Understanding OSHA’s Rules for T&D Equipment Grounding
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There seems to be a question of the month every month. Recently I’ve answered a lot of questions about when and how to ground distribution and transmission equipment, particularly bucket trucks, uninsulated line trucks and cranes. My standard response to those questions is, “What is required by the OSHA regulations?” I know some people do not like to attempt to read the regulations and interpret their intent, so in this installation of “Voice of Experience,” I’m going to review OSHA 29 CFR 1910.269(p), “Mechanical equipment,” which addresses equipment grounding.
Specifically, 1910.269(p)(4)(iii) covers equipment grounding when working near energized equipment and conductors. That paragraph states, “If, during operation of the mechanical equipment, that equipment could become energized, the operation also shall comply with at least one of paragraphs (p)(4)(iii)(A) through (p)(4)(iii)(C) of this section.”
I have bolded the parts of that paragraph that I want to discuss here. “Could become energized” references equipment that is functioning in or near the minimum approach distance (MAD) of the energized parts, or equipment that, by extended reach, could become energized.
Paragraph 1910.269(p)(4)(iii)(A) states the following: “The energized lines or equipment exposed to contact shall be covered with insulating protective material that will withstand the type of contact that could be made during the operation.”
This paragraph indicates that energized equipment needs to be covered. That sounds reasonable, but does it mean that’s all we have to do? Remember that proper cover-up is not intended for severe pressure; “incidental brush contact” would be a better description of proper use of cover equipment. In paragraph 1910.269(p)(4)(iii)(C), OSHA states that “[u]nless the employer can demonstrate that the methods in use protect each employee from the hazards that could arise if the mechanical equipment contacts the energized line or equipment, the measures used shall include” four different techniques. Hold that thought for a few moments.
Per paragraph 1910.269(p)(4)(iii)(B), “The mechanical equipment shall be insulated for the voltage involved. The mechanical equipment shall be positioned so that its uninsulated portions cannot approach the energized lines or equipment any closer than the minimum approach distances, established by the employer under paragraph (l)(3)(i) of this section.”
So, if I do not cover the equipment, I can position it so that uninsulated portions of the equipment cannot encroach the MAD, or the equipment must be insulated for the voltage involved. This is referring to an insulated bucket truck that is current with dielectric testing of the boom and bucket. If we position the vehicle to keep the insulated portion in the MAD, should we cover for additional protection? I recommend always using properly rated cover when equipment and personnel are working near energized parts. You can see why in 1910.269(p)(4)(iii)(C), which fully states the following: “Each employee shall be protected from hazards that could arise from mechanical equipment contact with energized lines or equipment. The measures used shall ensure that employees will not be exposed to hazardous differences in electric potential. Unless the employer can demonstrate that the methods in use protect each employee from the hazards that could arise if the mechanical equipment contacts the energized line or equipment, the measures used shall include all of the following techniques …”
The question here is, which employees are being referred to? Gradient step potentials may be a risk for employees on the ground, and employees at work in aerial devices may have exposure to arc flashes.
Explaining ‘The Following Techniques’
Also, what are “the following techniques” referenced in 1910.269(p)(4)(iii)(C)? There are four found at (p)(4)(iii)(C)(1) through (4):
• Using the best available ground to minimize the time the lines or electric equipment remains energized.
• Bonding mechanical equipment together to minimize potential differences.
• Providing ground mats to extend areas of equipotential.
• Employing insulating protective equipment or barricades to guard against any remaining hazardous electrical potential differences.
The best available ground is the neutral on a wye system or a permanent driven ground on a delta system. A temporary driven ground is the last choice unless the resistance in the ground is checked using a Megger test to ensure there is a low-resistance impedance path to ground.
What hazards do employees face when grounding to neutral? The equipment is now part of the system. If an employee is in contact with the grounded equipment and a nearby fault occurs, there is always a voltage rise on the neutral. Depending on the distance from the fault and how many pole grounds can dissipate the voltage between the fault and the grounded equipment, there will be a momentary rise in voltage on the neutral and equipment that could be hazardous to anyone in contact with them while standing on the ground. This is true for any equipment grounded to neutral, including dielectrically insulated bucket trucks. Also, any equipment that employees can physically touch – such as trailers or other vehicles in the immediate work area – and that puts an employee in series should be bonded to the grounded equipment to prevent differences of potential between vehicles.
The grounded vehicles should also have a physical barricade around them to prevent accidental contact when work is in progress. Grounding mats attached to vehicles for access are one of the four options noted above, but remember, you have to get to the mat. Many companies obligate their employees to wear super dielectric boots or shoes for step potential protection during operations with equipment near energized lines or when setting poles, performing fault location on underground cables, switching or opening underground equipment, among other tasks.
If you’re looking for more guidance, a note to 1910.269(p)(4)(iii)(C) informs readers that “Appendix C to this section contains information on hazardous step and touch potentials and on methods of protecting employees from hazards resulting from such potentials.”
The Bottom Line
The bottom line is that bucket trucks may or may not be required to be grounded according to employer rules. If the bucket truck is positioned so that no part of the knuckle of the boom may contact energized parts or equipment, it is not necessary to ground the equipment. With barricades and grounding mats employed, I recommend dielectric boots as secondary protection for those working in close proximity to the equipment.
Digger derrick line trucks, cranes and non-dielectric equipment should be grounded when working close to energized lines. Barricades, mats, and dielectric boots or shoes should also be utilized.
Other tasks requiring specific types of grounding are found in 1910.269(q), “Overhead lines and live-line barehand work.” We will discuss these tasks in a future issue.
About the Author: Danny Raines, CUSP, safety consultant, distribution and transmission, retired from Georgia Power after 40 years of service and opened Raines Utility Safety Solutions LLC, providing compliance training, risk assessments and safety observation programs. He also is an affiliate instructor at Georgia Tech Research Center OSHA Outreach in Atlanta.
Learn more from Danny Raines on the Utility Safety Podcast series. Visit https://incident-prevention.com/podcasts or scan the QR code to listen now!