NERC Practice Test Questions With Verified Answers

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? - Answer 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? - Answer 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? - Answer 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? - Answer 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? - Answer Turbine Reactive reserve response during a disturbance is best obtained from which devise? - Answer 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? - Answer A produces more reactive power than B. Lightly loaded transmission lines essentially behave like? - Answer 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? - Answer 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? - Answer 63% Which statement best describes how reactive power MVAR power normally flows? - Answer High Voltage to Low Voltage Which of the following types of data are BA and RC not required to share with one another? - Answer 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? - Answer Planned outages of generation units A 1000 MVA rated generator that produces 800 MW and 100 MVAR is best described as? - Answer Operating in a lagging mode. Inductive system Which of the following types of MW load is the most impacted by an intentional frequency reduction? - Answer 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? - Answer Angle Instability The phase voltage in a wye-connected load is 277 V. What is the line to line voltage? - Answer 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? - Answer 300 MW and No The best prediction of system load is the load forecast tool that uses? - Answer Forecasted Weather If the phase angel at an open breaker is equal to 1/10 of a cycle, this is the the same angle as? - Answer 1/10 of 360 so 36 A ___________ tool is used to ensure the power system can respond within acceptable limits of N-1 - Answer Contingency Analysis Which of the following activities would not be included in the procedures for transmission reliability? - Answer Ancillary service pricing The transmission Operator and BA shall provide documentation that operating personnel have ______ to implement real time actions to ensure the stable and reliable operation of the BES. - Answer Proper NERC Certification Credential A utility distribution bus has the following customer loads attached. What is the total customer MW load and is the total customer load capacitive or inductive? 5 MW 1 MVAR & 3 MW 1 MVAR & 2 MW -2 MVAR & 10 MW 3 MVAR - Answer 20 mw and Inductive How many MVARs does a 230 kV, 50 MVAR capacitor bank provide when the voltage id 207 kV - Answer Actual MW/ Rated MW ^2 x Capacitor Rating 40 You are a system operator and the load forecast is for an all time summer peak load day, generations and reactive resources will be tight. Which scheduled job would you allow to proceed? - Answer 735 kV shunt reactor maintenance. A contingency results in the exceedance of an IROL. What could be the result if the IROL is allowed to be exceeded longer than T sub v - Answer 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 orator should expect system stage to? - Answer Increase The actual voltage is 362kV on a 345 bus. What is the p.u. voltage? - Answer 1.05 In the initial stages of a system restoration condition high transmission system voltage problems are more likely than low transmission system voltage problems why? - Answer 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? - Answer 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? - Answer 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? - Answer Shed Load The transmission operator shall take corrective actions necessary to prevent voltage collapse when reactive resources are insufficient including? - Answer Shedding Load There is a SPS/RAS system out of service for maintenance in your BA. What actions do you take? - Answer 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? - Answer On line and AGC responsive What is the approximate MVAR/Mile production for a 345kV line? - Answer 3/4 The MSSC for your BA Area is 850 MW. A defined disturbance for DCS reporting would be qual to how many MWs? - Answer 680 Of the following which would be the best indicator of voltage collapse prone conditions? - Answer 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 - Answer 36 A__________Tool is used to ensure the power system can respond within acceptable limits N-1conditions? - Answer 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. - Answer Proper NERC certification credential How many MVAR does a 230 kV, 50 MVAR capacitor bank provide when the voltage is 207 kV? - Answer 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? - Answer 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? - Answer 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? - Answer Increase The actual voltage is 362 kV on a 345 caliber bus. What is the p.u. voltage? - Answer Actual/nominal x 100. 1.05 In the initial stages of a system restoration condition, high tansmission system voltage problems are more likely than low transmission system voltage problems. Why? - Answer Because of excessive MVAR Supply from the energization of transmission lines Reactive resources are used to? - Answer Maintain acceptable voltage levels All TOP shall operate so that instability, uncontrolled separation, or cascading outages will not occur as a result of the? - Answer Most severe single contingency N-1 A 230 kV transmission line is energized at 230 kV and is 100 miles long what is the approximate line charging contribution of this transmission line? - Answer 30 MVAR 230 kV= 1/3 MVAR per mile When a system is on the verge of a voltage collapse and nothing else can be done to alleviate the problem Operating personnel should? - Answer Shed load The TOP shall take corrective actions necessary to prevent voltage Collabs when reactive resources are insufficient including - Answer Shedding firm load There is a SPS/RAS system out of service for maintenance and you're balancing area what actions do you take? - Answer Operate within the system limits that the SPS/RAS is designed to protect against A bus with a closed breaker and then open end breaker. Draw a line of the voltage profile - Answer Close to open Voltage profile will increase when getting closer to the open breaker If a balancing authority has a 500 MW spinning reserves and of that, 300 MW are regulating reserves by definition NERC requires the regulating reserves must be? - Answer Online, and automatic generation control AGC responsive What is the approximate and the MVAR/Mile For a 345 kV overhead line? - Answer 3/4 or 1 The most severe single contingency for your balancing authority area is 850 MW.A defined disturbance for DCS reporting would be equal to how many MW? - Answer Most severe single contingency is computed using 80% of given MW 680MW A simple power system is composed of three transmission lines that connect the generation area to the load area. Three transmission lines are the same length but each line has a different impedance. Line 1 is 30 ohms, line 2 is 40 ohms , and line 3 at 60 ohms. The operating security limit of each line is 500 MW. If 1000 MW is flowing from generation to load what will the flow be online number two if the line 1 trips? Or line to violate its operating security limit? - Answer Yes, 600 MW Of the following, which would be the best indicator for voltage collapse prone conditions? - Answer Low reactive power reserves Pseudo-Tie is entered into what proportion of the balancing authorities tie line bias ACE equation - Answer 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? - Answer 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 = -3.6 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 - Answer Interruptible load