Summary of the earth connection diagram SLT


Summary of the earth connection diagram SLT
The ground connection diagram defines the grounding method of the neutral point of a distribution transformer and of the masses on the user side to ensure the protection of persons and equipment against insulation defects.

We find 5 different neutral regimes namely:
Resistor grounding
Grounding by low reactance
Earthing by compensation reactance (due to the capacitive effect of HV lines)
Direct grounding (not used on European networks)

A grounding pattern is characterized by two letters. The first indicates the connection of the neutral of the transformer, it can be:

T for grounded
I for insulated (or impedant) with respect to earth.

The second letter indicates how to connect the user masses, it can be:

T for grounded
N for connection to the neutral, which is connected to earth.

Earth connection diagram TT

This connection is used by ONE for public low voltage distribution
The neutral of the transformer is earthed via a resistor grounding conductor Rn
All the masses of the equipment protected by a single protective device must be interconnected and connected by a protective conductor called PF to a ground connection
TN-C ground connection diagram
Earth connection diagram TN-S

Earth connection diagram IT


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