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residual current pro- 230 V socket outlet residual current
tective device (RCD) for the devices (CEE) protective device (RCD)
L L

N N
PE
230 V socket
outlet (CEE)

earth-termination without overcurrent to metal parts in contact with
system (ashore) protection the water surrounding the ship

Figure 9.34.4 Use of an isolation transformer to prevent corrosion

For corrosion protection reasons, the protective conductor of If lightning strikes the air-termination rod or the metal mast
the shoreside power supply system must not be connected of the yacht at anchor which is supplied with electricity, the
to the earthed metal parts of the water vehicle. The protec- potential of this yacht is raised above the connection of the
tive conductor of the shoreside power supply system is not shoreside power supply system. A part of the lightning current
required to protect persons on the yacht against electric shock is passed to the water and flashover to the power cable of
since an isolation transformer on the yacht ensures protection the shoreside power supply system will occur depending on
against electric shock in connection with a residual current the conductivity of the water. This flashover can damage the
protective device (Figure 9.34.4). cables / equipment on the yacht and cause fire. However, it is
even more likely that a yacht at anchor, which is supplied with
Equipotential bonding electricity, is threatened by a shoreside lightning strike. In this
In general, all protective conductors of the board electronics case, the lightning current flows in the direction of the yacht
and all metal parts of yachts must be connected to the com- and causes the damage described above.
mon equipotential bonding / earth-termination system of the If a type 1 combine arrester is installed, it must be ensured
power supply system. This measure prevents dangerous touch that the connection of the earth-termination / equipotential
voltage / sparking. The copper protective bonding conductors, bonding system of the yacht to the protective conductor of
which do not carry lightning currents, must have a minimum the shoreside power supply system does not cause corrosion.
cross-section of 6 mm . For this purpose, stranded, solid or The surge protective devices shown in Figure 9.34.6 consider
2
flexible conductors must be used. Flexible conductors should that the polarity (L, N) is changed, which is typical of earthed
be preferred due to vibrations. In this context, it must be ob- socket outlets (not standard-compliant, but may be the case).
served that the conductors can be damaged by the corrosive In this case, the phase conductor (L) and the neutral conductor
environment (saline, moist) and the capillary effect. Therefore, (N) are twisted until they reach the L and N connections of the
the cable lug at the ends of the flexible conductors must be on-board supply system. The increased voltage protection level
sheathed with a heat shrinkable sleeve. is sufficient for the electric strength of the primary winding.
Irrespective of whether a yacht is made of metal or non-met-
Internal lightning protection / surge protection al material, there is the risk that lightning hits, for example,
A combined arrester, which is directly installed in the power marine radio antennas or wind sensors installed on the mast,
supply system, is one of the most important protection meas- which can damage these pieces of equipment and downstream
ures (Figure 9.34.5). The necessity of such an arrester is radio or evaluation devices. Since these pieces of equipment
shown based on the following two scenarios. are located in the protected volume (air-termination tip on the

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