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NERC Transmission Operator Exam ACTUAL EXAM
COMPLETE QUESTIONS AND CORRECT ANSWERS LATEST
UPDATE THIS YEAR
SUMMARIZED EXAM COVERAGE: NERC TRANSMISSION OPERATOR (TO)
Exam Domains
I. Resource and Demand Balancing (≈ 16-18 questions)
• Interchange Scheduling & Coordination (e-Tag, Interchange Confirmation, Point of
Receipt/Delivery)
• Operating Reserves: Spinning, Non-Spinning, Regulation, Contingency
• Automatic Generation Control (AGC), Area Control Error (ACE), Frequency Bias, Flat Tie-Line
Control
• Load Forecasting (Next-day, Real-time), Generation Equipment (ramp rates, min/max limits,
AVRs, governors)
• Balancing Authority Area (BAA) operations, inadvertent interchange, payback
II. Transmission (≈ 28-30 questions) – HEAVIEST SECTION
• Protection & Control: Zones of protection, relay types (overcurrent, distance, differential,
reclosing), breaker failure, Special Protection Systems (SPS)/Remedial Action Schemes (RAS)
• Voltage & Reactive: Voltage schedules, reactive resources (capacitors, reactors, SVCs,
STATCOMs, generator var limits), Excitation systems, transformer LTCs, tap changers
• Electrical Current: Thermal limits, line ratings (Normal, Emergency, Seasonal), dynamic ratings
• Reconfiguration & Switching: Switch types (air break, oil, vacuum, SF6, load break), grounding
(personal protective grounds, system grounding), tagging, clearance procedures
• Operating Limits: System Operating Limits (SOLs), Interconnection Reliability Operating Limits
(IROLs), Available Transfer Capability (ATC), Total Transfer Capability (TTC)
• Transmission Equipment: Lines, transformers, series capacitors, phase shifters, circuit breakers,
disconnect switches
III. Emergency Preparedness (≈ 8-10 questions)
• Current-Day & Next-Day Planning: Resource adequacy, capacity deficiency, Transmission
Loading Relief (TLR)
• Severe Weather, Natural Disasters, Geomagnetic Disturbances (GMD), Solar Storms
• Anticipated Capacity Deficiency: Energy Emergency Alerts (EEA Levels 1-3), load shed
procedures
IV. Emergency Response (≈ 20-22 questions)
• System Restoration: Blackstart resources, restoration plans, cranking paths, load pickup,
synchronization
• Response to System Disturbances: Separation (islanding), frequency excursions (Underfrequency
Load Shed - UFLS, Under/Over voltage), total blackout
• Response to Capacity Emergencies: Manual load shed, voltage reduction, public appeals
• Loss of Control Center: Remote operations, backup control centers
• Loss of Analysis & Monitoring Tools: EMS/SCADA failure backup procedures
V. Contingency Analysis & Reliability (≈ 12-14 questions)
• Contingency Analysis: N-1, N-2 contingencies (loss of line, generator, transformer, bus), single
pole vs. 3-pole
• Network Analysis Tools: State Estimator, Power Flow, Real-time Contingency Analysis (RTCA)
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• Response to Analysis Results: SOL/IROL violations, nomograms, operator actions prior to next
contingency
• System Operating Limits (SOLs): Pre-contingency handling, post-contingency expectations
• Interconnection Reliability Operating Limits (IROLs): Must be protected within 30 minutes (15
for primary IROL)
• Reliability Coordinator (RC) role, BA-TO-RC coordination
VI. Communications & Data (≈ 10-12 questions)
• Reporting Requirements: NERC alerts, CEII (Critical Energy Infrastructure Information), reports
to RC
• Communication Methods: Three-Part Communication (Read back / Repeat back), RCIS
(Reliability Coordinator Information System), telephone protocols
• Data Validity & Verification: SCADA data quality, bad data detection, telemetry failure, manual
backup
• Telemetry & Communications Equipment: RTUs, satellite phones, microwave, fiber, redundancy
Below are 250 random, scenario-based multiple-choice questions covering all TO Exam Knowledge
Areas, with answers and concise rationales.
Q1. A Transmission Operator notices the Area Control Error (ACE) is consistently positive for 15 minutes.
What does this indicate?
A) Generation is less than load, and frequency is low
B) Generation exceeds load, and frequency is high
C) Interchange schedule is exactly met
D) ACE cannot be calculated due to telemetry failure
Answer: B
Rationale: Positive ACE means actual net interchange (NIa) is less than scheduled (NIs) OR generation >
load → ACE positive; generation > load causes frequency > 60 Hz .
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Q2. An operator receives an Interchange e-Tag that has been "Confirmed" but not yet "Implemented."
What is the operator's next action?
A) Approve the Interchange at the scheduled time
B) Reject the e-Tag because it is too late
C) Begin ramping generation to match the schedule immediately
D) Wait for the Reliability Coordinator to approve
Answer: A
Rationale: e-Tag status proceeds: Proposed → Approved → Confirmed → Implemented. The
Transmission Operator/Balancing Authority must Implement at the scheduled start time .
Q3. A transmission line is protected by a permissive over-reaching transfer trip (POTT) scheme. This
scheme requires:
A) The relay to trip instantaneously without communication
B) Communication between line terminals to allow tripping for internal faults
C) One terminal to trip and the other to block automatically
D) Reclosing after 30 seconds only
Answer: B
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Rationale: POTT schemes use communication channels (pilot) to send a permissive trip signal to the
remote terminal when a fault is detected within the zone. Tripping occurs only if the remote relay also
detects the fault and sends permission.
Q4. A Balancing Authority reports a frequency of 59.92 Hz. Which of the following should the
Transmission Operator expect?
A) Generators are automatically increasing output via governor response and AGC
B) Underfrequency load shedding (UFLS) has already activated
C) All tie lines are open
D) Frequency will recover without any action
Answer: A
Rationale: At 59.92 Hz, frequency is low; generators with governors will automatically increase real
power output (droop response). AGC will also adjust base points. UFLS typically begins at 59.5 Hz or
lower .
Q5. The term "N-1 contingency" refers to:
A) Loss of a single Bulk Electric System element
B) Loss of one entire Balancing Authority area
NERC Transmission Operator Exam ACTUAL EXAM
COMPLETE QUESTIONS AND CORRECT ANSWERS LATEST
UPDATE THIS YEAR
SUMMARIZED EXAM COVERAGE: NERC TRANSMISSION OPERATOR (TO)
Exam Domains
I. Resource and Demand Balancing (≈ 16-18 questions)
• Interchange Scheduling & Coordination (e-Tag, Interchange Confirmation, Point of
Receipt/Delivery)
• Operating Reserves: Spinning, Non-Spinning, Regulation, Contingency
• Automatic Generation Control (AGC), Area Control Error (ACE), Frequency Bias, Flat Tie-Line
Control
• Load Forecasting (Next-day, Real-time), Generation Equipment (ramp rates, min/max limits,
AVRs, governors)
• Balancing Authority Area (BAA) operations, inadvertent interchange, payback
II. Transmission (≈ 28-30 questions) – HEAVIEST SECTION
• Protection & Control: Zones of protection, relay types (overcurrent, distance, differential,
reclosing), breaker failure, Special Protection Systems (SPS)/Remedial Action Schemes (RAS)
• Voltage & Reactive: Voltage schedules, reactive resources (capacitors, reactors, SVCs,
STATCOMs, generator var limits), Excitation systems, transformer LTCs, tap changers
• Electrical Current: Thermal limits, line ratings (Normal, Emergency, Seasonal), dynamic ratings
• Reconfiguration & Switching: Switch types (air break, oil, vacuum, SF6, load break), grounding
(personal protective grounds, system grounding), tagging, clearance procedures
• Operating Limits: System Operating Limits (SOLs), Interconnection Reliability Operating Limits
(IROLs), Available Transfer Capability (ATC), Total Transfer Capability (TTC)
• Transmission Equipment: Lines, transformers, series capacitors, phase shifters, circuit breakers,
disconnect switches
III. Emergency Preparedness (≈ 8-10 questions)
• Current-Day & Next-Day Planning: Resource adequacy, capacity deficiency, Transmission
Loading Relief (TLR)
• Severe Weather, Natural Disasters, Geomagnetic Disturbances (GMD), Solar Storms
• Anticipated Capacity Deficiency: Energy Emergency Alerts (EEA Levels 1-3), load shed
procedures
IV. Emergency Response (≈ 20-22 questions)
• System Restoration: Blackstart resources, restoration plans, cranking paths, load pickup,
synchronization
• Response to System Disturbances: Separation (islanding), frequency excursions (Underfrequency
Load Shed - UFLS, Under/Over voltage), total blackout
• Response to Capacity Emergencies: Manual load shed, voltage reduction, public appeals
• Loss of Control Center: Remote operations, backup control centers
• Loss of Analysis & Monitoring Tools: EMS/SCADA failure backup procedures
V. Contingency Analysis & Reliability (≈ 12-14 questions)
• Contingency Analysis: N-1, N-2 contingencies (loss of line, generator, transformer, bus), single
pole vs. 3-pole
• Network Analysis Tools: State Estimator, Power Flow, Real-time Contingency Analysis (RTCA)
, Page 2 of 150
• Response to Analysis Results: SOL/IROL violations, nomograms, operator actions prior to next
contingency
• System Operating Limits (SOLs): Pre-contingency handling, post-contingency expectations
• Interconnection Reliability Operating Limits (IROLs): Must be protected within 30 minutes (15
for primary IROL)
• Reliability Coordinator (RC) role, BA-TO-RC coordination
VI. Communications & Data (≈ 10-12 questions)
• Reporting Requirements: NERC alerts, CEII (Critical Energy Infrastructure Information), reports
to RC
• Communication Methods: Three-Part Communication (Read back / Repeat back), RCIS
(Reliability Coordinator Information System), telephone protocols
• Data Validity & Verification: SCADA data quality, bad data detection, telemetry failure, manual
backup
• Telemetry & Communications Equipment: RTUs, satellite phones, microwave, fiber, redundancy
Below are 250 random, scenario-based multiple-choice questions covering all TO Exam Knowledge
Areas, with answers and concise rationales.
Q1. A Transmission Operator notices the Area Control Error (ACE) is consistently positive for 15 minutes.
What does this indicate?
A) Generation is less than load, and frequency is low
B) Generation exceeds load, and frequency is high
C) Interchange schedule is exactly met
D) ACE cannot be calculated due to telemetry failure
Answer: B
Rationale: Positive ACE means actual net interchange (NIa) is less than scheduled (NIs) OR generation >
load → ACE positive; generation > load causes frequency > 60 Hz .
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Q2. An operator receives an Interchange e-Tag that has been "Confirmed" but not yet "Implemented."
What is the operator's next action?
A) Approve the Interchange at the scheduled time
B) Reject the e-Tag because it is too late
C) Begin ramping generation to match the schedule immediately
D) Wait for the Reliability Coordinator to approve
Answer: A
Rationale: e-Tag status proceeds: Proposed → Approved → Confirmed → Implemented. The
Transmission Operator/Balancing Authority must Implement at the scheduled start time .
Q3. A transmission line is protected by a permissive over-reaching transfer trip (POTT) scheme. This
scheme requires:
A) The relay to trip instantaneously without communication
B) Communication between line terminals to allow tripping for internal faults
C) One terminal to trip and the other to block automatically
D) Reclosing after 30 seconds only
Answer: B
, Page 4 of 150
Rationale: POTT schemes use communication channels (pilot) to send a permissive trip signal to the
remote terminal when a fault is detected within the zone. Tripping occurs only if the remote relay also
detects the fault and sends permission.
Q4. A Balancing Authority reports a frequency of 59.92 Hz. Which of the following should the
Transmission Operator expect?
A) Generators are automatically increasing output via governor response and AGC
B) Underfrequency load shedding (UFLS) has already activated
C) All tie lines are open
D) Frequency will recover without any action
Answer: A
Rationale: At 59.92 Hz, frequency is low; generators with governors will automatically increase real
power output (droop response). AGC will also adjust base points. UFLS typically begins at 59.5 Hz or
lower .
Q5. The term "N-1 contingency" refers to:
A) Loss of a single Bulk Electric System element
B) Loss of one entire Balancing Authority area
