Page 120 - Electrical Safety of Low Voltage Systems

TT Grounding System 103

FIGURE 6.7 Values of R GT as a function of the residual operating currents of
the RCD.

6.5 Neutral-to-Ground Fault in TT Systems
If the neutral conductor comes into contact with a grounded enclosure,
or the protective conductor, or if neutral and ground connections are
inverted at the load, a neutral-to-ground first fault occurs (Fig. 6.8).
When the load is off, the RCD will trip only if the neutral is en-
ergized and able to impress a sufficient earth current through the
6
user’s ground. In this abnormal condition of the neutral, the RCD will

FIGURE 6.8
Neutral-to-ground
fault in TT
systems.