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The following definitions help clarify general electrical safety:

Amps The standard unit for measuring electrical current.
Authorized Employee A person who locks out or tags out equipment for service or maintenance. Authorized employees have been formally trained in proper lockout/tagout procedures.
Breaker Box An insulated box on which interconnected circuits are mounted.
Circuit Breaker A device designed to open and close a circuit by non-automatic means and to open the circuit automatically on a predetermined overcurrentwithout damage to itself when properly applied within its rating.
Current Flow The rate of flow of an electrical charge, generally expressed in amps.
Electrical Load The amount of power delivered by a generator or carried by a circuit. A device to which the power is delivered.
Electrical Panel An insulated panel on which electrical wires are mounted.
Energy-Isolating Device

A mechanical device that prevents the transmission or release of energy. Examples include the following:

  • Manually operated circuit breakers
  • Disconnect switches
  • Line or block valves
Pushbuttons, selector switches, and other control circuit devices do not isolate energy.

Energy-isolating devices should be lockable by means of a hasp or other type of attachment. It should not be necessary to dismantle or reassemble a device to lock it.

Ground-Fault Circuit Interrupter (GFCI) A GFCI detects grounding problems and shuts electricity off to prevent a possible accident.
Hazardous Energy Sources This term applies to stored or residual energy such as that in capacitors, springs, elevated machine members, rotating flywheels, hydraulic systems, and air, gas, steam, or water pressure.
High Voltage The term high voltage applies to electrical equipment that operates at more than 600 Volts (for terminal to terminal operation) or more than 300 Volts (for terminal to ground operation). Low voltage, high current AC or DC power supplies are also considered to be high voltage.
Lockout The placement of a lock on an energy-isolating device. This act prevents workers from energizing and operating a piece of equipment until the lock is removed.
Tagout The placement of a tag on an energy-isolating device. A tagout device is a prominent warning device of a lockout.
Voltage Electromotive force expressed in volts.
Watt A unit of electrical power, equal to the power developed in a circuit by a current of amp flowing through a potential difference of one volt.


May 2011
Revised November 2014