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Electric Power >> Generation vs. Transmission/Distribution >> Substations

Generation vs. Transmission/Distribution

SubstationSubstations are located throughout electric power transmission and distribution systems and serve a variety of functions, such as:
  • Transmission system switching points.
  • Voltage transformation and regulation.
  • Sources of distribution circuits.
Substations may be indoors or outdoors, and may be metal clad or open bus. Typically substations are unoccupied and are considered "field" work locations. Where workers report to and work regularlySubstation at substations, these substations would be "fixed" work locations. This distinction is important when applying the medical and first aid requirements found in 1910.269(b) and discussed in this eTool (see Medical and First Aid)

The "269" standard's general requirements for T&D systems apply to substations; additional requirements specifically for substations are listed in 1910.269(u) and include:
  • Sufficient access and working space must be provided around equipment to ensure safe operation and maintenance work.
  • "Draw-out" types of circuit breakers must be open and the control circuit inoperative (if possible) when installing or removing the breaker.
    1910.269 Photo credit: Oak Ridge National Laboratory See: 1910.269(u) on Substations
  • Conductive fences must be grounded. If a section of fence is moved or removed, ground continuity must be maintained.
  • Access to rooms and spaces containing exposed live equipment must be designed to restrict entry to 269-unqualified employees. Signs must be posted at entry points warning 269-unqualified people to keep out, and unattended entrances to "live" areas must be kept locked.
  • Uninsulated live parts over 150 volts to ground must be guarded with some form of insulating barrier if they are located in a position that could allow for accidental contact.
  • Upon entering an attended substation, all personnel except those normally assigned to the location must report to the person in charge to receive information on any special conditions that could affect safety.
  • Only qualified persons are permitted entry into rooms or spaces containing electric supply equipment when electric supply lines are energized.
Transmission vs. Distribution

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