Ground
Conductive mass of ground whose electric potential is set to zero at all points
according to agreement.
Ground electrode
Conductive part or parts that make good contact with ground and form an
electrical connection with it.
Total grounding resistance
Resistance between the main ground terminal/busbar and ground.
A.2 Power systems and protective devices
The various power systems are dened in DIN VDE 0100-300. The permissible
protective devices for these systems are listed in DIN VDE 0100-410. The power
systems are identied by means of codes where the individual characters have
the following meanings:
1st character: Relationship of power system to ground
T: Direct grounding of a point
I: Either insulation of all live parts from ground or connection
of one point with ground via impedance
2nd character: Relationship of the exposed conductive part of the installation
to ground
T: Exposed conductive part directly connected to ground, indepen-
dently of the grounding of any point of the power system
N: Exposed conductive part directly connected with the ground
electrode (the grounded point in AC networks is generally
the neutral point)
Subsequent
characters: Arrangement of the neutral and protective conductors in a
TN system
S: Separate conductors for neutral and protective earth functions
C: Neutral and protective conductor functions combined in a single
conductor (PEN conductor)
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