February – March 2022 Q&A
Q: Is it a good idea to wear dielectric boots in a substation? Do they provide additional protection to a worker? We feel that the worker is at equipotential – given the grid and stone are maintained per design – so we don’t believe that dielectric boots would provide extra protection. What are your thoughts?
A: The design of the substation’s grid has two purposes in its construction. One incorporates ground rods to create a low-resistance electrical path to get harmful voltage and current into the earth to protect the equipment in the station. The grid itself helps by interconnecting the rods. To most of us, the second purpose is more important. The grid creates a plane of bonded equipotential across the ground in the substation. The cross-members of the grid are coordinated with the conductivity of earth to ensure that no hazardous step potentials develop in a worst-case scenario. The grid goal is to create equipotential protection for the worker within the confines of the fence, including touch potentials between equipment and earth. The substation granite rock cover serves as an insulating barrier above the soil-covered grid. As you noted in your question, the integrity of the system, grid, rods, soil and rock is important.
As to protective boots, there is no OSHA requirement for electrical workers to wear electrically protective boots of any type. Around the 1980s, there was an OSHA rule for electrical workers to wear electrically protective-soled shoes or boots. Studies showed that the electrical protection of the boot could be compromised and that there was no effective way of testing the in-service boots to gauge the level of protection provided to the wearer. OSHA and those who developed the standards that regulate design and manufacturer testing of boots as personal protective equipment were concerned that workers would take advantage of what they thought was reliable protection and take chances with electrical hazards.
There is testing for manufacturers that shows that materials have a protective quality. Testing and standards are found in ASTM F1116, F1117 and F2413. The consensus standards clearly define the design and testing as performance and acceptance testing, and specified claims for performance are to be based on user testing performed within two months of receipt of the boots by the customer. Many labs will perform testing based on the ASTM F1116 standard even though at present, with the technology available, there is no consensus-standard-compliant way to assure protection of the worker using protective boots once they have been in service. Since that’s the case, OSHA quietly issued a directive to regional directors to suspend enforcement of the boot requirement and then removed the rule during the next revision of the related standard. That does not mean the protective role of the boot has no value in the industry. In its guidance to employers, OSHA still recommends insulating boots as part of a system of protection. There are utilities with a requirement for workers in the substation to wear electrical-hazard-rated boots.
We also know of some utilities that, due to testing results on some substations, have requirements for dielectric boots or rubber insulating boots. That is reasonable if testing shows the grid performance indicates risk. However, no boots of any protective design should be relied upon as a primary means of protecting the worker. A system of protection includes design, work procedures, the grid, ground rods, relaying, testing of the grid, the rock cover barrier and maintenance of the substation’s protective system. In that system, boots are effective as part of a system of protection that backs up the protective design of the substation grid. A recent EPRI study concluded that electrical-hazard-rated boots provided protection for workers as well as dielectric overshoes in most applications. We do feel it is important to point out that there is a good argument that the long-term daily use of dielectric overshoes can result in soft tissue damage because the shoes are hard to walk in. We recommend that employers seek the advice of orthopedic professionals in developing a use or limited-use policy.
As far as the condition of the grid, about the only things that can limit the grid’s protection are a dig-in and missing grid members, either by removal (usually theft) or corrosion. The rock bed is an additional buffer layer that should be periodically refreshed every 20 years or so depending on traffic and the rate of decomposition. We also want to add that any substation entry policy should include a visual scan for fence bonding and soil disturbances that might suggest the grid system has been compromised.
Q: We have had several incidents during which a mini-excavator or other digging equipment has struck an energized power line. Currently, we don’t have any protective measures/direct controls in place to protect the worker/equipment, but we have been discussing a practice of grounding the equipment with a screw ground and either a 2/0 or a 4/0 ground cable. The question is, are there any industry practices that we could/should be using in these instances? Is grounding the equipment the right option?
A: Ultimately, each employer must analyze work practices for risks and adopt practical and defensible safe work procedures. It’s not very practical to try to temporarily ground a mobile excavator. It makes movement of the excavator difficult, and there are better ways to protect workers. Grounding itself will not protect a worker who is standing on the ground and touching the excavator during an event. They would simply be a parallel path with the ground path, and the division of current between the two paths would not be sufficient to assure protection of the worker. As far as the operator is concerned, they are not at risk of electrocution if they stay on the machine.
Grounding the machine would create a better ground path for tripping the circuit that is cut by the machine, but most underground circuits are short-time ground settings, and the blade of the excavator assures a path between phase conductor and ground during the dig-in. So, grounding of the machine has little effect on improving the speed of tripping. And, as pointed out, it would not matter if the circuit tripped quickly since grounding does not assure protection of the worker.
In all of industry, the persons injured or killed by dig-ins were workers on the ground who were touching the machine. There is a very simple solution, and it is OSHA approved: Don’t touch the machine while it is operating. No, we are not joking – that is the best practice for the hazard you are concerned with. If you don’t touch the machine, you won’t be electrocuted. There is always a theoretical risk of ground gradients that must be analyzed by the employer, but that risk is very slight. As discussed in the preamble to OSHA 29 CFR 1910.269, the greater risk is associated with direct contact with an energized surface with the worker standing on the ground.
There is no OSHA or consensus standard, but we find a common practice across industry – maintaining a 6- to 10-foot clearance from an operating excavator for protection from gradients – is also a best practice. Operators typically lift the bucket in a fault, and once that is done, there is no longer an electrocution risk.
Q: Our questions are about mechanical jumpers that we call “macs.” Are they considered insulated, and are they safe to touch?
A: No is the short answer to both questions. The effectiveness of the insulation of a mac, which is technically known as an insulated temporary bypass jumper, depends on the storage conditions, use, testing and application. Each employer should perform a hazard assessment of mechanical jumpers and develop a use policy for them. In most cases, macs are untested for the performance of their insulating qualities. Even when tested, macs are considered to be like rubber or plastic insulation – brush contact only. Most employers don’t have macs tested since they are not allowing contact and isolate them with additional blankets or rubber if they are in contact with a pole or another conductive surface. OSHA is silent on macs and testing. ASTM F2321 has an acceptance electrical test for manufacturers that many test labs use for in-service testing of mechanical bypass jumper insulation. ASTM F2321 4.2 qualifies macs as “insulated to temporarily protect personnel from brush or accidental contact only.” Most consultants agree that macs should be insulation-tested, that testing is a condition of use for limited insulating quality, and that exposure is “don’t touch” or brush contact only. Many lineworkers know of instances where macs lying on a crossarm began smoking, which is indicative of their insulating qualities. Many more lineworkers have had the opportunity to brush against a mac from the pole and have found the insulation to be somewhat less than effective.
Q: One of our crews was removing a chain from a substation gate and it began arcing. Is this considered induced voltage?
A: Induction is likely the answer. You could conceivably have voltage flowing horizontally across a station grid to the gate. The gates are in series, so if the electrical path across the latch and/or chain were interrupted, arcing would occur. However, there are many reasons why that is not likely unless the whole grid system was not conducting to earth, leaving an insulated pathway out to the gate. IEEE 80, “IEEE Guide for Safety in AC Substation Grounding,” and part 17.3 in particular, discusses various fence grounding scenarios. Some grids extend outside the fence line and the fence is bonded to the grid. Some fences are outside the grid and grounded by the fence posts themselves. Some fences are isolated from the substation with their own grounded system.
Gates that arc most often have had their bonding or grounding system compromised, usually by theft. Theft of fence and gate grounding continues to rise in frequency across utility systems. If a gate post is set in highly resistive soil and the grounding system is compromised, there is a difference in potential between the two gates. With latches closed and chains in place, the gates are incidentally bonded across by the contact through the latch and chain. In substations, current can reach a fence during an event, but even that is rare and most likely occurs in small substations with small grid areas. When you can see constant arcing, it is most likely a result of the electromagnetic field around the transmission bus into which the fence and gate are projected.
Most fences with intact grounds and earth bonds include a buried mat that extends outside the gate so that a worker swinging the gate will not be exposed to a difference in potential between gate and earth. That earth bonding typically keeps the earth near the gate or fence at near the same potential so that anyone touching the fence will not be shocked. There are a few other redundant conditions that would have to be compromised. Removal of those redundant system grounds or bonds is typically the reason gates arc.
In most incidents we are familiar with, the arcing resembles the arcing you see when clamping battery jumpers. That low-level arcing is in the range of 60 volts or less. When arcing is sustained, well-defined and bright, the voltage present is certainly hazardous. There is another indicator of electrical hazard that few utilities teach, and that is an awareness of the physics of galvanic action. So, here is some fun with science that really does have a role in training.
Galvanic action is the principle of battery function. Two dissimilar metals in an electrolyte produce an electrical charge flowing from the more negative metal to the more positive metal (this has to do with the number of free electrons). The more negative metal will give up electrons and decompose, causing the eventual failure of the battery.
In nature, this galvanic action occurs in the same way. Dissimilar metals exposed to water as an electrolyte will create a galvanic cell. If a steel chain is run through a galvanized fence, the galvanizing will decompose in reaction to the steel chain, producing a pattern of rust around the chain. This decomposition and the rust that follows do not occur when you install a galvanized chain through the galvanized gate mesh. When normal galvanic action occurs, the pattern of rust is usually quite uniform under the very low voltage caused by the galvanic action. However, if you increase voltage, such as when the bonding is removed from a gate, the chain and latch will show very defined corrosion created by the greater galvanic action. Those well-defined, isolated rust spots are indicators that a higher voltage is present and serve as a warning to the aware worker that there is a problem. Simple training on the physics of galvanic cells or galvanic series can be useful.
By the way, in our experience, these gate/induction issues are most often encountered in 345-kV to 500-kV stations, but that doesn’t mean lower voltages don’t deserve consideration regarding employee risk. These risks can occur in any substation. We recommend that all substation entry training begin with observation of substation gates and fences. Gate or fence installation that is missing grounding and/or bonding should be considered a potential hazard.
Q: We have line crews installing 5G antennas at the top of distribution structures with conduit and cable down the pole to below the secondary. Can communications workers be legally qualified to service these installations?
A: There are very simple OSHA rules for answering this question when it comes to safety, and they are based on qualification. The problem is, what is qualification? Danny Raines tackled this question in a recent issue of Incident Prevention (see https://incident-prevention.com/blog/installing-fiber-optic-cable-in-electric-supply-spaces/), but it won’t hurt to look at it again here. OSHA defines “qualified” in 1910.269 as an employee knowledgeable in the construction and operation of the electric power generation, transmission and distribution equipment involved, along with the associated hazards. In addition to that definition is this note: “A person must have the training required by (a)(2)(ii) of this section to be considered a qualified person.”
The issue with using these rules to qualify a 5G employee is that 5G is not transmission or distribution work. The OSHA standard for qualifying communications workers in electrical environments was written before the advent of 5G. At that time, communications above distribution were on separate structures. All other facilities were below uninsulated power facilities.
As stated above, 5G communications work is not related to either 1910.269 or 1926 Subpart V; 5G communications work is related to 1910.268, “Telecommunications.” The communications worker cannot work within a minimum approach distance established in the 1910.268 tables. The closest the 1910.268 standard comes to instruction near power lines is for line-clearance work by communications workers. Those rules require communications workers performing line-clearance tree trimming to be qualified line-clearance workers who are not permitted to enter the MAD.
There are also requirements for barriers and protective devices in 1910.268 that mandate cover in some applications. But if you compare those to 1910.268(n)(12), “Working position on poles,” you can conclude that OSHA would not permit work on facilities above the bus. A key requirement of 1910.268 is found in (n)(12), which states, “Climbing and working are prohibited above the level of the lowest electric power conductor [italicized for emphasis] on the pole (exclusive of vertical runs and street light wiring), except where communications facilities are attached above the electric power conductors, and a rigid fixed barrier is installed between the electric power facility and the communications facility, or where the electric power conductors are cabled secondary service drops carrying less than 300 volts to ground and are attached 40 inches or more below the communications conductors or cables.” We suggest that installations of 5G above the bus would be prohibited by a communications worker unless that worker is also qualified as a lineworker under the (a)(2) rules of 1910.269.
Q: Can an employer withhold pay when an employee leaves without returning expensive PPE, such as body harnesses, gloves and sleeves, or even barehand conductive suits?
A: Yes, an employer can withhold pay. Those devices are still the property of the employer, giving the employer rights to recover them. OSHA recognizes and addresses that. In Part C of the 2007 PPE final rule, OSHA wrote, “If the employer retains ownership of the PPE, then the employer may require the employee to return the PPE upon termination of employment. If the employee does not return the employer’s equipment, nothing in the final rule prevents the employer from requiring the employee to pay for it or take reasonable steps to retrieve the PPE, in a manner that does not conflict with federal, state or local laws concerning such actions. In these situations, OSHA notes that the employer is not allowed to charge the employee for wear and tear to the equipment that is related to the work performed or workplace conditions.”
We recommend that employers issue a written agreement to employees regarding the disposition of employer-owned and issued equipment and the employees’ responsibility to return or “make whole” the employer’s loss for unreturned equipment. Again, employers cannot charge an employee for damage to equipment, a result of normal wear and tear caused during acceptable use.
Do you have a question regarding best practices, work procedures or other utility safety-related topics? If so, please send your inquiries directly to firstname.lastname@example.org. Questions submitted are reviewed and answered by the iP editorial advisory board and other subject matter experts.
- February – March 2022 Q&A
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- Safety Advancements in the Line-Clearance Industry
- ANSI A92.2: 2022 Changes and Training Requirements
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- The End of a Career
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