SOPD Emergency Procedures 3 — Questions and Answers
Question 1: When executing a controlled system separation to prevent cascading failures, the operator should separate the system along boundaries that:
- Achieve near-equal load-generation balance in each island (Correct answer)
- Maximize the number of generation units in the largest island
- Minimize transmission distance between separated sections
- Prioritize keeping industrial loads energized over residential loads
Correct answer: Achieve near-equal load-generation balance in each island
System separation points should be chosen to create islands where generation and load are closely balanced to prevent immediate collapse of either island.
Question 2: An operator receives a 'loss of field' alarm on a large synchronous generator. What is the immediate risk to the power system?
- The unit may absorb reactive power and cause voltage depression (Correct answer)
- The unit will immediately trip and cause a frequency decline
- The unit will overspeed and damage the turbine
- The unit will inject excessive reactive power causing overvoltage
Correct answer: The unit may absorb reactive power and cause voltage depression
A loss-of-field condition causes the generator to operate as an induction generator, absorbing VArs from the system and depressing local voltage.
Question 3: During a major blackout restoration, why must operators restore load incrementally rather than all at once?
- Cold load pickup causes high inrush currents that can overload equipment and trip lines (Correct answer)
- Regulatory rules require incremental restoration to document each step
- Generators cannot produce full output immediately after a blackout
- Customer billing systems require load to be restored sequentially
Correct answer: Cold load pickup causes high inrush currents that can overload equipment and trip lines
Cold load pickup—the surge of inrush current when de-energized load is reconnected—can exceed equipment ratings and cause additional protective relay trips.
Question 4: What is 'load shedding' as used in bulk power system emergency operations?
- Deliberately disconnecting blocks of customer load to balance generation with demand (Correct answer)
- Transferring load from one feeder to another to reduce congestion
- Reducing generator output to match reduced customer demand
- Curtailing interruptible wholesale contracts ahead of retail customers
Correct answer: Deliberately disconnecting blocks of customer load to balance generation with demand
Load shedding is the intentional disconnection of customer load to prevent total system collapse when generation cannot meet demand.
Question 5: A system operator observes that real power flows on several transmission lines are approaching emergency ratings. What is the MOST appropriate immediate action?
- Re-dispatch generation to relieve the overloaded lines before ratings are exceeded (Correct answer)
- Wait for the thermal protection relays to trip the overloaded lines automatically
- Notify customers on those lines to voluntarily reduce consumption
- File an incident report and continue monitoring
Correct answer: Re-dispatch generation to relieve the overloaded lines before ratings are exceeded
Re-dispatching generation to shift power flows away from overloaded lines is the correct proactive response before thermal limits are exceeded.
Question 6: Under what condition should an operator use the 'last resort' authority to shed firm load without prior authorization?
- When the system is in imminent danger of total collapse and there is no time to obtain approval (Correct answer)
- When more than 10% of scheduled generation is unavailable
- When the reliability coordinator requests a feasibility analysis
- When interruptible load contracts have not been fully curtailed
Correct answer: When the system is in imminent danger of total collapse and there is no time to obtain approval
NERC standards grant operators last-resort authority to shed firm load immediately when system collapse is imminent and delay would make the situation irreversible.
Question 7: After a successful system restoration from a blackout, what is a key post-event responsibility for the system operator?
- Document all actions taken and conduct a cause analysis to prevent recurrence (Correct answer)
- Immediately transfer control to the day-shift operator regardless of time
- Restart all previously tripped generators simultaneously to minimize restoration time
- Issue a public press release about the restoration timeline
Correct answer: Document all actions taken and conduct a cause analysis to prevent recurrence
NERC and internal procedures require thorough documentation and post-event analysis to identify root causes and prevent future occurrences.
SOPD Emergency Procedures 3
When executing a controlled system separation to prevent cascading failures, the operator should separate the system along boundaries that: