Comprehensive OHM Power System Reliability
and Control Concepts-– Complete Exam Study
Guide 2026/2027 with Verified Answers |
Newest Version. A+
What is the Balancing Authority's Inadvertent Interchange for the 4-hour period with a Net
Interchange Schedule of -250 MWs?
The Balancing Authority's Inadvertent Interchange is 6 MWs out.
What type of units provide the biggest adjustments in megawatt output in response to a
frequency disturbance?
Units that have large capacity and small droop setting.
What does ACE indicate if Balancing Authority 'A' is importing 225 MWs with a Bias Setting of
200 MWs/0.1 Hz at a frequency of 59.99 Hz?
ACE indicates 20 MW under-generating.
What value must the ACE return to avoid a DCS violation after a 600-MW generator trips
offline?
Must return ACE to 0 MW in 15 minutes.
What actions can a Balancing Authority system operator take to limit additional on-peak
inadvertent accumulation when system load is decreasing?
Decrease transactions into their system and decrease generation.
What actual operating values must two adjacent Balancing Authorities agree on regarding
Inadvertent Interchange?
The hourly integrated values of Net Interchange Schedule and the hourly integrated values of
Net Actual Interchange.
When are inadvertent energy accumulations between power systems normally balanced?
During periods corresponding to those in which the inadvertent energy was accumulated.
Which control system is affected by a difference in Net Actual Interchange and Net Scheduled
Interchange?
,Automatic Generation Control.
What is the ACE reading for Balancing Authority A with a frequency of 59.98 Hz and a Bias
Setting of 100 MW/0.1 Hz?
ACE is -20.
What does a CPS1 violation indicate?
A BA's ACE is hindering frequency.
What is the most common cause of frequency fluctuations?
System generation and load imbalance.
What should the operator do if ACE is +25 MWs and load is expected to increase by 100 MWs?
Decrease generation by 25 MW.
What is Balancing Authority A's ACE reading if it is scheduled to import 300 MW but is only
importing 260 MW?
ACE reading is -32 MW.
What should Balancing Authority A's AGC do if the frequency is 60.06 Hz and Net Actual
Interchange is +100 MW?
Increase MW output.
What must the Balancing Authority do after losing 800 MW of generation and meeting DCS
reporting criteria?
Notify the RC that Energy Emergency Alert is required to return ACE to ZERO.
What is the first step an Operator should take to reduce line loading if a transmission line is
loaded 25% above its SOL?
Shed load at the downstream bus.
What is the system operator's priority during a system restoration?
Restoration of interchange.
What action must a Transmission Operator take to unload an overloaded radial transmission
line?
Shed load at the end of the radial line.
,What type of emergency condition occurs when unable to meet load requirements of retail
customers?
Energy Emergency.
What should operating personnel consider when a system is on the verge of a voltage
collapse?
Reducing load in the area with the low voltage.
What does the Reliability Coordinator do when notified of a potential Energy Emergency?
Initiate the Energy Emergency Alert (EEA) process.
What is the Energy Emergency Alert (EEA) process?
A procedure initiated by the Reliability Coordinator to manage energy emergencies as detailed
in specific operational plans.
What actions would the Reliability Coordinator coordinate with other Reliability Coordinators
that have available resources?
Remove system operating limits, implement voltage reduction, request another Balancing
Authority to shed load, and arrange emergency sales to deficient Balancing Authorities.
What could cause problems during system restoration?
Factors include the interchange transactions prior to system collapse, the Area Control Error
(ACE) reading, cold-load pickup, and the cost of available generation.
What is Under Frequency Load Shedding (UFLS)?
A method to stabilize the imbalance between generation and load created by a system
disturbance, typically by shedding load.
Where should voltage reduction for load relief be made?
On tie-lines with other Balancing Authority Areas, the transmission system, or the entire
interconnection simultaneously.
What is the first action a Transmission Operator must take when energizing a blacked-out
area?
Turn all voltage regulators to the manual position.
What should the coordination of emergency operating plans include?
, Processes to prepare for and mitigate emergencies, cancellation of outages, and roles and
responsibilities for activating the operating plan.
Who should a Balancing Authority notify if it cannot meet demand and reserve requirements?
Its Reliability Coordinator and other Balancing Authorities.
Before shedding firm load to alleviate voltage collapse, who must be consulted?
The Load Serving Entity.
How much load should be shed manually to return frequency to normal if the frequency is
steady at 58.5 Hz?
20 MWs.
What must an RC verify before approving the synchronization of two islands?
Frequency matching, load balancing, generation balancing, and the existence of synchronizing
equipment at the tie point.
What corrective actions must be taken if a Transmission Operator cannot restore power
balance?
Notify the Regional Reliability Organization, implement manual load shedding, reduce voltage
on the distribution system, and reduce interchange.
What type of emergency condition arises from not meeting load requirements for retail
customers?
Capacity Emergency.
Why should system restoration plans establish the transmission system backbone using the
highest voltage line?
Because of the lower impedance of higher voltage lines.
What is the NERC requirement for reporting after shedding firm load?
A report must be submitted following the shedding of at least 100 MW.
What Energy Emergency Alert (EEA) level should be declared if a Balancing Area's projected
load exceeds available generation?
EEA 2.
What actions should a Balancing Authority take to restore an area in blackout condition?
and Control Concepts-– Complete Exam Study
Guide 2026/2027 with Verified Answers |
Newest Version. A+
What is the Balancing Authority's Inadvertent Interchange for the 4-hour period with a Net
Interchange Schedule of -250 MWs?
The Balancing Authority's Inadvertent Interchange is 6 MWs out.
What type of units provide the biggest adjustments in megawatt output in response to a
frequency disturbance?
Units that have large capacity and small droop setting.
What does ACE indicate if Balancing Authority 'A' is importing 225 MWs with a Bias Setting of
200 MWs/0.1 Hz at a frequency of 59.99 Hz?
ACE indicates 20 MW under-generating.
What value must the ACE return to avoid a DCS violation after a 600-MW generator trips
offline?
Must return ACE to 0 MW in 15 minutes.
What actions can a Balancing Authority system operator take to limit additional on-peak
inadvertent accumulation when system load is decreasing?
Decrease transactions into their system and decrease generation.
What actual operating values must two adjacent Balancing Authorities agree on regarding
Inadvertent Interchange?
The hourly integrated values of Net Interchange Schedule and the hourly integrated values of
Net Actual Interchange.
When are inadvertent energy accumulations between power systems normally balanced?
During periods corresponding to those in which the inadvertent energy was accumulated.
Which control system is affected by a difference in Net Actual Interchange and Net Scheduled
Interchange?
,Automatic Generation Control.
What is the ACE reading for Balancing Authority A with a frequency of 59.98 Hz and a Bias
Setting of 100 MW/0.1 Hz?
ACE is -20.
What does a CPS1 violation indicate?
A BA's ACE is hindering frequency.
What is the most common cause of frequency fluctuations?
System generation and load imbalance.
What should the operator do if ACE is +25 MWs and load is expected to increase by 100 MWs?
Decrease generation by 25 MW.
What is Balancing Authority A's ACE reading if it is scheduled to import 300 MW but is only
importing 260 MW?
ACE reading is -32 MW.
What should Balancing Authority A's AGC do if the frequency is 60.06 Hz and Net Actual
Interchange is +100 MW?
Increase MW output.
What must the Balancing Authority do after losing 800 MW of generation and meeting DCS
reporting criteria?
Notify the RC that Energy Emergency Alert is required to return ACE to ZERO.
What is the first step an Operator should take to reduce line loading if a transmission line is
loaded 25% above its SOL?
Shed load at the downstream bus.
What is the system operator's priority during a system restoration?
Restoration of interchange.
What action must a Transmission Operator take to unload an overloaded radial transmission
line?
Shed load at the end of the radial line.
,What type of emergency condition occurs when unable to meet load requirements of retail
customers?
Energy Emergency.
What should operating personnel consider when a system is on the verge of a voltage
collapse?
Reducing load in the area with the low voltage.
What does the Reliability Coordinator do when notified of a potential Energy Emergency?
Initiate the Energy Emergency Alert (EEA) process.
What is the Energy Emergency Alert (EEA) process?
A procedure initiated by the Reliability Coordinator to manage energy emergencies as detailed
in specific operational plans.
What actions would the Reliability Coordinator coordinate with other Reliability Coordinators
that have available resources?
Remove system operating limits, implement voltage reduction, request another Balancing
Authority to shed load, and arrange emergency sales to deficient Balancing Authorities.
What could cause problems during system restoration?
Factors include the interchange transactions prior to system collapse, the Area Control Error
(ACE) reading, cold-load pickup, and the cost of available generation.
What is Under Frequency Load Shedding (UFLS)?
A method to stabilize the imbalance between generation and load created by a system
disturbance, typically by shedding load.
Where should voltage reduction for load relief be made?
On tie-lines with other Balancing Authority Areas, the transmission system, or the entire
interconnection simultaneously.
What is the first action a Transmission Operator must take when energizing a blacked-out
area?
Turn all voltage regulators to the manual position.
What should the coordination of emergency operating plans include?
, Processes to prepare for and mitigate emergencies, cancellation of outages, and roles and
responsibilities for activating the operating plan.
Who should a Balancing Authority notify if it cannot meet demand and reserve requirements?
Its Reliability Coordinator and other Balancing Authorities.
Before shedding firm load to alleviate voltage collapse, who must be consulted?
The Load Serving Entity.
How much load should be shed manually to return frequency to normal if the frequency is
steady at 58.5 Hz?
20 MWs.
What must an RC verify before approving the synchronization of two islands?
Frequency matching, load balancing, generation balancing, and the existence of synchronizing
equipment at the tie point.
What corrective actions must be taken if a Transmission Operator cannot restore power
balance?
Notify the Regional Reliability Organization, implement manual load shedding, reduce voltage
on the distribution system, and reduce interchange.
What type of emergency condition arises from not meeting load requirements for retail
customers?
Capacity Emergency.
Why should system restoration plans establish the transmission system backbone using the
highest voltage line?
Because of the lower impedance of higher voltage lines.
What is the NERC requirement for reporting after shedding firm load?
A report must be submitted following the shedding of at least 100 MW.
What Energy Emergency Alert (EEA) level should be declared if a Balancing Area's projected
load exceeds available generation?
EEA 2.
What actions should a Balancing Authority take to restore an area in blackout condition?
