Electrical, Electronic and Control Engineering
What this domain tests
The electrical domain covers generation and distribution, protection, motors and starters, automation and alarms, UPS, and safe working practice. The chief engineer is examined on paralleling generators, load sharing, blackout prevention and recovery, and on how automation fails in ways that endanger the plant.
Core rules and concepts
- Generation and distribution. Three-phase AC at 380/440 V, 50/60 Hz; main switchboard, bus ties, essential and emergency switchboards; the emergency generator is independent and must supply designated services, tested regularly and on load.
- Paralleling and load sharing. Synchronise on voltage, frequency and phase; adjust governor speed for kW and excitation for kVAr; the reverse power relay protects the prime mover, the overcurrent relay the alternator and cables.
- Protection. Discrimination between protective devices so a fault trips the smallest affected circuit; earth faults on an insulated system are alarmed and located, not left.
- Motors and starters. Direct-on-line, star-delta, soft starter, VFD; overload relay setting matched to the motor, single phasing consequences, insulation resistance testing (typically ≥1 MΩ at 500 V for a 440 V motor, per maker's guidance) and the necessity to disconnect and isolate before testing.
- Automation. Programmable controllers, sensors, alarm and monitoring system, dead-man and safety interlocks; bypassing an interlock requires the master's or chief engineer's authorisation and a documented risk assessment.
- Blackout recovery. Emergency generator start, emergency switchboard energised, main generator restoration, sequential restart of auxiliaries, steering gear restored as a priority. Know the automatic start time of the emergency generator.
- Safe practice. Lock-out/tag-out, arc flash awareness, no work on live equipment without authorisation, insulated tools, correct PPE, and the permit to work.
Worked example
Two generators are running; the kW share differs by 20% while frequency is correct. Reasoning: frequency is common, so voltage and excitation are not the problem; the governor droop or the load-sharing signal is. Action: adjust the speed droop setting, check the load-sharing line and the electronic governor feedback, and rebalance. Scoring answers show that kW is governed by the prime mover and kVAr by excitation.
Traps that cost marks
- Adjusting excitation to change kW.
- Forgetting reverse power protection when a prime mover loses fuel.
- Testing insulation resistance without isolation.
- Leaving an interlock bypassed without documentation.
- Not mentioning steering gear priority after blackout.