hvpres (2).ppt

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