Electrical Safety 030101e

Question 1

What are Arc Faults?

Answer 1

High power discharges of electrical energy that change into heat. Can occur through normal aging of a system or while personnel are present when resetting a breaker, racking a breaker or completing work without panel covers.

Question 2

What is Arc Flash?

Answer 2

An electrical current that passes through air between ungrounded and grounded conductors that produces high temperatures.

Question 3

What are some causes of Arc Flash?

Answer 3

Dust or Conductive dust in electrical equipment.
Dropping tools inside of electrical equipment.
Accidental touching of electrical equipment.
Condensation.
Material failure.
Corrosion.
Faulty installation.

Question 4

What are a few things that can increase Arc Flash Hazards?

Answer 4

Removing covers from energized equipment.

Overcurrent conditions where the gap between conductors is compromised.

Energized equipment operating near flammable or conductive dusts or hazardous environments.

Question 5

What are 3 main factors that determine the severity of an arc flash injury?

Answer 5

Proximity of the worker to the hazard.
Temperature of the arc flash.
Time it takes the circuit to break.

Question 6

What are some hazards caused by an arc flash event?

Answer 6

Flying objects.
Blast pressure upwards of 9700 kg/m².
Ultraviolet radiation.
Toxic vapours.
Sound blast up to 165 dB.
Heat upwards of 20 000℃.

Question 7

What are the two shock approach boundaries?

Answer 7

Limited approach boundary.
Restricted approach boundary.

Question 8

What is the limited approach boundary?

Answer 8

The distance within which a shock hazard exists, but no shock related PPE, tools or equipment are required.

Question 9

What is the restricted approach boundary?

Answer 9

The distance within which there is an increased risk of shock due to being close enough proximity to accidentally come in contact with conductors or circuit parts. Only a qualified person using proper PPE, tools and equipment rated for the voltage are allowed to cross the boundary.

Question 10

What are the limited and restricted approach boundaries for 120 Volts?

Answer 10

Limited - 3 ft 6 inches (42 inches)/1.0 meters
Restricted - Avoid Contact

Question 11

What are the limited and restricted approach boundaries for 208 V - 600 V?

Answer 11

Limited - 3 ft 6 inches (42 inches)/1.0 meters.
Restricted - 1 ft/0.3 meters.

Question 12

What is the incident energy level used for?

Answer 12

Determining the proper PPE to use while working on energized equipment.

Question 13

What factors can affect the required arc flash PPE?

Answer 13

System voltage

Maximum available fault current

Arc duration

Working distance.

Question 14

How many Arc Flash PPE Categories are there and what are their minimum arc rating requirements?

Answer 14

5 categories.
Category 1 - 4 cal/cm²
Category 2 - 8 cal/cm²
Category 3 - 25 cal/cm²
Category 4 - 40 cal/cm²
Category 5 - 75 cal/cm²

Question 15

What are the 6 hierarchy of risk control methods?

Answer 15

1. Elimination (De-Energize)
2. Substitution (Reduced Voltage)
3. Engineering (Guarding of Energized Conductors)
4. Awareness (Signage to Indicate Presence of Hazards)
5. Administrative Controls (Electrical Safety Procedures)
6. PPE (Shock and Arc Flash Rated PPE)

Question 16

What are the 6 steps to a lockout procedure?

Answer 16

1. Warn personnel
2. Use proper shutdown procedures
3. Disconnect Equipment from the supply
4. Padlock and tag equipment.
5. Confirm
6. Re-energize

Question 17

How much resistance does dry skin have?

Answer 17

100 000 Ω to 600 000 Ω

Question 18

How much resistance does wet skin have?

Answer 18

1000 Ω

Question 19

How much internal body resistance is there from hand to foot?

Answer 19

400 Ω to 600 Ω

Question 20

How much resistance is there from ear-to-ear?

Answer 20

As low as 100 Ω

Question 21

What are the effects of 1 mA of current?

Answer 21

No sensation.

Question 22

What are the effects of 1-8 mA of current?

Answer 22

Shock sensation but not painful. No control is lost.

Question 23

What are the effects of 8-15 mA of current?

Answer 23

Painful shock. No loss of control.

Question 24

What are the effects of 15-20 mA of current?

Answer 24

Painful shock. Muscular control of adjacent muscles is lost. Cannot let go.

Question 25

What are the effects of 20-75 mA of current?

Answer 25

Painful shock. Severe muscular contractions. Breathing is difficult.

Question 26

What are the effects of 100-200 mA of current?

Answer 26

Painful shock, causing ventricular fibrillation of the heart. It is most often a fatal heart condition.

Question 27

What are the effects of over 200 mA of current?

Answer 27

Severe burns, severe muscular contractions that clamp the heart and stop it during the duration of the shock. Artificial respiration should be administered immediately and in many cases the victim can be revived.

Question 28

How often do rubber gloves need to be properly inspected?

Answer 28

Every 6 months.

Question 29

What are the 5 steps in an emergency?

Answer 29

1. Remove the victim from the source of shock.
2. Prevent further injury.
3. Send for qualified help
4. Eliminate the danger.
5. Report the accident.

Question 30

What is the safe clearance distance when operating machinery near overhead power lines?

Answer 30

7 meters.