TN-C-S system
TN-C-S: A combined earth and neutral system (PEN conductor) is used in certain systems but eventually
split up into two separate conductors PE and N. A typical application of combined PEN conductor is from
the substation to the building but within the building PEN is separated into the PE and N conductors.
Direct connection of PE and N conductors to many earthing points at different locations in the field will
reduce the risk of broken neutrals. Therefore this application is also known as protective multiple earthing
(PME) in the UK or as multiple earthed neutral (MEN )in Australia
TT system
TT: The neutral point (N) of the low voltage transformer and the equipment frames (PE) are connected to
a separate earthing point. The Neutral (N) of the transformer and electrical equipment are connected.
Generator or
transformer
Earth
Consumer
Generator or
transformer
Earth
Consumer
L1
L2
L3
PEN
7
L1
L2
L3
N
PE