Test your knowledge with the 100 quiz questions and answers on the electrical circuit breaker, generators, and electrical equipment.
Electrical Circuit Breaker Quiz
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The below mentioned the sample 15 questions from the quiz.
When a typical 4,160 volt breaker is racked to the TEST position, control power is __________ the breaker; and the breaker is __________ the load.
A) removed from; connected to
B) available to; connected to
C) removed from; isolated from
D) available to; isolated from
While remotely investigating the condition of a normally-open 480 VAC motor control center (MCC) feeder breaker, an operator observes the following indications:
Green breaker position indicating light is out.
Red breaker position indicating light is lit.
MCC voltmeter indicates 480 VAC.
MCC ammeter indicates zero amperes.
Based on these indications, the operator should report that the feeder breaker is __________ and racked __________.
A) open; in
B) open; to an unknown position
C) closed; in
D) closed; to an unknown position
Which one of the following evolutions will draw the highest current from the main generator during operation of the output breaker?
A) Closing the output breaker with voltages out of phase
B) Opening the output breaker under no-load conditions
C) Closing the output breaker with voltages in phase
D) Opening the output breaker under full-load conditions
If a breaker is racked to the TEST position, the
A) breaker can only be operated remotely from its associated remote control panel.
B) normal breaker opening and closing operations cannot be tested because the TEST position is for overload testing only.
C) electrical jumpers must be connected to the operating coils to operate the breaker.
D) remote position indication for the breaker is still operational
Which one of the following results from a loss of control power to a breaker supplying a motor?
A) The breaker position will remotely indicate closed regardless of actual position.
B) The breaker will trip open due to the actuation of its protective trip device.
C) The motor ammeter indication will be zero regardless of actual breaker position.
D) The charging motor will not recharge the closing spring after the breaker closes.
A main generator is being connected to an infinite power grid that is operating at 60 Hz.
Generator output voltage is equal to the grid voltage but generator frequency is at 57 Hz.
Which one of the following generator conditions is most likely to occur if the generator output breaker is closed with voltages in phase (synchronized), but with the existing frequency difference?
(Assume no generator breaker protective trip occurs.)
C) Reverse power
Loss of breaker control power will cause
A) the remote breaker position to indicate open regardless of actual breaker position.
B) inability to operate the breaker locally and remotely.
C) failure of the closing spring to charge following local closing of the breaker
D) breaker line voltage to indicate zero regardless of actual breaker position.
A typical 120 VAC manual circuit breaker tripped due to overload.
To close this circuit breaker, the handle must be moved from the
A) midposition directly to the ON position; trip latch reset is not required.
B) OFF position to the midposition to reset the trip latch, and then to the ON position
C) midposition to the OFF position to reset the trip latch, and then to the ON position.
D) OFF position directly to the ON position; trip latch reset is not required
Which one of the following will provide the first motor protection against electrical damage caused by gradual bearing degradation?
A) Overcurrent trip relay
B) Thermal overload device
C) Undervoltage device
D) Underfrequency relay
Breaker local overcurrent trip flag indicators, when actuated, indicate that
A) a breaker overcurrent condition is responsible for a breaker trip.
B) a breaker trip will occur unless current is reduced.
C) the associated breaker has failed to trip open during an overcurrent condition
D) an overcurrent condition has cleared and the breaker can be closed.
A diesel generator (DG) was initially operating at 80 percent of rated load supplying an isolated electrical bus when a malfunction caused the DG output breaker to trip.
The breakers for all of the bus loads-all of which are large motors remained closed, preparing the motors to restart upon restoration of power to the bus.
The DG output breaker has been repaired.
With all of the bus load breakers still closed, which one of the following will occur when the DG output breaker is closed to reenergize the bus?
A) The DG will experience severe overload conditions.
B) The DG will return directly to its initial load.
C) The DG will experience slight overload conditions.
D) The DG will become lightly loaded.
A 480 VAC motor control center supplies a load through a breaker and a manual disconnect switch.
Which one of the following sequences will provide the greatest level of personnel safety when de-energizing the load for maintenance, and when re-energizing the load after the maintenance is complete?
A) DE-ENERGIZING – Open disconnect switch first, RE-ENERGIZING – Shut breaker first
B) DE-ENERGIZING – Open breaker first, RE-ENERGIZING – Shut disconnect switch first
C) DE-ENERGIZING – Open disconnect switch first, RE-ENERGIZING – Shut disconnect switch first
D) DE-ENERGIZING – Open breaker first, RE-ENERGIZING – Shut breaker first
A thermal overload device for a large motor protects the motor from.
A) sustained overcurrent by opening the motor breaker or motor line contacts
B) sustained overcurrent by opening contacts in the motor windings.
C) instantaneous overcurrent by opening the motor breaker or motor line contacts.
D) instantaneous overcurrent by opening contacts in the motor windings
During a routine inspection of a main generator output breaker, a technician discovers severely damaged main contact surfaces.
Which one of the following is the most likely cause of the damaged contact surfaces?
A) The main generator breaker automatically tripped open due to a faulty trip relay actuation while the main generator was operating unloaded.
B) The main generator breaker automatically tripped open after it was closed with the generator and power grid voltages 60 degrees out of phase.
C) The main generator breaker automatically tripped open after it was closed with the generator and power grid voltages in phase but with generator frequency 0.2 Hz lower than power grid frequency.
D) The main generator breaker automatically tripped open on a loss of offsite power while the main generator was operating at its maximum rated load.
Which one of the following generator conditions is most likely to result in equipment damage from high current flow?
A) Tripping the generator prime mover under full-load conditions.
B) Closing the output breaker onto a bus that has a short-circuit fault.
C) Tripping the output breaker under full-load conditions.
D) Closing the output breaker onto a bus that has an open-circuit fault.
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