for public supplies. 2. The supply cable uses combined
. 14.
THE EARTHED SUPPLY CONDUCTOR
The earthed supply conductor arrangements are indicated the third
letter, where means separate neutral and protective conductor and C
means that the neutral and protective conductors are combined single
conductor.
CABLE SHEATH EARTH SUPPLY (TN-S SYSTEM)
This one the most common types supply system found the
United Kingdom where the electricity companies’ supply provided by
underground cables.
THE INSTALLATION EARTHING
The installation earthing arrangements are indicated the second let-
ter, where means the exposed conductive parts are connected directly to
earth and means the exposed conductive parts are connected directly to
the earthed point the source the electrical supply.1 and Fig.3 the
IEE Regulations.
An efficient and effective earthing system essential allow protective
devices operate.2 41. The protective earth conductor (PE) the metal
sheath and armour the underground cable, and this connected the
consumer’s main earthing terminal. All extraneous conductive parts the
installation, gas pipes, water pipes and any lightning protective system are
connected the protective conductor via the main earthing terminal of
the installation.
Systems are classified capital letter designation.
PROTECTIVE MULTIPLE EARTHING SUPPLIES (TN-C-S SYSTEM)
This type underground supply becoming increasingly popular sup-
ply new installations the United Kingdom.
THE SUPPLY EARTHING
The supply earthing arrangements are indicated the first letter, where
T means one more points the supply are directly connected earth
and means the supply not earthed one point earthed through a
fault-limiting impedance. The neutral and protective conductor are separate
throughout the system.4 the IEE Regulations, and Chapter andWiring
Systems Part gives details the earthing arrangements incor-
porated the supply system meet the requirements the Regulations. more commonly referred
to protective multiple earthing (PME).Electrical installations and wiring systems
281
Other items equipment this position are the energy meter and the
consumer’s distribution unit, providing the protection for the final circuits
and the earthing arrangements for the installation
