1. ELECTRICAL SAFETY
Part 2: Working Safely

2. ELECTRICITY - THE DANGERS
SHOCK
BURNS
ARC FLASH
FALLS
Note that the word electrocution usually means death.

3. ELECTRICAL SHOCK
An electrical shock is a current flow through the body.
The shock occurs when any part of your body completes a circuit by being:
• In contact with two wires
• In contact with a wire and ground
• In contact with a metal part that is in contact with a wire in a circuit and ground.
Give a common example of each situation.

4. ELECTRICAL SHOCK
The response could range from a faint tingling sensation to death.
You can perceive a current as low as 1 milliamp.
At 5 mA you will feel a slight shock. Most people can let go.
Give a common example of each situation.

5. and sustained muscle contraction.
ELECTRICAL SHOCK
“Can’t Let Go” Current
10 mA to 30 mA
Painful shock
and sustained muscle contraction.
Explain that experienced electricians who sometimes must deal with live wires always use the back of their hands to move the wires. If a current were present, the contracting muscles would cause the hand to pull away from the wire.
Demonstrate this with your hand and some object representing a wire.

6. ELECTRICAL SHOCK
50 mA to 150 mA Extreme pain, respiratory arrest, severe muscle contractions, possible death 1,000 mA to 4,300 mA
Ventricular fibrillation, muscle contractions,
nerve damage, death likely.

7. ELECTRICAL SHOCK

8. ELECTRICAL SHOCK The duration and the amount of current
affect the severity of an electrical shock injury.
Death can occur in 2 seconds with a
current of 0.1 amps (100 milliamps).
100 mA for 3 seconds is as dangerous as 900 mA for 0.03 seconds.
Point out that working with defective power tools can be especially dangerous because at 10 milliamps “can’t let go” occurs which increases the duration of the current through the body.

9. ELECTRICAL SHOCK
Other factors that may affect the severity of the shock are: • The voltage of the current.
• The presence of moisture. • The phase of the heart cycle when the shock occurs. • The general health of the person prior to the shock.

10. I = E/R R = E/I ELECTRICAL SHOCK
High voltages increase shock injuries because a higher voltage produces a greater current.
I = E/R
Resistance - the lower the resistance, the greater the current will be.
Review the relationship of I, E, and R
R = E/I

11. I = E/R ELECTRICAL SHOCK
Resistance between  major  extremities  of  an   average human body is 1,500 ohms hand to hand or hand to foot.
 If you grabbed a wire carrying 120 volts alternating current  how much current would flow through your body?
Point out that resistance values vary greatly in different parts of the body. 
After the group answers the question - 80 mA, ask what the possible effects might be at 80 mA?
Note that it is beyond the “let go” threshold and with the potential
death range.
Demonstrate with an ohmmeter giving the group to measure resistance with dry hand, wet hands or other conditions that affect resistance.
I = E/R

12. ELECTRICAL SHOCK PATHWAYS
1. Right hand
left hand
2. Right foot left foot path
3. Right hand
right foot path
4. Left hand left foot path
The path of the current will determine which tissue will be damaged.
Touch potential, 2. Step potential, 3 and 4 Touch/step potential
Discuss the circumstances in which each of these pathways could occur. Ask which could have the most severe results.
Explain that this is why it is strongly recommended that people working with exposed parts of electrical machines should work with only one of their hands. The best way to do this is to keep your left hand in your pocket. This is because if both hands make contact with the wrong surfaces, the current flows through the body from one hand to the other. This can lead the current to pass through the heart. If the current passes from one hand to the feet (No. 3), little current will probably pass through the heart.

13. ELECTRICAL BURNS
Electrical burns are the result of heat generated by the flow of electric current through the body.
The dark spot is where the current entered the body.
High resistance of skin transforms electrical energy into heat, which produces burns around the entrance point (dark spot in center of wound). This man was lucky; the current narrowly missed his spinal cord.

14. ELECTRICAL BURNS
Electricity arced through the air as a result of a power box explosion.
The arc was drawn to this man’s arm pits because of perspiration.
This man was near a power box when an electrical explosion occurred. Though he did not touch the box, electricity arced through the air and entered his body. The current was drawn to his armpits because perspiration is very conductive.

15. ELECTRICAL BURNS
Current exited this man at his knees, catching his clothing on fire and burning his upper leg.
Thermal Contact Burns occur when skin comes in contact with overheated electric equipment, or when clothing is ignited in an electrical incident.

16. ELECTRICAL BURNS The current exited the foot of this man. Because
of severe internal injuries, the foot had to be amputated a few days later.
Current flows through the body from the entrance point, until finally exiting where the body is closest to the ground. This foot suffered massive internal injuries which weren't readily visible, and had to be amputated a few days later.

17. This worker was shocked by a tool he was holding.
ELECTRICAL BURNS
This worker was shocked by a tool he was holding.
A few days later.
A few days later, massive subcutaneous tissue damage had caused severe swelling (swelling usually peaks hours after electrical shock). To relieve pressure , which would have damaged nerves and blood vessels, the skin on the arm was cut open

18. ARC FLASH
An arc flash is a short circuit through the air. It can occur if a conductive object gets too close to a high-amp current source or by equipment failure such as opening or closing disconnects.
The temperature of an arc can reach more than 5000 F (up to 35,000 F). It creates a brilliant flash of light and a loud noise. An enormous amount of concentrated radiant energy explodes outward from the electrical equipment, spreading hot gases, melting metal, causing death or severe radiation burns, and creating pressure waves that can damage hearing or brain function and a flash that can damage eyesight. The fast-moving pressure wave also can send loose material such as pieces of equipment, metal tools, and other objects flying, injuring anyone standing nearby.
Arc faults are generally limited to systems where the bus voltage is in excess of 120 volts. Lower voltage levels normally will not sustain an arc. An arc fault is similar to the arc obtained during electric welding and the fault has to be manually started by something creating the path of conduction or a failure such as a breakdown in insulation.

19. FALLS
Workers who get shocked while on a ladder or other elevated location can fall, resulting in serious injury or death.

20. ELECTRICAL HAZARDS Electrical shocks, fires or falls can result from:
• Exposed electrical parts • Overhead power lines • Inadequate wiring • Defective insulation
• Wet conditions
• Improper grounding
• Improper PPE • Improper tools • Overloaded circuits

21. ELECTRICAL HAZARDS Exposed Electrical Parts
Electrical hazards exist when wires or other electrical parts are exposed. Wires and parts can be exposed if a cover is removed from a wiring or breaker box. The overhead wires coming into a home may be exposed. Electrical terminals in motors, appliances, and electronic equipment may be exposed. Older equipment may have exposed electrical parts. If you contact exposed live electrical parts, you will be shocked. You need to recognize that an exposed electrical component is a hazard.

22. ELECTRICAL HAZARDS Overhead Power Lines NIOSH Case Study
Overhead powerlines are usually not insulated. More than half of all electrocutions are caused by direct worker contact with energized powerlines. Powerline workers must be especially aware of the dangers of overhead lines. In the past, 80% of all lineman deaths were caused by contacting a live wire with a bare hand. Due to such incidents, all linemen now wear special rubber gloves that protect them up to 34,500 volts. Today, most electrocutions involving overhead powerlines are caused by failure to maintain proper work distances.
Five workers were constructing a chain-link fence in front of a house, directly below a 7,200-volt energized powerline. As they prepared to install 21-foot sections of metal top rail on the fence, one of the workers picked up a section of rail and held it up vertically. The rail contacted the 7,200-volt line, and the worker was electrocuted. Following inspection, OSHA determined that the employee who was killed had never received any safety training from his employer and no specific instruction on how to avoid the hazards associated with overhead powerlines.In this case, the company failed to obey these regulations:• Employers must train their workers to recognize and avoid unsafe conditions on the job.• Employers must not allow their workers to work near any part of an electrical circuit UNLESS the circuit is de-energized (shut off) and grounded, or guarded in such a way that it cannot be contacted.• Ground-fault protection must be provided at construction sites to guard against electrical shock.
NIOSH Case Study
Untrained worker raising a 21 foot fence rail under a 7,200 volt power line. Worker was electrocuted.

23. ELECTRICAL HAZARDS Inadequate Wiring
Wire Gauge - wire size or diameter
Ampacity - the maximum amount of current a wire can carry safely without overheating
An electrical hazard exists when the wire is too small a gauge for the current it will carry. Normally, the circuit breaker in a circuit is matched to the wire size. However, in older wiring, branch lines to permanent ceiling light fixtures could be wired with a smaller gauge than the supply cable. Let's say a light fixture is replaced with another device that uses more current. The current capacity (ampacity) of the branch wire could be exceeded.
When a wire is too small for the current it is supposed to carry, the wire will heat up. The heated wire could cause a fire.
When you use an extension cord, the size of the wire you are placing into the circuit may be too small for the equipment. The circuit breaker could be the right size for the circuit but not right for the smaller-gauge extension cord.
A tool plugged into the extension cord may use more current than the cord can handle without tripping the circuit breaker. The wire will overheat and could cause a fire.The kind of metal used as a conductor can cause an electrical hazard.
Special care needs to be taken with aluminum wire. Since it is more brittle than copper, aluminum wire can crack and break more easily. Connections with aluminum wire can become loose and oxidize if not made properly, creating heat or arcing. You need to recognize that inadequate wiring is a hazard.
Incorrect wiring practices can cause fires! If you touch live electrical parts, you will be shocked. Overloaded wires get hot!

24. ELECTRICAL HAZARDS
Copper Wire Ampacity Table    Wire Gauge  Maximum Ampacity  14    
12    
10    
8    
6    
4    
2    
0    
2/0    
4/0  

25. ELECTRICAL HAZARDS Defective Insulation
Insulation that is defective or inadequate is an electrical hazard. Usually, a plastic or rubber covering insulates wires. Insulation prevents conductors from coming in contact with each other. Insulation also prevents conductors from coming in contact with people.
Extension cords may have damaged insulation. Sometimes the insulation inside an electrical tool or appliance is damaged. When insulation is damaged, exposed metal parts may become energized if a live wire inside touches them.
Electric hand tools that are old, damaged, or misused may have damaged insulation inside. If you touch damaged power tools or other equipment, you will receive a shock. You are more likely to receive a shock if the tool is not grounded or double-insulated. (Double-insulated tools have two insulation barriers and no exposed metal parts.) You need to recognize that defective insulation is a hazard.

26. ELECTRICAL HAZARDS Defective Insulation
Hanford Project Lessons Learned
On January 30, 2003, a panel cover screw penetrated the insulation of a deenergized 480-volt cable inside a panel at T Plant when Construction Forces electricians replaced the cover. When power was restored to the panel, the screw caused a phase-to-ground fault, the workers saw a slight arc flash, the 480-volt branch breaker opened, the main 480-volt panel breaker opened, and the panel 480-volt feeder breaker opened.
Exercise extreme care when installing electrical panel covers. Verify the proper location of wires and cables prior to installing screws into panels, especially when replacing missing screws without removing the cover. Removing the panel cover may be necessary in some cases. Carefully inspect electrical panels after modifying them and during periodic inspections to ensure bolts and screws that mount panel covers will not contact or penetrate wiring. Use appropriate length and type of screws in panels to ensure they do not contact electrical components.
Screw penetrated insulation creating a
small arc flash.

27. ELECTRICAL HAZARDS Wet Conditions
Ask group to identify any other hazards beside the water.
Wet clothing, high humidity, and perspiration also increase your chances of being electrocuted.

28. ELECTRICAL HAZARDS Improper grounding
The appliance will operate normally without the ground wire because it is not a part of the conducting path which supplies electricity to the appliance. In fact, if the ground wire is broken or removed, you will normally not be able to tell the difference. But if high voltage has gotten in contact with the case, there may be a shock hazard. In the absence of the ground wire, shock hazard conditions will often not cause the breaker to trip unless the circuit has a ground fault interrupter in it. Part of the role of the ground wire is to force the breaker to trip by supplying a path to ground if a "hot" wire comes in contact with the metal case of the appliance.
In the event of an electrical fault which brings dangerous high voltage to the case of an appliance, you want the circuit breaker to trip immediately to remove the hazard. If the case is grounded, a high current should flow in the appliance ground wire and trip the breaker. That's not quite as simple as it sounds - tying the ground wire to a ground electrode driven into the earth is not generally sufficient to trip the breaker, which was surprising to me. The U.S. National Electric Code Article 250 requires that the ground wires be tied back to the electrical neutral at the service panel. So in a line-to-case fault, the fault current flows through the appliance ground wire to the service panel where it joins the neutral path, flowing through the main neutral back to the center-tap of the service transformer. It then becomes part of the overall flow, driven by the service transformer as the electrical "pump", which will produce a high enough fault current to trip the breaker.This just touches the tip of the iceberg of the major subject of proper grounding and bonding of electrical systems.

29. ELECTRICAL HAZARDS Improper grounding
Three electrical connections are made to a standard appliance like a clothes washing machine. The "hot" wire carries an effective voltage of 120 volts to the appliance and the neutral serves as the normal return path. The third wire is the electrical ground which is just connected to the metal case of the appliance.
If the hot wire shorts to the case of the appliance, the 120 volt supply will be applied to the very low resistance path through the ground wire. This will cause an extremely high current to flow and will cause the breaker or fuse to interrupt the circuit.One problem with this arrangement is that if the ground wire is broken or disconnected, it will not be detectable from the operation of the appliance since the ground wire is not a part of the circuit for electric current flow. In that case, if the hot wire shorts to the case and the neutral wire does not, then the breaker may not trip and the entire 120 volts will be applied to the metal case of the appliance, representing a shock hazard. The ground wire of an appliance is the main protection against shock hazard.

30. ELECTRICAL HAZARDS Overloaded Circuits
Hanford Project Lessons Learned
Picture on the right - August 28, 1999, a Kensington Power Tree 20, model # multi-outlet power strip with surge protection failed and started a small fire in a trailer at the Stanford Linear Accelerator Center (SLAC). This graphic shows the damaged power strip.
Surge protection devices in some older model multi-outlet power strips can overheat and create a potential fire hazard.
Too much current in a circuit can lead to a fire or electrical shock.

31. THE REGULATIONS CalOSHA Low voltage (600V) Electrical Safety Orders
Article 3, §
Only qualified persons shall work on electrical equipment or systems.
A qualified person is defined as a person designated by the employer, who by reason of experience or instruction has demonstrated familiarity with the operation to be performed and the hazards involved.
Low voltage is 600 volts or less. High voltage regulations apply to more than 600 volts.
NFPA 70E-1995, Standard for Electrical Safety Requirements for Employee Workplaces defines a qualified person in Section as one "trained and knowledgeable of the construction and operations of equipment or a specific work method, and be trained to recognize and avoid the electrical hazards that might be present with respect to that equipment or work method. Such persons shall also be familiar with the proper use of special precautionary techniques, personal protective equipment, insulating and shielding materials, and insulated tools and test equipment. A person can be considered qualified with respect to certain equipment and methods but still be unqualified for others.”
Ask who would be considered qualified in the group and why?

32. THE REGULATIONS §
Work SHALL NOT be perform on energized parts of equipment or systems until the following conditions are met:
Responsible supervision has determined that the work is to be performed while the equipment or system are energized.
Involved personnel have received instructions on the work techniques and hazards involved in working on energized equipment.
Discuss each point and give real life examples on how each condition is met.

33. THE REGULATIONS § 2320.2 (cont’d)
Suitable personal protective equipment and safeguards (approved insulated gloves or insulated tools) are provided and used.
Approved insulated gloves shall be worn for voltages in excess of 250 volts to ground.
Discuss each point and give real life examples on how each condition is met.
Show group ASTM approved gloves and hand tools. Point out identifying marks of approval.

34. THE REGULATIONS § 2320.2 (cont’d)
Suitable barriers or approved insulating material shall be provided and used to prevent accidental contact with energized parts Suitable eye protection has been provided and used.
Discuss what would be a suitable barrier and give examples.

35. THE REGULATIONS § 2320.2 (cont’d)
Where required for personnel protection, suitable barricades, tags, or signs are in place.

36. THE REGULATIONS § 2320.2 (cont’d)
Each employee who is exposed to the hazards of flames or electric arcs wears apparel that, when exposed to flames or electric arcs, does not increase the extent of injury that would be sustained by the employee.

37. THE REGULATIONS
§ All electrical equipment and systems shall be treated as energized until tested or otherwise proven to be de-energized.

38. THE REGULATIONS General Safety Orders § 3314 (g)
A hazardous energy control procedure shall be developed and utilized by the employer when employees are engaged in the cleaning, repairing, servicing, setting-up or adjusting of prime movers, machinery and equipment.
LOCKOUT/TAGOUT

39. LOCKOUT/TAGOUT Overview of Procedures
Must use own lock and keep key on his/her person until job is done.
Procedures apply to all
Sources of energy - electrical,
thermal, hydraulic, pneumatic, mechanical, etc.
Point out that these are basic procedures and each agency will have some variation to these procedures such as color coded locks and more detailed procedures.
Point out that although this training is on electrical safety, lockout/tagout procedures apply to all sources of potential hazardous energy.

40. LOCKOUT/TAGOUT Notify all affected employees.
Identify all applicable isolating devices - breakers, switches, valves, etc.

41. LOCKOUT/TAGOUT Obtain a padlock and tag from lockout station.
Isolate source of power at the
circuit breaker on MCC panel and at other sources of hazardous energy.

42. LOCKOUT/TAGOUT BLOCK DRAIN BLEED TEST
On the tag, write name, date, time and why equipment is locked out.
BLOCK
DRAIN
BLEED TEST
Test to be sure there is no release of hazardous energy.
Discuss the importance of this procedure and give or ask for examples of cases in which lives were lost because test procedure was not done, e.g., wrong breaker switch locked out, faulty switch, other sources of energy not considered, etc.

43. LOCKOUT/TAGOUT
Always take precautions to guard against the possibility of faulty switches or short circuits when locking out equipment. Test the equipment with a meter when doing electrical work.

44. THE REGULATIONS
Do not use conductive measuring tapes or ropes when working near energized parts of equipment.
Legibly mark each motor controller to indicate the motor it controls and provide a corresponding marking on each motor.
When a circuit is discontinued, remove the conductors from the raceway or treat the circuit as if it is in use.
Point out that these are selected CalOSHA regulations that most commonly apply to the group and that some have been paraphrased for clarity.

45. THE REGULATIONS
Do not use conductive fish tape in raceways entering enclosures with exposed energized parts unless the parts are isolated by barriers.
At least 3 feet of cleared space (no storage) shall be available in the direction of access to control panels, circuit breakers, switchboards, fused switches, and similar equipment.
The access space must be 30 inches wide

46. THE REGULATIONS
All electrical equipment shall have markings giving voltage, current, wattage, or other ratings.
Circuit breakers shall clearly indicate whether they are in the open “off” or closed “on” position.

47. THE REGULATIONS Flexible cords or cables SHALL NOT be used
• as a substitute for fixed wiring of a structure,
• where run through holes in walls, ceilings or floors,
• where run through doorways, windows
or similar openings,
• where attached to building surfaces, or • where concealed behind building walls, ceilings or floors

48. THE REGULATIONS
Flexible cords shall be used only in continuous lengths without splice or tap.
Hard service flexible cords No. 12 or larger can be spliced as long as the splice retains the insulation, outer sheath properties, and usage characteristics of the cord.
Explain that that hard service refers to the durability of the cord and is rated by NEC. NEC requires that te ratings be indelibly marked every foot along the length of the cord: S, ST, SO and STO for hard service, and SJ, SJO, SJT, and SJTO for junior hard service.
Graphic: “W” refers to outdoor rating.
Show the group the markings on a cord. Remind the group that the No. 12 refers to the size of the wire and the smaller the number, the larger the conducting wire.
Provide samples of cords and ask that the group find the rating and whether it can be spliced.

49. GROUND FAULT CIRCUIT INTERRUPTER
Use a GFCI when working on circuits or using electrical equipment in damp or wet areas.
A ground-fault circuit interrupter (GFCI) is an electrical device that detects a leakage of electrical current and reacts immediately by quickly interrupting the current flow. The leak can be caused by an accident or through equipment malfunction. GFCIs are required in certain locations specified by the NEC (Article 210-8). These locations include bathrooms, kitchens, garages, outbuildings, crawl spaces, unfinished basements, wet bar sinks, and any exterior receptacle.
A good general rule to follow is that if you are working in a potentially damp or wet environment or have direct contact to earth then the receptacle you use should be GFCI-protected. If no GFCI receptacle is located nearby, then use an extension cord that has a built-in GFCI.

50. DOUBLE INSULATED TOOLS
Use double insulated tools if GFCI is not available.
Always check cord and plug on all power tools before use
Hand-held tools manufactured with non-metallic cases are called
double-insulated. If approved, they do not require grounding under the National Electrical Code. Although this design method reduces the risk of grounding deficiencies, a shock hazard can still exist.
Such tools are often used in areas where there is considerable moisture or wetness. Although the user is insulated from the electrical wiring components, water can still enter the tool's housing. Ordinary water is a conductor of electricity. If water contacts the energized parts inside the housing, it provides a path to the outside, bypassing the double insulation. When a person holding a hand tool under these conditions contacts another conductive surface, an electric shock occurs.
If a power tool, even when double-insulated, is dropped into water, the employee should resist the initial human response to grab for the equipment without first disconnecting the power source.
NOTE: Show approved marking on tool. Point out that double insulated tool should be marked as such. Can’t tell by the outer non-conductive material.

51. ELECTRICAL FIRES NEVER put water on an electrical fire.
Use Class C or ABC fire extinguishers.
Electrical fires are different than other fires. Because water conducts electricity, throwing water on an electrical fire can cause the fire to get larger and can electrocute you.

52. BE SAFE ! THE REGULATIONS
Wrist watches, rings, or other jewelry should not be worn while working with or around machinery with moving parts in which such objects may be caught, or around electrically energized equipment.
BE SAFE !

53. THE END