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8.2 Earthing systems
8.2.1 TN earthing system
In a TN earthing system, one of the points on the generator or transformer is connected
to earth. In a three-phase system, this is typically the star point.
TN−S earthing:
Protective earth (PE) and neutral (N) are separate conductors.
This system is currently used in most residential houses and commercial plants in
North America and Europe.
Figure 19: TN−S earthing
8.2.2 TT earthing system
In a TT earthing system (Terra–Terra), the protective earth connection for the
consumer is provided by a local earth electrode and another earth electrode is
independently installed at the generator. There is no earth cable between the two earth
electrodes.
Figure 20: TT earthing
Note!
TN / TT earthing system.
For the LMV6, it is preconditioned that either a TN earthing system or a TT earthing
system is used.
When using the TT earthing system, the special requirements for the design of the
earthing resistors and the residual current protection circuit must be taken into account.
It is essential to ensure that no impermissible potential differences arise between the
earthing point and N.
LMV6 Installation Guide
8 Earthing and shielding of the LMV6
27/39
CC1J7560en
4/21/2020
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