Protection and Control - B Flashcards
What is the first thing a system operator should do after a relay operation?
A. Notify adjacent Balancing Authorities
B. Check power system stabilizers
C. Check targets and equipment
D. Call the supervisor
C. Check targets and equipment
What type of relay will detect faults within the nearest 80 - 90% of the transmission line?
A. Zone 3 Impedance
B. Zone 2 Impedance
C. Differential
D. Zone 1 Impedance
D. Zone 1 Impedance
Which type of protective relay monitors the ratio of secondary voltage divided by secondary current and activates when this ratio falls below a certain value?
A. Differential
B. Undervoltage
C. Overcurrent
D. Distance
D. Distance
What can cause a synchronous machine to have a negative torque angle?
A. The machine is absorbing active power
B. The machine is producing active power
C. The machine is absorbing reactive power
D. The machine is producing reactive power
A. The machine is absorbing active power
Which statement best describes how high-speed protective equipment (relays, circuit breaker, etc.) will enhance power system stability margins?
A. High speed protective equipment clears the fault before the current wave has a chance to reach a current-zero
B. High speed protective equipment increases the fault duration and thereby increases the acceleration/deceleration of the power system
C. High speed protective equipment reduces the fault duration and thereby reduces the MWh Absorbed by the fault
D. High speed protective equipment reduces the fault duration and thereby reduces the acceleration/deceleration of the power system
D. High speed protective equipment reduces the fault duration and thereby reduces the acceleration/deceleration of the power system
What type of protective relay system always incorporates telecommunication facilities in the protection scheme?
A. Overcurrent relay schemes
B. Pilot protection schemes
C. Differential relay schemes
D. Distance relay schemes
B. Pilot protection schemes
Which of the following is the major purpose of protective relaying?
A. Transformer tap changing
B. Protection of equipment
C. High voltage
D. Controlling frequency
B. Protection of equipment
You suspect a differential relay (87 device) has operated in a substation. You tell your substation operator to search for which of the following to verify that the differential relay has indeed operated?
A. Relay operating coil
B. Relay restraint coil
C. Relay target and/or flag
D. Relay cut-off switch
C. Relay target and/or flag
When must changes or additions to protective relay schemes on interconnected transmission lines be coordinated with neighboring systems?
A. After the line relays operate due to suspect causes
B. During heavy load periods
C. Before the neighboring system is affected
D. When the line exceeds its thermal operating limit
C. Before the neighboring system is affected
While adjusting the tap changer on a large power transformer, one of the transformer’s protective relays operate/ The most likely relay to operate would be?
A. Differential
B. Over-excitation
C. Over-current
D. Sudden pressure
A. Differential
Why would a system combine a shunt capacitor tripping scheme with their under-frequency load shedding scheme?
A. As frequency drops, generator excitation increases
B. As frequency drops, generator excitation decreases
C. As load is tripped, MVAR supply may become excessive
D. As load is tripped, MW supply may become excessive
C. As load is tripped, MVAR supply may become excessive
Under voltage load shedding (UVLS) schemes should consider all of the following except what?
A. Power flow levels
B. Rate of voltage decay
C. Voltage levels
D. Short circuit levels
D. Short circuit levels
Why would a weak source bus lead to incorrect power system protective relay response?
A. Abnormally low current flow
B. Excessively high voltages
C. Insufficient fault current level
D. Abnormally high current flow
C. Insufficient fault current level
What is the current interrupting capability of a regular disconnect switch?
A. 500 Amps
B. 50 Amps
C. 0 Amps
D. 5000 Amps
C. 0 Amps
When closing a circuit breaker between two systems (or islands) through a synch-check relay, the circuit breaker will close when:
A. The two systems are exactly in phase
B. The two systems are within 10 minutes of top dead center
C. The two systems have a 0.05 Hz frequency difference
D. The two systems are within the relay’s settings
D. The two systems are within the relay’s settings
