Page 23 - Electrical Safety of Low Voltage Systems

Basic Definitions and Nomenclature 5

FIGURE 1.4 TN-C grounding system. Neutral and protective functions are
combined in a single conductor throughout the electrical system.

1.2.19 TN Grounding System
A solidly grounded power system; the system has one point directly
grounded and the ECPs directly connected to that point by protective
conductors.

1.2.20 TN-C Grounding System
Same definition as that for TN grounding system; neutral and protec-
tive functions are combined in a single conductor (i.e., PEN conductor)
throughout the electrical system (Fig. 1.4).

1.2.21 TN-C-S Grounding System
Same definition as that for TN grounding system; neutral and protec-
tive functions are combined in a single conductor (i.e., PEN conductor)
in a part of the electrical system (Fig. 1.5).

1.2.22 TN-S Grounding System
Same definition as that for TN grounding system; separate neutral
and protective conductors are used throughout the system (Fig. 1.6).

1.2.23 TT Grounding System
A solidly grounded power system; ECPs are directly connected to the
ground, independently of the grounding of any point of the power
supply system (Fig. 1.7).