Furuno FELCOM251, Руководство по установке

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4. GROUNDING AND RF PROTECTION
4-4
4.3 About Marine Grounding
There is great confusion about the different Ground terms used when dealing with ma-
rine electrical installations. The various terms are listed below for reference.
Terms for Ground in maritime installations
Term Definition
DC Negative Actually not a ground but a current-carrying
conductor which carries the same current that
flows in the positive conductor. The DC Nega-
tive may be electrically connected to seawater
(at one point only, via the engine negative ter-
minal though the shaft and the propeller) or left
completely floating.
Lightning Ground Ground potential immersed in seawater. Pro-
vides a path to ground lightning strike energy.
Please note that this is not a functional part of
any other electrical system.
Corrosion System Ground Bonding arrangement that ensures equal elec-
trical potential for all dissimilar underwater met-
al parts and provides galvanic protection by
means of sacrificial anodes.
AC Ground (Protective Earth) Ground potential immersed in seawater (typi-
cally the hull for steel and aluminium vessels).
Serves as safety ground (protective earth) thus
preventing shocks or electrocution in the event
of a fault situation.
RF Ground (Capacitive) Underwater ground potential that is capacitive-
ly coupled to seawater ground. Typically nu-
merous pieces of bonded underwater metal
parts such as keel (isolated), water tank, en-
gine block etc. will act as a capacitive RF
ground (that is; no DC connection to seawater).
Often referred to as “counterpoise” for the SSB/
HF aerial system.
RF Ground (Electrical) Underwater ground potential that is electrically
coupled to seawater ground by means of a sep-
arate ground plate (e.g. Dynaplate). Also re-
ferred to as "counterpoise" for the SSB/HF
aerial system.