Overcurrent And Service Equipment

Question 1

Does the electrical code apply to the supply authority?

Answer 1

No.

Question 2

What is section 6 in the code?

Answer 2

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

Question 3

What is a combination panel?

Answer 3

The service box and the panel board.

Question 4

The max height of triplex service drop for landscaped yard

Answer 4

3.5m

Question 5

The max height of triplex service drop for residential driveway

Answer 5

4m

Question 6

The max height of triplex service drop for commercial driveway

Answer 6

5m

Question 7

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

Answer 7

5.5m

Question 8

Point of attachment may not exceed _____m above finished grade

Answer 8

9

Question 9

Max ____V between conductors

Answer 9

300

Question 10

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

Answer 10

600

Question 11

Total length of drip loop allowed

Answer 11

750mm

Question 12

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

Answer 12

The utility company

Question 13

Always check with ______ before commencing work

Answer 13

Local utility and inspection authority

Question 14

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

Answer 14

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

Question 15

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

Answer 15

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

Question 16

Which side of the meter base is dedicated?

Answer 16

Line side.

Question 17

What is the size of a meter base?

Answer 17

450 x 300 x 112.5 mm

Question 18

What is the purpose of grounding?

Answer 18

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

Question 19

Effective grounding occurs when _______

Answer 19

A low impedence ground path is provided

Question 20

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

Answer 20

I^2t

Question 21

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

Answer 21

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

Question 22

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

Answer 22

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

Question 23

When bonding a sun panel, what must be removed?

Answer 23

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

Question 24

What value of current can cause death?

Answer 24

0.01 amp

Question 25

Cost of electrical energy calculation

Answer 25

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

Question 26

All protective devices serve the same purpose:

Answer 26

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

Question 27

What is an overload?

Answer 27

Moderate increase in current beyond the normal rates current value

Question 28

Typical values of overload currents may range as high as _____

Answer 28

6 times the normal current

Question 29

What is overcurrent?

Answer 29

Extreme increase in current well beyond the normal rates current value

Question 30

Two types of shorts

Answer 30

Line to ground, and line to line

Question 31

What is a short circuit?

Answer 31

Larger than normal current which flows outside the normal current path

Question 32

What is a common cause of arc faults?

Answer 32

Loose connections at terminals

Question 33

Formula to calculate %Z

Answer 33

%Z = E short circuit / E rated

Question 34

Formula to calculate fault currents

Answer 34

I short cct = I Full Load / %Z

Question 35

What is mechanical forces?

Answer 35

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

Question 36

How can thermal energy be minimized?

Answer 36

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

Question 37

Four important factors in influencing choice of circuit protection.

Answer 37

Voltage rating, current rating, interrupting rating, clearing time

Question 38

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

Answer 38

Equal or greater

Question 39

What are the standard fuse voltage ratings?

Answer 39

125V, 250V, 300V, 600V

Question 40

What is the interrupting rating?

Answer 40

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

Question 41

What interrupting rating do HRc fuses usually have?

Answer 41

200,000A

Question 42

Time current characteristics compare _______

Answer 42

Fault magnitude and speed of response

Question 43

Time delay fuses are marked with the letter

Answer 43

D

Question 44

Non time delay fuses are marked with

Answer 44

P

Question 45

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

Answer 45

Inverse time current characteristics

Question 46

What are the two general categories of fuses?

Answer 46

Plug and cartridge

Question 47

The max voltage allowed for plug fuses is ____

Answer 47

125V between conductors

Question 48

The two interchangeable plug fuse types

Answer 48

Type C(T), and S

Question 49

The three types of cartridge fuses

Answer 49

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

Question 50

What class are standard fuses?

Answer 50

H.

Question 51

What are standard class H fuses filled with?

Answer 51

Silica sand.

Question 52

What is the exterior of fuses made of?

Answer 52

Porcelain

Question 53

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

Answer 53

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

Question 54

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

Answer 54

Non time delay. Link must not be spiked.

Question 55

Explain how a time delay fuse works.

Answer 55

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

Question 56

All standard P fuses have an interrupting capacity rating of _______

Answer 56

10000A

Question 57

What are HRC fuses?

Answer 57

High rupturing capacity. Interrupt large short circuit currents without disintegrating

Question 58

How does the sand work in an HRC fuse?

Answer 58

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

Question 59

What are the two types of HRC fuses?

Answer 59

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

Question 60

Current and voltage rating if Class R fuses.

Answer 60

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

Question 61

Amp and voltage ratings of Class J fuses.

Answer 61

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

Question 62

Characteristics of class CA fuses

Answer 62

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

Question 63

Characteristics of CB fuses

Answer 63

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

Question 64

Characteristics of class Cc fuses

Answer 64

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

Question 65

Four types of molded case circuit breakers

Answer 65

Thermal, thermal magnetic, magnetic, solid state

Question 66

CEC requires all breakers to be ______

Answer 66

Trip free

Question 67

What does the CEC define a breaker as

Answer 67

Electro mechanical device

Question 68

What current causes a GFI to trip?

Answer 68

5mA

Question 69

Ferrule dudes have current ratings from

Answer 69

0-60

Question 70

Knife blade have current ratings

Answer 70

0-600

Question 71

What does eutecfic alloy mean?

Answer 71

Low melting point

Question 72

Max ratings of class H fuses

Answer 72

600v, 600a

Question 73

What is clearing time

Answer 73

Total time from fault to no current

Question 74

Max interrupting eating for a class H

Answer 74

10,000A

Question 75

The only classes that are HRCII

Answer 75

Class C, HRCII Misc

Question 76

What is the outer shell of a fuse made of?

Answer 76

Class H: porcelain HRC: fibreglass.

Question 77

Which type of switch can be used as disconnecting means

Answer 77

Double pole single throw