Substations
This article highlights OSHA’s requirements for substations and work within substations. Substations have significant step and touch and arc flash hazards located within relatively small, restricted areas. Various types of non-electrical and electrical work are performed inside areas with extremely high voltages and minimal air clearances.
Energized substations are considered restricted work areas that contain electric power system hazards with extremely high risk. Workers who enter restricted work areas must be appropriately trained to recognize the electrical hazards and to demonstrate the required skills and safe work practices to control or avoid the hazards for the work performed. Many fatal incidents have occurred because unqualified workers contacted energized parts while performing non-electrical work tasks in substations.
The substation standard can be found at 29 CFR 1910.269(u) and 1926.966. When referencing the standard, remember that all other applicable OSHA electric power requirements must be followed in addition to these standard requirements when performing work within substations. The standard has seven major paragraphs: application; access and working space; draw-out-type circuit breakers; substation fences; guarding of rooms and other spaces containing electric supply equipment; guarding of energized parts; and substation entry. This article provides an overview of several of the major paragraphs found within the standard.
Access and Working Space
Employers are required to provide and maintain sufficient access and working space around electrical equipment to permit safe operation and maintenance of the equipment. This is an extremely important rule designed to prevent employees from contacting exposed live parts due to insufficient maneuvering room. Keep in mind that older substations can have insufficient maneuvering room as they may have been built to specifications and consensus standards that were in effect during the time of the installation’s construction. Substation equipment and configuration designs continue to develop, so OSHA refers to consensus standards – which are based on industry best practices for the work performed – for compliance information.
One consensus standard that OSHA references is the ANSI/IEEE C2-2012 National Electrical Safety Code – which addresses electrical equipment workplace design – to determine sufficient access and working space around electrical equipment. Installations that do not conform to ANSI/IEEE C2-2012 must comply with the following criteria:
- The installation must conform to the edition of ANSI/IEEE C2 that was in effect when the installation was made.
- The configuration of the installation must enable employees to maintain the minimum approach distance while working on exposed energized parts.
- The precautions taken when employees perform work on the installation must provide protection equivalent to the protection provided by ANSI/IEEE C2-2012.
Substation Fences
It is critical to understand the importance of equipment and fence grounding and bonding requirements to control step and touch potentials that can occur due to hazardous voltages. Hazardous voltages can be impressed or induced on large metal objects near substation equipment. OSHA requires conductive fences to be grounded. And when fences are expanded or a section is removed, they must be isolated, grounded or bonded to protect employees from hazardous differences in electrical potential.
Further, OSHA references IEEE 80-2000, “IEEE Guide for Safety in AC Substation Grounding,” in this portion of the standard; IEEE 80-2000 contains guidelines for protection against hazardous differences in electrical potential.
Guarding of Rooms and Other Spaces
OSHA addresses guarding exposed live parts operating at 50-600 volts and greater than 600 volts to ground and other working surfaces inside rooms and other spaces guarded only by location. It is important to reference the standard to ensure an understanding of the guarding requirements in this paragraph.
Additionally, OSHA requires “Keep Out” warning signs at entrances to rooms and other spaces containing energized electrical equipment; these are intended to warn unqualified people to stay away. Rooms and other spaces must be locked unless the entrance is under the observation of a person who is attending the space for the purpose of preventing unqualified employees from entering. OSHA defines an attendant as an “employee assigned to remain immediately outside the entrance to an enclosed or other space to render assistance as needed to employees inside the space.” It is important to review definitions found within the OSHA electric power standard to better understand their application within the standard.
Guarding of Energized Parts
OSHA requires guarding around all live parts operating at more than 150 volts to ground without an insulating covering unless the location of the live parts provides sufficient clearance – horizontal, vertical or both – to minimize the possibility of accidental employee contact. The OSHA definition of “guarded” is “covered, fenced, enclosed, or otherwise protected, by means of suitable covers or casings, barrier rails or screens, mats, or platforms, designed to minimize the possibility, under normal conditions, of dangerous approach or inadvertent contact by persons or objects.”
OSHA again references the ANSI/IEEE C2-2012 National Electrical Safety Code to determine guidelines for the dimensions of clearance distances about electrical equipment in substations. Installations that do not conform to ANSI/IEEE C2-2012 must comply with the following criteria:
- The installation must conform to the edition of ANSI/IEEE C2 that was in effect when the installation was made.
- Each employee must be isolated from energized parts at the point of closest approach.
- The precautions taken when employees perform work on the installation must provide protection equivalent to the protection provided by ANSI/IEEE C2-2012.
Substation Entry
Employees must report their presence to the employee in charge of substation activities prior to entering an attended substation so that they can receive information on any special system conditions affecting their safety.
Additional requirements for job briefings are included within this paragraph. Job briefings must cover information on special system conditions affecting safety, including but not limited to the location of energized equipment in or adjacent to the work area and the limits of any de-energized work. These additional job briefing requirements apply equally to unattended and attended substations as well as to employees working and those who are entering a substation.
Summary
It is critical to have a good understanding of the substation requirements found within the OSHA standard. Too many fatalities occur due to a poor understanding of the step and touch hazards found within electric power substations. OSHA’s Appendix C to 1910.269 and 1926 Subpart V, “Protection From Hazardous Differences in Electric Potential,” is an excellent resource. If you have not read this appendix lately, it will provide a great overview of the hazards and the mitigation required to protect workers.
About the Authors: Pam Tompkins, CUSP, CSP, is president and CEO of SET Solutions LLC. She is a 40-year veteran of the electric utility industry, a founding member of the Utility Safety & Ops Leadership Network and past chair of the USOLN executive board. Tompkins worked in the utility industry for over 20 years and has provided electric power safety consulting for the last 20-plus years. An OSHA-authorized instructor, she has supported utilities, contractors and other organizations operating electric power systems in designing and maintaining safety improvement methods and strategies for organizational excellence.
Matt Edmonds, CUSP, CIT, CHST, is vice president of SET Solutions LLC. A published author with over 15 years of safety management experience, he also is an OSHA-authorized instructor for general industry and construction standards. Edmonds provides specialty safety management services for electric power organizations throughout the U.S. He has been instrumental in the development of training courses designed for electric power organizations, including OSHA 10- and 30-hour courses and SET Solutions’ popular OSHA Electric Power Standards Simplified series.
About OSHA Electric Power Standards – Simplified: Topics in this series are derived from SET Solutions’ popular OSHA electric power course offered through the Incident Prevention Institute (https://ip-institute.com). The course is designed to help learners identify standard requirements and to offer practical ways to apply the standards.
