Basic Electrical Safety

Basic Electrical Safety

• Course not designed to teach you to work on electrical equipment.
• You will not be qualified to work on electrical equipment.
  
• If you spot problems with electrical equipment you should report it to your supervisor.

Objectives

• Be familiar with the fundamental concepts of electricity.
• Be familiar with the effects of electricity on the human body.
• Be able to recognize common electrical hazards.
  
• Be familiar with electrical protective devices.

Fundamentals of Electrical Hazards

• To flow electricity must have a complete path.
• Electricity flows through conductors
• water, metal, the human body
  
• Insulators are non-conductors
• The human body is a conductor

Have You Ever Been Shocked?

THE BASICS

• More than 3 ma
• painful shock
  
• More than 10 ma
• muscle contraction "no-let-go" danger
  
• More than 30 ma
• lung paralysis- usually temporary
  
• More than 50 ma
• possible ventricular fob. (heart dysfunction, usually fatal)
  
• 100 ma to 4 amps
• certain ventricular fibrillation, fatal
  
• Over 4 amps

• heart paralysis; severe burns. Usually caused by >600 volts

• Hazards of Electricity
• Electrocution/Shock/Burns/Death
  
• Minimum distance from overhead lines 10 ft.
• Inspect all electrical tools and equipment

Frayed, cut, broken wires
grounding prong missing
Improper use of cube taps
improperly applied or missing strain relief

Electrical Protection

• Circuit Breakers
  
  
  • Provided to protect EQUIPMENT not people
    
  • Do not reset breakers with a line voltage higher than 120V and only reset if you know why it tripped
    
• GFCI's
  
  
  • Provided to protect people
  • Trip range 4-6ma
  • Monthly test

• Distance
• If you sense the presence of an electrical hazard or exposed conductors that may be energized, keep you distance and STAY AWAY

Terminology

Electrical Grounding

Figure 12 : Current flow in a properly grounded circuit

Figure 14: Shock from improperly grounded tool

Figure 15: Fault conditions sensed by a GFCI

Figure 16: Correctly wired duplex receptacle

Fundamentals of Electrical Hazards

• Voltage
• electrical pressure (water pressure)
  
• Amperage
• electrical flow rate (gallons/min)
  
• Impedance
  
  
  • restriction to electrical flow (pipe friction)

• Circuit
  
  
  • path of flow of electricity
    
    
• Circuit Element
  
  
  • objects which are part of a circuit and though which current flows.
    
    
• Fault
  
  
  • current flow through an unintended path.

• What is Grounding?
  
  
  • Protection from electric shock
    
    
    • normally a secondary protection measure
      
      
• A ground is a conductive connection
  
  
  • between electrical circuit or equipment and earth or ground plane
    
    
  • creates a low resistance to the earth.

Basic Rules of Electrical Action

• Electricity isn’t live until current flows
• Electrical current won’t flow until there is a complete loop, out from and back to the power source.

Preventing Accidental Electrical Contact

Do's and Don'ts

• Do plug power equipment into wall receptacles with power switches in the Off position.
  
• Do unplug electrical equipment by grasping the plug and pulling. Do not pull or jerk the cord to unplug the equipment.
  
• Do not drape power cords over hot pipes, radiators or sharp objects.
  
• Do check the receptacle for missing or damaged parts.
  
• Do not plug equipment into defective receptacles.
  
• Do check for frayed, cracked, or exposed wiring on equipment cords
  
• Do check for defective cords clamps at locations where the power cord enters the equipment or the attachment plug.
  
• Extension cords should not be used in office areas. Generally, extension cords should be limited to use by maintenance personnel
  
• “Cheater plugs”, extension cords with junction box receptacle ends or other jury-rigged equipment should not be used.
  
• Consumer electrical equipment or appliances should not be used if not properly grounded. (Look for the UL Label)
  
• Employees should know the location of electrical circuit breaker panels that control equipment and lighting in their respective areas. Circuits and equipment disconnects must be identified
  
• Temporary or permanent storage of any materials must not be allowed within 3 feet of any electrical panel or electrical equipment.
  
• Any electrical equipment causing shocks or with high leakage potential must be tagged with a Danger tag or equivalent.

Myths and Misconceptions

• Electricity takes the path of least resistance.
  
• Electricity wants to go to ground.
  
• If an electric tools falls into a sink or tub of water, the item will short out.
  
• AC reverse polarity is not hazardous.
  
• It takes high voltage to kill; 120 volts is not dangerous.
  
• Double insulated power tools are doubly safe and can be used in wet and damp locations.