Substation safety requirements

The substation rules in 1926.966 apply to substations and to work performed in them. The regulation states that this section "provides additional requirements for substations and for work performed in them" (1926.966(a)).

• Employers should use these provisions in addition to other applicable parts of 29 CFR part 1926 when planning and performing substation work.

The employer must provide and maintain sufficient access and working space about electric equipment so employees can operate and maintain it safely. The rule says the employer shall "provide and maintain sufficient access and working space about electric equipment to permit ready and safe operation and maintenance of such equipment by employees" (1926.966(b)).

• Installations that meet the dimensions in the American National Standard National Electrical Safety Code, ANSI/IEEE C2-2012, are considered to comply with this paragraph.
• If you design or modify access, follow ANSI C2 dimensions where practicable or be prepared to document how your space provides equivalent protection.

OSHA will judge nonconforming installations by whether they met the applicable ANSI edition when installed, whether employees can maintain the employer-established minimum approach distances, and whether protective precautions provide equivalent protection to ANSI/IEEE C2-2012 clearances. The criteria are: (1) conformity to the edition of ANSI C2 in effect when installed; (2) whether the configuration enables employees to maintain the minimum approach distances established under 1926.960(c)(1)(i) while working on exposed energized parts; and (3) whether precautions give equivalent protection to ANSI/IEEE C2-2012 (1926.966(b)).

• Be prepared to document the ANSI edition that applied when the equipment was installed and how employees will maintain minimum approach distances and equivalent protections.

When employees remove or insert draw-out-type circuit breakers, the breaker must be in the open position, and the employer must render the control circuit inoperable if the equipment design allows. The standard requires both conditions: open position for the breaker and inoperable control circuit when the design permits (1926.966(c)).

• If the equipment permits rendering the control circuit inoperable, do so before personnel remove or insert the breaker.
• Document procedures and train qualified employees on the required steps to prevent unexpected energization.

Substation fences must be grounded, and when a fence is expanded or a section removed, the affected sections must be isolated, grounded, or bonded as necessary to protect employees from hazardous potential differences. The rule explicitly requires grounding of conductive fences and protective actions when fences are altered (1926.966(d)).

• When you temporarily remove or add fence sections, ensure you isolate and either ground or bond adjacent sections so employees are not exposed to dangerous step or touch voltages.
• Keep records of grounding/bonding steps and verify continuity after modifications.

Rooms or spaces must meet the guarding requirements when they contain live parts that are within 2.4 meters (8 feet) of the ground or any working surface at specified voltages, or whenever live parts over 600 volts are present unless special enclosure or mounting exceptions apply. Specifically, guarding is required if: (i) exposed parts at 50–150 volts to ground are within 2.4 meters (8 ft); (ii) live parts at 151–600 volts within 2.4 meters are guarded only by location; or (iii) any live parts over 600 volts are present unless they are enclosed in grounded metal enclosures with openings designed to deflect objects or installed at a height providing equivalent protection (1926.966(e)(1)(i)–(iii)).

• If your installation relies on enclosure openings to keep objects away from energized parts, check the exception in 1926.966(e)(1)(iii)(A).

Employers must enclose rooms and spaces so unqualified persons are unlikely to enter, prohibit unqualified persons from entering while equipment is energized, post warning signs at entrances, and keep entrances locked unless an observer is present to prevent unqualified entry. These are the explicit requirements: enclosure to prevent access (1926.966(e)(2)); no entry by unqualified persons when energized (1926.966(e)(3)); warning signs at entrances (1926.966(e)(4)); and locked entrances unless attended (1926.966(e)(5)).

• Typical controls include fences, locked doors, partitions, and a designated attendant to monitor access when doors must remain unlocked.

Guards are required around all live parts operating at more than 150 volts to ground that do not have insulating coverings, unless the location provides sufficient horizontal and/or vertical clearance to minimize accidental contact. The standard directs employers to provide such guards or meet clearance dimensions that minimize contact (1926.966(f)(1)).

• Installations meeting ANSI/IEEE C2-2002 clearance guidelines are considered to comply with this paragraph (see the note to 1926.966(f)(1)).

Except for necessary access tasks like fuse replacement, employers must maintain guarding of energized parts during operation and maintenance to prevent accidental contact and to stop dropped tools or equipment from contacting live parts. The standard requires guards to remain in place during operation and maintenance except where limited access by qualified persons is needed (1926.966(f)(2)).

• When temporary access is necessary, plan the work to minimize guard removal time and protect others in the area.

Before removing guards from energized equipment, employers must install barriers around the work area to prevent employees who are not working on the equipment from contacting the exposed live parts. The regulation requires barriers to isolate the work area when guards are temporarily removed (1926.966(f)(3)).

• Barriers can be physical (temporary fencing, barricade tape plus stanchions) and should be tall/sturdy enough to deter unauthorized entry and accidental contact.
• Use signage and an attendant as needed to keep unqualified persons out of the barrier zone.

OSHA will evaluate nonconforming installations by checking whether the installation met the ANSI C2 edition in effect when installed, whether each employee is isolated from energized parts at the point of closest approach, and whether precautions taken provide protection equivalent to ANSI/IEEE C2-2002 clearances (1926.966(f)(1)).

• Document how employees are isolated (guards, platforms, insulating barriers, procedures) and how work practices maintain safe clearances.
• Demonstrating equivalence often requires written procedures, training, and engineering controls that provide the same level of protection as the ANSI clearances.

Every employee who enters an attended substation, except those who regularly work in the station, must report their presence to the employee in charge of substation activities to receive information on special system conditions that affect safety. The rule states this reporting requirement explicitly (1926.966(g)(1)).

• Make sure your site has a procedure for visitors or temporary entrants to check in with the person in charge and receive any necessary safety information.

The job briefing required by 1926.952 must include 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 deenergized work area (1926.966(g)(2)).

• See the general job briefing requirement in 1926.952 for additional topics that the briefing must address.

Live parts over 600 volts are exempt from the general room guarding requirement if they are enclosed within grounded metal-enclosed equipment whose openings are designed so that foreign objects inserted will be deflected from energized parts. This is the exception listed in 1926.966(e)(1)(iii)(A).

• Verify enclosure integrity and opening geometry so inserted objects cannot reach energized parts; document the enclosure features and inspection records.

Live parts over 600 volts may be left unguarded if they are installed at a height above ground or any working surface that provides protection equivalent to a 2.4-meter (8-foot) height at 50 volts, per the exception in 1926.966(e)(1)(iii)(B).

• You must be able to show that the installed height gives equivalent protection for the voltage involved; document the rationale and safe work procedures for any elevated live parts.

The employer must display signs at entrances warning unqualified persons to keep out. The rule requires warning signs at entrances to rooms or spaces that contain electric supply equipment (1926.966(e)(4)).

• Use clear wording such as "Danger: High Voltage — Authorized Personnel Only" or similar language appropriate to the hazard and in languages understood by your workforce.
• Keep signs visible, legible, and maintained.

Entrances may be left unlocked only if the entrance is under the observation of a person attending the room or space for the purpose of preventing unqualified employees from entering; otherwise each entrance must be kept locked (1926.966(e)(5)).

• If you rely on an attendant, ensure that person is trained, assigned, and able to prevent unauthorized entry for the duration the door is unlocked.

The employer is responsible for establishing minimum approach distances for employees and ensuring substation configuration allows employees to maintain those distances while working on exposed energized parts; the nonconformance criteria refer to the distances established under 1926.960(c)(1)(i) and to the access and working-space requirements in 1926.966(b).

• Employers should record the employer-established minimum approach distances and show how work practices and equipment layout allow workers to meet them.

Employers must assess the workplace to determine the hazards present and whether PPE is needed; if PPE will be required, employers must complete the hazard assessment and prepare a written certification of the assessment as required by OSHA PPE rules (see 29 CFR 1910.132) and the related OSHA interpretation on PPE hazard assessment (OSHA interpretation on PPE hazard assessment, 2024-03-28).

• Although 1926.966 covers physical guarding and access of substations, PPE selection and documentation should follow the hazard assessment and the employer’s written certification requirements in 29 CFR 1910.132(d) as explained in OSHA's PPE hazard assessment interpretation.
• Document the assessment, selection rationale, training, and inspection schedules for PPE used in substation work.