Basic Electrical Safety

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Summary Statement

A presentation on the basics of electrical safety, including terminology, an introduction to fundamentals of electricity, and ways to prevent electrocution.

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.


  • 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?


  • 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


Electrical Grounding

Figure 12 : Current flow in a properly grounded circuit

Figure 12 Illustration

Figure 12 Illustraction Continued
Figure 14: Shock from improperly grounded tool

Figure 14 Illustration

Figure 15: Fault conditions sensed by a GFCI

Figure 15 Illustration

Figure 16: Correctly wired duplex receptacle

Figure 16 Illustration

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.

Safety First: The Safe Way is the Best Way