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NERC RC Exam Questions and Correct
Answers/ Latest Update / Already Graded
What is ACE?
Ans: (NIa - NIs) - 10β(fa - fs) - Ime
Calculated every 6 seconds
Uses Tie line Frequency Bias
What is Tie line deviation?
Ans: Largest offset to ACE
What is NIA?
Ans: Net Interchange Actual (sum of all tie-line values)
What is NIS?
Ans: Net Interchange Scheduled (sum of all interchange
schedules)
What is the multiplier for frequency bias?
Ans: 10
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What is β?
Ans: Frequency bias - represented as negative number in ACE
calculation - reflects area natural response to frequency
changes (Inertia, Governor, Load) - atleast 1% of annual peak
load for areas with native load - 1% of peak generation output
for area with no load
What is FA?
Ans: Frequency Actual
What is FS?
Ans: Frequency Schedule - normally 60.00 HZ except for time
corrections - +/- .02 Hz
What is IME?
Ans: Meter error
fudge factor
used for inadvertent bilateral payback
Negligible
What should be done if unable to calculate ACE for 30 minutes?
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Ans: Contact RC
How often should time error and frequency devices be
checked/calibrated?
Ans: Annually
Negative Ace
Ans: The BA is Undergenerating
Positve ACE
Ans: The BA is Overgenerating
What happens during Internal Loss of Load?
Ans: Frequency and ACE increase.
What happens during External Loss of Load?
Ans: Frequency increases, no change in ACE.
What is the Frequency Bias Setting?
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Ans: Monthly average >= 1% of estimated yearly peak demand
per 0.1 Hz
When should the Balancing Authority recalculate its Frequency Bias
Setting?
Ans: By January 1 of each year
What happens when there is internal generation loss?
Ans: Frequency and ACE drop, tie-line flows increase into the
system
What happens when there is external generation loss?
Ans: Frequency drops, no change in ACE, net tie -line flows
increase out of the system
What happens when Frequency bias setting is lower than frequency
response?
Ans: ACE will be positive causing the AGC to lower generation
What is the percentage change in load required for a 1% change in
frequency?
All rights reserved © 2025/ 2026 |
NERC RC Exam Questions and Correct
Answers/ Latest Update / Already Graded
What is ACE?
Ans: (NIa - NIs) - 10β(fa - fs) - Ime
Calculated every 6 seconds
Uses Tie line Frequency Bias
What is Tie line deviation?
Ans: Largest offset to ACE
What is NIA?
Ans: Net Interchange Actual (sum of all tie-line values)
What is NIS?
Ans: Net Interchange Scheduled (sum of all interchange
schedules)
What is the multiplier for frequency bias?
Ans: 10
All rights reserved © 2025/ 2026 |
, Page |2
What is β?
Ans: Frequency bias - represented as negative number in ACE
calculation - reflects area natural response to frequency
changes (Inertia, Governor, Load) - atleast 1% of annual peak
load for areas with native load - 1% of peak generation output
for area with no load
What is FA?
Ans: Frequency Actual
What is FS?
Ans: Frequency Schedule - normally 60.00 HZ except for time
corrections - +/- .02 Hz
What is IME?
Ans: Meter error
fudge factor
used for inadvertent bilateral payback
Negligible
What should be done if unable to calculate ACE for 30 minutes?
All rights reserved © 2025/ 2026 |
, Page |3
Ans: Contact RC
How often should time error and frequency devices be
checked/calibrated?
Ans: Annually
Negative Ace
Ans: The BA is Undergenerating
Positve ACE
Ans: The BA is Overgenerating
What happens during Internal Loss of Load?
Ans: Frequency and ACE increase.
What happens during External Loss of Load?
Ans: Frequency increases, no change in ACE.
What is the Frequency Bias Setting?
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, Page |4
Ans: Monthly average >= 1% of estimated yearly peak demand
per 0.1 Hz
When should the Balancing Authority recalculate its Frequency Bias
Setting?
Ans: By January 1 of each year
What happens when there is internal generation loss?
Ans: Frequency and ACE drop, tie-line flows increase into the
system
What happens when there is external generation loss?
Ans: Frequency drops, no change in ACE, net tie -line flows
increase out of the system
What happens when Frequency bias setting is lower than frequency
response?
Ans: ACE will be positive causing the AGC to lower generation
What is the percentage change in load required for a 1% change in
frequency?
All rights reserved © 2025/ 2026 |
