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Level 2 Electrical, Canada > Overcurrent And Service Equipment > Flashcards

Overcurrent And Service Equipment Flashcards

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1
Q

Does the electrical code apply to the supply authority?

A

No.

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2
Q

What is section 6 in the code?

A

Covers requirements for the installation of consumers services and service equipment.
Applies to all electrical installations operating at 750v or less

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3
Q

What is a combination panel?

A

The service box and the panel board.

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4
Q

The max height of triplex service drop for landscaped yard

A

3.5m

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5
Q

The max height of triplex service drop for residential driveway

A

4m

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6
Q

The max height of triplex service drop for commercial driveway

A

5m

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7
Q

The max height of triplex service drop for public street, alley, or highway

A

5.5m

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8
Q

Point of attachment may not exceed _____m above finished grade

A

9

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9
Q

Max ____V between conductors

A

300

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10
Q

The distance between the roof and the bottom of the drip loop is ____mm

A

600

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11
Q

Total length of drip loop allowed

A

750mm

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12
Q

The TX and primary high voltage conductor are installed by and are the responsibility of

A

The utility company

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13
Q

Always check with ______ before commencing work

A

Local utility and inspection authority

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14
Q

Rule 6-300 installation of underground consumer service conductor means:

A

This rule deal with protection of conductors against damage and sealing of underground conduits where they enter a building

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15
Q

Can you use both PVC FA and TA in a meter base hub?

A

No. Only FAs can be used. Must use a chase nipple threaded into hub and then FA over the chase nipple.

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16
Q

Which side of the meter base is dedicated?

A

Line side.

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17
Q

What is the size of a meter base?

A

450 x 300 x 112.5 mm

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18
Q

What is the purpose of grounding?

A

Minimize voltage spikes, stabilizes normal voltage to ground. Overcurrent devices can operate faster when responding to ground faults.

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19
Q

Effective grounding occurs when _______

A

A low impedence ground path is provided

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20
Q

The arching damage to electrical equipment and conductor insulation is closely related to the value of

A

I^2t

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21
Q

What does the word ‘system’ mean in equipotential grounding system

A

The service neutral conductor, grounding electrode, cold water pipes, gas pipes, service entrance equipment, jumpers installed around meters. All must be bonded together.

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22
Q

Rule 10-002 sets out objectives of bonding and grounding. What are they?

A

To protect life from the danger of electric shock, limit voltage upon a circuit, facilitate the operation of electrical apparatus and systems, limit voltage on a circuit when exposed to lightning, limit AC circuit voltages to ground to 150 volts or less on circuits supplying interior wiring systems

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23
Q

When bonding a sun panel, what must be removed?

A

The bonding jumper, remove and place it on bottom of panel.

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24
Q

What value of current can cause death?

A

0.01 amp

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25
Q

Cost of electrical energy calculation

A

Cost = (watts • hours used per day • cost per kWh) / 1000

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26
Q

All protective devices serve the same purpose:

A

Protect conductors and insulation from excess amounts of heat arising from overload and overcurrent

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27
Q

What is an overload?

A

Moderate increase in current beyond the normal rates current value

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28
Q

Typical values of overload currents may range as high as _____

A

6 times the normal current

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29
Q

What is overcurrent?

A

Extreme increase in current well beyond the normal rates current value

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30
Q

Two types of shorts

A

Line to ground, and line to line

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31
Q

What is a short circuit?

A

Larger than normal current which flows outside the normal current path

32
Q

What is a common cause of arc faults?

A

Loose connections at terminals

33
Q

Formula to calculate %Z

A

%Z = E short circuit / E rated

34
Q

Formula to calculate fault currents

A

I short cct = I Full Load / %Z

35
Q

What is mechanical forces?

A

High fault currents exerting terrific magnetic stress on bud bars and equipment

36
Q

How can thermal energy be minimized?

A

By using a current limiting device that clears a high fault current within the first half cycle

37
Q

Four important factors in influencing choice of circuit protection.

A

Voltage rating, current rating, interrupting rating, clearing time

38
Q

Voltage rating of a fuse must be _______ than the voltage of the circuit

A

Equal or greater

39
Q

What are the standard fuse voltage ratings?

A

125V, 250V, 300V, 600V

40
Q

What is the interrupting rating?

A

The maximum short circuit current an over current protective device can safely handle without damaging itself

41
Q

What interrupting rating do HRc fuses usually have?

A

200,000A

42
Q

Time current characteristics compare _______

A

Fault magnitude and speed of response

43
Q

Time delay fuses are marked with the letter

A

D

44
Q

Non time delay fuses are marked with

A

P

45
Q

The higher the current the quicker the fuse opens. This process is

A

Inverse time current characteristics

46
Q

What are the two general categories of fuses?

A

Plug and cartridge

47
Q

The max voltage allowed for plug fuses is ____

A

125V between conductors

48
Q

The two interchangeable plug fuse types

A

Type C(T), and S

49
Q

The three types of cartridge fuses

A

Ferrule contact (flat ends), knife (blades), and bolt on (blades with holes)

50
Q

What class are standard fuses?

A

H.

51
Q

What are standard class H fuses filled with?

A

Silica sand.

52
Q

What is the exterior of fuses made of?

A

Porcelain

53
Q

What is the purpose of the silica sand in a fuse?

A

Fire extinguishing powder. Prevents arc from continuing or bursting through the tubing of the fuse.

54
Q

What type of fuse is a renewable link fuse? Time delay or non time delay?

A

Non time delay. Link must not be spiked.

55
Q

Explain how a time delay fuse works.

A

Consists of two fuse links, joined by thermal cutout unit or overload element, has a copper heat sink, and spring loaded connector. The connector is held in by a soldering pot (low melting point)

Sometimes referred to as dual element

56
Q

All standard P fuses have an interrupting capacity rating of _______

A

10000A

57
Q

What are HRC fuses?

A

High rupturing capacity. Interrupt large short circuit currents without disintegrating

58
Q

How does the sand work in an HRC fuse?

A

Under heavy current and short circuit condition the silica sand turns to a glass like material, blocking formation of an arc.

59
Q

What are the two types of HRC fuses?

A

HRCI - protects from overloads and short circuits.
HRCII - protects from only short circuits

60
Q

Current and voltage rating if Class R fuses.

A

0-600A, 250v and 600v. 200,000 A interrupting capacity

61
Q

Amp and voltage ratings of Class J fuses.

A

0-600A, 600v, 200,000a interrupting capacity. Available in time delay and fast acting

62
Q

Characteristics of class CA fuses

A

0-30A
600V
200,000 interrupting capacity
Peak let thru current of 8000A
Non interchanagble

63
Q

Characteristics of CB fuses

A

0-60A
600V
200,000A
Peak let through current of 10,000A for 30A or less, 15000A for 31-60A
Non interchangeable

64
Q

Characteristics of class Cc fuses

A

0-30A
600V
Interrupting current of 200,000A
Maximum peak let through of 12000A
Non interchangeable

65
Q

Four types of molded case circuit breakers

A

Thermal, thermal magnetic, magnetic, solid state

66
Q

CEC requires all breakers to be ______

A

Trip free

67
Q

What does the CEC define a breaker as

A

Electro mechanical device

68
Q

What current causes a GFI to trip?

A

5mA

69
Q

Ferrule dudes have current ratings from

A

0-60

70
Q

Knife blade have current ratings

A

0-600

71
Q

What does eutecfic alloy mean?

A

Low melting point

72
Q

Max ratings of class H fuses

A

600v, 600a

73
Q

What is clearing time

A

Total time from fault to no current

74
Q

Max interrupting eating for a class H

A

10,000A

75
Q

The only classes that are HRCII

A

Class C, HRCII Misc

76
Q

What is the outer shell of a fuse made of?

A

Class H: porcelain
HRC: fibreglass.

77
Q

Which type of switch can be used as disconnecting means

A

Double pole single throw

Level 2 Electrical, Canada (19 decks)

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