Deck 13: System Protection

Question 1

The three major types of circuit breakers are air, oil, and .

A) water
B) vacuum
C) alcohol
D) mercury

Answer 1

B

Question 2

A system containing only is the easiest situation to coordinate.

A) main circuit breakers
B) branch-circuit breakers
C) ground-fault protectors
D) fuses

Answer 2

D

Question 3

When an electric arc occurs in air, gas molecules in the air .

A) become polarized
B) become ionized
C) form dimers
D) start a chain reaction

Answer 3

B

Question 4

One method used by circuit breakers to sense circuit current is to connect a(n) in series with the load.

A) battery
B) ammeter
C) coil
D) resistor

Question 5

What is an auxiliary switch?

Question 6

In magnetic-type circuit breakers , there is time delay in the opening of the contacts when an overload occurs.

A) zero
B) very little
C) medium
D) very high

Question 7

air circuit breakers are used in low-voltage (600 volts or less), low-current circuits.

A) Low-voltage
B) Molded-case
C) Medium-voltage
D) High-voltage

Question 8

Classify low oil (also called oil poor) circuit breakers.

Question 9

Circuit breakers actually have two different current ratings. One is the trip rating, and the other is the rating.

A) fuse
B) ground
C) selective
D) interrupt

Question 10

There are two basic types of oil circuit breakers, the full tank or dead tank type and the low oil or type.

A) half tank
B) oil poor
C) low tank
D) oil-free

Question 11

Low-voltage power circuit breakers commonly have set(s) of contacts.

A) one
B) two
C) three
D) four

Question 12

The is the point at which a breaker responds to a short-circuit current through a magnetically actuated trip arrangement.

A) long-time delay
B) frame size
C) instantaneous pickup current
D) instantaneous opening

Question 13

A ground-fault protective device consists of a ground-fault sensor and a .

A) relay
B) circuit breaker
C) transformer
D) fuse

Question 14

What are some required and recommended uses for ground-fault protection devices?

Question 15

trips are used to open the circuit breaker contacts by energizing the solenoid from an external source.

A) Shunt
B) Fuse
C) Interrupt
D) Coil

Question 16

Coordination among multiple ground-fault protectors is achieved by using a lower setting and progressively shorter time settings on each of the downstream devices.

A) trip
B) interrupt
C) fuse
D) arc

Question 17

What is indicated by the long-time delay portion of the time-current curve?

Question 18

means that when an overload or fault condition occurs, only the part of the electrical system that is in jeopardy is disconnected.

A) Dependent coordination
B) Ground-fault protection
C) Selective coordination
D) System protection

Question 19

The amount of current that will flow during a short-circuit condition is determined by two factors: the voltage and the ____.

A) impedance
B) power
C) coil strength
D) fuse strength

Question 20

What is the mechanism behind the operation of a thermal circuit breaker?