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NERC Practice Test Questions | Actual Questions and Answers Latest
Updated 2025 /202 6 (Graded A+)
A transmission line is operating with a voltage phase angle different of 30 degrees between the sending Vs and the receiving bus Vr. If the receiving end load is suddenly increased, the voltage phase angle difference will be? - ✔✔The phase angle will increase. When load is increased phase angle will increase. A load has a power factor of 0.9 lagging. If the load draws 100 MVA, what is the MW draw? - ✔✔ 90 pf= mw/mva The high side of a delta-wye connection transformer is connected to a power system with 199 kV L-G high side voltage. What is the voltage across the delta winding of the transformer? - ✔✔Vl-l= square root of 3 times Vl-g 1.73x191= 345kV If a transmission line is carrying 400 MW and 300 MVAR what is the MVA? - ✔✔ 3 - 4 - 5 triangle 500 MVA The prime mover is the component of the generator that creates the rotational force. In a typical coal fired steam generator what component spins the rotor? - ✔✔Turbine Reactive reserve response during a disturbance is best obtained from which devise? - ✔✔Synchronous condensers For two identically constructed transmission lines where Line A is 150 miles long and line B is 15 miles long, if both lines are lightly loaded? - ✔✔A produces more reactive power than B. Lightly loaded transmission lines essentially behave like? - ✔✔Shunt Capacitors You receive an alarm that indicates low oil pressure on an underground transmission cable. SCADA shows the pressure is continuing to drop. What is the first step you take to protect the line? - ✔✔Isolate the line
Computer simulations show that for a 100 MW schedule from Bus A to Bus B, 63% of the schedule will flow on the scheduled path and the remainder will flow on other parallel paths. What is the distribution factor for the scheduled path? - ✔✔63% Which statement best describes how reactive power MVAR power normally flows? - ✔✔High Voltage to Low Voltage Which of the following types of data are BA and RC not required to share with one another? - ✔✔Generator start up cost TOP must develop, maintain, and implement formal policies and procedures to provide for transmission reliability. Which of the following DOES NOT need to be addressed in these policies and procedures? - ✔✔Planned outages of generation units A 1000 MVA rated generator that produces 800 MW and 100 MVAR is best described as? - ✔✔Operating in a lagging mode. Inductive system Which of the following types of MW load is the most impacted by an intentional frequency reduction? - ✔✔Motor Assume there are two 250 mile long transmission lines exporting an excessive amount of MW from a generation area to a load area. One of the lines suddenly trips and the area power system collapses within a few seconds. The most likely cause of the collapse? - ✔✔Angle Instability The phase voltage in a wye-connected load is 277 V. What is the line to line voltage? - ✔✔ 480 V A simple power system is composed of three lines connecting generation to load. Each lines the same impedance, is initially loaded at 200 MW, and has a thermal limit of 400 MW. If one line trips, what the loading on the shortest remaining line be and will the thermal limit either remaining line be violated? - ✔✔ 300 MW and No The best prediction of system load is the load forecast tool that uses? - ✔✔Forecasted Weather
In the initial stages of a system restoration condition high transmission system voltage problems are more likely than low transmission system voltage problems why? - ✔✔Because of excessive MVAR supply from the energization of transmission lines All transmission operators shall operate so that instability uncontrolled separation or cascading outages will not occur in result of? - ✔✔Most severe single contingency MSSC A 230kV transmission line is energized at 230kV and is 100 miles long. What is the approximate line charging contribution? - ✔✔30MVAR When the system is on the verge of a voltage collapse and nothing else can be done to alleviate the problem, operating personnel should? - ✔✔Shed Load The transmission operator shall take corrective actions necessary to prevent voltage collapse when reactive resources are insufficient including? - ✔✔Shedding Load There is a SPS/RAS system out of service for maintenance in your BA. What actions do you take? - ✔✔Operate within system limits that the SPS/RAS is designed to protect against If a BA has 500 MW of spinning Reserves and of that 300 MW are Regulating Reserves by definition NERC requires the Regulating Reserves must be? - ✔✔On line and AGC responsive What is the approximate MVAR/Mile production for a 345kV line? - ✔✔3/ The MSSC for your BA Area is 850 MW. A defined disturbance for DCS reporting would be qual to how many MWs? - ✔✔ 680 Of the following which would be the best indicator of voltage collapse prone conditions? - ✔✔Low reactive power reserves
If the phase angle add an open breaker is equal to 1/10 of a cycle this is the same as an angle of degrees - ✔✔ 36 A Tool is used to ensure the power system can respond within acceptable limits N- 1conditions? - ✔✔Contingency analysis Transmission operator and balancing authority shall provide documentation that operation personnel have the to implement real-time actions to ensure the stable and reliable operation of the bulk electric system. - ✔✔Proper NERC certification credential How many MVAR does a 230 kV, 50 MVAR capacitor bank provide when the voltage is 207 kV? - ✔✔ 40 MVAR You are a system operator in the load forecast is for an all time summer peek load day, generation and reactive resources will be tight which scheduled job would you allow to proceed? - ✔✔735 kV Shunt reactor maintenance A contingency results in the accidents of a IROL.What could be the result if the IROL is allowed to be exceeded longer than its Tv? - ✔✔Interruption of power to a large part of the BES Generators have the ability to be used as voltage control devices. If a generator raises its VAR output, the system operator should expect this system voltage to? - ✔✔Increase The actual voltage is 362 kV on a 345 caliber bus. What is the p.u. voltage? - ✔✔Actual/nominal x 100.
In the initial stages of a system restoration condition, high tansmission system voltage problems are more likely than low transmission system voltage problems. Why? - ✔✔Because of excessive MVAR Supply from the energization of transmission lines Reactive resources are used to? - ✔✔Maintain acceptable voltage levels
Of the following, which would be the best indicator for voltage collapse prone conditions? - ✔✔Low reactive power reserves Pseudo-Tie is entered into what proportion of the balancing authorities tie line bias ACE equation - ✔✔Actual interchange The initial interconnection time error is zero seconds. The interconnection then experiences four hours of 60.02 hurts and then three hours of 59.98 Hz frequency. What is the accumulated time error? - ✔✔1.2 seconds per hour, Over frequency is a positive value so 1.2×4 = 4.8, under frequency is a negative value 1.2×3 = - 3. NERC requires that all BAs Carrie sufficient operating reserves to ensure adequate a GC and to ensure response to contingencies operating reserves can be provided from which of the following resources - ✔✔Interruptible load BA A is importing 225 MW and it's only scheduled to import 200 MW the balancing authorities Beta is 200 MW/ 0.1 Hz and frequency is 59.99 hurts what does ace indicate - ✔✔45 MW under generating The value such as MW, MVAR, amperes, frequency of volts That satisfies the most limiting of prescribed operating criteria for a specified system configuration to ensure operation within acceptable reliability criteria is called - ✔✔System operating limit (SOL) A transmission line loaded above it surge impedance loading (SIL) is a - ✔✔Net user of MVAR From the system Regardless of the process that uses, the reliability coordinator must direct it's balancing authorities and transmission operators to return the transmission system to within it's a IROL as soon as possible, but no longer than? - ✔✔30 min Relay station for microwave telecommunication system is solely dependent on a local AC power system source. What would be the disadvantage of such an arrangement? - ✔✔The relay station is lost if the AC power is lost the system has no back up
When can a transmission operator disconnect from the Interconnection? - ✔✔When equipment is endangered The basic uses of transformers include all the following except? - ✔✔Generating a voltage What are the basic uses of transformers? - ✔✔Creating electrical references, changing electrical values to a practical level to be measured, and enabling efficient power transmission Transmission line has a flow of 400 MW, 300 MVAR. The thermal limit of the line is 600 MVA. Assuming the line voltage is 352 kV, what is the MVA loading on the line and there's a line within its thermal limits? - ✔✔Yes, 500 MVA Studies have indicated that for a voltage reduction of 5% non-motor load magnitude will, on average, decreased by what percentage? - ✔✔10% A transmission path as a short term thermal limit of 1000 MVA, a long term limit of 900 NBA, a voltage stability related transfer limit of 1050 MVA, and an angle stability related transfer limit of 1100 MVA. What is the transmission pass short term operating? - ✔✔1000 MVA A transmission operator she'll have responsibility and clear decision making authority to? - ✔✔Alleviate operating emergencies A contingency results in the exceedance of an IROL. What could be the result if the IROL is allowed to be exceeded longer than Tv? - ✔✔Interruption of power to a large part of the BES Frequency shows a disturbance then from point B to point C we see a slight increase. What could be happening? - ✔✔Automatic governor response (AGR) A generator delivers its power to a multi line transmission system. Of the multiple lines connected to the generator bus, line X absorbs 25% of the generator output is line X as a transfer limit of 200 MW what is the maximum output of the generator? - ✔✔800 MW .25/200 = 1/x cross multiply
During extreme low load conditions, what are the primary system conditions a system operator typically works to alleviate? - ✔✔High-voltage and over generation Which of the following actions is used to prevent a voltage collapse due to a reactive power deficiency? - ✔✔Implement load reduction A reactor is rated at 100 MVAR nominal and is operating at a voltage of 90% how many MVAR is it absorbing from the system? - ✔✔(V actual/V nominal) ^2 ) x MVAR 81 MVAR Reactive resources are used to - ✔✔Maintain acceptable voltage levels When I system is on the verge of voltage collapse and nothing else can be done to alleviate the problem operating personnel should? - ✔✔Shed Firm load To be effective, reactive resources should be? - ✔✔Located close to load areas If the line is loaded above it's SIL, how does that affect the line and the voltage? - ✔✔The line becomes more inductive and the voltage drops If the line is below it SIL, how does that affect the line voltage? - ✔✔The line becomes more capacitive and the voltage raises. The value of MVAR,MW,MVA,Ampere,Hz, and volts that satisfies the most limiting of the prescribed operating criteria for a specified system configuration to ensure operation within acceptable reliability criteria is called? - ✔✔System Operating Limit (SOL) A system operator is attempting to synchronize two systems together in preparation of supplying customer load. The synchroscope it not moving. A system operator should first? - ✔✔Adjust generation to verify the synchroscope is working
Which condition is likely to lead to potential voltage collapse - ✔✔Insufficient dynamic reactive resources Several SCADA Alarms indicate a disturbance in area B. They are for transmission lines connecting area A the area B which have become heavily loaded due to the disturbance. One of the lines above it's SOL. Reid dispatching of generation has no effect on line flows. As the operator, which answer best applies to the situation? - ✔✔There is a possible separation or island in an area B When reactive resources are woefully inadequate to meet reactive power demand, A likely ultimate outcome is: - ✔✔Voltage collapse and separation of the system Why is location of transmission system reactive power reserves important? - ✔✔Reactive power is difficult to transmit through high impedance Of the following reactive Reserve sources, which would fall into the static reactive reserve category - ✔✔Static VAR compensator in automatic mode Of the following reactive reserve possibilities, which could be counted as dynamic reactive reserve from rotating source? - ✔✔Generator in automatic voltage regulation Following a contingency or other even that results in an IROL violation, the appropriate TOP shall return it transmission system to within limits as soon as possible but no longer than: - ✔✔30 min Under what circumstances can low voltage occur without an initiating event? - ✔✔When reactive resources are deficient Inadvertent Interchange accumulations may be paid back by one or both of the following methods? - ✔✔Unilateral and or bilateral. The entity which has the highest level of authority for reliable operation of the BES, and has a wide-area and operating tools, processes and procedures to prevent or mitigate emergency operating situations is the: - ✔✔Reliability Coordinator
Assume a TLR procedure has been implemented and Interchange Transactions have been curtailed. Assume further that the Operating Security Limits violation has been removed and some Interchange Transactions can be resumed. Which Interchange Transactions should if possible be re-established? - ✔✔Those with the highest Transmission Service Priority BA A sells 100 MW to another BA. The ramp begins at the top of the hour and is ramped for 10 min. How much energy is actually transferred within the first clock hour? - ✔✔92 MWh Operating authorities have the responsibility and the authority to take actions necessary to ensure reliable system operation within their operating areas. This could include all except which of the following? - ✔✔Selling power to purchasers will to pay higher than current bid price Which of the following will contribute favorably to a BA's CPS1 score? - ✔✔A negative ACE when frequency is above schedule A 230/115 kV transformer is rated at 100 MVA and has 80 MW entering the primary side. What would you expect the real power output to be on the secondary side? - ✔✔80 MW Several SCADA alarms indicate a disturbance in area B. There are four transmission lines connecting area A to area B which have become heavily loaded due to the disturbance. One of the lines is above SOL. Re- dispatching of generation has no effect on the line flows. As the operator, which answer best applies to this situation? - ✔✔There is a possible separation or islanding in area B Of the following reactive reserve sources, which would fall into the static reactive reserve category? - ✔✔Static VAR compensator in automatic mode The complete interchange Transaction Tag must be provided to all of the following except? - ✔✔NERC RE personal Can a synchronous machine have a negative torque angle? What does this mean? - ✔✔Yes, the machine is absorbing active power
A pseudo-tie is entered into what proportion of a BAs tie-line ACE equation? - ✔✔Actual Interchange Assume a 345/115 kV auto-transformer has NLTC on its high side winding with a range of +/- 5%. If the NLTC is initially at its neutral position, what would happen to the low side voltage if the high side tap were reduced by 5? - ✔✔Rise by 5% Which BA is responsible for initiating the implementation of each Interchange Transaction as tagged? - ✔✔The Sink BA The Source BA and Sink BA shall evaluate information for Arranged Interchange. Which data must be included in that assessment? - ✔✔Energy Profile, Ramp and Schedule Path Voltage is high in an area due to off-peak demand. There are several lightly loaded high voltage transmission lines going to radial loads. All capacitor banks are out of service. Generators still have reactive reserves both leading and lagging. What should be done first to lower the voltage? - ✔✔Use generators to absorb VARs A BA with a bias setting of - 200MW/0.1Hz changed NIs by +40MW as their part of a time error correction. The BA system operator decides instead of changing their NIs they will change their Fs value. The Fs value would be what? - ✔✔60.02 Hz Unless agreed to by all involved Ba, the normal ramp duration for an interchange Schedule between the Eastern and TRE Interconnections is? - ✔✔10 min All involved Ba, the normal ramp duration for an interchange Schedule between the Western and TRE Interconnections is? - ✔✔20 min A certain dynamic schedule is tagged for an average flow of 100 MW. By what minimum amount would this schedule have to change before the Tag must be updated? - ✔✔26 MW If in the course of operations during emergency conditions it becomes necessary to implement a voltage reduction, where should the voltage reduction take place? - ✔✔On the distribution system
A portion of a RC is experiencing low voltage. What directives should the RC give? - ✔✔Lower transfer across the area and decrease generation. A study shows that a single contingency would result in an IROL violation and the corrective action would require opening a breaker with no SCADA control due to a failed RTU. What should the system operator do first? - ✔✔Dispatch field personnel to the breaker's substation Your system is in the process of recovering from an 8 hour blackout during extreme cold weather. A "controlled operation" switching strategy would preferred in this case over the "all open" approach due to which of the following reasons? - ✔✔TO minimize battery power depletion Each TOP, TO, and DOP shall provide hours of system restoration training every calendar years to their field switching personnel identified as performing unique tasks associated with the TOPs restoration plan that are outside of their normal tasks. - ✔✔2 hours, 2 calendar years During a system restoration, a system operator is receiving high MVAR and MVA alarms from the 345 kV system. What is the best way to bring the system back to an acceptable condition? - ✔✔Energize shunt reactors Assume you are TOP. Further assume that you have both manually controlled shunt capacitors and automatically controlled generator MVAR available to use. Which type of MVAR resource would you utilize first and why? - ✔✔Shunt capacitors to increase generator dynamic reactive reserve A power system has ten units on AGC. The units have different capacities and droop settings. The biggest adjustments in MW output in response to frequency disturbance will be provided by units that have? - ✔✔Large capacity and small droop setting You are a BA, you anticipate a capacity shortage as your system moves into the days peak load hours. You should immediately? - ✔✔Inform all affected systems During operating emergencies, plans should be in place to ensure adequate supplies of fuel, including: - ✔✔Optimize the operation of generating plants, do fuel switching at plants where shortages may occur, request exemptions from environmental constraints
A 500 MW generator trips in a BA to external to your BA. Which of the following responses would you expect to see in your Area? - ✔✔Positive Net Actual Interchange deviation There are several AGC modes available to most BA. A BA that is operating asynchronously should switch its AGC mode to? - ✔✔Flat Frequency mode Real-Time Tags for interchange transactions of less than an hour from Ramp start time must be submitted? - ✔✔10 min Real-Time Tags for interchange transactions 1 - 4 hours from Ramp start time must be submitted? - ✔✔ 20 min Real-Time Tags for interchange transactions 4 hours + from Ramp start time must be submitted? - ✔✔ 120 min 2 hrs Your system load is 4000 MW. An event report to NERC is required if you shed load how many MWs to maintain continuity of the BES? - ✔✔> 100 MW The transmission path used to connect a black start resource to the next generator to start is called - ✔✔Cranking path If a BA does not meet the DCS during a given quarter, what category of reserve must be increased for the subsequent quarter? - ✔✔Contingency Reserve Which type of protection relay utilizes CTs to ensure a normal conditions balance between current inflow and outflow? - ✔✔Differential Of the following possibilities which is a GMD most likely to cause? - ✔✔Transformer Overheating A ___________tool is used to ensure the power system can respond within acceptable limits N- 1 conditions - ✔✔Contingency Analysis
Which of the following is a common method used to compensate bilaterally inadvertent interchange? - ✔✔Compensating energy flow during the appropriate on-peak off-peak hours Which of the following is a common method used to compensate unilaterally inadvertent interchange? - ✔✔Adjusting the AGC to off-set the ACE zero and consequently supply or draw more energy from the interconnection The purpose of a series capacitor is best described by which of the following statements? - ✔✔Decrease the impedance and boots power transfer capability A transmission service provider has studied their system and determined that its ATC is 1000MW from A to B. Assume that this Transmission Service Provider sells 500 MW of this ATC as non Firm. No other ATC is sold. What amount of firm ATC does this transmission service provider have from area A to B after this 500 MW non-firm sale is completed? - ✔✔1000MW Each BA and TOP shall coordinate its seasonal planning and operations with? - ✔✔Neighbouring BA's, Neighboring TOPs, RC If an interchange transaction is implemented to replace an unexpected generation loss, no Tag is required if the interchange Transaction lasts less than? - ✔✔60 min BA A has four interchange schedules active for the hour beginning 10am. Schedule 1 of 60 is in from BA B 2 of 100 is in from BA C 3 of 50 is out of BA D 4 of 100 is out of BA E Assume that a generator in BA B trips at 10:33am. The BA B system operator notifies the BA A system operator or of the unit at 10:38 am BA A and B agree to cut their schedule of 60 MW at 10:45. What is the net integrated schedule of BA A for the hour beginning at 10 am and ending at 11. - ✔✔+ mW
Transaction tags must contain certain types of information, including but not limited to the following? - ✔✔Physical path, Transmission Service Provider,POR/POD, Energy profile energy to be produced by the generator for east time segment of the Transaction, Transmission reservation number Each BA shall agree withe the Adjacent BA that their Composite Confirmed Interchange are: - ✔✔Identical in magnitude, opposite in sign Why is location of transmission reactive resource reserves important? - ✔✔Reactive power is difficult to transmit through high Impedance BA A has the following schedules implemented. What is the BAs' NIs and are they an exporting or an importing BA? Import BA B 100MW Import BA C 200 MW Export BA D 800 MW - ✔✔ 500 export A certain dynamic schedule is tagged for an average flow of 100 MW. By what min amount would this schedule have to change before the tag must be updated? - ✔✔26 MW If a capacitor bank is removed from service, what is the immediate effect will there be on the voltage? - ✔✔Decrease If system frequency were to run at 60.02 Hz for two hours how much positive time error would occur? - ✔✔2.4 seconds The Interconnection frequency suddenly drops from 60Hz to 59.94Hz while your BA ACE is zero. The Low frequency condition exists 15 min later. Assuming you have the following options which would you take? - ✔✔Make known your ability to provide emergency assistance: Act bilaterally to raise frequency What percentage of Contingency Reserve does NERC require be the frequency responsive type of Spinning Reserve? - ✔✔NO requirement
