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Practice Test NERC Questions and Correct Answers
(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?
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
If the phase angel at an open breaker is equal to 1/10 of a cycle, this is the the same angle as?
1/10 of 360 so 36
A ___________ tool is used to ensure the power system can respond within acceptable limits of N-
Contingency Analysis
Which of the following activities would not be included in the procedures for transmission reliability?
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.
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
20 mw and Inductive
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
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. 1.
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
All TOP shall operate so that instability, uncontrolled separation, or cascading outages will not occur as a result of the?
Most severe single contingency N-
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?
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?
Shed load
The TOP shall take corrective actions necessary to prevent voltage Collabs when reactive resources are insufficient including
Shedding firm load
There is a SPS/RAS system out of service for maintenance and you're balancing area what actions do you take?
Operate within the system limits that the SPS/RAS is designed to protect against
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
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
Each balancing authority and transmission operator shall coordinate it's seasonal planning and operations with?
Neighboring BA, TOP, and RC
When an IROL or SOL violation occurs,________are responsible for responding to the IROL and SOL violations.
The transmission operators contributing to the violations and those affected by the violation
What type of HVDC system has two conductors, one energized with a positive voltage and one with a negative voltage?
Bipolar
Which of the following would be an example of "supplementary excitation control"equipment?
Power system stabilizer
The mega white loading on a transmission line is at the point where the natural MVAR production of the line matches the lines MVAR usage. This MW loading point is called the?
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
