NERC System Operator (SOS) Reliability Practice Test

These questions are part of the practice quiz. Start practicing

• In preparations to synchronize two islands with differing frequencies, what action should be taken?
• Steady-State Stability occurs when which of the following conditions are present?
• Who must approve a Reliability Adjustment Arranged Interchange before it becomes Confirmed Interchange?
• What action should be taken if the system is approaching a high voltage alarm level?
• Which entity is responsible for initiating an Energy Emergency Alert?
• If a Balancing Authority has a Net Interchange Schedule of -250 MWs, what is the Balancing Authority's Inadvertent Interchange for a specified period based on actual interchange values?
• What is the maximum block of load that can be restored to maintain frequency control with 600 MW of generation and 200 MW of spinning reserve?
• What action is required when a Transmission Operator makes significant changes to system operations?
• Which of the following is NOT a requirement of the Reliability Coordinator concerning geomagnetic disturbances (GMDs)?
• What action is necessary when a Reliability Coordinator communicates an Operating Instruction?
• What mode should an asynchronously operating Balancing Authority switch its AGC to?
• What is the proper response regarding voltage control for a tied line crossing two Reliability Coordinators’ areas?
• What term describes the loading on a transmission line when the MVAR supplied from the line's natural capacitance equals the MVAR needed to support its voltage?
• What entity is responsible for taking corrective action after a tie line trip causes a thermal overload?
• What practice can mitigate the risk of excessive voltage increases during heavy loads?
• If a 50 MVA transformer has 30 MW's of load, how many MVARs can flow through the transformer?
• How does a Transmission Operator ensure the safe operation of the grid during unexpected system conditions?
• Who is responsible for notifying all parties when Interchange has transitioned to confirmed status?
• After declaring an NERC EEA Level 3, what is an effective tool to restore generation to load balance if load exceeds generation resources?
• What condition leads to voltage collapse in a power system?
• Given an available transfer capability of 1200 MW, what is the maximum net interchange that can be scheduled from A to B considering other flows?
• If a high voltage transmission line is scheduled for maintenance but other outages have occurred, what is the best course of action for the system operator?
• To maximize effectiveness, where should reactive resources be located?
• What information is essential for the next-day analysis conducted by the Reliability Coordinator?
• In a system restoration scenario, what is a critical factor that must be addressed regarding load?
• If the Source Balancing Authority denies a Reliability Adjustment Arranged Interchange due to reliability issues, what action must they take?
• Voltage reduction for load relief should primarily be made on which system?
• Which type of relay acts as a safeguard for transmission lines?
• What is the appropriate action for a Balancing Authority to restore an area after a blackout due to severe weather conditions?
• What term describes a situation where a Load-Serving Entity can no longer meet energy requirements?
• Why do system operators monitor system conditions closely?
• What is a primary cause of low voltage levels in the Transmission and Distribution system?
• In an Arranged Interchange, who must receive the Arranged Interchange for reliability assessment?
• What is the relationship between the available transfer capability and the maximum scheduled interchange when dealing with unscheduled flows?
• How can the operator verify synchronization before energizing an emerging power line?
• During system restoration, which strategy should be prioritized for effective load management?
• In the event of damaged transmission lines and tripped generators, what should the system operator do?
• What is the first action required to manage an SOL violation due to an overloaded flow gate?
• What is the purpose of a Special Protection System?
• What type of relay is a 51?
• When a Transmission Operator is expecting to shed load due to an SOL, which parties must be notified?
• Who is responsible for updating the tag when a Dynamic Schedule varies significantly?
• When is the best time to schedule an outage for a 161 kV shunt capacitor bank for non-emergency work?
• Given a system frequency of 60.00 Hz and a frequency bias setting of 100 MW/0.1 Hz, what is the ACE if the Net Actual Interchange is +100 MW?
• What is a key factor for ensuring the reliability of a power system?
• A transformer rated at 50 MVA is currently carrying 30 MW of load. At this load, what is the maximum allowable MVAR flow through the transformer?
• A System Operator has three generators online with 1200 MWs capacity and loads at 500 MWs. What is the max load they can restore without risking re-collapse?
• Balancing Authorities on the Scheduling Path are responsible for assessing which aspects of the Interchange Transaction?
• The Reliability Coordinator shall coordinate what with other Reliability Coordinators as needed?
• In coordinating under frequency load shedding, when should generators trip?
• A capacitor rated at 50 MVAR is supplying 45 MVARs to the system. What is the most likely reason for this situation?
• What must the Source Balancing Authority assess before approving Arranged Interchange?
• A report must be submitted to NERC after shedding how much firm load?
• In an electrical system, when will voltage support equipment be most necessary?
• If a Transmission Operator recognizes potential reliability threats from line loading, what should they do?
• What does a positive ACE indicate when dealing with balancing authorities?
• In a Power System, cold load can best be described as which of the following?
• Which type of power is essential for voltage support on loaded transmission lines and crucial for dynamic reserves?
• If a Balancing Authority is running low on resources, which Energy Emergency Alert Level should they request?
• If a Balancing Area's ACE is initially -40 MW and loses 800 MW generation but stabilizes at -42 MW, what is the required action if it meets DCS?
• What is the role of a Reliability Coordinator when a transmission operator reports an overload condition?
• What should a Reliability Coordinator have in place if analysis tools are unavailable due to planned maintenance?
• Who is responsible for notifying entities when an Arranged Interchange transitions to a Confirmed Interchange?
• A conductor is rated for 180 MVA, a current transformer at one end is rated at 160 MVA, and the bus is rated at 200 MVA. What is the MVA limit for this transmission line?
• Which of the following best describes the consequence of allowing a power angle to exceed 90 degrees?
• What is the process of strategically placing generators to alter the flow of active and reactive power called?
• What should the Transmission Operator do when voltage levels at substation buses are below nominal after a trip?
• During the restoration of a full system shutdown, what is the best practice to avoid re-collapsing the system?
• What signifies an Emergency Energy Alert (EEA) Level 3?
• When experiencing low voltages, what should Balancing Authority A do when Neighboring Balancing Authority B requests emergency assistance?
• Prior to installing new relays on major transmission tie lines, who should the Transmission Operator notify?
• Two phase conductors of a 138kV transmission line come in contact due to a storm, creating a phase to phase fault. What two measured parameters caused the distance relay to operate?
• When two identical A/C generating units operate in parallel with different governor droops, which unit tends to take the lesser portion of load changes?
• What resources should a system operator utilize to address emergency conditions?
• Which consequence is likely without adequate reactive power resources?
• As system loads increase, how must a System Operator respond effectively?
• What is the minimum expected recovery time for re-synchronizing after a generation trip?
• Entities that have a reliability relationship with a Reliability Coordinator must provide data to monitor operations of what?
• Which metered data is included in the calculation of Area Control Error (ACE)?
• If a Transmission Operator cannot restore Real and/or Reactive Power Balance, what immediate action should be taken?
• If a Balancing Authority has a frequency bias and ACE equals 0, what should the interconnection ties equal?
• What is one primary reason for operator involvement in protective schemes?
• What does an Operational Planning Analysis assess regarding planned operations for the next day?
• If reactive resources are limited, what should a Transmission Operator consider doing?
• In a 345 kV transmission system, which device can be used to increase the voltage?
• When comparing the two lines connected to a bus, which factor is most critical in determining voltage behavior at the open ends?
• What is typically monitored by the Reliability Coordinator during low-frequency events?
• What happens if the system voltage remains below .9 p.u. for an extended period?
• What should a system operator prioritize to prevent cascading failures in the event of generator trips?
• What is the definition of a contingency in power systems?
• When generators are supplying reactive power, they are considered to be which of the following?
• What is the expected result when adjusting an under load tap changer (ULTC) tap setting to support low side voltage?
• What is the risk of excessive MVAR supply during restoration attempts?
• Which disturbance would be reportable for Disturbance Control Performance evaluation under NERC DCS criteria?
• How many MVars are gained when energizing a capacitor rated at 100 MVar on a 345 kV line at 90% of normal voltage?
• What occurs during reconfiguration when trying to offload heavily loaded lines?
• Who must have the authority to direct reliability entities to mitigate critical conditions?
• If an 800 MW generator trips in an external Balancing Authority, what would you likely observe in your area?
• What is the first action to take when an alarm indicates low oil pressure on a transmission cable?
• Which of the following constitutes a reliability event?
• A portion of a Reliability Coordinator Area is experiencing declining voltage and is running short on reactive reserves. Which Operating Instruction should the Reliability Coordinator give?
• If a step-down transformer has a 2 to 1 turn ratio and 140 MWs power is entering, what is the output power?
• What is the primary responsibility of a Reliability Coordinator during system restoration?
• What alert level must a deficient entity request when all available resources are committed?
• What should be done if the Interconnection frequency is 60.20 Hz and the ACE is a large positive value?
• Where should synchronization of islands occur in a power system?
• What action must a Transmission Operator take to unload an overloaded radial transmission line?
• If a fault is indicated at Substation A and B, what does this suggest about the location of the fault?
• What does the term "Dynamic Schedule" refer to in the context of energy management?
• What should the Transmission Operator consider when reactive resources are limited?
• What operational practice must Transmission Operators follow regarding the handling of emergency situations?
• Which factor can cause complications during system restoration?
• What must be included in the considerations for scheduling arrangements in energy interchange?
• How much load needs to be shed for a 1 Hz frequency deviation when in an island?
• A Transmission line is loaded at 125% of its System Operating Limit. What action would be acceptable under these conditions?
• If substantial generation is offline due to issues, what action should not be taken until further reviewed?
• The maximum and minimum voltage, current, frequency, real and reactive power flows on individual equipment are determined by which factor?
• In an over-capacitive system, what effect does a leading current sine wave have on voltage?
• Which action is appropriate when a 500 MW generator fails, causing system instability?
• Which relay would be engaged to protect against overcurrent conditions in a power system?
• Which of the following factors would not be considered in determining ratings of transmission facilities?
• To unload an overloaded radial transmission line, what action must the Transmission Operator take?
• Which phrase describes the state of voltage collapse?
• What should a generator operator do while the voltage regulator is out of service for repairs?
• Who is responsible for developing and implementing load shedding plans?
• What is the most common effect of a Geomagnetic Disturbance on the power system?
• Before shedding firm load to alleviate voltage collapse, whom must the operator confirm the action with?
• What action is required if system voltage drops below .87 p.u. for 10 minutes?
• If the ACE is calculated using incorrect or incomplete data, what potential issue can arise during operations?
• What is the role of a Regional Reliability Organization in response to system disturbances?
• If Line #2 is twice as long as Line #1 and Line #1 shows a higher voltage, what can you conclude about the voltage at the open end of Line #2?
• In system restoration, what should be the priority for restoring power?
• If a transmission line has a System Operating Limit (SOL) of 650 MWs and a firm transaction scheduled will load it to 665 MWs, how much of the non-firm transactions must be cut?
• When is voltage reduction for load relief acceptable on the transmission system?
• What is the loading on the shortest remaining line after one line trips, if initially loaded at 200 MW?
• During a lightning storm, what should a Transmission Operator do after realizing possible cascading outages from a locked-out transmission line?
• What causes angle instability in a power system?
• To effectively manage frequency during the restoration process, how much load should ideally be avoided from being energized?
• What is the most likely occurrence after a major transmission system disturbance causes a large loss of load?
• What is an important measure when facing a disturbance in the power system?
• What action should a Transmission Operator take after experiencing an unexpected loss of a transmission line with an upcoming peak demand?
• Which entities can determine if a Dynamic Schedule deviation is a reliability concern?
• Which entity integrates resource plans ahead of time and maintains load-interchange-generation balance within a Balancing Authority Area?
• When adjusting voltage levels, what is a necessary consideration for stability during transmission?
• If a circuit breaker lacks a synch-check and has a large standing phase angle, how should the operator confirm it is safe to close?
• What is the net actual interchange for Balancing Authority B given its tie-line readings with BA A and BA C?
• The Reliability Coordinator shall identify sources of large _______________________ that may be contributing to Frequency Error, Time Error, or Inadvertent Interchange.
• What constitutes a reportable disturbance based on NERC DCS criteria for a Balancing Authority with a 900 MW unit?
• What is a common strategy for managing reactive power during unexpected outages?
• What happens to the transformer’s power when the voltage is reduced?
• If a Balancing Authority cannot meet demand and reserve requirements, which entity should it notify?
• What should the Balancing Authority do to handle a voltage drop resulting from a generator trip?
• What does a GMD refer to in the context of Reliability Coordinators?
• How is Power Factor defined?
• What is the correct response to a Balancing Authority experiencing all resources committed to firm load?
• As a Transmission Operator, what device should you operate to raise the voltage level back to normal?
• Which action transitions an Arranged Interchange to Confirmed Interchange status?
• What consequence arises from failing to meet the DCS criteria of recovery within 15 minutes?
• What should a transmission operator do if they observe a large power angle approaching 88 degrees between generation and load areas?
• What is one of the key functions of under frequency load shedding?
• How many zones of protection do distance relay schemes often utilize?
• After a frequency recovery, what is the total load a Transmission Operator must restore manually if the system frequency falls and subsequently returns to normal?
• If a frequency bias setting is less negative than the response of a Balancing Authority during a frequency increase, what will be the ACE result?
• What must a Balancing Authority do if voltage drops to 200 kV for 3 minutes after a generator trip?
• If a high voltage DC tie is on the Scheduling Path for a transaction, who shall coordinate the Interchange Schedule with the Transmission Operator of the HVDC tie?
• Who is the key point of contact during emergencies?
• Which of the following correctly describes the role of the Balancing Authority?
• Which of the following actions is most critical for maintaining system reliability during peak load periods?
• If a System Operator identifies a transmission line at 100% of its SOL, what action should be taken?
• What action should a Transmission Operator avoid when encountering high system loading?
• When should the Transmission Operator seek reactive power support?
• How should a system operator respond if a 230 kV transmission line experiences an overload with specific MW and MVAR flows?
• What is the primary goal of Under Frequency Load Shedding (UFLS)?
• To predict the system's near-term load pattern, which of the following is essential information for a system operator?
• What critical function does a System Operator perform regarding abnormal operating conditions?
• If the actual frequency runs from 60.035 to 60.045, what does this indicate to a Balancing Authority Operator?
• What is typically a consequence of a major disturbance within a Balancing Authority?
• What should be used as benchmark loading conditions when scheduling maintenance for system reliability?
• A 360 MW Interchange Transaction is curtailed to 0 MWs at 1540. What is the hourly integration for the hour ending at 1600?
• To keep inadvertent interchange down to a minimum, which action is the most effective?
• All real-time system operators must monitor ___________.
• What is the best course of action if a real-time contingency analysis shows a radial transmission line will overload?
• What typically occurs if system frequency drops significantly during operation?
• What is the primary goal of the Reliability Coordinator regarding interconnection reliability?
• During a slow time error correction, if the EMS system does not allow frequency changes, what is an appropriate response?
• Bulk Electric System facilities should not be removed from service unless which conditions are met?
• What equipment is typically used to transform current from the primary circuit to a smaller proportional amount for protective relays?
• Which protective device calculates the impedance of a line by measuring the voltage and current of that line?
• Which phenomenon can affect the voltage stability of a power system?
• When faced with a large generation trip, what should a Balancing Authority notify the Reliability Coordinator?
• Which is a primary function of a Balancing Authority during an emergency?
• During peak hours, what is the appropriate notification to make when firm load shedding is necessary to prevent voltage collapse?
• As load increases throughout the day, how do two adjacent lines, one overhead and one underground, respond?
• For a 345 kV line with a MW flow of 400 and a MVAR flow of 300, what is the MVA loading on the line?
• System Operators must act to maintain reliability through actions like canceling outages and load shedding for which purpose?
• Which relay type is specifically designed to prevent excessive current flow?
• In evaluating a line outage request, what must you ensure regarding contingencies?
• Interchange Schedules must begin and end at times agreed upon by which entities?
• What is a key responsibility of the Balancing Authority regarding frequency control?
• What is the first action a Transmission Operator must take when energizing a blacked-out area?
• 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?
• What actions can a Reliability Coordinator direct reliability entities within its area to take to restore system reliability?
• What type of relays are primarily used for power system equipment protection rather than line protection?
• Under what condition should the Reliability Coordinator use the Operating Procedure to open one end of the 161 kV line?
• When a large block of load is lost, which error is expected to reflect that change?
• What happens to ACE if there is a frequency decline due to a loss of generation in an external balancing area?
• What type of relay operates based on the ratio of potential transformer to current transformer measurements?
• What must the transmission system operate to avoid due to the most severe single contingency?
• According to reliability practices, what must a System Operator prevent regarding transmission system operations?
• What action should a transmission operator take when a major transmission line is overloaded and imminent damage is possible?
• 150 MW is flowing into the high side of a 200 MVA transformer. If the transformer windings have a 2 to 1 ratio, what MW value is flowing out of the low side winding of the transformer?
• For which elements to be metered is essential for proper ACE equation functionality?
• What values change instantaneously during a sudden loss of a large block of load?
• During which scenario is it essential for an operator to be aware of the interchange transactions prior to a system collapse?
• Before energizing a blacked-out area, a system operator must do which of the following?
• What action should be taken when informed of a slow time error correction that cannot change the scheduled frequency?
• What is the main purpose of the Operating Plans developed by the Transmission Operator and Balancing Authority?
• What happens to the bus voltage when a long transmission line is connected from that bus and the other end is left open?
• What is the best course of action for a System Operator when faced with potential equipment failure on a transmission line?
• What should an Operator do first if a transmission line is overloaded above its SOL?
• The 138/13 kV transformer was tripped to protect what from damage?
• What must the Balancing Authorities do prior to implementing the Interchange Agreement with an HVDC Transmission Operator?
• When is the ideal time to schedule a capacitor bank outage?
• What should a Reliability Coordinator do if a flow gate becomes overloaded due to a parallel line failure?
• Who should a Generator Operator contact about issues with the generator voltage regulator?
• When implementing a system restoration plan, what should be the operator's first priority?
• Which Energy Emergency Alert level is required if firm load shed is imminent?
• When experiencing multiple contingencies, at what interval should they be treated as a single contingency?
• Which type of transmission line is the best choice to energize a generator facility?
• If emergency resources are exhausted, what's the next step a system operator should take?
• What is considered when determining the priority of load shedding during a frequency drop?
• Which of the following would you expect to experience during a Geo-Magnetic disturbance?
• Which equipment should be used first for maintaining or increasing system voltages?
• Who should a Generator Operator notify if there are vibration problems leading to a reduction in reactive power production?
• What is an objective of voltage reduction during system stress?
• What is the most critical factor for accurate load forecasting?
• When a disturbance causes a frequency drop to 59.94 Hz, what should the Reliability Coordinator do first?
• What action should the Reliability Coordinator coordinate if a real-time contingency analysis shows a high voltage transmission transformer overloading?
• Which Dynamic Schedule must have a modified tag?
• What values must be monitored by a synchronous check relay before a circuit breaker can close automatically?
• What indicators alert a system operator about potential voltage collapse on a heavy load day?
• What action can be taken to prevent voltage collapse with insufficient reactive resources?
• Who should notify the Sink Balancing Authority for a curtailed Interchange Transaction?
• The Roxboro - Milburnie Black 230-kV line has 80 MW and 60 MVAR flowing into Milburnie Substation. What is the power factor?
• What is the purpose of having correct interchange schedules?
• When should manual load reductions be executed according to the Operating Plan?
• In restoring power after a system collapse, what crucial step ensures stability before load restoration?
• If Balancing Authority A is importing 400 MWs from Balancing Authority B, what should they do to address the potential SOL issue?
• What is the significance of a system's frequency bias setting in operations?
• In the context of reliability, what best defines 'Frequency Error'?
• Under what condition should the Transmission Operator disconnect from the interconnection?
• In what scenario might a Transmission Operator need to disconnect from the grid?
• What is defined as the collection of transmission assets that the Transmission Operator is responsible for operating?
• What issue is caused by high transmission system voltages during restoration?
• What impedance characteristic should system restoration plans establish to enhance the transmission system backbone?
• Re-synchronization with the Interconnection is ideally performed at which type of location?
• Who must the Transmission Operator inform when an SOL has been exceeded?