Overview of Electrical Safety

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Overview of Electrical Safety

Electrical Safety

Electrically powered equipment can pose a significant hazard to workers, particularly when mishandled or not maintained.  Many electrical devices have high voltage or high power requirements, carrying even more risk.

Electrically powered equipment can pose a significant hazard to workers, particularly when mishandled or not maintained.  Many electrical devices have high voltage or high power requirements, carrying even more risk.

Electrical Shock Hazards

The major hazards associated with electricity are an electrical shock, fire and arc flash.  Electrical shock occurs when the body becomes part of the electric circuit, either when an individual comes in contact with both wires of an electrical circuit, one wire of an energized circuit and the ground, or a metallic part that has become energized by contact with an electrical conductor.

The severity and effects of an electrical shock depend on a number of factors, such as the pathway through the body, the amount of current, the length of time of the exposure, and whether the skin is wet or dry.  Water is a great conductor of electricity, allowing current to flow more easily in wet conditions and through wet skin.

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The effect of the shock may range from a slight tingle to severe burns to cardiac arrest.  The chart below shows the general relationship between the degree of injury and amount of current for a 60-cycle hand-to-foot path of one second’s duration of shock.  While reading this chart, keep in mind that most electrical circuits can provide, under normal conditions, up to 20,000 milliamperes of current flow.

Current Reaction
1 Milliampere Perception level
5 Milliamperes Slight shock felt; not painful but disturbing
6-30 Milliamperes Painful shock; “let-go” range
50-150 Milliamperes Extreme pain, respiratory arrest, severe muscular contraction
1000-4,300 Milliamperes Ventricular fibrillation
10,000+ Milliamperes Cardiac arrest, severe burns, and probable death

In addition to the electrical shock hazards, sparks from electrical equipment can serve as an ignition source for flammable or explosive vapors.

Arc Flash

A hazardous arc flash can occur in any electrical device, regardless of voltage, in which the energy is high enough to sustain an arc. Potential places where this can happen include:

  • Panelboards and switchboards
  • Motor control centers
  • Metal-clad switchgear
  • Transformers
  • Motor starters and drive cabinets
  • Fused disconnects
  • Any place that can have equipment failure

In an arc flash incident, an enormous amount of concentrated radiant energy explodes outward from electrical equipment.  The explosion creates pressure waves that can damage a person’s hearing, a high-intensity flash that can damage their eyesight and a superheated ball of gas that can severely burn a worker’s body and melt metal.

Electrical Safety-Related Work Practices

Only qualified workers who have been trained in the avoidance of electrical hazards are permitted to work on or near exposed energized parts.  Safety-related work practices are employed to prevent electric shock or other injuries resulting from either direct or indirect electrical contact when work is performed near or on equipment or circuits which are or may be energized.  The specific safety-related work practices must be consistent with the nature and extent of the associated electrical hazards.

Qualified Personnel vs. Unqualified Personnel

For the purposes of electrical safety-related work practices, there are two types of employees in the workplace that may come in contact with electrical equipment on a job site: qualified and unqualified. A Qualified employee is defined as a worker who

  • Has been trained to avoid electrical hazards when working on or near exposed energized parts.
  • Is familiar with the safety-related work practices as required by OSHA standards.
  • Is able to distinguish exposed live parts of electrical equipment.
  • Is knowledgeable of the skills and techniques used to determine the nominal voltages of exposed parts and components.

An Unqualified employee is defined as a worker who has little or no training regarding electrical hazards. Even though unqualified persons should not be exposed to energized parts, they should be provided with information and training necessary to perform their job in a safe manner and understand the following:

  • Be familiar with any electrical hazards in the workplace.
  • Understand procedures to follow and to protect themselves when they work around electricity.
  • Understand which tasks that can only be performed by qualified workers (e.g. maintenance and repairs).
  • Know when and how to report electrical problems.
  • Know what to do in the event of an emergency involving electricity.
  • Know how to inspect electrical tools and equipment before use to make sure insulation and wiring are in good condition.

Live parts to which an employee may be exposed must be de-energized before the employee works on or near them unless de-energizing the parts introduces additional or increased hazards or is unfeasible due to equipment design or operational limitations. Examples of increased or additional hazards include interruption of life support equipment, deactivation of emergency alarm systems, the shutdown of hazardous location ventilation equipment, or removal of illumination for an area.  Live parts that operate at less than 50 volts to ground need not be de-energized if there are no increased exposures to electrical burns or to explosions due to electric arcs.

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Working On or Near Energized Circuits

Live parts to which an employee may be exposed must be de-energized before the employee works on or near them unless de-energizing the parts introduces additional or increased hazards or is unfeasible due to equipment design or operational limitations. Examples of increased or additional hazards include interruption of life support equipment, deactivation of emergency alarm systems, the shutdown of hazardous location ventilation equipment, or removal of illumination for an area.  Live parts that operate at less than 50 volts to ground need not be de-energized if there are no increased exposures to electrical burns or to explosions due to electric arcs.

Deenergized Parts

When employees work on de-energized parts or near enough to them to expose the employees to any electrical hazard they present, the following safety-related work practices must be followed:

  • Treat as energized any conductors and parts of electrical equipment that have been de-energized, but have not been properly locked out or tagged.
  • While any employee is exposed to contact with parts of fixed electric equipment or circuits which have been de-energized, the circuits energizing the parts shall be locked out or tagged or both.  In addition, electrical hazards must be controlled; a qualified person must test the circuit to verify de-energization from all voltage sources.
  • Safe procedures for de-energizing circuits and equipment must be determined before circuits or equipment are de-energized.  All electric energy sources must be disconnected.  Control circuit devices, such as push buttons, electric switches, and interlocks must not be used as the sole means of de-energizing circuits or equipment.  Interlocks must not be used as a substitute for lockout and tagging procedures.

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