This training presentation covers the basic on arc flash and other electrical hazards, including the effects of an arc flash incident and how to determine shock and flash protection boundaries for a safe workplace

1. Arc Flash Basics
TRAINING
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2. Electrical Hazards
• Shock
(A) Touch Potential (B) Step Potential (C and D) Touch / Step Potential
• Arc Flash
• Arc Blast
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3. Arc Flash & Arc Blast
• Arc Flash
– Heat
– Fire
• Arc Blast
– Pressure
– Shrapnel
– Sound
SM Example of an arcing fault

4. Arc Flash
• As much as 80% of all electrical injuries are burns resulting
from an arc flash and ignition of flammable clothing
• Arc temperature can reach 35,000°F - this is four times
hotter than the surface of the sun
• Fatal burns can occur at distances over 10 ft
• Over 2000 people are admitted into burn centers each year
with severe electrical burns
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5. Arc Blast
• An arc fault develops a “pressure wave”
• Sources of this blast include:
– Copper expands 67,000 times its original volume when
vaporized
– Heat from the arc, causes rapid air expansion
• This may result in a violent explosion of circuit
components and thrown shrapnel
• The blast can destroy structures, knock workers from
ladders, or across the room
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6. Arcing Fault - Effects
Molten Metal
35,000 F
Pressure Waves
Sound Waves
Shrapnel
Copper Vapor:
Solid to Vapor Hot Air-Rapid Expansion
Expands by
67,000 times
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Intense Light

7. Arc Flash Hazard
• Energy of Arc Flash determined by:
– Arcing fault duration or time to clear
• Speed of the overcurrent protective
device
– Arcing fault current magnitude
• Available fault current
• Current-limitation can reduce
– Distance to Arcing Fault
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8. Test 4 Still Photo Before
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9. Test 4 Still Photo INITIAL
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10. Test 4 Still Photo DURING
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11. Test 4 Still Photo FINAL
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12. Test 4 RESULTS
• Burns
– 3rd Degree at Neck and Hands
– Shirt did not ignite and reduced to
below 2nd degree burn
• Sound – 141.5 db
• Pressure – Collapsed Lungs
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13. NFPA70E - Electrical Hazard Analysis
NFPA 70E 110.8(B)(1)
– Requires an electrical hazard analysis if working
on or near exposed conductors or circuit parts
• Shock Hazard Analysis
– “Approach Boundaries”
• Flash Hazard Analysis
– Flash Protection Boundary
– Incident Energy / PPE
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14. Shock Hazard Analysis
• NFPA 70E 130.2(A)
• A shock hazard analysis shall determine:
– The voltage to which exposed
– The boundary requirements
– The personal protective equipment necessary
in order to minimize the possibility of electric
shock to personnel
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15. Shock Protection Boundaries
• NFPA 70E 130.2(B)
• The shock protection boundaries identified
– Limited Approach: Qualified persons and
unqualified if accompanied by qualified person
– Restricted Approach: Qualified persons only
– Prohibited Approach: Qualified persons only –
PPE as if in direct contact with live part
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16. Shock Protection Boundaries
NFPA 70E Table 130.2(C)
Column Number (1) (2) (3) (4) (5)
Limited approach Boundary Restricted Prohibited
Nominal System Approach Approach
Voltage Range Boundary Boundary
Includes Includes
Exposed Exposed Inadvertent Reduced
Movable Fixed Movement Inadvertent
Phase-to-Phase Conductor Circuit Part Adder Movement
Adder
Energized Part to Employee - Distance in feet - Inches
Less than 50 V Not Specified Not Specified Not Specified Not Specified
50 V to 300 V 10 ft. 0 in. 3 ft. 6 in. Avoid Contact Avoid Contact
301V to 750 V 10 ft. 0 in. 3 ft. 6 in. 1 ft. 0 in. 0 ft. 1 in.
751 V to 15 kV 10 ft. 0 in. 5 ft. 0 in. 2 ft. 2 in. 0 ft. 7 in.
15.1 kV to 36 kV 10 ft. 0 in. 6 ft. 0 in. 2 ft. 7 in. 0 ft. 10 in.
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17. Flash Hazard Analysis
• NFPA 70E 130.3 Flash Hazard Analysis: Flash hazard
analysis shall be done in order to protect personnel
from the possibility of being injured by an arc flash. …”
• What is required?
– Determine Flash Protection Boundary
– Determine the personnel protective equipment (incident
energy determination)
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18. Flash Protection Boundary
Linear distance from exposed live parts within
which a person could receive second degree
burns (1.2 cal/cm2) resulting from an arc flash
480V
MCC
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19. Flash Hazard Analysis
Three common methods (600V or less):
1) Default FPB and task-hazard/ PPE tables
• Qualifiers and limitations
2) Utilize NFPA 70E equations
• Incident energy – select PPE
• FPB
3) IEEE1584: equations or calculator
• Incident energy – select PPE
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20. Flash Hazard Analysis
• NFPA 70E 130.7(C)(10) Protective Clothing
and Personal Protective Equipment Matrix
– Determine after calculating the incident energy
of the arc
– Hazard Risk Category
• HRC 0: 0-1.2 cal/cm²
• HRC 1: 1.2-4 cal/cm²
• HRC 2: 4-8 cal/cm²
• HRC 3: 8-25 cal/cm²
• HRC 4: 25-40 cal/cm²
• DANGEROUS: > 40 cal/cm²
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21. NFPA70E - Electrical Hazard Analysis
Flash Protection Boundary (FPB)
Equipment
Must wear appropriate PPE
PROHIBITED RESTRICTED LIMITED
Q Q Q Q Q
U U U U U
Arc Flash PPE Q U
Shock PPE
+
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