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High Voltage, Ship's electrical networks

CBT 45 questions

First 5 of 45 questions — with answers

The correct answer is marked. Unlock the rest to study the whole test, online or offline.

  1. Question 1

    A ship has a 3 phase electrical network with a neutral point earthed through a 200 Ω resistor. The generator phase voltage is 3 000 V and the synchronous impedance of the generator is 0,1 Ω. What will be the potential fault current if an earth fault occurs on the generator output cable?
    • 15 Amps.
    • 1 500 Amps.
    • 3 000 Amps.
    • 30 000 Amps.

  2. Question 2

    A ship has a 3 phase electrical network with star connected generators and an earthed neutral point. The network line voltage is 440 V and phase voltage 254 V. If an earth fault occurs on one phase through a circuit of 1 Ω impedance what will be the potential fault current?
    • 25,4 Amps.
    • 0,004 Amps.
    • 440 Amps.
    • 254 Amps.

  3. Question 3

    Earth leakage circuit breakers are commonly used ashore to protect people from earth faults. Which of the following best describes why earth leakage circuit breakers have not been commonly used on ship's electrical networks in the past?
    • Continuity of supply is preferred.
    • Earth leakage circuit breakers are expensive.
    • Earth leakage circuit breakers are not reliable.
    • Earth leakage circuit breakers do not work on insulated neutral networks.

  4. Question 4

    Even on a large passenger ship which generates electricity at 6 000 Volts lighting is normally supplied at voltages of 220 Volts or less. Which one of the following best describes why lighting is not supplied at a higher voltage?
    • Lighting switches are operated by people with no electrical training.
    • Electrical loads for lighting are low enough to allow lower voltages to be used without excessive cable losses.
    • Light fittings are not available for electrical supplies over 220 Volts.
    • High voltage lights have an annoying flicker.

  5. Question 5

    High voltage ships tend to use earthed neutral electrical networks. Which one of the following best describes how excessive fault currents are prevented in the event of an earth fault on these ships?
    • An impedance is placed in the neutral earthing line.
    • The risk of earth faults is reduced by extra planned maintenance.
    • Earth leakage circuit breakers are used on every circuit.
    • An impedance is placed in each output cable from the generators.

Preview — 5 of 45 questions

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About this CBT test

High Voltage, Ship's electrical networks is a CBT test with 45 questions and verified answers. Common topics include: electrical network, earth fault, distribution system, neutral point, main switchboard, power factor, prime mover, generator.

You can practise the free questions online — one at a time, with the correct answer — or unlock the whole test and download it to study offline, without internet.

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