NERC PRACTICE SET 2 Flashcards
What causes high voltage on lightly loaded transmission line?
a. Ferranti Effect
b. Natural capacitance of the line
c. Surge Impedance Loading
d. Impedance of the system
b. Natural capacitance of the line
Your power system is experiencing heavy power flow from West to East and low voltage in the East. What should the System Operator do first in response?
a. Take lines out of service
b. Ensure all available capacitors are in service
c. Put reactors in service
d. Shed Load
b. Ensure all available capacitors are in service
Which of these is the best way to mitigate a transmission line reaching its System Operating Limit due to heavy power transfer between systems?
a. Put parallel lines in service
b. Put a capacitor in service
c. Put a reactor in service
d. Increase schedules sourcing from the direction the power is flowing from
a. Put parallel lines in service
Line A is a 100 mile long 500 kV transmission line. Line B is a 10 mile long 500 kV transmission line. Both lines are lightly loaded. Line B is contributing 3.2 MVAR to the bus. How much MVAR will Line A contribute to the bus?
a. Less than Line B
b. 32 MVAR
c. Equal to Line B
d. More than Line B
d. More than Line B
Which situations could result in planned automatic load shedding?
a. High Frequency, High Voltage
b. Over generation, Over Voltage
c. Low Frequency, Low Voltage
d. Relay mis-operation, Remedial Action Scheme
c. Low Frequency, Low Voltage
Station A is at 345 kV. Station B is at 343 kV. Megawatts flow from Station A to Station B.
Which direction will MVAR flow?
a. From high impedance to low impedance
b. From high power angle to low power angle
c. From Station B to Station A
d. From Station A to Station B
d. From Station A to Station B
Between two substations, MVARs are flowing from Station A to Station B, when the line between the substation trips. What would you expect the voltage impacted to be?
a. Voltage A will be higher than Voltage B
b. There will be no difference between Voltage A and Voltage B
c. Voltage B will be higher than Voltage A
d. There will be no voltage at either point
a. Voltage A will be higher than Voltage B
Power is flowing from Station A to SE area through a radial transmission line which has exceeded its thermal limit. What must the system operator do?
a. Shed load at A
b. Shed load at the area SE
c. Increase generation at A
d. Decrease generation at SE
b. Shed load at the area SE
What must a Reliability Coordinator be concerned with when their Transmission Operators are ready to synchronize systems?
a. System loads are equal on both sides, MW generation must be the same on both sides
b. System load and generation must be balanced on both sides, voltage and frequency must closely match on both sides
c. System load are balanced on both sides, frequency must be matched on both sides
d. Phase angle, frequency, and voltage must be exact on both sides
b. System load and generation must be balanced on both sides, voltage and frequency must closely match on both sides
What are the effects of transmission line loading above surge impedance loading?
a. The line acts like a capacitor
b. The line acts like an inductor
c. The line ceases to function
d. The line’s losses decrease
b. The line acts like an inductor
A 50 MVA transformer has 30 MW flowing into it from the high side. How many MVARS
could flow through it without exceeding limits?
a. 50 MVAR
b. 40 MVAR
c. 30 MVAR
d. 20 MVAR
b. 40 MVAR
Balancing Authority A is currently reading a system frequency of 59.94 Hz. Its Net Actual
Interchange is +100 MW and its Net Scheduled Interchange is +120 MW. If Balancing
Authority A’s frequency bias setting is -100 MW/0.1 Hz, Balancing Authority A’s AGC
should be pulsing its generators to __________.
a. Remain at current MW output level
b. Increase MW output
c. Decrease MW output
d. Increase excitation on the field windings
b. Increase MW output
A system operator notices that frequency has dropped to 59.95 Hz but his Balancing Areas ACE is zero. The Balancing Authority System Operator has plenty of generation and increases his generators until ACE is a positive 50 MW. The deficient BA recovered and frequency is 60.02 Hz. Which of these statements apply to the System Operator’s action?
1. Contributed to a high frequency
2. Helped the deficient BA
3. Cost the company money
4. Created unscheduled power flow
a. 1, 2
b. 2, 3
c. 1, 4
d. 1, 3, 4
c. 1, 4
Your system had a forced outage and contingency analysis shows that one more outage will cause an IROL violation. You have a line out for scheduled maintenance that will mitigate the contingent IROL violation. What should the System Operator consider first in this situation?
a. Initiate the return of the parallel line with protection
b. Be prepared to take corrective actions if the contingency occurs
c. Make sure no other lines will trip by taking protective tripping off the line
d. Call the RC and ask for direction
a. Initiate the return of the parallel line with protection
Frequency and voltage magnitude on each side of the breaker and the power angle across the breaker must be within proper limits when synchronizing transmission systems that have separated or islanded. To adjust these values, what would the system
operator do?
a. Adjust the tap changer on the nearest transformer
b. Adjust the power angle on one side of the breaker to 90 degrees
c. Adjust area generation output
d. Open additional lines until the voltage is matched
c. Adjust area generation output
