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WorksheetsShip Electrical Distribution Quiz
Total questions: 45
Worksheet time: 23mins
What is an advantage of closed-loop distribution?
Cheaper installation
Easy maintenance
Less cable required
Ability to operate even if one cable fails
Why do ports often require ships to use shore power instead of onboard generators?
To reduce fuel costs
To minimize air and noise pollution in port areas
To save generator life
To increase efficiency
Essential services in ship electrical distribution include:
Cargo pumps and lighting
Air conditioning and refrigeration
Steering gear and navigation aids
Galley equipment
In Engine Room Simulator (ERS) KONGSBERG MAN B&W MC90-V Electrical Distribution System. Which is the Main Directory for the Emergency Switchboard?
MD 70
MD 71
MD 72
MD 73
Normal voltage at a ship's main AC switchboard is usually:
220 V
440 V
380 V
660 V
Which AC distribution device combines the functions of fuse and circuit breaker for small loads up to 100 A?
Cartridge fuse
Isolator switch
Miniature circuit breaker (MCB)
Earth leakage relay
If a generator supplies 400 kVA at 0.9 power factor lagging, what is the real power in kW?
400 kW
360 kW
380 kW
450 kW
An insulated distribution system is one that is totally electrically insulated from earth (ship's hull)
Earthed system
Insulated system
Parallel system
Ring system
Which distribution system is commonly used to supply winches and cranes?
Radial system
Ring system
Insulated system
Parallel system
In earth lamp indication for DC systems, both lamps glow equally if:
One earth fault exists
There is no fault and insulation is intact
One lamp is open
Short circuit exists
A fuse is designed to:
Switch on loads
Detect earth faults
Act as a weak link to protect against excessive current
Reduce voltage fluctuations
In an earthed distribution system, a single earth fault on the line conductor:
Has no effect
Causes lamps to dim
Causes fuse or breaker to operate immediately
Creates harmonics
When a ship undergoes major repair or dry-docking, why is shore power required?
To test new equipment
To supply electricity when main and auxiliary engines are shut down
To avoid generator synchronization
To reduce load
In a 440V, 3φ, 60Hz ship power supply, how much voltage will you get when measuring one of the line and earth?
220 V
254 V
440 V
380 V
The typical letter marking for generator 'bus bars' on ships:
U, V, W
R, S, T
X, Y, Z
A, B, C
In a wye-connected generator, the line current is equal to:
√3 × phase current
Phase current
Half phase current
Double phase current
Why is an Earth Fault Indicator important during shore power connection?
To measure power factor
To balance load
To detect insulation faults and protect crew safety
To stabilize voltage
Why is a phase sequence meter used before connecting shore power?
To check current rating
To confirm correct rotation direction of 3-phase supply
To measure frequency
To balance loads
Which of the following best describes the function of the ship's electrical distribution system?
To protect equipment
To distribute electrical energy from generators to loads
To save fuel
To detect faults
Which type of fault immediately interrupts a circuit?
Earth fault
Short circuit fault
Open circuit fault
Overload
If the system is healthy, using earth lamps, how many lamps equally glow?
0
2
1
3
Neutral Earthing Resistor (NER) is designed to:
Increase power factor
Limit earth fault current to generator full load current
Control frequency
Reduce harmonics
What is the main purpose of using shore power when a ship is in port?
To test synchronizing panel
To reduce generator maintenance and fuel consumption
To avoid generator overload
To balance bus load
Circuit breakers differ from fuses because they:
Are cheaper
Can be reset without replacement
Provide faster protection
Do not trip
In ERS KONGSBERG MAN B&W MC90-V Electrical Distribution System. Which is the Main Directory for the Electrical Plant?
MD 70
MD 71
MD 72
MD 73
In DC distribution, 'bus bars' are located:
On motors
On the distribution panels
On generators
On transformers
What is the function of the shore connection circuit breaker on a ship?
Balances phases
Protects the system from overcurrent and ensures safe transfer to shore power
Synchronizes generators
Stabilizes frequency
Which of the following fault/s is/are very critical and hazardous?
Earth fault
Both short circuit fault and open circuit faults
Open circuit only
Overload fault
In the AC power triangle, the horizontal side represents:
Reactive power (kVAR)
Apparent power (kVA)
Real power (kW)
Power factor
If R line is earthed, using earth lamps, how many lamps equally glow?
2
1
0
3
What is the primary purpose of an Automatic Voltage Regulator (AVR) in a ship's generator?
Protect against earth faults
Maintain steady output voltage
Improve power factor
Reduce frequency fluctuations
Which type of fuse provides more reliable protection?
Rewireable fuse
Cartridge fuse
Glass fuse
Thermal fuse
Which type of fault does not immediately interrupt an insulated distribution system?
Short circuit fault
Single earth fault
Open circuit fault
Overload fault
The ratio of line voltage to phase voltage in a three-phase generator supply is:
1.5
1.73
2.0
1.2
Which type of generator is commonly used onboard ships for main power generation?
DC generator
Synchronous AC Generator or Alternator
Induction generator
Stepper generator
Which type of distribution system requires TWO earth faults before disconnection occurs?
Earthed system
Insulated system
Radial system
Ring system
The rule 'To find EARTHS – make BREAKS; To find BREAKS – make EARTHS' is used for:
Synchronizing generators
Tracing circuit faults
Measuring insulation resistance
Balancing phases
When connecting shore power to the ship, what is the first step to ensure safety?
Start auxiliary generator
Check voltage, frequency, and phase sequence compatibility
Switch off all breakers
Connect earth cable
High voltage systems (3.3 kV and above) on board ships are normally:
Solidly earthed
Earthed via a resistor
Floating
Radial
A short-circuit fault occurs due to:
Open wire
Break in insulation causing conductors to touch the hull
Earth cable disconnected
Low frequency
What is the standard frequency of shipboard AC electrical supply in most merchant vessels?
50 Hz
60 Hz
400 Hz
25 Hz
The ratio of phase voltage to line voltage in a three-phase generator supply is:
0.67
0.57
0.50
0.75
Which method is commonly used to locate earth faults on ships?
Using insulation tester
Sequentially opening circuit breakers while observing earth fault indicators
Overload trip test
Using shore power test
The typical letter marking for motor 'terminals' on ships:
R, S, T
U, V, W
X, Y, Z
A, B, C
Shore power is especially important during which of the following shipboard situations?
During sea trials
During anchoring
Long periods of cargo operations at berth
During maneuvering
