Electrical SafetyElectrical Safety

Training

• Qualified workers – Only Qualified workers are allowed to work on or near exposed energized

equipment.

• Unqualified workers– Unqualified workers are not permitted to work on or near exposed energized

equipment

Concerned About Electricity?

• How many sets of Christmas lights do you plug into one extension cord?

• Do you still use your hot and sparking electric drill?

• Is your vacuum cleaner’s cord twisted and frayed?

• Have you installed outlet covers to protect your probing fingers?

Electrical Safety Outline

• Electricity and the human body

• Electrical hazards and safe work practices

• Quiz

Electrical Circuits

A basic completed electrical circuit requires three things to function correctly:

• Electrical source

• Electrical user

• Wires

Rules of Electricity

• Electricity travels in a completed circuit

• Electricity always travels in the path of least resistance

• Electricity tries to travel to ground

Electricity and People

• A person usually offers a lessor resistance for the electricity

• The person forms a completed circuit when touching the ground

• Electricity always tries to travel to ground

Voltages and Amperes

• Voltage = Amps X Ohms(resistance)

• Converting voltage to amps

• Typical Industrial Voltages– 110/120 Volts = 60

milli-amps (mA)

– 220/240 Volts = 120 mA

– 440/480 Volts = 240 mA

Effects on the Human Body

• 1 mA: Can be felt by the body

• 2-10 mA: Minor shock, might result in a fall

• 10-25 mA: Loss of muscle control, may not be able to let go of the current

• 25-75 mA: Painful, may lead to collapse or death

• 75-300 mA: Last for 1/4 second, almost always immediately fatal

Body’s Resistance

• Skin offers most of the body’s electrical resistance

• Increased resistance – Thick and callused skin (foot or hand)

– Dry skin

• Decreased resistance– Thin skin (inner forearm)

– Wet or sweaty skin

– Broken or abraded skin (scratches)

Resistance Varies

• Different levels of electrical resistance for each person

• Ranges from 500 ohms to many thousands of ohms

• The greater the body’s resistance, the less chance of harm

• A similar voltage shock can be minor to one person and deadly to another.

Additional Resistance

• Gloves

• Shoes

• Mats

Hazard Control

• Electrical systems are inherently safe

• Injuries typically occur when:– Procedures are inappropriate

– Procedures are not followed or ignored

– Safety systems are circumvented

General Electrical Hazards

• High-voltage overhead power lines

• Damaged insulation on wires

• Digging or trenching near buried lines

• Broken switches or plugs

• Overloaded circuits

• Overheated appliances or tools

• Static electricity

• Flammable materials

Portable Power Tools

• Inspect portable power tools

• Never use damaged equipment– Tag it out of service

– Have it repaired or replaced

• Never use portable power equipment in wet or damp areas

• Stop using power tools if they become hot or start sparking

Extension Cords

• Inspect and check for capacity

• For temporary work only

• Do not use as a rope to pull or lift objects

• Should not be fastened with staples or hung over hooks

Electrical Cord Inspection

• Deformed or mission pins

• Damaged outer jacket or insulation

• Evidence of internal damage

• If damaged, take out of service until repaired

Circuit Protection

• Energize or de-energize with appropriate switches, breakers, etc.

• Do not energize or de-energize with fuses, terminal lugs, or cable splice connections

• If circuit protection device is tripped—inspect

Grounding Equipment

• Most electrical equipment is designed with a grounding system

• Do not use equipment with damaged grounding connectors

• Do not use adapters that interrupt the grounding connection

Ground Fault Circuit Interrupters

• GFCIs reduce the likelihood of fatal shocks

• Detect small amount of earth current and automatically switch off the power

• Used with extension cords and portable tools

• Fuses and circuit breakers protect equipment, not people

Static Electricity

• Created when materials rub together

• Can cause shocks or even minor skin burns

• Reduced or prevented by:– Proper grounding

– Rubber matting

– Grounding wires, gloves, or shoes

Flammable/Ignitable Materials

• Flammable gases, vapors, or liquids

• Combustible dust

• Can be ignited by static electricity

• Require specially designed electrical equipment

Machine Operators

• Never tamper with electrical interlocks

• Do not repair electrical components of your machine

• Properly shut off machinery before working in the point of operation

• Obey warning signs and follow safe procedures

Summary

• Electricity will try to reach ground even if it means going through a person

• Even the “small” voltage from your home can cause serious injury

• Always inspect power tools and cords and do not use them if damaged

• Do not attempt to repair electrical equipment unless trained and qualified

Electrical Injuries

Call for emergency help immediately

• Everyone experiences minor electrical shocks from time to time. In some cases, however, even small amounts of electricity can be life-threatening because they can produce unconsciousness, cardiac arrest, and cessation of breathing.

• Electrical shocks also can produce serious, deep burns and tissue injury, although often even a serious electrical burn appears as only a minor mark on the skin.

• If you find a person whom you think has been electrocuted, look first--do not touch. He or she may still be in contact with the electrical source, and touching him or her may only pass the current through you.

• If possible, turn off the source of electricity. If this is not possible, move the source away from you and the affected person using a non-conducting object made of cardboard, plastic, or wood.

• Once the person is free of the source of electricity, check the person's breathing and pulse. If either has stopped or seems dangerously slow or shallow, initiate resuscitation immediately .

• If the person is faint or pale or shows other signs of shock, lay the person down with the head slightly lower than the trunk of his or her body and the legs elevated.

• Treat any major burns and wait for emergency medical assistance to arrive.

Question 1

Where does electricity always want to go, even if it means traveling through a person?

Question 1

Where does electricity always want to go, even if it means traveling through a person?

Electricity always wants Electricity always wants to travel to to travel to groundground, , which will complete the which will complete the circuit.circuit.

Question 2

A shock from an outlet at home may be painful, lead to collapse, or even death. (True or False)

Question 2

A shock from an outlet at home may be painful, lead to collapse, or even death. (True or False)

True. A 120-volt outlet at True. A 120-volt outlet at home can give the home can give the average person a shock of average person a shock of 60 mA.60 mA.

Question 3

Which part of the human body offers the most electrical resistance?

Question 3

Which part of the human body offers the most electrical resistance?

The The skinskin offers the most offers the most electrical resistance.electrical resistance.

Question 4

Flammable materials can easily be ignited by ___________ electricity.

Question 4

Flammable materials can easily be ignited by ___________ electricity.

StaticStatic electricity can electricity can easily ignite a easily ignite a flammable material.flammable material.

Question 5

Only ___________________ workers are permitted to work on or near exposed electrical components.

Question 5

Only ___________________ workers are permitted to work on or near exposed electrical components.

Only Only qualifiedqualified and trained and trained workers can repair or workers can repair or troubleshoot electrical troubleshoot electrical

equipment.equipment.

Question 6

When should power tools and extension cords be inspected?

Question 6

When should power tools and extension cords be inspected?

Inspect power tools and Inspect power tools and extension cords before extension cords before each use.each use.

Question 7

Fuses and circuit breaker are designed to protect people from shocks. (True or False)

Question 7

Fuses and circuit breaker are designed to protect people from shocks. (True or False)

False. Fuses and circuit False. Fuses and circuit breaker protect breaker protect machinery and electrical machinery and electrical systemssystems

Question 8

When a circuit breaker trips, you should immediately reset it. (True or False)

Question 8

When a circuit breaker trips, you should immediately reset it. (True or False)

False. A tripped breaker False. A tripped breaker could indicate a could indicate a

problem, so it should problem, so it should be checked by a be checked by a qualified worker.qualified worker.

Question 9

Extension cords should never be used as a permanent power source. (True or False)

Question 9

Extension cords should never be used as a permanent power source. (True or False)

True. Extension cords True. Extension cords are designed as a are designed as a temporary power temporary power source.source.

Question 10

What should be done with a damaged power tool or extension cord?

Question 10

What should be done with a damaged power tool or extension cord?

Tag it as “out of service” Tag it as “out of service” and have it replaced or and have it replaced or repaired by a qualified repaired by a qualified electrician.electrician.

Power Line Safety

• http://www2.worksafebc.com/Publications/Multimedia/Videos.asp?ReportID=34818

The hazards of power lines

• You cannot tell if a downed power line is energized just by looking at it.

• The electricity in a power line always seeks a path to the ground. This path might include a tree, a vehicle, or a fence. These objects then become energized. If you touch the energized line or object, the electricity can flow through your body. Keep away from any object that is in contact with a power line.

• Once electricity reaches the ground, the ground itself becomes energized. This can happen if a broken power line falls to the ground or onto a vehicle or tree. The electricity then flows through the ground over a wide area, spreading out like ripples in a pool of water.

Safe work practices for first responders• Treat downed power lines and anything in contact with them as energized.

• Park away from the power lines. When you arrive at the scene, park your vehicle well away from any downed lines. Before you exit your vehicle at night, shine a flashlight through the window to make sure you are not near a downed power line.

• Stop traffic and keep people away. Pedestrians or motorists may not see power lines that are on the ground. The surrounding area will be energized. Secure the area and keep everyone back at least 10 metres (33 feet) - more if the voltage is over 60 kilovolts.

• Don't become a victim yourself. You cannot help anyone if you are injured or electrocuted. Never touch anything that is in contact with a downed power line, including injured or trapped victims, puddles, vehicles, or trees. Do not use a dry stick or piece of hose as they will not protect you.

• Call the power company immediately. The power company can ensure that automatic switching equipment will not restore power to the line. A crew with proper training and equipment will arrive as soon as possible.

• Wait for the power company representative to confirm that it is safe to approach the scene. Only the power company can confirm that the system has been de-energized and that power will not automatically be restored.

Staying safe inside a vehicle that is in contact with power lines

• If possible, move the vehicle away to break contact with the power line.

• If the vehicle cannot be moved, stay inside until emergency crews can safely approach. If anyone approaches the vehicle, open the window and call out. Tell them to keep away and to call 9-1-1 for help.

• If there is a fire and you must leave the vehicle, jump out with your feet together. Never touch the ground and the vehicle at the same time. Move away slowly by shuffling and keeping both feet close together.

Questions?