Page 261 - Electrical Safety of Low Voltage Systems

244 Chapter Fifteen

Publicly exposed installations (e.g., lighting systems for public
places, roads, etc.) with which persons may come in contact.

In the above installations and locations, additional or tighter re-
quirements for safety must be met.

15.2 Electrical Safety in Marinas
1
Marinas are facilities for the mooring of pleasure craft with fixed
wharves. They are equipped with a.c. receptacles to feed the boats,
installed in marine-style pedestals located as close as possible to the
berth. As per IEC standards, the nominal supply voltage must not
exceed 230 V single phase, or 400 V three phase. Mechanically sup-
ported flexible cables will directly connect the receptacles to the boats
(Fig. 15.1).
The metal hull acts as a grounding electrode to the shipboard’s
electrical system, both during navigation, when it is a TN system, and
when the vessel is berthed. The seawater, in fact, acts as the earth to
2
a land-based installation. Thus, an “earthing” conductor (EC) is em-
ployed to link the shipboard’s main grounding bus to the hull, which,
therefore, becomes an EXCP (i.e., at zero potential). Supplementary
equipotential bonding connections may be additionally required be-
tween hull and onboard equipment to reduce further potential differ-
ences caused by faults.
Marinas are “unfriendly” environments, electrically speaking, as
the person’s body resistance because of salt and moisture is lower than
the standard values shown in Fig. 5.15 in dry conditions. For this rea-
son, international standards do not permit in marinas the protection
against indirect contact by nonconducting location or earth-free local
equipotential bonding; for the same reason, protection against direct

FIGURE 15.1 Direct single-phase connection of the vessel to the dockside
outlet equipped with RCD.