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HV exit exam questions and answers — Set 2 — High Voltage Safety Officer & Switchgear Operations

Set 2 of the High Voltage Safety Officer & Switchgear Operations (HV) exit exam bank — 30 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 2 — 30 HV exit exam questions with answers

1. What safety enclosure rating (IP Rating) is required for High Voltage marine switchboard cubicles?

  • A. IP00
  • B. IP10
  • C. No rating
  • D. IP2X minimum (protection against touch) up to IP44/IP54 for splash protection
Answer: D — IP2X minimum (protection against touch) up to IP44/IP54 for splash protection
IP ratings prevent accidental tool or finger contact with live HV busbars.

2. What is the function of a High Voltage bus tie breaker?

  • A. Ties ropes
  • B. Connects or isolates two separate HV busbar sections for operational flexibility and redundancy
  • C. Connects battery charger
  • D. Regulates water
Answer: B — Connects or isolates two separate HV busbar sections for operational flexibility and redundancy
Bus tie breakers allow split-busbar operation so a fault on one side does not shut down the entire ship.

3. What device measures temperature continuously inside HV motor or generator stator windings?

  • A. Pressure gauge
  • B. Glass thermometer
  • C. Resistance Temperature Detectors (RTD - PT100) or Thermocouples
  • D. Hydrometer
Answer: C — Resistance Temperature Detectors (RTD - PT100) or Thermocouples
Embedded PT100 RTDs trigger alarm and trip signals if winding insulation temperature exceeds limits.

4. What procedure is followed during Sanction to Test on High Voltage equipment?

  • A. Temporarily remove safety earths under strict control to perform insulation or hi-pot testing, then re-earth
  • B. Remove warning signs
  • C. Turn on generator full load
  • D. Cancel permit
Answer: A — Temporarily remove safety earths under strict control to perform insulation or hi-pot testing, then re-earth
Sanction to Test allows controlled temporary removal of earths for insulation diagnostics.

5. What is High Potential (Hi-Pot) dielectric testing on HV cables?

  • A. Testing battery with bulb
  • B. Applying elevated DC/AC voltage (e.g. 2x rated voltage) to verify cable dielectric withstand strength
  • C. Measuring length
  • D. Checking cable color
Answer: B — Applying elevated DC/AC voltage (e.g. 2x rated voltage) to verify cable dielectric withstand strength
Hi-Pot testing proves that cable insulation can withstand over-voltage surges without breakdown.

6. What is the function of a surge arrestor connected to HV generator terminals?

  • A. Cool generator
  • B. Reduce noise
  • C. Divert high-voltage switching surges and lightning spikes safely to ground
  • D. Increase generator power
Answer: C — Divert high-voltage switching surges and lightning spikes safely to ground
Surge arrestors clamp fast transient voltage spikes, protecting expensive stator insulation.

7. What risk occurs if an HV circuit breaker is closed into a solid phase-to-phase short circuit fault?

  • A. Massive fault current flows; instantaneous overcurrent relays must trip breaker within cycles
  • B. Heats up slowly over hours
  • C. Voltage increases smoothly
  • D. Speed increases
Answer: A — Massive fault current flows; instantaneous overcurrent relays must trip breaker within cycles
Fault currents reach tens of thousands of Amperes; fast electromagnetic tripping clears the short circuit instantly.

8. What safety floor matting must be placed in front of marine High Voltage switchboards?

  • A. Aluminum plate
  • B. Steel mesh mat
  • C. Wet cloth rag
  • D. Tested dielectric insulating rubber matting (rated for operating voltage, e.g. 15 kV - 30 kV rating)
Answer: D — Tested dielectric insulating rubber matting (rated for operating voltage, e.g. 15 kV - 30 kV rating)
Certified insulating rubber mats provide secondary shock protection for operators standing at switchboards.

9. What type of fire extinguisher is mandatory near High Voltage switchboard rooms?

  • A. Foam pipe
  • B. Water jet
  • C. Carbon Dioxide (CO2) or Clean Agent non-conducting gas extinguishers
  • D. Saltwater hose
Answer: C — Carbon Dioxide (CO2) or Clean Agent non-conducting gas extinguishers
CO2 and clean gas agents extinguish electrical fires without leaving conductive or corrosive residue.

10. Who keeps primary key to safety padlocks securing an HV isolation point under a Permit to Work?

  • A. Messman
  • B. Anyone on deck
  • C. Pilot
  • D. The High Voltage Authorised Person (HVAP) / Person in Charge of work
Answer: D — The High Voltage Authorised Person (HVAP) / Person in Charge of work
Key control ensures no unauthorized person can remove padlocks or re-energize equipment during maintenance.

11. What is the function of a zero-sequence current transformer (ZSCT) in core-balance earth fault protection?

  • A. Control temp
  • B. Measure RPM
  • C. Detect vector sum of 3-phase currents; any non-zero value indicates earth leakage current
  • D. Measure battery
Answer: C — Detect vector sum of 3-phase currents; any non-zero value indicates earth leakage current
ZSCTs enclose all three phase cables; balanced current sums to zero, whereas earth leakage produces unbalance output.

12. What is the effect of harmonics generated by large High Voltage variable frequency drives (VFD)?

  • A. Cleans contacts
  • B. Reduces cable size
  • C. Increases efficiency 50%
  • D. Voltage waveform distortion, overheating of transformers/generators, and electronic interference
Answer: D — Voltage waveform distortion, overheating of transformers/generators, and electronic interference
VFD switching generates high-frequency harmonic currents requiring active/passive harmonic filters.

13. What maintenance step is required before cleaning HV switchboard busbar compartments?

  • A. Complete isolation, prove dead, apply portable earths, post warning signs, and issue HV PTW
  • B. Spray solvent live
  • C. Blow compressed air live
  • D. Wipe live with damp cloth
Answer: A — Complete isolation, prove dead, apply portable earths, post warning signs, and issue HV PTW
Busbar compartments MUST be totally de-energized, tested dead, earthed, and permitted before opening panels.

14. What is the function of an Automatic Voltage Regulator (AVR) on an HV generator?

  • A. Control generator field excitation to maintain steady terminal voltage under changing load
  • B. Measure oil pressure
  • C. Cool bearings
  • D. Control engine RPM
Answer: A — Control generator field excitation to maintain steady terminal voltage under changing load
AVRs adjust rotor field current to keep generated voltage stable despite load swings.

15. What is the purpose of an anti-condensation heater fitted inside HV electric motors and switchboards?

  • A. Heat engine room
  • B. Warm lube oil
  • C. Dry clothes
  • D. Maintain internal temperature slightly above ambient when stopped to prevent moisture condensation
Answer: D — Maintain internal temperature slightly above ambient when stopped to prevent moisture condensation
Anti-condensation space heaters energize automatically when equipment stops, keeping internal air dry.

16. What safety precaution must be observed when using a high voltage test probe to prove equipment dead?

  • A. Use low voltage light
  • B. Test probe on known live source FIRST, test target equipment, then re-test probe on known live source ('Live-Dead-Live' test)
  • C. Test on table
  • D. Assume indicator works
Answer: B — Test probe on known live source FIRST, test target equipment, then re-test probe on known live source ('Live-Dead-Live' test)
The 'Live-Dead-Live' protocol proves the voltage detector itself was working before and after the test.

17. What device trips an HV transformer if gas accumulation or oil surge occurs due to internal fault?

  • A. Speed governor
  • B. Thermocouple
  • C. Buchholz Relay
  • D. Reverse power relay
Answer: C — Buchholz Relay
Buchholz relays mounted on oil-immersed transformers detect internal arcing gas bubbles and oil surges.

18. What is the purpose of Lockout / Tagout (LOTO) padlocks on HV isolators?

  • A. Prevent theft
  • B. Hold door open
  • C. Decorate panel
  • D. Physically lock isolator handles in OPEN/OFF position with warning tags so no one can re-energize circuit
Answer: D — Physically lock isolator handles in OPEN/OFF position with warning tags so no one can re-energize circuit
LOTO padlocks prevent accidental or unauthorized re-closure of isolation switches.

19. What action must be taken immediately if a colleague contacts a High Voltage live conductor and collapses?

  • A. Throw water
  • B. Grab victim's arm bare hands
  • C. Run away
  • D. DO NOT touch victim directly; isolate HV power source immediately or use certified HV insulating rescue hook to pull victim away, then call emergency CPR
Answer: D — DO NOT touch victim directly; isolate HV power source immediately or use certified HV insulating rescue hook to pull victim away, then call emergency CPR
Touching an HV casualty before isolating power turns the rescuer into a second high-voltage casualty.

20. Who has overall responsibility for enforcing High Voltage safety management systems on board?

  • A. Ship cook
  • B. Port Agent
  • C. Shore electrician
  • D. The Chief Engineer and Ship's Master
Answer: D — The Chief Engineer and Ship's Master
The Chief Engineer leads technical HV management while the Master maintains overall safety responsibility.

21. Which document contains the shipyard's description of operations regarding the vessel's High Voltage (HV) equipment?

  • A. Preliminary operation manual
  • B. High voltage operation manual
  • C. Performance manual
  • D. Equipment manual
Answer: A — Preliminary operation manual
The Preliminary Operation Manual supplied by the shipyard provides the initial operational philosophy, system architecture, and operating parameters for the vessel's high-voltage equipment.

22. A low voltage protection circuit is used in electric motor starting equipment to:

  • A. Trip circuit contactor when the motor over-speeds due to low voltage
  • B. Trip circuit contactor when the motor develops short circuit due to low voltage
  • C. Allow the motor to restart automatically on restoration of voltage without manual resetting
  • D. Prevent motor from restarting automatically upon restoration of supply voltage
Answer: D — Prevent motor from restarting automatically upon restoration of supply voltage
Under-voltage (low voltage) protection prevents unexpected automatic restarting of motors upon voltage restoration, which protects personnel from mechanical injury and the electrical network from excessive starting surges.

23. In air blast circuit breakers, the compressed air pressure used for arc quenching is in the order of:

  • A. 100 mm Hg
  • B. 1 kg/cm²
  • C. 20 to 30 kg/cm²
  • D. 200 to 300 kg/cm²
Answer: C — 20 to 30 kg/cm²
Air blast circuit breakers (ABCB) utilize high-pressure dry air at approximately 20 to 30 kg/cm² (2 to 3 MPa / 20 to 30 bar) directed across the contacts to rapidly cool and deionize the arc.

24. What is the primary means by which an electrical maintenance worker is protected from electrical hazards while performing work on an electrical circuit?

  • A. Shutting down the necessary equipment only
  • B. Using personal protective equipment (PPE) alone
  • C. Posting safety warning signs
  • D. Performing a lockout / tagout (LOTO) and grounding procedure
Answer: D — Performing a lockout / tagout (LOTO) and grounding procedure
Lockout/Tagout (LOTO) coupled with proving dead and applying safety earths provides positive isolation, preventing accidental re-energization of circuits during maintenance.

25. What is the Polarisation Index (PI) in insulation resistance testing?

  • A. Ratio of 10-minute insulation resistance to 1-minute insulation resistance
  • B. Ratio of 1-minute insulation resistance to 10-minute insulation resistance
  • C. Ratio of 5-minute insulation resistance to 25-minute insulation resistance
  • D. Ratio of test voltage to leakage current after 1 minute
Answer: A — Ratio of 10-minute insulation resistance to 1-minute insulation resistance
Polarisation Index (PI) is defined as the ratio of insulation resistance measured at 10 minutes to the insulation resistance measured at 1 minute (R10 / R1). A PI value above 2.0 indicates clean, dry insulation.

26. The direction of mechanical force experienced by a current-carrying conductor placed in a magnetic field is determined by:

  • A. Fleming's left-hand rule
  • B. Fleming's right-hand rule
  • C. Helix rule
  • D. Corkscrew rule
Answer: A — Fleming's left-hand rule
Fleming's left-hand rule is used for electric motors and determining mechanical force on a conductor (Thumb = Force/Motion, Forefinger = Field, Middle finger = Current).

27. Which of the following insulating media can be used in sphere gaps and high-voltage test setups?

  • A. Liquid insulation (e.g., transformer oil)
  • B. Solid insulation (e.g., polyester, resin-bonded paper)
  • C. Gas insulation (e.g., SF6, N2, CO2, CCl2F2)
  • D. Any of the above
Answer: D — Any of the above
High voltage insulation testing and arc gaps can employ gaseous (air, SF6, N2), liquid (dielectric mineral oils), or solid insulating barriers depending on application requirements.

28. Cartridge and rewireable fuse protection in general distribution circuits is typically used for continuous current ratings up to:

  • A. 10 A
  • B. 20 A
  • C. 50 A
  • D. 100 A
Answer: D — 100 A
Standard general-purpose distribution rewireable/cartridge fuse holders are commonly rated up to 100 A, beyond which High Rupturing Capacity (HRC) bolted fuses or circuit breakers are preferred.

29. Which of the following circuit breakers provides high operating reliability and minimal maintenance requirements?

  • A. Air blast circuit breaker
  • B. SF6 gas circuit breaker
  • C. Vacuum circuit breaker
  • D. Bulk oil circuit breaker
Answer: B — SF6 gas circuit breaker
Sulphur Hexafluoride (SF6) circuit breakers operate in a sealed, non-corrosive environment with high dielectric regeneration, resulting in minimal contact erosion and extended maintenance intervals.

30. Which type of work procedure involves electrical installations that are completely de-energized, isolated, proven dead, and earthed?

  • A. Live working
  • B. Dead working
  • C. Working in the vicinity of live parts
  • D. Hot line working
Answer: B — Dead working
Dead working is defined as work carried out on electrical equipment or installations that are isolated from all sources of supply, proven dead, locked out, and earthed.

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