NERC BI - System Operations Exam | Actual Questions and
Answers Latest Updated 2026/2027 (Graded A+)
•
Disturbance
- ✔✔Any perturbation to the electric system or the unexpected change in ACE that is caused
by the sudden loss of generation or interruption of load
•
Interconnection reliability operating limit ( IROL)
- ✔✔The value (such as MW, MVar, Amperes, Frequency or Volts) derived from, or a subset
of the System Operating Limits, which if exceeded, could expose a widespread area of the
Bulk Electric System to instability, uncontrolled separation(s) or cascading outages.
•
Interconnection reliability operating limit
- ✔✔A System Operating Limit that, if violated, could lead to instability, uncontrolled
separation, or Cascading outages4 that adversely impact the reliability of the Bulk Electric
System.
•
Impedence
- ✔✔The AC version of resistance to power flow, it includes inductive and capacitive
reactance ( note when lines run in parallel it lowers the path of impedance)
•
Phase Angle
- ✔✔
•
Power Angle
- ✔✔
•
Voltage
- ✔✔an electromotive force or potential difference expressed in volts.
•
System Operating limit
i. - ✔✔The value (such as MW, MVar, Amperes, Frequency or Volts) that satisfies the most
limiting of the prescribed operating criteria for a specified system configuration to ensure
operation within acceptable reliability criteria. System Operating Limits are based upon
certain operating criteria. These include, but are not limited to:
ii. Facility Ratings (Applicable pre- and post-Contingency equipment or facility ratings)
iii. Transient Stability Ratings (Applicable pre- and post-Contingency Stability Limits)
, iv. Voltage Stability Ratings (Applicable pre- and post-Contingency Voltage Stability) System
Voltage Limits (Applicable pre- and post-Contingency Voltage Limits)
•
What is the maximum power angle degree in the power transfer equation? Greater than this will cause
system instability.
- ✔✔90 Degrees
•
What three elements make up impedance in an alternating current power system
- ✔✔Capacitance inductance and resistance
•
Which elements make up power
- ✔✔current impedance and voltage
•
Steady state stability
- ✔✔when the system parameters monitored by the reliability coordinators, transmission
operators and balancing authorities such as voltages, frequency and power flows may be
changing but the changes are small and occur gradually
•
Transient stability
- ✔✔Transient stability describes the ability of the power system where a sudden large
change takes place within the system without violating system operating limits. This could
be the loss of a major generator or a severe system fault
•
Generators as the source of real and reactive power are the stabilizing force in the power system
•
Power angle across a section of the system is ...
- ✔✔20 degrees
•
What happens if a transmission line outage occurs
- ✔✔MW flows increase on the existing transmission lines still in service
•
As Amps increase MVAR losses as a result of existing inductive reactance
- ✔✔Increases
•
Transient instability
- ✔✔power angle greater than 90 degrees from power transfer, when a disturbance causes
power angle greater than 90 degrees or when heavy power transfers to one or more
transmission segments such as a loss in generation
Answers Latest Updated 2026/2027 (Graded A+)
•
Disturbance
- ✔✔Any perturbation to the electric system or the unexpected change in ACE that is caused
by the sudden loss of generation or interruption of load
•
Interconnection reliability operating limit ( IROL)
- ✔✔The value (such as MW, MVar, Amperes, Frequency or Volts) derived from, or a subset
of the System Operating Limits, which if exceeded, could expose a widespread area of the
Bulk Electric System to instability, uncontrolled separation(s) or cascading outages.
•
Interconnection reliability operating limit
- ✔✔A System Operating Limit that, if violated, could lead to instability, uncontrolled
separation, or Cascading outages4 that adversely impact the reliability of the Bulk Electric
System.
•
Impedence
- ✔✔The AC version of resistance to power flow, it includes inductive and capacitive
reactance ( note when lines run in parallel it lowers the path of impedance)
•
Phase Angle
- ✔✔
•
Power Angle
- ✔✔
•
Voltage
- ✔✔an electromotive force or potential difference expressed in volts.
•
System Operating limit
i. - ✔✔The value (such as MW, MVar, Amperes, Frequency or Volts) that satisfies the most
limiting of the prescribed operating criteria for a specified system configuration to ensure
operation within acceptable reliability criteria. System Operating Limits are based upon
certain operating criteria. These include, but are not limited to:
ii. Facility Ratings (Applicable pre- and post-Contingency equipment or facility ratings)
iii. Transient Stability Ratings (Applicable pre- and post-Contingency Stability Limits)
, iv. Voltage Stability Ratings (Applicable pre- and post-Contingency Voltage Stability) System
Voltage Limits (Applicable pre- and post-Contingency Voltage Limits)
•
What is the maximum power angle degree in the power transfer equation? Greater than this will cause
system instability.
- ✔✔90 Degrees
•
What three elements make up impedance in an alternating current power system
- ✔✔Capacitance inductance and resistance
•
Which elements make up power
- ✔✔current impedance and voltage
•
Steady state stability
- ✔✔when the system parameters monitored by the reliability coordinators, transmission
operators and balancing authorities such as voltages, frequency and power flows may be
changing but the changes are small and occur gradually
•
Transient stability
- ✔✔Transient stability describes the ability of the power system where a sudden large
change takes place within the system without violating system operating limits. This could
be the loss of a major generator or a severe system fault
•
Generators as the source of real and reactive power are the stabilizing force in the power system
•
Power angle across a section of the system is ...
- ✔✔20 degrees
•
What happens if a transmission line outage occurs
- ✔✔MW flows increase on the existing transmission lines still in service
•
As Amps increase MVAR losses as a result of existing inductive reactance
- ✔✔Increases
•
Transient instability
- ✔✔power angle greater than 90 degrees from power transfer, when a disturbance causes
power angle greater than 90 degrees or when heavy power transfers to one or more
transmission segments such as a loss in generation
