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NERC SOS PREP-RELIABILITY EXAM QUESTIONS
AND ANSWERS LATEST UPDATE 202 5/2026 ACTUAL
EXAM
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. A) Increase Net Interchange Schedule by 20 MWs. 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?
- Actual Net Interchange
- Scheduled Frequency
- Scheduled Net Interchange
- Area Control Error A) 4 only B) 1 & 3 C) 1 & 4
D) 3 & 4
C) 1 & 4
Metered Data included in the calculation of ACE are: dynamic schedules, pseudo ties, actual frequency, and all. A) Tie lines readings B) Generators output C) Scheduled frequency indications D) Transformer load A) Tie lines readings 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 A) - 100 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 B) 25 MWs in
If the frequency bias setting is less negative than the frequency response of a Balancing Authority and a frequency decline is caused by a sudden loss of generation in an external balancing area, what will be the result? A) The ACE will be a negative value and AGC will increase generation. B) This will not affect the ACE. C) The ACE will be a positive value and AGC will lower generation. D) The ACE will be zero and will take no AGC action. C) The ACE will be a positive value and AGC will lower generation. It is the responsibility of which entity/entities to develop, maintain, and implement load shedding plans? A) Transmission Operators and Balancing Authorities B) Reliability Coordinator C) Load Serving Entities D) Balancing Authority A) Transmission Operators and Balancing Authorities A Transmission line is loaded 25% above its SOL. A parallel line is out for routine maintenance and can be placed in service in 10 minutes. What is the first step the Operator should take to reduce the line loading?
A) Shed load at the downstream bus. B) Open the line. C) Re-Dispatch Generation. D) Initiate the restoration of the parallel line. D) Initiate the restoration of the parallel line. As a Transmission Operator, you realize that the voltage level is starting to decline in the North West part of the system. Which of the following devices should you, as a Transmission Operator, be able to operate, and/or have another entity operate to raise the voltage level back to normal in the North West part of the system? A) Transformer Underload Tap Changers B) Shunt Capacitor Banks C) Generator Reactive Output D) All answers are correct D) All answers are correct Voltage reduction for load relief should be made on the. A) Distribution system B) Entire Interconnection simultaneously C) Tie-lines with other Balancing Authority Areas D) Transmission System A) Distribution system
Preparations are being made to tie two islands together during restoration. Island "A" has a frequency of 58.95 Hz and Island "B" has a frequency of 59.97 Hz. What action should be taken to synchronize the two islands? A) Shed load in Island "B" B) Shed load in Island "A". C) Disable the Synch Check Relay. D) Increase generation in Island "B". B) Shed load in Island "A". You experience a full system shutdown. You are in the process of restoring load and you are concerned about re-collapsing the system. Which is the best approach in the restoration process that will help ensure your system will be restored successfully? A) Maintain frequency between 59.5 HZ and 60.5 HZ. B) If the system has stabilized at below 60 HZ, shed 15% - 20% of the load to raise the frequency to 61 HZ. C) Avoid energizing loads in excess of 5% of the online generation capacity of the system. D) Operating reserves should be maintained to cover the largest generator currently in service. C) Avoid energizing loads in excess of 5% of the online generation capacity of the system. In the event a Balancing Area experiences multiple contingencies occurring within of each other, it shall be treated as a single contingency.
A) five minutes B) one minute or less C) fifteen minutes D) two minutes B) one minute or less When coordinating under frequency load shedding and under frequency generator tripping the . A) generators should trip before the UFLS B) load should not be shed during the process C) generators should trip after the UFLS D) breakers should open at the same time as the UFLS C) generators should trip after the UFLS One of the functions of under frequency load shedding is to within an electrical island that may have been created by a system disturbance. A) balance generation and load B) establish balance between load and interchange C) stabilize balance between generators D) stabilize the Interconnection A) balance generation and load A major transmission line has become overloaded and the transmission operator has taken actions to unload the line. However, the overload persists, and the equipment is now in imminent danger of damage. What is the next action to take?
A radial transmission line feeding a load is overloaded. The Transmission Operator must do which of the following to unload the line? A) Raise interchange schedule B) Lower interchange schedule C) Re-dispatch generation D) Shed load at the end of the line D) Shed load at the end of the line If a Balancing Authority is unable to purchase capacity or energy to meet its demand and reserve requirements on a day-ahead or hour-by-hour basis, which entity (or entities), is it expected to notify? A) All Reliability Coordinators. B) Its Reliability Coordinator and other Balancing Authorities C) All Reliability Coordinators and marketers D) Transmission Operators B) Its Reliability Coordinator and other Balancing Authorities Each Transmission Operator is required to have a system restoration plan. What is the first thing a Transmission Operator must do when energizing a blacked out area? A) Isolate the load. B) Turn all voltage regulators to the manual position.
C) Contact the Regional Reliability Organization. D) Close any capacitor banks which are open. A) Isolate the load. After declaring an NERC EEA Level 3, load goes higher than your generation resources, what is an effective tool in restoring generation to load balance? A) Firm Load Shed B) Exceeding emergency limits C) TLR D) Voltage Reduction A) Firm Load Shed An 800 MW generator trips in a Balancing Authority external to your Balancing Authority Area. Which of the following indications would you expect to see in your area? A) Net Actual Interchange would decrease significantly. B) ACE would drop to approximately - 800 MW. C) Frequency would drop, and ACE would remain relatively unchanged. D) Frequency would drop, and ACE would increase significantly. C) Frequency would drop, and ACE would remain relatively unchanged.
D) Energy Emergency Alert Level 2 B) Energy Emergency Alert Level 1 A Transmission Operator's Emergency Operating Plan states when voltages fall below .87 per unit (p.u.) or 87% of nominal voltage and remains at that level for a sustained period of 10 minutes or longer, manual load reduction actions are required. When the system voltage returns to .9 p.u. or 90% manual load disconnection is not required. If a generator trips off line within the BA and the nearby 230 kV system voltage immediately drops to 200 kV and remains at that level for the next 3 minutes. What is the BA required to do? A) Wait 7 minutes for the remaining generator AVRs to respond; close capacitor banks; adjust Transformer Taps. B) Immediately disconnect firm system load until the voltage returns to at least .9 p.u. Notify the RC of the amount of load disconnected. C) Immediately take actions to raise the voltage EXCEPT removing firm system load. Notify the RC and neighboring BA's. Prepare for manual load r C) Immediately take actions to raise the voltage EXCEPT removing firm system load. Notify the RC and neighboring BA's. Prepare for manual load reduction if the voltage remains below .9 p.u. over the next 7 minutes. A condition when a Load-Serving Entity has exhausted all other options and can no longer provide its customers' expected energy requirements is referred to as? A) Energy Emergency B) Energy deficiency C) Load shortage D) Energy shortage
A) Energy Emergency You are currently in the early stages of restoration with 600 MWs of synchronized generation. There is 200 MWs of spinning reserve available. To maintain acceptable frequency control, what is the largest block of load that can be restored at one time? A) 10 MWs B) 20 MWs C) 30 MWs D) 60 MWs C) 30 MWs If firm Load shed is imminent or in progress, what level Energy Emergency Alert is required? A) EEA 0 B) EEA 3 C) EEA 1 D) EEA 2 B) EEA 3 Why are high transmission system voltages a problem during system restoration? A) Because of the excessive MVAR supply from generators. B) Because of the excessive MVAR supply from energizing transmission lines.
C) Zero D) Total Generation C) Zero A simple power system is composed of three transmission lines that connect the generation area to the load area. The three lines are different lengths, but each line has the same impedance. Each line is initially loaded at 200 MW. The SOL of each line is 400 MW. If one of the three lines trips, what will be the loading on the shortest remaining line and will the SOL of either remaining line be violated? A) 400 MW/Yes B) 400 MW/No C) 300 MW/Yes D) 300 MW/No D) 300 MW/No During a lightning storm, a fault on a transmission line results in the transmission relay operating and locking-out. The transmission line cannot be returned to service. After running a contingency analysis, the Transmission Operator realizes that if another transmission line relays, there could be cascading outages into a neighboring system. Which of the following actions is appropriate for the Transmission Operator? A) Reduce transmission voltages by 5% to reduce customer demand. B) Notify others in the Interconnection of the situation via an Interconnection-wide telecommunications system. C) Continue operations without notifying anyone but try to reduce system loading. D) Prepare a disturbance report and forward it to the Reliability Coordinator.
B) Notify others in the Interconnection of the situation via an Interconnection-wide telecommunications system. A Generator Operator has some vibration problems with a 500MW coal fired steam generator. As the result of the vibration problems the Generator Operator has to set the maximum reactive power production for that unit at 25 Megavar instead of the normal 200 Megavar. Who should the generator operator notify as the result of this problem? A) Transmission Operator B) System Coordinator C) Department of Energy (DOE) D) Regional Reliability Organization A) Transmission Operator A high voltage transmission line was scheduled out for routine maintenance several weeks in advance. On the scheduled outage date, field personnel call to inform the system operator that they will be taking the line out of service. Bad weather the previous day has forced other outages. What should the system operator do? A) Wait until peak is over to make a decision B) Run a power flow study to determine the effects of this line outage C) Do not allow the outage D) Allow the outage because it was scheduled in advanced B) Run a power flow study to determine the effects of this line outage
You are a transmission operator and you have several large generators operating at full load on the western portion of your transmission system with 34 kV and 230 kV transmission lines connecting the generators to the larger metropolitan and Industrial areas in the eastern portion of your transmission system. You realize by SCADA indications that there is a large power angle approaching 88 degrees between some of the sending busses at the generation sites and the receiving buses around the load areas. You realize that the slightest contingency on the system could elevate the power angle above 90 degrees which could cause the generation and load areas to lose synchronism. What would be some of your first immediate responses to prevent this from happening? A) Raise the bus voltage at the receiving buses and at the sending buses, if possible. Then, have the balancing operator provide additional generation on line on th A) Raise the bus voltage at the receiving buses and at the sending buses, if possible. Then, have the balancing operator provide additional generation on line on the eastern portion of the large metropolitan area A System Operator must operate the transmission system so that instability, uncontrolled separation, or cascading outages will not occur as a result of. A) The most severe single contingency B) Normal operations C) External disturbances D) Any unplanned outage A) The most severe single contingency Which of the following actions would be required in accordance with COM- 002 - 4 when communicating an Operating Instruction? A) A Balancing Authority repeats the operating instruction back to the Reliability Coordinator. B) A Reliability Coordinator clearly states the Operating Instruction.
C) A Reliability Coordinator confirms the instruction was understood correctly or corrects the response if it is not repeated back correctly. D) All the Above D) All the Above The largest single contingency for Balancing Authority A is a unit rated at 900 MW. Which of the following disturbances would constitute a reportable disturbance for DCS evaluation based on the NERC DCS criteria? A) The loss of the 900 MW generating unit at 60% output. B) The loss of two 400 MW units 30 seconds apart. C) The loss of 750 MW of firm load. D) The loss of a 700 MW generating unit at 100% output. B) The loss of two 400 MW units 30 seconds apart. On a mild spring day, a transmission line trips. The line then trips again when energized. Which of the following is least likely to be the problem? A) Vandalism B) Overload C) Equipment failure D) Sabotage B) Overload
