NERC TRANSMISSION OPERATOR (TOP)
Actual SYSTEM OPERATIONS EXAM –
Complete Solutions | Verified Review
Guide
Module: Generator Operation & Power System Basics
Q1. At what torque angle of operation does power typically begin to
flow from the generator to the system?
• A) 90 degrees
• B) 60 degrees
• C) 30 degrees
• D) 10 degrees
Correct ,,answer,,: D) 10 degrees
Rationale: Power begins to flow from a generator to the system at a
small torque angle of approximately 10 degrees. As the torque angle
increases, more power is transferred up to the stability limit .
Q2. Choose the ,,answer,, that best describes the operation of a
rotor.
, • A) The stationary part of the transmission system
• B) A type of superconductor
• C) The stationary element of a generator that has its windings
connected to the system
• D) The excited (energized) field winding that rotates inside the
stator to induce current into the stator windings
Correct ,,answer,,: D) The excited (energized) field winding that
rotates inside the stator to induce current into the stator windings
Rationale: The rotor is the rotating component of a generator containing
the field windings. When energized with DC current, it creates a
magnetic field that rotates inside the stator, inducing AC current in the
stator windings .
Q3. In a system that is more capacitive than inductive, the current
sine wave will ______ the voltage sine wave, which tends to
___________ voltage.
• A) lag; raise
• B) lead; raise
• C) lead; lower
• D) lag; lower
Correct ,,answer,,: B) lead; raise
Rationale: In a capacitive system, current leads voltage. Capacitive
reactive power (MVAR) injection raises voltage levels, which is why
capacitor banks are used for voltage support .
,Q4. Sustained operation with a power angle or torque angle above
______ can lead to system instability.
• A) 10 degrees
• B) 90 degrees
• C) 120 degrees
• D) 360 degrees
Correct ,,answer,,: B) 90 degrees
Rationale: Sustained operation with a power angle above 90 degrees
can lead to loss of synchronism and system instability. The maximum
power transfer occurs at 90 degrees .
Q5. Which of the following conditions may cause transient instability
in the power system?
• A) When the power angle increases to 90 degrees or more
• B) When a disturbance causes momentary power angle excursions
greater than 90 degrees
• C) When heavy power transfers occur in the system, such as when
there is a loss in generation
• D) All of the above
Correct ,,answer,,: D) All of the above
Rationale: Transient instability can be caused by any condition that
forces power angles beyond stability limits, including large disturbances,
loss of generation, or heavy power transfers .
, Q6. Which of the following is a method that Reliability Coordinators
and Balancing Authorities may use to manage transmission outages?
• A) Coordinate and adhere to voltage schedules to minimize
reactive power flow
• B) Optimize the use of Load Tap Changer transformers, capacitors,
and reactors
• C) Verify voltage control equipment are on automatic to supply the
required voltage support
• D) All of the above
Correct ,,answer,,: D) All of the above
Rationale: Managing transmission outages requires a comprehensive
approach including voltage coordination, optimization of reactive
resources, and ensuring automatic voltage control equipment is properly
configured .
Q7. When a large generator on an Interconnection trips off line, the
____________ of the Interconnection ____________.
• A) frequency; drops
• B) transformer temperature; drops
• C) AVRs; drops
• D) voltage; increases
Correct ,,answer,,: A) frequency; drops
Actual SYSTEM OPERATIONS EXAM –
Complete Solutions | Verified Review
Guide
Module: Generator Operation & Power System Basics
Q1. At what torque angle of operation does power typically begin to
flow from the generator to the system?
• A) 90 degrees
• B) 60 degrees
• C) 30 degrees
• D) 10 degrees
Correct ,,answer,,: D) 10 degrees
Rationale: Power begins to flow from a generator to the system at a
small torque angle of approximately 10 degrees. As the torque angle
increases, more power is transferred up to the stability limit .
Q2. Choose the ,,answer,, that best describes the operation of a
rotor.
, • A) The stationary part of the transmission system
• B) A type of superconductor
• C) The stationary element of a generator that has its windings
connected to the system
• D) The excited (energized) field winding that rotates inside the
stator to induce current into the stator windings
Correct ,,answer,,: D) The excited (energized) field winding that
rotates inside the stator to induce current into the stator windings
Rationale: The rotor is the rotating component of a generator containing
the field windings. When energized with DC current, it creates a
magnetic field that rotates inside the stator, inducing AC current in the
stator windings .
Q3. In a system that is more capacitive than inductive, the current
sine wave will ______ the voltage sine wave, which tends to
___________ voltage.
• A) lag; raise
• B) lead; raise
• C) lead; lower
• D) lag; lower
Correct ,,answer,,: B) lead; raise
Rationale: In a capacitive system, current leads voltage. Capacitive
reactive power (MVAR) injection raises voltage levels, which is why
capacitor banks are used for voltage support .
,Q4. Sustained operation with a power angle or torque angle above
______ can lead to system instability.
• A) 10 degrees
• B) 90 degrees
• C) 120 degrees
• D) 360 degrees
Correct ,,answer,,: B) 90 degrees
Rationale: Sustained operation with a power angle above 90 degrees
can lead to loss of synchronism and system instability. The maximum
power transfer occurs at 90 degrees .
Q5. Which of the following conditions may cause transient instability
in the power system?
• A) When the power angle increases to 90 degrees or more
• B) When a disturbance causes momentary power angle excursions
greater than 90 degrees
• C) When heavy power transfers occur in the system, such as when
there is a loss in generation
• D) All of the above
Correct ,,answer,,: D) All of the above
Rationale: Transient instability can be caused by any condition that
forces power angles beyond stability limits, including large disturbances,
loss of generation, or heavy power transfers .
, Q6. Which of the following is a method that Reliability Coordinators
and Balancing Authorities may use to manage transmission outages?
• A) Coordinate and adhere to voltage schedules to minimize
reactive power flow
• B) Optimize the use of Load Tap Changer transformers, capacitors,
and reactors
• C) Verify voltage control equipment are on automatic to supply the
required voltage support
• D) All of the above
Correct ,,answer,,: D) All of the above
Rationale: Managing transmission outages requires a comprehensive
approach including voltage coordination, optimization of reactive
resources, and ensuring automatic voltage control equipment is properly
configured .
Q7. When a large generator on an Interconnection trips off line, the
____________ of the Interconnection ____________.
• A) frequency; drops
• B) transformer temperature; drops
• C) AVRs; drops
• D) voltage; increases
Correct ,,answer,,: A) frequency; drops
