Overcurrent
100: Overcurrent is current in excess of the equipment ampere rating or ampacity of the wires. It may result from a(an) _.
a. overload
b. short circuit
c. ground fault
d. any of these
d. any of these
100: Fuses consist of a _ element connected to end blades or caps, surrounded by silica sand filler material enclosed in a tube.
a. conductive
b. foam
c. light
d. nonconductive
a. conductive
100: _ circuit breakers operate on the principle that as the current increases, the time it takes for the device to open decreases.
a. Inverse time
b. Adjustable trip
c. Instantaneous trip
d. all of these
a. Inverse time
100: What is the approximate available short-circuit current on the secondary of a 50 kVA, 480V to 240V single-phase transformer having an impedance rating of 1.20 percent?
a. 10,000A
b. 12,000A
c. 14,000A
d. 17,000A
d. 17,000A
100: Equipment must have a(an) _ current rating that permits the protection device to clear a short circuit or ground fault without extensive damage to the equipment components.
a. overload
b. short-circuit
c. ground-fault
d. none of these
b. short-circuit
200: A(An) _ is the operation of equipment or wires in excess of their rated ampacity.
a. overload
b. short circuit
c. ground fault
d. all of these
a. overload
200: When a sustained overload occurs through the element(s) of a fuse, the heat melts _, stopping the flow of current.
a. several elements
b. all of the elements
c. a portion of the element
d. none of these
c. a portion of the element
200: The _ trip element of a circuit breaker operates on the time-current principle of being inversely proportional to the magnitude of the current.
a. magnetic
b. electronic
c. thermal
d. none of these
c. thermal
200: The factor(s) that impact the available short-circuit current on the load side of a transformer is(are) _.
a. system voltage
b. kVA rating
c. impedance
d. all of these
d. all of these
200: If the protective device is not rated to _ the available fault current at its listed voltage rating, it can explode while attempting to clear the fault.
a. interrupt
b. withstand
c. hold
d. break
a. interrupt
300: A(An) _ occurs when an unintentional electrical connection occurs between a phase wire and metal parts of enclosures, raceways, and/or equipment.
a. overload
b. short circuit
c. ground fault
d. all of these
c. ground fault
300: A _ fuse is referred to as a nontime-delay fuse and is the least expensive type.
a. single-element
b. dual-element
c. current-limiting
d. all of these
a. single-element
300: Inverse time circuit breakers have a(an) _ trip unit that responds to short-circuit and ground-fault currents.
a. adjustable
b. instantaneous
c. electromagnetic
d. none of these
c. electromagnetic
300: The available short-circuit current is different at each point of the electrical system; it is highest at the _.
a. branch circuit
b. feeder
c. service
d. utility transformer
d. utility transformer
300: Selective coordination of overcurrent protective devices prevents _ power losses to loads not part of the faulted circuit.
a. intended
b. unintended
c. excessive
d. none of these
b. unintended
400: The available short-circuit current is highest at the utility transformer and lowest at the _ load because of the impedance of the circuit.
a. branch-circuit
b. feeder
c. service
d. utility transformer
400: a. branch-circuit
400: A _ fuse is designed to clear a short circuit or ground fault in less than one-half a cycle.
a. one-time fuses
b. dual-element fuses
c. special trip fuses
d. current-limiting
d. current-limiting
400: _ circuit breakers permit the thermal and electromagnetic trip current and/or time settings to be adjusted to provide the user with flexibility for specific applications.
a. Inverse time
b. Adjustable trip
c. Instantaneous trip
d. all of these
b. Adjustable trip
400: The available short-circuit current at the _ transformer is provided by the electric utility; no calculation is required.
a. occupancy
b. building
c. premises
d. utility
d. utility
400: Lack of selective coordination of overcurrent protective devices can result in unintended _ to loads not part of the faulted circuit.
a. surges
b. power losses
c. blackouts
d. shutdowns
b. power losses
500: To quickly clear a(an) _, the ground-fault current needs to rise to a level between ten and twenty times the rating of the circuit overcurrent protective device.
a. overload
b. arcing fault
c. ground fault
d. none of these
c. ground fault
500: When a short circuit or ground fault occurs through the element of a fuse, the heat in the element rises to a point where _ in the fuse melt to stop electrical current flow.
a. multiple conductive segments
b. a small portion of the segment
c. all of the segments
d. none of these
a. multiple conductive segments
500: Circuit breakers and fuses are intended to interrupt the circuit, and they must have an ampere interrupting rating (AIR) _ for the available short-circuit current.
a. inadequate
b. sufficient
c. sustainable
d. none of these
b. sufficient
500: As the overload current _, the time it takes for the thermal trip element to open decreases.
a. increases
b. decreases
c. remains the same
d. none of these
a. increases
500: _ of overcurrent protective devices is when the devices are designed to clear a short circuit or ground fault in a manner that localizes the short circuit or ground fault to that given circuit.
a. Plotting
b. Sequencing
c. Selective coordination
d. none of these
c. Selective coordination