||Electric Power >> Generation vs. Transmission/Distribution >> Substations
Generation vs. Transmission/Distribution
are located throughout electric power transmission and distribution systems and
serve a variety of functions, such as:
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 regularly 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)
- Transmission system switching points.
- Voltage transformation and regulation.
- Sources of distribution circuits.
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:
Transmission vs. Distribution
- 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.
- 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
- 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.