NERC NERC Protection and Control Systems 2 — Questions and Answers
Question 1: What is a 'misoperation' in the context of NERC protection system standards?
- A relay that operates correctly to clear a fault
- Any unintended operation or failure to operate of a protection system (Correct answer)
- A manual trip of a breaker by an operator
- A scheduled maintenance outage of a relay
Correct answer: Any unintended operation or failure to operate of a protection system
A misoperation is any protection system operation or failure to operate that does not match the intended design, including false trips or failure to trip during a fault.
Question 2: Under NERC PRC-004, what must entities do when a protection system misoperation is identified?
- Immediately deactivate the relay until corrected
- Analyze the misoperation, identify the cause, and implement corrective actions (Correct answer)
- Report the misoperation to FERC within 24 hours
- Notify all neighboring transmission operators
Correct answer: Analyze the misoperation, identify the cause, and implement corrective actions
PRC-004 requires entities to analyze each misoperation within 120 days, determine the cause, and implement corrective actions to prevent recurrence.
Question 3: Which NERC standard requires generator owners to verify that generator protection systems coordinate with system protection?
- PRC-019
- PRC-024 (Correct answer)
- PRC-025
- PRC-027
Correct answer: PRC-024
PRC-024 requires generator owners to ensure that generator protective relay settings allow generators to remain online during specified voltage and frequency excursions.
Question 4: What is the primary concern addressed by NERC standard PRC-025?
- Transformer differential protection settings
- Load-responsive generator and motor protection relay settings to prevent unnecessary tripping (Correct answer)
- Sub-synchronous resonance protection
- Automatic transfer scheme coordination
Correct answer: Load-responsive generator and motor protection relay settings to prevent unnecessary tripping
PRC-025 requires that generator and motor protection relays be set so they do not operate in response to load changes that do not represent a fault condition.
Question 5: How does NERC define the 'Protection System' for purposes of PRC-005?
- Only the protective relay itself
- Protective relays, communications, voltage and current sensing devices, DC supply, and the control circuitry (Correct answer)
- The circuit breaker and associated disconnect switches only
- The SCADA system used to monitor relay status
Correct answer: Protective relays, communications, voltage and current sensing devices, DC supply, and the control circuitry
NERC's definition of Protection System includes relays, communications, sensing devices, DC supply (batteries and chargers), and all associated control circuitry.
Question 6: Under NERC standards, what is the significance of the 'N-1 contingency' in protection system design?
- The system must remain stable after any single protection system component fails
- The system must clear any single fault within 6 cycles
- The system must tolerate loss of any single transmission element (Correct answer)
- The system must have N minus 1 spare relays in inventory
Correct answer: The system must tolerate loss of any single transmission element
N-1 contingency means the bulk electric system must remain stable and within thermal, voltage, and stability limits following the loss of any single transmission element.
NERC NERC Protection and Control Systems 2
What is a 'misoperation' in the context of NERC protection system standards?