Substations are installations located throughout transmission and distribution systems that serve as switching points or sources of distribution circuits. They can also change AC voltage levels or convert AC to DC and vice versa. Essentially, they serve to “step down” high-voltage electricity for supply purposes. 

The size and layout of substations can vary dramatically. They may be indoors or outdoors, metal-clad or open bus. Workers may need to enter a substation for any number of reasons, including to conduct maintenance or take readings or photos. Employers are required to ensure safe entry.

Requirements 

Occupational Safety and Health Standards 1910.269(u) or “269” and 1926.966(b) lay out requirements for safe substation entry, including:

• Sufficient access and working space must be provided around equipment to ensure safe operation and maintenance work. ANSI/IEEE C2-2012 contains detailed guidelines for the dimensions of access and working space about electric equipment in substations.
• “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.
• Only qualified persons are permitted entry into rooms or spaces containing electric supply equipment when electric supply lines are energized.
• 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 150V to ground must be guarded with some form of insulating barrier if the location 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 a job briefing, which must cover information on special system conditions affecting employee safety, including the location of energized equipment in or adjacent to the work area and the limits of any de-energized work area. The minimum approach distance may also be calculated.

PPE

• Note that specific PPE requirements can vary by company,
  but you will likely be required to wear a hard hat, safety glasses, a face mask/shield, steel-toed boots and insulating gloves.
• As a rule, wear fire-retardant and arc-rated PPE. Chemically-resistant PPE may be important if dealing with battery
  storage rooms.  

Helpful Guidelines

Before entering

• Inform the responsible party when you’ll be going in. 
• Learn about the size and layout of the specific substation you’ll be entering.
• Walk outside along the substation fence and check for vandalism or damage. If the fence or grounds look damaged in any way, do not go inside, and inform the responsible party.
• Perform a sound, smell and taste assessment—are there any unusual odors? Do you smell burning? Does anything sound off? If so, do not go inside, and inform the responsible party.

Once inside

• Don’t bump anything. Control rooms may have “pistol grips” that can trip circuit breakers, and older electromechanical relays can sometimes be very sensitive. 
• Be mindful of arc flash hazards and residual energy.
• Stay alert and observant.
• Let the responsible party know when you leave.

Discussion questions

1. Who cannot enter rooms and spaces containing exposed live equipment?
2. What should you do upon entering an attended substation you’re not normally assigned to?
3. What standard can you go to for detailed guidelines on “sufficient access and working space”?