Page 170 - Electrical Safety of Low Voltage Systems

Protective Multiple Earthing (TN-C-S Grounding System) 153

FIGURE 8.13 Neutral-to-ground potentials.

than at User A. The neutral-to-ground voltage, which may reach sev-
eral volts, also exists between the neutral and the protective conduc-
tors. In the case of a defect in the insulation between these two conduc-
tors, a low-resistance object might bridge the gap between them, with
the possible result of setting on fire any flammable material eventually
present.

Endnotes

1. As a rule of thumb, the percentage of ground-fault current flowing through the
earth may be estimated as large as 20% of the return current.
2. M. Mitolo, M. Tartaglia, G. Gruosso, and A. Canova, “Evaluation of Voltage
Exposures Due to AC/DC Stray Currents,” Proceedings of the IEEE-IAS Industry
Application Society 42nd Annual Meeting, New Orleans, LA, September 2007.
3. M. Mitolo, G. Parise, “TN—Island Grounding System,” Proceedings of the IEEE-
IAS Industrial & Commercial Power Systems Technical Conference, Dearborn,
MI, May 2006.