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Safety BASICs TM ©2004 Cooper Bussmann B ussmann ® A wareness of S afety I ssues C ampaign Electrical Hazards.

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Presentation on theme: "Safety BASICs TM ©2004 Cooper Bussmann B ussmann ® A wareness of S afety I ssues C ampaign Electrical Hazards."— Presentation transcript:

1 Safety BASICs TM ©2004 Cooper Bussmann B ussmann ® A wareness of S afety I ssues C ampaign Electrical Hazards

2 ©2004 Cooper Bussmann Electrical Hazards What are the hazards as you approach electrical equipment to perform work?

3 ©2004 Cooper Bussmann Electrical Hazards Shock Arc flash –Heat –Fire Arc blast –Pressure –Shrapnel –Sound Example of an arcing fault

4 ©2004 Cooper Bussmann I = V / Z What happens with shock? What happens when there is a fault? What is the difference between a short- circuit and an arcing fault? Basic Electrical Theory

5 ©2004 Cooper Bussmann Electric Shock 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

6 ©2004 Cooper Bussmann Human Resistance Values Resistance (ohms) ConditionDryWet Finger touch40,000 to 1,000,0004,000 to 15,000 Hand holding wire15,000 to 50,0003,000 to 6,000 Finger-thumb grasp10,000 to 30,0002,000 to 5,000 Hand holding pliers5,000 to 10,0001,000 to 3,000 Palm touch3,000 to 8,0001,000 to 2,000 Hand around 1-1/2 inch pipe1,000 to 3, to 1,500 Two hands around 1-1/2 inch pipe500 to 1, to 750 Hand immersed200 to 500 Foot immersed100 to 300 Human body, internal, excluding skin 200 to 1,000 This table was compiled from data developed by Kouwenhoven and Milnor.

7 ©2004 Cooper Bussmann Electric Shock Human body resistance (hand to hand) across the body is about 1000 Ohms law: I= V / R amps = 480 volts / 1000 = 0.48 amps (480 mA) Product safety standards consider 5 mA to be the safe upper limit for children and adults

8 ©2004 Cooper Bussmann Electric Shock mA Affect on person Tingling sensations Muscle contractions and pain Let-go threshold Respiratory paralysis Ventricular fibrillation Heart clamps tight Tissue and organs start to burn

9 ©2004 Cooper Bussmann Electric Current Pathways (A) Touch Potential(B) Step Potential (C and D) Touch / Step Potential Current passing through the heart and lungs is the most serious

10 ©2004 Cooper Bussmann Electric Shock Injury

11 ©2004 Cooper Bussmann 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

12 ©2004 Cooper Bussmann 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 air to expand, in the same way that thunder is created from a lightning strike 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

13 ©2004 Cooper Bussmann Bolted Short Circuit AB Arcing Fault AB Current Thru Air

14 ©2004 Cooper Bussmann Electric Arc Copper Vapor: Solid to Vapor Expands by 67,000 times Intense Light Hot Air-Rapid Expansion 35,000 °F Pressure Waves Sound Waves Molten Metal Shrapnel

15 ©2004 Cooper Bussmann Personnel Hazards Associated With Arc Flash & Arc Blast Heat – burns & ignition of material –Arc temperature of 35,000 o F –Molten metal, copper vapor, heated air Second degree burn threshold: –80 o C / 175 o F (0.1 sec), 2 nd degree burn Third degree burn threshold: –96 o C / 205 o F (0.1 sec), 3 rd degree burn Intense light –Eye damage, cataracts

16 ©2004 Cooper Bussmann Pressures from expansion of metals & air Eardrum rupture threshold: –720 lbs/ft 2 Lung damage threshold: – lbs/ft 2 Shrapnel Flung across room or from ladder/bucket Personnel Hazards Associated With Arc Flash & Arc Blast

17 ©2004 Cooper Bussmann Flash protection boundaries and incident energy exposure calculations both dependent upon: Duration of arc-fault or time to clear Speed of the overcurrent protective device Arc-fault current magnitude Available fault current Current-limitation can reduce Overcurrent Protection Role

18 ©2004 Cooper Bussmann IEEE / PCIC & NFPA 70E Ad Hoc Safety Subcommittee –Users –Consultants –Manufacturers –Medical experts Following are some of the tests run –All of the devices used for this testing were applied according to their listed ratings

19 ©2004 Cooper Bussmann IEEE / PCIC Staged Arc Flash Test Set-up

20 ©2004 Cooper Bussmann 22.6 KA Symmetrical Available Fault 480V, 3 Phase Fault Initiated on Line Side of 30A Fuse 30A RK-1 Current Limiting Fuse Size 1 Starter Test No. 4 6 cycle STD 640A OCPD Non Current Limiting with Short Time Delay 6 cycle opening

21 ©2004 Cooper Bussmann

22 Test 4 Still Photo

23 ©2004 Cooper Bussmann Test 4 Still Photo

24 ©2004 Cooper Bussmann Test 4 Still Photo

25 ©2004 Cooper Bussmann Test 4 Still Photo

26 ©2004 Cooper Bussmann Test 4 Still Photo

27 ©2004 Cooper Bussmann Test 4 Still Photo

28 ©2004 Cooper Bussmann Test 4 Still Photo

29 ©2004 Cooper Bussmann >225 o C/437 o F >225 o C/ 437 o F Results: Test No.4 T1 T2 P1 T3 Sound ft. 50 o C/122 o F >2160 lbs/ft 2 > Indicates Meter Pegged

30 ©2004 Cooper Bussmann 22.6 KA Symmetrical Available Fault 480V, 3 Phase Fault Initiated on Line Side of 30A Fuse 30A RK-1 Current Limiting Fuse Size 1 Starter Test No A. Class L Current Limiting Fuse

31 ©2004 Cooper Bussmann

32 Test 3 Still Photo

33 ©2004 Cooper Bussmann Test 3 Still Photo

34 ©2004 Cooper Bussmann Test 3 Still Photo

35 ©2004 Cooper Bussmann Test 3 Still Photo

36 ©2004 Cooper Bussmann > 175 o C/ 347 o F Results: Test No.3 T1 T2 P1 Sound ft. 62 o C/143.6 o F 504 lbs/ft 2 T3 (No Change From Ambient) > Indicates Meter Pegged

37 ©2004 Cooper Bussmann 22.6 KA Symmetrical Available Fault 480V, 3 Phase 30A RK-1 Current Limiting Fuse Size 1 Starter Test No A. Class L Current Limiting Fuse Fault Initiated on Load Side of 30A Fuse

38 ©2004 Cooper Bussmann

39 Test 1 Still Photo

40 ©2004 Cooper Bussmann Test 1 Still Photo

41 ©2004 Cooper Bussmann Test 1 Still Photo

42 ©2004 Cooper Bussmann Test 1 Still Photo

43 ©2004 Cooper Bussmann

44 Non-Current Limiting Reduced Fault Current via Current-Limitation Test 1 Test 4 Test 3 Current-Limitation: Arc Energy Reduction

45 ©2004 Cooper Bussmann Summary Shock, arc flash and arc blast are the three recognized electrical hazards Shock injuries result from electrical current flowing through the body Arcing faults can generate enormous amounts of energy Injuries from arcing faults are a result of the tremendous heat and pressure generated

46 ©2004 Cooper Bussmann Summary Overcurrent protective devices have an impact on the two most important variables of arc flash hazards: –Time (speed of the OCPD) –Fault current magnitude (current-limitation may help reduce) Current-limitation may be able to significantly reduce the energy released during arcing faults


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