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Safety BASICsTM
What are the hazards as you approach
electrical equipment to perform work?
• Shock• Arc-Flash
– Heat– Fire
• Arc-Blast– Pressure– Shrapnel– Sound
Example of an arcing fault
Electrical Hazards
Safety BASICsTM
Over 30,000 non-fatal electrical shock accidents occur each year
Over 600 people die from electrocution each year
Electrocution remains the fourth (4th) highest cause of industrial fatalities
Most injuries and deaths could be avoided
Shock
Safety BASICsTM
Safety BASICsShock (Resistance Table)
TM
Safety BASICs TM
Shock
(A) Touch Potential (B) Step Potential (C and D) Touch / Step Potential
Current passing through the heart and lungs is the most serious
Safety BASICsShockHuman body resistance (hand to hand)
across the body is about 1000
Ohms Law: I = V / R (Amps.)I = 480 volts / 1000 = 0.48 amps (480 mA)
The National Electrical Code® considers 5 mA to be the safe upper limit for children and adults.
TM
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
Arc-Flash
Safety BASICsTM
Electrical Arc
Copper Vapor:Solid to VaporExpands by67,000 times
Intense Light
Hot Air-Rapid Expansion
35,000 °F
Pressure Waves
Sound Waves
Molten Metal
Shrapnel
Personnel Hazards Associated with Arc Flash
Heat – Burns & Ignition of Materials Arc temperature of 35,000 ºF Molten metal, copper vapor, heated air
Second Degree Burn Threshold :80 ºC / 175 ºF (0.1 sec), 2nd degree burn
Third Degree Burn Threshold:96 ºC / 205 ºF (0.1 sec), 3rd degree burn
Intense LightDamage eyes – cataracts
Personnel Hazards Associated with Arc Flash
Pressures From Expansion of Metals & AirEardrum Rupture Threshold
720 lbs/ft2
Lung Damage - Threshold1728 - 2160 lbs/ft2
Shrapnel Flung Across Room or From Ladder/Bucket
IEEE/PCIC & NFPA 70EArc Flash Hazard
Arc Flash Hazard
• Following are some of the tests run by IEEE Ad Hoc Safety Committee
•All of the devices used for this testing were applied according to their listed ratings
Setup Area For TestsSetup Area For Tests #1 Through #4#1 Through #4
Close-up of Test AreaClose-up of Test AreaA
rc-F
l ash
22.6 KA SymmetricalAvailable Fault Current
@ 480V, 3 Phase
Fault Initiated on Line Side of 30AFuse
30A RK-1Current Limiting Fuse
Size 1 Starter
Test No. 46 cycle STD640A OCPDNon Current Limitingwith Short Time Delay
Set @ 6 cycle opening
TEST 4
TEST 4
TEST 4
TEST 4
TEST 4
TEST 4
TEST 4
22.6 KA SymmetricalAvailable Fault Current
@ 480V, 3 Phase
Fault Initiated on Line Side of 30AFuse
30A RK-1Current Limiting Fuse
Size 1 Starter
640A OCPDNon Current Limitingwith Short Time Delay
Results:Test No. 4
Opened in six cyclesNo CurrentLimitation
> 225 C /437 F> 225 C /
437 F
Results: Test No.4
T1T2
P1
T3
Sound
141.5 db @ 2 ft.
50 C / 122 F
>2160 lbs/sq.ft
> Indicates Meter Pegged
22.6 KA SymmetricalAvailable Fault Current
@ 480V, 3 Phase
Fault Initiated on Line Side of 30AFuse
30A RK-1Current Limiting Fuse
Size 1 Starter
Test No. 3601A.Class LCurrent Limiting Fuse
TEST 3
TEST 3
TEST 3
TEST 3
22.6 KA SymmetricalAvailable Fault Current
@ 480V, 3 Phase
Fault Initiated on Line Side of 30AFuse
30A RK-1Current Limiting Fuse
Size 1 Starter
601A.Class LCurrent Limiting Fuse
Results:Test No. 3
Cleared in 1/4 CycleCurrent-Limitation Reduced Energy
> 175 C/347 F
Results: Test No.3
T1T2
P1
Sound133 db @ 2 ft.
62 C / 143.6 F504 lbs/sq.ft.
T3(No Change
From Ambient)
> Indicates Meter Pegged
X
22.6 KA SymmetricalAvailable Fault Current
@ 480V, 3 Phase
30A RK-1Current Limiting Fuse
Size 1 Starter
Test No. 1601A.Class LCurrent LimitingFuse
Fault Initiated on Load Side of 30AFuse
TEST 1
TEST 1 Close-up
TEST 1 Close-up
TEST 1 Close-up
TEST 1 Close-up
TEST 1 Close-up
22.6 KA SymmetricalAvailable Fault Current
@ 480V, 3 Phase
30A RK-1Current Limiting Fuse
Size 1 Starter
Results:Test No. 1
601A.Class LCurrent Limiting Fuse
Class L FuseDid Not Open,System wasSelectivelyCoordinated
30 A RK-1 FuseCleared Fault inLess Than 1/4 Cycle
Fault Initiated on Load Side of 30AFuse
Results: Test No.1
T1T2
P1
T3
Sound(No Change From Ambient)
(No Change From Ambient)
(No Change From Ambient)
(No Change From Ambient)
(No Change From Ambient)
Safety BASICsTM
Current-Limitation - Arc-Energy Reduction
Consider that:• Magnetic Force -- varies with the square of the Peak Current• Thermal Energy -- varies with the square of the RMS Current
Non-Current Limiting Current Limiting
Available Fault Current Reduced Fault Current
Safety BASICsTM
Current-Limitation: Arc-Energy Reduction
Non-Current Limiting
Reduced Fault Current
via Current-LimitationTest 1
Test 4
Test 3
Safety BASICsTM
What are the hazards as you What are the hazards as you approachapproach
electrical equipment to electrical equipment to perform work?perform work?
• Shock• Arc Flash• Arc Blast
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