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HV exit exam questions and answers — Set 14 — High Voltage Safety Officer & Switchgear Operations

Set 14 of the High Voltage Safety Officer & Switchgear Operations (HV) exit exam bank — 38 of 428 questions, with the correct option marked and a one-line explanation for every one. Read it end to end, jump to a single set, or search it — then sit the same bank as a timed paper. The real DG Shipping exit exam is 30 marks with 15 to pass.

These are the bank's original groupings. Practising deals the whole bank out again every time you reshuffle, so a practice “Set 3” is a different 30 questions each time — the set numbers below are the source file's, and are only used here so the key stays navigable. Options are listed in their original order with fixed letters; when you practise, those move too.

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Set 14 — 38 HV exit exam questions with answers

1. A protection relay has tripped an HV motor feeder on overcurrent. Before the breaker is reclosed, the engineer should:

  • A. Reclose immediately several times to see if it holds
  • B. Increase the relay setting
  • C. Bypass the relay
  • D. Investigate the cause of the trip and check the motor and cable, rather than repeatedly reclosing
Answer: D — Investigate the cause of the trip and check the motor and cable, rather than repeatedly reclosing
Reclosing onto a fault in HV equipment can cause severe damage and arc flash. The trip indication, motor, cable and driven load must be checked, and insulation tested if a fault is suspected, before restoring supply.

2. The 'switching strategy' for isolating a component of an HV system requires the engineer to consider:

  • A. The colour of the cubicle
  • B. Maintaining supply to essential services, possible back-feeds, generator capacity and sequence of operations
  • C. The time of the next meal
  • D. Only the shortest route to the switchboard
Answer: B — Maintaining supply to essential services, possible back-feeds, generator capacity and sequence of operations
A switching strategy plans how to isolate equipment while keeping essential services available, avoiding overloads and back-feeds, and ordering operations safely. STCW B-III/2 lists producing such a strategy as a management-level skill.

3. Which test equipment is suitable for proving an HV circuit dead before applying earths?

  • A. An insulation resistance tester
  • B. A neon screwdriver
  • C. A standard 600 V multimeter
  • D. An approved HV voltage detector rated for the system voltage
Answer: D — An approved HV voltage detector rated for the system voltage
Only a voltage detector designed and rated for the system voltage, such as a capacitive or contact-type HV indicator, may be used. LV instruments are unsafe and may give false readings or fail catastrophically.

4. An HV vacuum contactor feeding a motor is usually used in combination with HV HRC fuses because:

  • A. The contactor cannot carry normal load current
  • B. Fuses eliminate the need for overload protection
  • C. The fuses provide speed control
  • D. The fuses interrupt high short-circuit currents beyond the contactor's breaking capacity
Answer: D — The fuses interrupt high short-circuit currents beyond the contactor's breaking capacity
Vacuum contactors are designed for frequent switching of normal and overload currents but have limited breaking capacity. Current-limiting HRC fuses clear severe short circuits, while relays and the contactor handle overloads.

5. Partial discharge monitoring of HV machines and switchgear is valuable because:

  • A. It replaces the need for a Permit to Work
  • B. It measures earth resistance of the hull
  • C. It gives early warning of insulation deterioration while the equipment remains in service
  • D. It measures the speed of the motor
Answer: C — It gives early warning of insulation deterioration while the equipment remains in service
Partial discharges occur in voids and at surfaces of degrading insulation long before breakdown. Online PD monitoring trends the discharge activity, allowing maintenance to be planned before failure.

6. When removing portable earthing leads after HV work, the correct order is to:

  • A. Remove all ends simultaneously by hand
  • B. Disconnect the earth end first, then the conductors
  • C. Leave the earth end connected and energise
  • D. Disconnect the leads from the conductors first using an insulated stick, then disconnect the earth end last
Answer: D — Disconnect the leads from the conductors first using an insulated stick, then disconnect the earth end last
Earthing leads are connected earth end first and removed earth end last. This ensures that the lead is never connected to a conductor while its earth end is free, which could make the lead itself live.

7. In the event of an HV circuit breaker failing to trip on a fault, the system remains protected because:

  • A. The AVR will reduce generator voltage to zero immediately
  • B. The fault will clear itself
  • C. Earth fault relays always open all breakers instantly
  • D. Upstream breakers trip via breaker failure or backup protection after a time delay
Answer: D — Upstream breakers trip via breaker failure or backup protection after a time delay
Protection is coordinated so that if a breaker fails to clear a fault, breaker failure protection or time-graded backup relays trip the next upstream breaker, such as the generator or bus tie breaker, isolating the fault.

8. An HV cable is suspected of a fault after repeated tripping. Which test is most appropriate to confirm the insulation condition after isolation?

  • A. Measuring cable length with a tape
  • B. An insulation resistance test at the appropriate DC voltage under a Sanction to Test
  • C. Running the cable at overload
  • D. Visual check only
Answer: B — An insulation resistance test at the appropriate DC voltage under a Sanction to Test
After isolation and with the cable disconnected at both ends, an IR test at the correct DC voltage shows whether insulation has broken down. Where required, further tests such as fault location are carried out by specialists.

9. Why should the operation counter of an HV vacuum circuit breaker be recorded during maintenance?

  • A. To compare the number of operations with the manufacturer's mechanical and electrical endurance limits
  • B. To determine the generator's age
  • C. To calculate fuel consumption
  • D. To set the AVR
Answer: A — To compare the number of operations with the manufacturer's mechanical and electrical endurance limits
Breaker mechanisms and interrupters have rated numbers of operations. Recording the counter at each maintenance supports condition-based maintenance and ensures interrupters or mechanism parts are replaced before these endurance limits are exceeded.

10. For the same gap length in air, which electrode arrangement generally has the lowest breakdown voltage?

  • A. Point (needle) to plane
  • B. Uniform-field Rogowski electrodes
  • C. Parallel plates
  • D. Sphere to sphere with large spheres
Answer: A — Point (needle) to plane
Sharp electrodes concentrate the electric field at the tip, so ionisation and corona start at a lower voltage and breakdown follows sooner. Sphere and plane electrodes give a more uniform field and higher breakdown voltage for the same gap.

11. In HV insulation design, 'clearance' is defined as:

  • A. The thickness of cable insulation
  • B. The shortest distance through air between two conductive parts
  • C. The distance between the switchboard and the bulkhead
  • D. The distance along the surface of an insulator
Answer: B — The shortest distance through air between two conductive parts
Clearance is the shortest air path between conductors at different potentials and protects against air breakdown. Creepage is the path along the insulating surface, which is affected by pollution and moisture.

12. Why do HV insulators and bushings often have sheds or ribs on their surface?

  • A. To improve cooling of the conductor
  • B. To make them lighter
  • C. To increase the creepage distance and reduce surface leakage and flashover
  • D. To reduce clearance distance
Answer: C — To increase the creepage distance and reduce surface leakage and flashover
Sheds lengthen the surface path between conductor and earth without increasing the overall length. This increases creepage distance, so contamination and moisture are less likely to cause surface tracking and flashover.

13. Surface tracking on HV insulation is the formation of:

  • A. Rust on the switchboard frame
  • B. Carbonised conductive paths caused by leakage currents across a contaminated surface
  • C. Cracks due to mechanical shock only
  • D. Bubbles inside transformer oil
Answer: B — Carbonised conductive paths caused by leakage currents across a contaminated surface
Leakage current across a dirty or damp insulating surface causes small discharges that carbonise the material. These conductive tracks grow until they bridge the insulation and cause flashover.

14. A protection CT has a ratio of 1000/1 A. If the secondary current measured is 0.6 A, the primary current is:

  • A. 1,666 A
  • B. 600 A
  • C. 6,000 A
  • D. 60 A
Answer: B — 600 A
The primary current equals secondary current multiplied by the CT ratio: 0.6 A x 1000 = 600 A. Standard CT secondary ratings are 1 A or 5 A so meters and relays can be standardised.

15. A voltage transformer on a 6.6 kV switchboard with a secondary of 110 V has a ratio of:

  • A. 60:1
  • B. 110:1
  • C. 600:1
  • D. 6:1
Answer: A — 60:1
6,600 V divided by 110 V gives a ratio of 60:1. The VT steps down HV to a safe level for metering, synchronising and protection relays.

16. Unlike a current transformer, the secondary of an energised voltage transformer must never be:

  • A. Connected to a voltmeter
  • B. Open-circuited
  • C. Earthed at one point
  • D. Short-circuited
Answer: D — Short-circuited
A VT behaves like a voltage source; a short circuit on its secondary draws excessive current and can destroy it, so VT secondaries are fused. A CT secondary, by contrast, must never be opened while primary current flows.

17. A Circuit Main Earth (CME) is applied:

  • A. Only during insulation testing
  • B. At the point of isolation after proving dead, before a Permit to Work is issued
  • C. While the circuit is still live, to discharge it
  • D. At the point of work by the work party after the permit is issued
Answer: B — At the point of isolation after proving dead, before a Permit to Work is issued
Circuit main earths are applied by the Authorised Person at the point of isolation, using an earthing switch or approved earthing device, after proving dead. They are listed on the PTW, and any additional earths are applied later at the point of work.

18. Portable earthing equipment used for HV circuit main earths must be:

  • A. Made of the thinnest flexible wire available
  • B. Insulated only, with no conductor
  • C. Rated to carry the prospective fault current of the system for the specified time
  • D. Connected to the conductors before the earth point
Answer: C — Rated to carry the prospective fault current of the system for the specified time
If the circuit is accidentally energised, earthing leads must carry the full fault current until protection operates. Undersized leads could melt or explode, so equipment rated for the system's fault level is required.

19. During an HV laboratory demonstration, corona is observed at a sharp conductor edge before complete breakdown. This happens because:

  • A. The voltage is DC only
  • B. The local electric field at the edge exceeds the ionisation strength of air while the average gap field is lower
  • C. The conductor is cold
  • D. The air pressure is very high
Answer: B — The local electric field at the edge exceeds the ionisation strength of air while the average gap field is lower
At sharp points the field is strongly enhanced. Air ionises locally, producing corona glow and noise, while the rest of the gap still withstands the voltage. Increasing voltage further causes full breakdown.

20. In a ship's power management system, 'heavy consumer start request' logic is used to:

  • A. Prevent any motor from starting at sea
  • B. Trip the bow thruster when the main engine is running
  • C. Check that sufficient spare generator capacity is available, starting another generator if necessary, before a large motor is allowed to start
  • D. Start all generators whenever a fan starts
Answer: C — Check that sufficient spare generator capacity is available, starting another generator if necessary, before a large motor is allowed to start
Before starting a large load such as a bow thruster or cargo pump, the PMS verifies available power. If capacity is insufficient, it starts and connects another generator first, preventing overload and blackout.

21. Preferential tripping in a ship's electrical system is designed to:

  • A. Disconnect non-essential loads in stages when generators are overloaded
  • B. Increase generator speed
  • C. Trip essential services such as steering gear first
  • D. Synchronise incoming generators
Answer: A — Disconnect non-essential loads in stages when generators are overloaded
When a generator approaches overload, preferential trips shed non-essential consumers such as galley and air conditioning loads. This keeps essential services and generators online, avoiding blackout.

22. Following a blackout on a ship with PMS, the automatic sequence typically includes:

  • A. Automatic start of standby generator(s), closing on to the dead bus, and sequential restart of essential consumers
  • B. Opening of all generator breakers permanently
  • C. Starting the emergency generator only, with no further action
  • D. Manual start of all motors at once
Answer: A — Automatic start of standby generator(s), closing on to the dead bus, and sequential restart of essential consumers
The PMS starts standby generators and closes the first available one on to the dead busbar. Essential motors are then restarted in sequence to avoid excessive simultaneous starting current.

23. Which instrument on an HV switchboard continuously monitors insulation level on an insulated system and alarms on low insulation?

  • A. A kilowatt-hour meter
  • B. A synchroscope
  • C. A tachometer
  • D. An insulation monitoring device (earth fault monitor)
Answer: D — An insulation monitoring device (earth fault monitor)
On insulated or high-resistance earthed systems, an insulation monitoring or earth fault indication device continuously checks insulation to earth. It alarms when insulation falls, so faults can be located before a second fault occurs.

24. Capacitive voltage detecting systems (VDS) fitted on HV switchgear panels are used to:

  • A. Measure motor speed
  • B. Trip the breaker on overcurrent
  • C. Measure insulation resistance
  • D. Indicate the presence or absence of voltage on each phase without opening the compartment
Answer: D — Indicate the presence or absence of voltage on each phase without opening the compartment
Capacitive VDS indicators coupled to the busbar or cable bushings show voltage presence per phase. They allow a check before earthing, though the indicator itself must be proven with a suitable test device.

25. The load-dependent start/stop function of a PMS works by:

  • A. Running all generators at all times
  • B. Starting a further generator when load exceeds a set percentage and stopping one when load falls below a set level for a time
  • C. Stopping all generators at night
  • D. Varying the frequency to 40 Hz at low load
Answer: B — Starting a further generator when load exceeds a set percentage and stopping one when load falls below a set level for a time
Load-dependent start and stop optimises the number of generators on line. Time delays and hysteresis prevent hunting, keeping generators reasonably loaded and with spare capacity for sudden load increases.

26. In a metal-clad HV switchboard, each panel is divided into separate earthed metal compartments for:

  • A. Busbars, circuit breaker, cable termination and LV control equipment
  • B. Ventilation fans only
  • C. Only the control equipment
  • D. Spare parts storage
Answer: A — Busbars, circuit breaker, cable termination and LV control equipment
Metal partitions between compartments confine faults and arcs and allow safe access to one compartment while others remain live. The LV compartment is separated so control work can be done without exposure to HV parts.

27. HV switchgear is often tested for internal arc classification (IAC) according to IEC 62271-200 to demonstrate that:

  • A. The breaker can interrupt 100 kA
  • B. It is watertight
  • C. It can be operated without interlocks
  • D. Persons in front of or around the switchgear are protected from the effects of an internal arc
Answer: D — Persons in front of or around the switchgear are protected from the effects of an internal arc
IAC testing confirms that hot gases and debris from an internal arc are vented safely, for example through pressure relief flaps, and that covers and doors remain closed. It defines accessibility types for operator protection.

28. Access to HV switchboard rooms and HV equipment spaces on board should be:

  • A. Restricted only during port stay
  • B. Open to all crew for ventilation
  • C. Controlled by the galley staff
  • D. Restricted to authorised persons, with doors kept locked and warning signs posted
Answer: D — Restricted to authorised persons, with doors kept locked and warning signs posted
HV spaces are kept locked with keys under the control of the Chief Engineer or Authorised Person. Clear warning signs and access control prevent untrained persons coming into contact with HV hazards.

29. Why are HV switchboard operations increasingly performed remotely from a control room or with a remote racking device?

  • A. Because local controls are not permitted by SOLAS
  • B. To save electrical power
  • C. To keep the operator at a distance from the switchgear in case of an arc flash
  • D. To speed up synchronising
Answer: C — To keep the operator at a distance from the switchgear in case of an arc flash
Most arc flash injuries occur during switching or racking close to equipment. Remote operation keeps the operator outside the arc flash boundary, which is why the course stresses carrying out HV operations from a safe distance.

30. Pressure relief flaps or ducts on top of HV switchgear panels are provided to:

  • A. Drain condensation
  • B. Admit cooling air
  • C. Release the high-pressure hot gases of an internal arc in a controlled direction away from personnel
  • D. Allow inspection of busbars
Answer: C — Release the high-pressure hot gases of an internal arc in a controlled direction away from personnel
An internal arc causes a rapid pressure rise. Relief flaps open to direct the gases upward or into ducts, preventing the doors bursting open towards personnel standing in front of the panel.

31. A crew member has received an HV electric shock and is unconscious and not breathing normally after being freed from the supply. The immediate action is to:

  • A. Apply ice to the chest
  • B. Call for help, start CPR (30 compressions to 2 breaths) and use an AED as soon as available
  • C. Give water to drink
  • D. Wait for him to recover on his own
Answer: B — Call for help, start CPR (30 compressions to 2 breaths) and use an AED as soon as available
Electric shock commonly causes cardiac arrest from ventricular fibrillation. Current guidance is immediate CPR at 30:2 with compressions of 5-6 cm at 100-120 per minute and early defibrillation with an AED.

32. Electrical burns from an arc flash should be first treated by:

  • A. Cooling with cool running water for about 20 minutes and covering loosely with cling film or a sterile dressing
  • B. Applying butter or oil
  • C. Bursting any blisters
  • D. Rubbing with ice
Answer: A — Cooling with cool running water for about 20 minutes and covering loosely with cling film or a sterile dressing
Current first-aid guidance is to cool burns with cool running water for 20 minutes, remove constricting items, and cover loosely. Ice, creams or bursting blisters worsen injury. HV burns may hide deep tissue damage, so medical advice is essential.

33. In a case study, an HV breaker was closed while portable earths were still connected at the work site, causing a violent arc flash. The key lesson is that:

  • A. Breakers should be closed slowly
  • B. Only the Master may close breakers
  • C. Earths should never be used
  • D. All earths must be removed and accounted for under formal clearance before re-energisation
Answer: D — All earths must be removed and accounted for under formal clearance before re-energisation
Closing onto applied earths creates a bolted three-phase fault. Recording every earth on the permit, removing all additional earths at clearance and following the restoration programme prevents this type of accident.

34. Why must even a person who appears to have recovered from an HV electric shock be referred for medical assessment?

  • A. It is required to obtain a new CoC
  • B. Internal burns and cardiac rhythm disturbances may develop or remain hidden
  • C. The shock may have changed their blood group
  • D. They will need new PPE
Answer: B — Internal burns and cardiac rhythm disturbances may develop or remain hidden
HV current passing through the body can cause deep tissue damage along its path and delayed heart arrhythmias. Visible injuries may be small, so medical evaluation and observation are needed.

35. An arc flash incident occurs in the HV switchroom. Which action should be taken first by the responding engineer?

  • A. Rush in immediately without PPE
  • B. Use water to cool the switchboard
  • C. Isolate the supply from a safe location and raise the alarm before entering
  • D. Open the faulty panel door to inspect
Answer: C — Isolate the supply from a safe location and raise the alarm before entering
Rescuers must not become victims. The supply is isolated remotely or from upstream breakers, the alarm is raised and appropriate PPE and fire-fighting means are prepared before entering the space.

36. Under HV safety rules, 'live working' on HV conductors on board ships is:

  • A. Permitted with rubber gloves only
  • B. Permitted for voltages up to 11 kV
  • C. Not permitted; HV equipment must be made dead, isolated and earthed before work
  • D. Permitted if the Master agrees
Answer: C — Not permitted; HV equipment must be made dead, isolated and earthed before work
Shipboard HV safety codes require that no work be done on or near exposed HV conductors unless they are dead, isolated, proved dead and earthed under a Permit to Work. Live testing is carried out only under strict procedures.

37. When proving an HV circuit dead, the test should be carried out:

  • A. Only at the switchboard, not at the point of work
  • B. Only on the neutral
  • C. On one phase only
  • D. On all phases at the point of work, after checking the detector on a known live source
Answer: D — On all phases at the point of work, after checking the detector on a known live source
Each phase may be fed differently or have induced voltage, so all phases must be tested. Testing at the point of work confirms the specific equipment is dead, with the detector proved before and after.

38. A Competent Person (HV) in shipboard HV safety rules is a person who:

  • A. Is any crew member on board
  • B. Is authorised to issue all safety documents
  • C. Has sufficient technical knowledge and experience to avoid danger and may receive safety documents and carry out work under them
  • D. Is responsible only for fire-fighting
Answer: C — Has sufficient technical knowledge and experience to avoid danger and may receive safety documents and carry out work under them
The Competent Person is trained and experienced enough to work safely on the isolated equipment and to lead a work party. The Authorised Person, formally appointed, issues and cancels safety documents.

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