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4th Year Electrical - Machines > Arc Flash And Electrical Safety > Flashcards

Arc Flash And Electrical Safety Flashcards

1
Q

What are six (6) effects that workers may experience when exposed to an arc-flash?

A
  • temps as high as 20000*C resulting in severe burns and fire
  • flying objects (molten metal/shrapnel)
  • blast pressures up to 9700 kg/m2
  • noise from blast up too 165 dB
  • IR and UV radiation
  • toxic vapours
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2
Q

What three (3) factors determine the severity of an injury due to arc flash?

A
  • proximity to arching fault
  • incident energy (heat)
  • time for circuit to open
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3
Q

Two information resources for employers to reduce injuries due to arc flash

A

CSA Z462

Alberta OH&S

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4
Q

Two shock approach boundaries

A
  • limited approach

- restricted approach

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5
Q

Eight (8) key elements of CSA Z462

A
  • training
  • developing
  • working exposed to hazards
  • safe work conditions
  • justification for live work
  • approach boundaries
  • arc flash hazard analysis
  • personal and other protective equipment
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6
Q

Minimum rating in cal/cm clothing when Arc flash PPE category is 1?

A

4 cal/cm2

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7
Q

Minimum rating in cal/cm clothing when Arc flash PPE category is 2?

A

8 cal/cm2

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8
Q

Minimum rating in cal/cm clothing when Arc flash PPE category is 3?

A

25 cal/cm2

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9
Q

Minimum rating in cal/cm clothing when Arc flash PPE category is 4?

A

40 cal/cm2

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10
Q

What class are goggles as per CSA standards?

A

2

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11
Q

What CSA standard must all safety glasses meet?

A

CSA Z94

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12
Q

What are the three (3) characteristics of clothing that the CSA Z462 considers when selecting them for PPE?

A
  • resists catching on fire
  • self-extinguishing
  • provides thermal insulation from heat radiation
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13
Q

What does the acronym ATPV stand for?

A

Arc Thermal Performance Value

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14
Q

Six (6) lockout steps

A
  • warn personnel
  • proper shutdown procedures
  • disconnect from supply
  • lock and tag
  • test before touch
  • reenergize
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15
Q

What is the purpose of a safety lockout hasp?

A

Allows more than one padlock to be used

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16
Q

How many keys per padlock?

A

1

17
Q

What CSA class are spectacles with impact and radiation?

A

1B

18
Q

PPE that protects from flames has what type of fabric characteristics?

A
  • resists flames
  • self-extinguishing
  • thermally insulated
19
Q

Canadian standard that addresses electrical safety requirements for employees

A

CSA Z462

20
Q

Heat from arc flash can reach temps up too

A

20 000 C

21
Q

Persons who cross restricted approach boundary must be qualified.

True or False?

A

True

22
Q

Three things arc flash victims can experience

A
  • severe burns
  • embedded blast shrapnel
  • temporary blindness
23
Q

Before working on any equipment that has just been deenergized you must

A

Test before touch

24
Q

Three documents an employer can reference to reduce injuries created by arc flashes

A

CZA Z462
NFPA 70E
OH&S Act

25
Q

Who sets criteria for training qualified persons to perform a hazard/risk analysis

A

CSA Z462

26
Q

CSA Z462 Risk assessment procedures are used to determine

A
  • risk level (low, med, high)
  • arc flash risk assessment
  • shock risk assessment
  • safe work practices
27
Q

Arc flash boundary is

A

Distance from arc fault a person may be exposed to an incident energy of 1.2 cal/cm2

28
Q

What is arc fault current measures in?

A

Kilo-amperes

29
Q

Typical working distance of high voltage switchgear

A

36” (910mm)

30
Q

Typical working distance of low voltage switchgear

A

24” (610 mm)

31
Q

Typical working distance of low-voltage MCC and panelboards

A

18” (455 mm)

32
Q

Three (3) factors to consider when determining proper arc flash PPE

A
  • material selection
  • thermal insulation
  • layers of protection

4th Year Electrical - Machines (7 decks)

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