August-September 2023 Q&A
Q: Is there a rule that determines at what voltage level we must ground downed primary (e.g., at voltages higher than 4 kV)?
A: No, there is no rule that you must ground downed primary when working to get it back up in the air. When conductors are on the ground, the objective of grounding is twofold. The first objective is to help collapse the voltage and trip the circuit should the circuit inadvertently become energized while crews are working on it. The second objective is to aid in bonding the conductor close to the potential of earth where the workers are in contact with the downed conductors; this is to keep the voltage low between conductor and earth. Both of these objectives help to limit the hazard. Grounding does not remove the hazard of electrocution; it limits time of exposure by tripping the source circuit and keeping the voltage rise low so that the remaining hazards are mitigated by rubber gloves, EH-rated work boots, arc-rated clothing and keeping the wire off your body.
The hazard is the same for 4 kV as it is for 13.8 kV. There is no difference in the level of hazard to the worker that would justify mandatory grounding of 7,200 volts and no grounding of 2,400 volts.
When evaluating hazards and planning restoration work, remember that you have three options for how you work the conductor:
- De-energize and ground if you are not certain you have isolated all sources of feed.
- Work it hot – even if it is de-energized – using sticks, rubber gloves, cover and minimum approach distance.
- Completely isolate from all sources, including induction and backfeeds.
We still promote isolation as a best practice. Cut down the wire or cut in a gap across a nylon hot hoist or a couple of bells at the last pole where the wire is still up. Piece it all back together on the ground isolated from the source, including customer services. Re-sag back at the hoist when you are done. If you can do this, isolation makes work much more comfortable in post-storm humidity.
Q: Can we use rubber gloves to install grounds?
A: OSHA 29 CFR 1910.269(n)(6)(i) allows the use of rubber gloves to ground at 600 volts and below. So, you can’t install grounds with rubber gloves above 600 volts, which would be 4 kV or 2,400 volts to ground. There really isn’t much call for voltages between 600 volts and 4 kV, with the exception of some specialty voltages in industry.
Regarding grounding with rubber gloves, there is a requirement that the employer ensures the conductor is not energized. That means the employer must have a procedure and training to ensure workers are testing for voltage before installing grounds with rubber gloves, just like testing for voltage when installing grounds with hot sticks.
Part of the reasoning is described on page 775 in the preamble to the final rule published April 11, 2014. The practical reason for using hot sticks at 4 kV and above is the hazard of making the ground connection if the circuit becomes energized after testing while you are grounding it. Despite the exception allowing rubber glove installation of grounds below 600 volts, workers should beware that grounding an energized circuit below 600 volts can be just as hazardous as grounding an energized circuit above 600 volts with hot sticks.
Q: Is there a standard in any of the regulations that spells out how we must place grounds on downed conductors?
A: No. The preeminent rule for grounding, found at 1910.269(n)(3), states the following: “Temporary protective grounds shall be placed at such locations and arranged in such a manner that the employer can demonstrate will prevent each employee from being exposed to hazardous differences in electric potential.” There are dozens of scenarios and arrangements that simply cannot be listed for the employer. That is why we stress the principles of bonding – to be able to identify where the difference in potential will exist and how to bond it out.
Q: Are there any regulations that state that we cannot handle downed conductors without grounding first?
A: No, but what the standards do state is, “If you ground …” Specifically, OSHA 1910.269(n)(2) states that “if the employer can demonstrate that installation of a ground is impracticable or that the conditions resulting from the installation of a ground would present greater hazards to employees than working without grounds, the lines and equipment may be treated as deenergized provided that the employer establishes that all of the following conditions apply: The employer ensures that the lines and equipment are deenergized under the provisions of paragraph (m) of this section; there is no possibility of contact with another energized source; and the hazard of induced voltage is not present.”
Section (m), which is referenced toward the end of the paragraph, is titled “Deenergizing lines and equipment for employee protection.”
So, do you have to ground? No. In the note to paragraph 1910.269(n)(1), OSHA states, “… whenever the employer chooses to ground such lines and equipment for the protection of employees.” There are some activities that require grounding, like the rules on induction while pulling conductors. Most other work we do can be performed safely in isolation or working hot, no grounding required. It is up to the employer to decide how and when certain work methods must be used.
By the way, in the last OSHA rulemaking, the agency changed the rules to read “the employer shall” or “the employer shall ensure,” both of which replace the prior “the employee shall.” The reasoning was to clearly hold the employer responsible for the safety of the employee. The employer can use safety committees, safety representatives, employee representation and/or consultants to develop their safe work standards. The rules simply require that the employer answer for and be able to defend the workplace hazard analysis and the safe work practices employed by workers.
Q: Where do we find guidance on grounding the metal-clad enclosed bus in power plants?
A: This is an answer that will surprise many, and we are wide open to inquiries for further explanation.
Grounding of metal-clad bus is an issue that has arisen in many power plants since the new emphasis on grounding of de-energized circuits appeared in the 2005 Notice of Proposed Rulemaking, which revised and updated many practices in the electric utility industry (see the 2014 final rule). None of those revisions added any grounding requirements for generation facilities.
Under 1910.269(d), “Hazardous energy control (lockout/tagout) procedures,” you will find rule 1910.269(d)(1), “Application,” which states, “The provisions of paragraph (d) of this section apply to the use of lockout/tagout procedures for the control of energy sources in installations for the purpose of electric power generation, including related equipment for communication or metering. …”
Throughout paragraph (d) – which includes the requirements for the LOTO program, training, application of locks and tags, removal of locks and tags, tagging out, testing and specifications for the equipment used – there is no mention of grounding.
The reason is that grounding does not protect workers. The requirement to bond workers into temporarily grounded systems protects workers, and it is almost impractical to effectively bond raceway and metal enclosures to a grounded bus. In addition, since generator plants with multiple generators have common ground and common neutral bus, it is practically impossible to ensure that neutral currents – including third harmonics – are isolated from the grounding system. That means any worker who gets in series with a grounded distribution bus and the surrounding enclosure is subject to an exposure to differences in potential between the grounded bus and any other conductive surface, including frames, supports, panels, enclosures and concrete in the work area. Just as in the non-utility industrial and commercial electrical world, ensured isolation following strict LOTO rules protects electrical workers. LOTO used in power plants affords the same guarantee of protection. That is the reason why OSHA addressed LOTO in 1910.269(d) and made a particular clarifying reference to paragraph (m) for transmission and distribution that includes grounding.
Metal-enclosed or metal-clad systems were not and are not designed to be grounded. They are designed to be isolated at switches and locked out. Workers can be injured if they get between grounded bus and enclosures where stray currents are introduced into the grounded bus, creating potential differences between bus and enclosure. You can ground if you want to as an added level of safety, but if you are not bonding in the worker as required by OSHA, you are not safer.
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