SOS NERC PREP – RELIABILITY EXAM
2025 QUESTIONS AND ANSWERS
A) Increase Net Interchange Schedule by 20 MWs. - ANS The Reliability Coordinator just
informed you of a slow time error correction which will begin at the top of the next hour. Your
EMS system will not let you change your scheduled frequency. Your Frequency Bias Setting is -
100 MW/.1Hz. What action should you take?
A) Increase Net Interchange Schedule by 20 MWs.
B) Inform the Reliability Coordinator that you cannot participate in the time error correction.
C) Decrease Net Interchange Schedule by 20 MWs.
D) Increase Net Interchange Schedule by 10 MWs.
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,C) 1 & 4 - ANS A Balancing Authority has a sudden loss of a large block of load in its area. This
loss will be seen instantaneously in the change of which of the following values?
1. Actual Net Interchange
2. Scheduled Frequency
3. Scheduled Net Interchange
4. Area Control Error
A) 4 only
B) 1 & 3
C) 1 & 4
D) 3 & 4
A) Tie lines readings - ANS Metered Data included in the calculation of ACE are: dynamic
schedules, pseudo ties, actual frequency, and all __________.
A) Tie lines readings
B) Generators output
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,C) Scheduled frequency indications
D) Transformer load
A) -100 - ANS Balancing Authority A is currently reading a system frequency of 60.00 Hz. Its
Net Actual Interchange is +100 MW and its Net Scheduled Interchange is +200 MW. If Balancing
Authority A's frequency bias setting is 100 MW/0.1 Hz, what is ACE?
A) -100
B) 0
C) 10
D) 100
B) 25 MWs in - ANS A Balancing Authority has a Net Interchange Schedule of -250 MWs from
1200 to 1600 on a summer day. The Net Interchange Actual for those same hours respectively
were -230 MW, -275 MW, -250 MW and -270 MW. What was the Balancing Authority's
Inadvertent Interchange for the 4-hour period?
A) 6 MWs out
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, B) 25 MWs in
C) 25 MWs out
D) 6 MWs in
D) Tie lines - ANS For the ACE equation to work properly, dynamic schedules, pseudo ties,
frequency, and all ________________ must be metered.
A) Generation
B) Communications
C) Transformers
D) Tie lines
B) The ACE will be a negative value and AGC will increase generation - ANS If the frequency
bias setting is set to a less negative value than the frequency response of a Balancing Authority
and a frequency increase is caused by a sudden loss of load in an external balancing area, what
will be the result?
A) The ACE will be zero and will take no AGC action
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2025 QUESTIONS AND ANSWERS
A) Increase Net Interchange Schedule by 20 MWs. - ANS The Reliability Coordinator just
informed you of a slow time error correction which will begin at the top of the next hour. Your
EMS system will not let you change your scheduled frequency. Your Frequency Bias Setting is -
100 MW/.1Hz. What action should you take?
A) Increase Net Interchange Schedule by 20 MWs.
B) Inform the Reliability Coordinator that you cannot participate in the time error correction.
C) Decrease Net Interchange Schedule by 20 MWs.
D) Increase Net Interchange Schedule by 10 MWs.
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,C) 1 & 4 - ANS A Balancing Authority has a sudden loss of a large block of load in its area. This
loss will be seen instantaneously in the change of which of the following values?
1. Actual Net Interchange
2. Scheduled Frequency
3. Scheduled Net Interchange
4. Area Control Error
A) 4 only
B) 1 & 3
C) 1 & 4
D) 3 & 4
A) Tie lines readings - ANS Metered Data included in the calculation of ACE are: dynamic
schedules, pseudo ties, actual frequency, and all __________.
A) Tie lines readings
B) Generators output
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,C) Scheduled frequency indications
D) Transformer load
A) -100 - ANS Balancing Authority A is currently reading a system frequency of 60.00 Hz. Its
Net Actual Interchange is +100 MW and its Net Scheduled Interchange is +200 MW. If Balancing
Authority A's frequency bias setting is 100 MW/0.1 Hz, what is ACE?
A) -100
B) 0
C) 10
D) 100
B) 25 MWs in - ANS A Balancing Authority has a Net Interchange Schedule of -250 MWs from
1200 to 1600 on a summer day. The Net Interchange Actual for those same hours respectively
were -230 MW, -275 MW, -250 MW and -270 MW. What was the Balancing Authority's
Inadvertent Interchange for the 4-hour period?
A) 6 MWs out
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, B) 25 MWs in
C) 25 MWs out
D) 6 MWs in
D) Tie lines - ANS For the ACE equation to work properly, dynamic schedules, pseudo ties,
frequency, and all ________________ must be metered.
A) Generation
B) Communications
C) Transformers
D) Tie lines
B) The ACE will be a negative value and AGC will increase generation - ANS If the frequency
bias setting is set to a less negative value than the frequency response of a Balancing Authority
and a frequency increase is caused by a sudden loss of load in an external balancing area, what
will be the result?
A) The ACE will be zero and will take no AGC action
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