Electrical system on board ships
Shallen S V
Asst. Prof.
SNGCE
•Climatic conditions
•Vibration
•Motion, temperature
electrical equipment is
Electrical equipment is Expected to last the lifetime of
the installation. During this time, maximum reliability is
important, particularly in regard to those services,
which are vital for propulsion and safety.
Axis of rotation while installing machineries…..?
(vertical and fore & aft)
SOLAS- Machinery
The standard requirement, now universally accepted, requires
propulsion and auxiliary machinery fitted in the ship or mobile
offshore installation to be capable of operating when the vessel is
upright and when inclined at any angle of list up to and including 15'
either way under static conditions and 22.5' under dynamic
conditions (rolling) either way and when simultaneously inclined
dynamically( pitching) 7.5' by bow or stern.
The emergency generator and its prime mover and any
emergency accumulator battery shall be so designed and
arranged as to ensure that they will function at full rated
power when the ship is upright and when inclined at any angle
of list up to 22.5’ or when inclined up to 10’ either in the fore
or aft direction or is in any combination of angles within those
limits.
Importance in regard to lubrication, contactors, switchgear,
relays, equipments with oil.
Ship’s Electrical System
It can be divided into supply and users or
consumers.
Supply is Divided into components which
generate and those which distribute.
Generation covers,
prime movers
Electrical generators(ac, dc)
Starting arrangements
Control devices to maintain correct values of
speed, frequency and voltage.
Distribution covers,
Main switchboard
Auxiliary switchboard
Section switchboard
Group starter panels
Circuit breakers
Transformers
Cabling
Switches, fuses etc
Users or consumers
Motors driving machines(pumps)
Heating installations
Lighting circuits
Portable equipment.
Electrical services
Propulsion of the ship, safety equipment and services,
navigation, steering , bilge pumping, ballast pumping, fire
fighting are all concerned with maintaining steerage
way and maneuverability.
1) Primary Essential Services
2) Secondary essential services
3) Main or Emergency electrical systems: the ship must
have an independent emergency electrical system,
some of these systems may also fall in the category of
essential services. The main system can be arranged to
feed the emergency system under normal operating
conditions.
Primary essential services
Steering gears
Pumps for cpp
Scavenging air blowers, fuel oil supply pumps, fuel valve cooling pumps,
LO pumps, cooling water pumps for main and auxiliary engines and
turbines necessary for propulsion
Ventilation necessary to maintain propulsion
Forced draft fans, feed water pumps, water circulating pumps, vacuum
pumps and condensate pumps for steam plants
Azimuth thrusters(lo pumps, cooling water pumps)
Electrical equipment for electric propulsion plant with lo pumps and
cooling water pumps
Hydraulic pumps
Viscosity control equipment for HFO
Control, monitoring and safetty devices/systems of equipment for
primary essential services
Fire detection and alarm systems
Secondary essential services
Windlass
Fuel oil transfer pumps and fo treatment equipment
Lo transfer pumps and lo treatment equipment
Preheaters for heavy fuel oil
Starting air and control air compressors
Bilge, ballast and heeling pumps
Fire pumps and other fire extinguishing medium pumps
Ventilating fans for engine and boiler rooms
Navigational lights, aids and signals
Internal communication equipment
Lighting system
Electrical equipment for watertight and fire-tight closing
appliances
Naval Architect can ensure……!!!
Axis of installation
Adequate ventilation
The shipbuilder must estimate the
number and power rating of the required
generators by assessing the power
demand of the load for all situations
whether at sea or in port.
……..!!!!
Systems and Major components
Generators
The generators (called alternators when they generate
alternating current) produce the required electrical
power. They may be driven by a diesel engine, by a
steam or gas turbine, or by the main propulsion engine.
The type of prime mover is determined by the design
of the ship and by economic factors.
Generators form the heart of the electrical system's
design and their correct rating is the key to a safe,
workable, and economical system. When choosing a
marine generator cognisance must be given to the
nature of the load.
SOLAS
At least two generators for a ship's main electrical
power system.
The generators are normally driven from their own
dedicated diesel engine but this can be expensive.
It can be economical to drive the generators from the
main propulsion plant.
at least one electrical generator to be independent of
the speed and rotation of the main propellers and
associated shafting.
owners opt to provide three generators
The output from each of these generators is fed to the
main switchboard and then distributed to the various
auxiliary services comprising the electrical load.
Power Supplies Commonly
Available
Electrical power on board a ship is
commonly generated at 440V, 60Hz
(sometimes 380V, 50Hz)
Lighting and other domestic supplies
usually operate at 115V or 220Va.c.
Main Switchboard
The main elements of a marine distribution system are
the main and emergency switchboards, power panel
panels, motor controllers, lighting and small power panel
boards.
The system is generally designed such that under all
normal conditions of operation, power is distributed
from the main switchboard.
The main switchboard is generally located near the
centre of the distribution system and this is normally the
main engine room or machinery control room.
These locations are normally below the ship's waterline
or below the uppermost continuous deck of the ship i.e.
the bulkhead or main deck. Consequently, in the event of
a fire or flooding it is likely that the main generators and
switchboard would be disabled.
Emergency Services
To ensure that electrical supplies are available to
emergency and safety systems, in the event of a main
power failure, an emergency generator and associated
emergency switchboard will be located above the
main deck in a separate space, completely isolated
from the main machinery spaces.
Emergency services would be supplied from the
emergency switchboard using distributed panels for
navigation, safety and emergency lighting services.
These distribution panels are also generally arranged
to be above the bulkhead deck.
Emergency Stop Panel
According to the requirements of the classification
societies, additional emergency stop circuits have to be
installed for certain consumers at a location that is
separate from their installation position, e.g., in order to
switch off fans, the fuel or oil pumps in the endangered area
if there is a fire.
Emergency services would be supplied from the emergency
switchboard using distributed panels for navigation, safety
and emergency lighting services.
These distribution panels are also generally arranged to be
above the bulkhead deck.
Ship's Auxiliary Services
Auxiliary services on board a ship range from engine room
pumps and fans, deck winches and windlasses to general
lighting, catering and air-conditioning
Recap
Difference between conductors &
insulators.
What is current, its unit?
Electromotive force or voltage
Electrical resistance, its unit
Power , unit
Electromagnetic induction.
Flemings right hand rule.
Electrical Safety
Ships are classed.
The International Electrotechnical Commission (IEC),
Recommendations for Electrical Installations in Ships,
gives guidance to national bodies, classification
societies & all involved in the marine industry.
Increasing adoption of these recommendations will
lead to a greater level of international
standardisation.
In addition to classification requirements, there are
statutory international requirements, namely the
International Convention for Safety of Life at Sea
(usually referred to as SOLAS) which is produced by
the International Maritime Organisation and
administered by National Governments.
Electrical safety
High voltage(above 1000V) and low voltage
safety(1000V).
Should be aware of hazards to avoid associated
danger.
Safe distance for high voltage systems.
Should wear dry, safe clothing, safety shoes, eye
protection, hard hat etc.
Safety measures
Highest level of safety for personnel.
Primary goal- avoiding failure.
Design philosophy-
o built according to SOLAS requirement.
o Class rules, regulations,
Make sure that electrical system has the ability
to withstand stresses generated externally and
within the system.
Challenge for Naval Architect…….!!!!!
Solutions
Components as per use, ambient conditions,
design specifications.
Select according to the location.(stresses varies
according to location).
Eg. 1) Cables- Follow IEC recommendations such
as flame retardant, high resistance to humidity, oil,
vapor, ageing etc.
2) Enclosures
Above ensures component quality.
Fail safe system.
Proper maintenance
Personal protection
Rules
Enclosures
Screening
Warning signboards
Limited accessibility
Accidentally touching rotating and moving
parts.
Other safety measures
Redundancy requirements(eg; pumps,
blackout(main switch board & emergency
switch board), main generators, power
transformers, lighting system).
Guidelines for Naval Architect(Safe
Installation of equipment)
Good workmanship and proper materials shall be used
throughout the installation.
The equipment shall be installed in such a way as to be
accessible for testing, inspection and maintenance as far as
is practical
Joints and connections shall be properly constructed,
regarding conductance, insulation, mechanical strength and
protection.
Circuits shall have suitably rated automatic protective
devices especially for protection against overcurrent.
Electrical equipment shall be earthed in such a manner that
earth leakage currents will be discharged without danger.
Circuits supplying electrical equipment shall have effective
means of isolation as necessary, to prevent or remove any
danger.
Safe means of access shall be ensured for
persons to operate or attend to installed
equipment.
Equipment exposed to adverse weather or
corrosive conditions shall be designed to
prevent any danger from this.
Testing shall be carried out on completion of
the installation, to the requirements as
specified in relevant regulations.
SHIPBOARD ELECTRICAL
EQUIPMENT
DC GENERATORS
A dc generator is a rotating machine that changes
mechanical energy to electrical energy. There are two
essential parts of a dc generator:
The yoke and field windings which are stationary
And armature which rotates.
AC GENERATORS
AC generators are also called alternators.
In an ac generator, the field rotates, and
the armature is stationary. To avoid
confusion, the rotating members of dc
generators are called armatures; in ac
generators, they are called rotors.
AC Distribution System
3-phase system
Single phase system is used only for short
distances and for relatively low voltages.
The distribution system begins at the shore sub
station where the power is delivered by overhead
transmission lines and stepped down by
transformers or as in the case of ships, in the
engine room and associated control rooms.
Advantages of AC Distribution System over DC
Distribution System:
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