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Electrical Theory Basics > Ch 4 > Flashcards

Ch 4 Flashcards

1
Q

If there is a neutral-to-case connection on the load side of f the GFCI protection device, the sensors detect the imbalance of the current returning on the _______ and prevents the GFCI device from being turned on

A

ECG or Equipment Grounding Conductor

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2
Q

A current-limiting type fuse is a fuse designed for operations relating to only what?

A

Short circuits

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3
Q

The electrical connection between any two conductors of the electrical system from line-to-line- or from line-to-neutral is called:

A

Short Circuit

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4
Q

What are the two ways in which power is transferred from the utility distribution transformer?

A

Overhead service drop : underground service lateral

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5
Q

The NEC requires a listed AFCI-protection device to be installed to protect the branch-circuit wiring for ______

A

Dwelling unit bedrooms

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6
Q

A GFCI operates on the principle of monitoring the imbalance of ____ between the circuits _____ and _____

A

Current : Ungrounded : Neutral

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7
Q

The opening time for an overcurrent protection device is _____ proportional to the ______ of the current

A

Inversely : Magnitude

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8
Q

A fault must quickly be removed by doing what?

A

Opening the circuit’s overcurrent protection device

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9
Q

Would you use a GFCI or AFCI to clear a Ground Fault Parallel Arc?

A

Either

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10
Q

What happens to a fuse when a sustained overload occurs?

A

A portion of the element is overheated and breaks, which prevents current from going through the fuse.

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11
Q

Electromagnetic circuit breakers open on the principle of ________ and _______

A

Thermal Energy and Electromagnetism

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12
Q

Ground-fault protection of equipment is a system intended to provide protection of equipment from damaging ground-fault currents by _____ all ungrounded conductors of the faulted circuit.

A

Opening

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13
Q

What kinds of protection do Instantaneous breakers offer?

A

Short circuit and ground fault. Not overload

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14
Q

This type of circuit breaker depends upon temperature rise in the sensing element for actuation. It has a predetermined calibration temperature.

A

Thermal Trip Element

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15
Q

The purpose of overcurrent protection is to protect equipment and the conductors from what?

A

Dangerous temperatures

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16
Q

What is a more dangerous arc fault, parallel or series?

A

Parallel

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17
Q

Typically, when a GFCI protection device fails, the switching contacts remain closed and the device will continue to provide power _____ GFCI protection

A

Without

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18
Q

What does “AIR” stand for?

A

Ampere Interrupting Rating

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19
Q

The most effective way to reduce conductor voltage drop and power loss is to:

A

Lower the current flowing through the conductors by increasing the circuit voltage

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20
Q

What are the two ways parallel arcing faults occur?

A

Short circuit or ground fault

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21
Q

Typically, circuit breakers and fuses are designed to open or clear short-circuit and ground-circuit fault current in how many cycles?

A

Less than 1

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22
Q

The electrical connection between any ungrounded conductors of the electrical system and any non-current-carrying metal object is called:

A

Ground Fault

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23
Q

Typically, a steam turbine is directly connected to an electrical generator, which produces _______ kV, three-phase power

A

13.80

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24
Q

What are the two most common types of overcurrent protection?

A

Fuses and Circuit Breakers

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25
Q

A series arc-fault current is ____ limited; the arc’s current cannot be greater than the load current the conductor serves.

A

Load

26
Q

What temperature do electric arcs operate at?

A

Between 5,000 and 15,000 F

27
Q

Conductor power losses are directly proportional to the length of the conductor and the ______ of the current

A

Square

28
Q

Various distribution feeders transfer the primary distribution voltage from step-down substations to ________ ________

A

Distribution transformers

29
Q

Metal parts of premises wiring are bonded to a low-impedance path designed and intended to carry fault current from _______ to _______

A

The point of a line-case fault on a wiring system : the neutral conductor at the electrical supply source

30
Q

This type of breaker operates on the principle that as the current increases, the time it takes for the device to open decreases

A

Inverse time breaker

31
Q

Step-down substations reduce the voltage from the high-voltage transmission lines to 34.50 kV, 13.80 kV, or sometimes as low as 4160V. This reduced voltage is knows as ________

A

Primary distribution voltage

32
Q

Thermal circuit breakers depend on ________ _______ in the sensing element for actuation.

A

Temperature rise

33
Q

Electrical connection between any two conductors of the electrical system from line-to-line or line-to-neutral

A

Short Circuit

34
Q

The magnetic time-delay circuit breaker operates under which principle and how does that work?

A

Solenoid Principle. A movable core held with a spring, in a tube, is moved by the magnetic field caused by a short circuit or ground fault.

35
Q

A condition where equipment or conductors carry current in excess of their rated ampacity is called:

A

Overload

36
Q

The most economical way to transfer electrical power over long distances is with ______ ________

A

High voltage

37
Q

Is short-circuit current higher at the utility transformer or the branch-circuit load?

A

Utility transformer

38
Q

A ground fault parallel arc can only occur when a ___ path is present.

A

Ground

39
Q

An AFCI-protection device protects again arcing faults by recognizing the characteristics unique to an arcing fault and by functioning to _____ the circuit when a parallel arc fault is detected

A

de-energize

40
Q

The current flow in a short-circuit type arc is limited by the system _____ and the impedance of the arcing fault itself.

A

Impedance

41
Q

What are two ways to solve the problem of excessive available fault current?

A

1) Install equipment with a higher short-circuit rating

2) Install a fast-clearing fuse to protect components in the circuit.

42
Q

Electrons leaving a power supply are always trying to go where?

A

Back to the power supply, not to Earth

43
Q

Overcurrent protection devices such as circuit breakers and fuses are intended to ________ the circuit

A

Interupt

44
Q

Electrical connection between any ungrounded conductors of the electrical system and any non-current-carrying metal object

A

Ground Fault

45
Q

Why does the electric utility ground the primary and secondary neutral in multiple locations?

A

To create a parallel path as to reduce the impedance of the return neutral current path

46
Q

The voltage drop of a conductor is directly proportional to the _____ of the conductor because conductor ______ is directly proportional to the conductor lenght

A

Length : resistance

47
Q

What might cause a short-circuit parallel arc?

A

Damage to the wire’s insulation

48
Q

What do you call the element electrically connected to the end blades on a fuse?

A

Ferrules

49
Q

Neutral current should only flow on the ______, not on the metal parts of the electrical installation

A

Neutral conductor

50
Q

Adjustable trip breakers permit the ____ _____ to be adjusted

A

Thermal Trip

51
Q

Condition where equipment or conductors carry current in excess of their rated ampacity

A

Overload

52
Q

Electrical equipment must have a ______ _____ current rating that permits the circuit overcurrent protection device to clear a short circuit or ground fault

A

Short-circuit

53
Q

To remove dangerous touch voltage on metal parts from a ground fault, the fault current path must have sufficiently low _______ to allow the fault current to quickly rise to facilitate the opening of the branch circuit overcurrent protection device

A

Impedance

54
Q

This type of breaker operates on the principle of electromagnetism only and is used for very large motors and sometimes called motor-circuit protectors

A

Instantaneous trip breakers

55
Q

An inverse time breaker provides overcurrent for what kinds of faults?

A

Overload : Short Circuit : Ground Fault

56
Q

(T/F) At the step-up substation, the 13.80 kV generated voltage is transformed to 69 kV, 500 kV or even higher.

A

True

57
Q

(T/F) f you touch the neutral and ungrounded conductors at the same time the GFCI protection device will turn turn on.

A

False

58
Q

Distribution transformers further reduce the primary distribution voltage from 34.50 kV or 13.80 kV to 240V or 480V, three-phase for the average commercial or small industrial customer. What is that called?

A

Secondary distribution voltage

59
Q

Electric power is typically generated and transmitted across _____ ______ lines to the electrical substation

A

Long transmission

60
Q

The electrical system begins at a generating plant that converts energy from ______, _______, or _______, power to ____, which turns the turbine of an electric generator.

A

Coal : Oil : Nuclear : Steam

61
Q

What is the purpose of grounding and bonding metal parts of the electric utility equipment to the neutral conductor?

A

To provide a low-impedance parallel path for the purpose of clearing a line-to-case ground fault

62
Q

What is the purpose of a GFCI?

A

To protect persons agains electrical shock

Electrical Theory Basics (11 decks)

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