Utility Safety Q & A Articles

Q: As a contractor doing transmission maintenance, we see many different constructions of statics at the tops of transmission poles and structures. They’re grounded, and we always thought they were safe to handle with leather gloves. Now we’re hearing that statics should be grounded temporarily for worker protection. What’s the explanation for that?

A: It’s called a “static,” but don’t forget that the voltage and current flowing on it is induction-coupled alternating current that will kill you. As an industry, there are a lot of utilities that have worked statics in leather gloves and have had no issues. There are others that had no issues for decades – right up until the day someone on their crew was injured by current on a static.

It’s not actually grounding that protects the worker; it’s bonding of the grounded static. Because of the hazard level associated with this discussion, we need to post a disclaimer here: Incident Prevention magazine publishes what it believes to be the best, most accurate advice available from industry experts, but the publication is not a training venue nor is it in the consulting business. It is the employer who is solely responsible for work methods employed in the field.

Q: Are utilities required to have a written fall protection program that follows a written hazard analysis?

A: It’s not a bad idea because the process assures a fairly complete assessment of fall risks that makes training and protection of workers more effective. We know the source of your confusion because it’s a question we get often, and we’ve looked into it. It takes some deciphering, but here is how the confusion starts. We often hear of power and telcom companies reading OSHA 29 CFR 1910 Subpart D, “Walking-Working Surfaces”; seeing 1910.28, “Duty to have fall protection and falling object protection”; and begin writing complex compliance programs following the Walking-Working Surfaces rule. There is nothing wrong with a robust hazard analysis program that drives training, but if you are doing it to comply with a standard, you may not need to. If you read closely, you will find an exception for both telcom (see 1910.28(a)(2)(vi)) and electric power transmission and distribution (see 1910.28(a)(2)(vii)). The T&D exception relies on compliance with 1910.269(g)(2)(i).

Q: What is considered a forklift? We use wheel loaders equipped with accessory forks on our rights-of-way to unload and move poles and pole sections. We were told by our client’s safety inspector that the loader operators have to be certified as forklift operators because the loaders are equipped with forks. We have always used loaders and loader operators and never had an issue. Where do I find the information to resolve this issue?

A: OSHA refers to forklifts as powered industrial trucks or PITs, while the industry commonly calls them forklifts. OSHA’s construction standard has a section on material-handling equipment. The very last rule is 1926.602(d), “Powered industrial truck operator training.” The rule consists of a single note that states, “The requirements applicable to construction work under this paragraph are identical to those set forth at §1910.178(l) of this chapter.”

I have had people tell me that this rule means that operators of construction equipment using forks, like a loader, are required to be licensed or certified as a PIT operator. That is not the case. The PIT standard that contains forklift operation and training rules is found in the general industry rules. The second sentence of paragraph 1910.178(a)(1) states the following: “This section does not apply to compressed air or nonflammable compressed gas-operated industrial trucks, nor to farm vehicles, nor to vehicles intended primarily for earth moving or over-the-road hauling.” Wheel loaders are designed to move earth. They are not PITs even if they are equipped with forks.

Q: We experienced an event that has caused some confusion among crew and supervisors about what we thought we knew about grounding. We were working midspan on a de-energized 345-kV circuit. We drove a ground rod, grounded our trucks to it and grounded the phases to it. Almost immediately, we smelled hot rubber, and then tires started to smoke. Can you help us understand why this happened?

A: That was likely much more serious than hot tires. For the benefit of readers, we spoke with you on the phone, got details and shared opinions. Here is what happened: Your crew was in a right-of-way with very high induction. The ground rod you drove was very high resistance. When you connected your trucks, essentially you made a radial connection from phase to truck through the ground rod connection. In doing so, you loaded very high induction current onto the truck, which passed into the earth across the tires and outriggers. Many utilities by procedure use ground rods at midspans, and often it goes without problems. This is why we stress learning the principles of current flow in grounded systems. If you can ground phases to the very low-resistance static, the induction load is handled without much risk to workers on the ground. If you do have to ground your truck, and there is high induction, a well-driven rod isolated from the phase grounds might be a good choice. If grounding to the same ground electrode as the phases can energize the truck, as happened in your case, dangerous gradients can occur around the truck, and touch potentials between earth and truck can be deadly.

Q: OSHA’s digger derrick exception – found at 29 CFR 1926.1400(c)(4) – includes digger derricks when they are used for augering holes for poles carrying electric or telecommunication lines, for placing and removing the poles, and for handling associated materials for installation on, or removal from, the poles, or when used for any other work subject to 1926 Subpart V. Substations are included in Subpart V, so why do some people say setting steel or regulators is not covered by the exception?

A: You might try to justify substations as being in Subpart V – except for what the substation rules cover in Subpart V. OSHA 1926.966, “Substations,” is not about construction of substations. It is about working in substations. The rule covers minimum approach distances, guarding of live parts, switching and electrical safety. Steel erection, just like concrete work, falls under horizontal standards. 

The logical thinking of very reasonable people regarding this issue often is challenged for sensibility, mostly because of their perspective. For instance, if I can hang a capacitor on a wood pole with a digger derrick, why can’t I hang a beam and capacitor in a substation with a digger derrick? It’s the same thing, it’s a capacitor. The right perspective is that all construction-related lifting of loads by cranes is regulated under 1926.1400, except lifting poles and pole-mounted equipment that are installed using a truck specifically designed for digging and setting poles. 

Q: We have crews working under a clearance on a de-energized circuit jointly controlled by two different utilities (employers). The concern is that the other employer’s personnel, wishing to bundle maintenance opportunities during the outage, are taking protective relays out of service on their end of the circuit. If a switch were inadvertently closed on their end, taking their relays out means no tripping protection since the other end of the circuit is open, too. Such an action could delay if not eliminate relay protection and raise current on the grounds protecting our workers. Is there an obligation between utilities to manage an outage under common rules?

A: There is an OSHA-based solution that comes in two parts. And even though your question is about grounding and tripping during inadvertent re-energizing, the solution to the issue actually lies ahead of grounding.

As you are aware, OSHA 29 CFR 1910.269(m) contains the rules for de-energizing lines and equipment for the protection of employees. That rule section is the pre-eminent means of ensuring no switch is ever closed without the permission of the employee in charge of the equipment or lines that have been de-energized and placed under their control. As you noted in your inquiry, we ground a circuit after the clearance process to ensure against any possibility of re-energizing. The grounding is based on an evaluation of relay trip settings to assure effective tripping to protect the crew under the clearance. Any change to the values or trip settings puts the crew at risk.

Q: With all the talk about grounding, cover-up, EPZ and minimum approach distances, we have been debating the best practice for setting steel poles in energized 138 kV. A big question is, what class gloves should ground personnel wear while handling the pole? How can Class 3 or 4 gloves protect against 138 kV?

A: The short answer is that a Class 4 glove won’t protect against 138 kV. However, if you do it right, there is a very good chance you won’t be exposed to 138 kV even if you do get the pole in the 138. Here is how and why. At transmission voltages, we rely on planning, equipment setup, and precise/predictable control of the equipment and airspace to prevent contacts. We then take additional equipotential bonding actions to protect against a worst-case scenario like loss of control and pole contact with a circuit.

Here are some recommendations for those additional actions. Grade the work area. Grading the area flat around the pole hole gives the crew space for equipotential mats or grids. In best-case planning, it is ideal to stand the pole up with little hands-on contact until you get to the grabbers. If you are using portable mats, the prime location is at the stand-up/grabber location. During handling, the crew members on the pole butt will be in an EPZ. The pole then gets swung to the hole without crew contact. At the hole, mats are used to line the hole for crew who will handle the pole setting. Many crews are now using cattle panels as grids to create equipotential mats in the pole-setting areas. The panels are available at feed stores, constructed of welded #4 steel wire and bonded to the ground rod to create a large walking area around the pole-handling area that will be at equal potential with the pole.

Q: We were recently sticking distribution for a small utility when the utilities inspector stopped us for not having safety latches on our hot hoist. We have now been told that OSHA requires safety latches, but we can’t find a rule for that in the OSHA 1910.269 standard. What are we missing?

A: This answer will surprise and confuse some safety folks, so we want to remind you that we are not necessarily advocating the information we provide – we are educating readers on the rules and best practices. In response to your question, you are not missing anything; there is no OSHA rule for our industry that requires safety latches on hooks. Latches make sense. With a latch, connections do not unexpectedly separate. However, hooks under strain do not unexpectedly separate either. Most hooks for hoists have a tab for installing a latch. Many come with latches, and many do not. In hot-sticking applications, it often is difficult to open a latch and remove a hook from a sling. OSHA does, however, have safety latch requirements for some vertical standards that have no effect on utilities.

Q: When does OSHA consider a pole hole an excavation requiring a barricade?

A: It depends on whether or how long the pole hole is open and/or unattended. The preamble has a discussion on pole holes in which OSHA, in a fit of practicality, agreed that if the hole is bored and the pole is set within a reasonable time – being tens of minutes – there is very little practical reason to install fall protection. However, if the hole is large enough that a worker could fall in even with the pole in place, then some measures should be taken. As a contractor, we would ensure spoils were stable and lay 6 to 8 feet of 12-inch scaffold board across the holes between pole and spoils to ensure stable footing and no void large enough that a person could fall through. The other issue is, a hole for what pole? Distribution is not an issue. Transmission starts to need activities for protection like the above. Some transmission holes are 50 inches for a pole that’s only 36 inches to allow for concrete ballast. Those are excavations. We know many contractors that have used half of a round hay-bale feeder from Tractor Supply Co. as a guardrail.

Q: I am brand new to the safety side of contracting and need guidance on finding information about heat stress. There are lots of guides on assessing heat illness as it occurs, but what about industry practices to prevent heat stress? What do successful heat-stress prevention plans look like?

A: We have three recommendations for you. First, some state plan safety and health agencies – such as California’s – have mandatory program requirements that include trigger temperatures. When a worksite reaches such a temperature, certain site practices for heat stress must be employed. Section III, Chapter 4 of the federal OSHA Technical Manual (see www.osha.gov/dts/osta/otm/otm_iii/otm_iii_4.html) also has detailed information about heat hazard assessments and programs.  

Second, call your local hospital or favorite occupational medicine specialist and review your heat-stress prevention plan with them. In the past, I have offered to pay a fee to have a doctor visit a safety meeting to talk about prevention, although doctors usually will come to speak for free.

Third, do just as you have done: Ask questions, and share information with individuals and companies that have good, effective programs.

Q: Whenever we see graphics for single-point grounding, it’s always a cluster, a connection to the neutral, a connection to a phase and a chain connecting to the other two phases. But when we check with other utilities or consultants, we see all kinds of arrangements, such as bracket grounds with a single point or two sets of single-point grounds bracketing the workspace. Where do we find the definitive arrangement, and why are there so many variations?

A: Under OSHA, the employer is solely responsible for determining how they will meet the requirements of 29 CFR 1910.269(n)(3), “Equipotential zone,” which requires that grounding of de-energized phases be installed in an arrangement that prevents employees from being exposed to differences in electrical potential. In addition to 1910.269(n)(3), there also is Appendix C to 1910.269, “Protection From Hazardous Differences in Electric Potential,” as well as IEEE 1048-2016, “IEEE Guide for Protective Grounding of Power Lines,” a consensus standard that may be considered the authoritative best practice. IEEE 1048 is filled with detailed electrical data – from modeling to application – to explain how to create equipotential protection and effective tripping of grounded circuits that may inadvertently be energized.

Q: Recently an event occurred during a trouble job that surprised us. We had an underbuild phase down that was broken midspan. Our crew was working from an insulated bucket, and we grounded both the feeder we were working on and the one above. While our crew was beginning to crimp the splice for the repair, an energized line a few spans away came in contact with the grounded phase our lineman was in contact with. The lineman was in an insulated bucket, but he still received a shock. He was not seriously injured. Can you help us understand this?

A: The explanation is simple. Grounded circuits will still have current flowing through them if they are energized. Where there are resistances in parallel paths with the grounded circuit, there will be a voltage drop and there will be current flow through the parallel path. The current level is limited by the resistance in the path. Insulated bucket trucks are not totally isolating. To confirm that, all you have to do is look at the electrical tests performed on insulating booms. The current flow on an insulating boom is limited to a value well below the current necessary to injure a worker. In your case, there was voltage drop in the gap between the grounded, energized phase and the insulating boom that was a path to ground. Your lineman bridged that gap when he was in contact with the phase while standing in the bucket. The voltage was high enough to penetrate his skin so that current could flow. He was protected from injury by the current-limiting function of the insulating boom. We know it takes about 50 milliamps of current through a worker to rise to the level of injury. Depending on the electrical integrity of the boom and the voltage involved, there were – and this is just a guess based on boom-test protocols – perhaps 50 microamps to 1 milliamp of current that could flow on the boom. That is well below the level of injury. Electrical integrity of the boom is paramount in protecting workers. That is why it is critical to wash and maintain the boom.

Editor’s Note: This installment of “Q&A” addresses some common questions Incident Prevention receives throughout the year. Most are misunderstandings of the wording or intent of OSHA standards. From time to time iP has addressed the following scenarios – or similar ones – because they never seem to go away. In the following answers, the research or interpretation methods employed have been summarized to help readers become more familiar with interpretation and construction of the standards.

Q: Does OSHA 29 CFR 1910.269(l)(12), “Opening and closing circuits under load,” prohibit the use of non-load-break dropout fused switches or lifting of hot-line clamps to break loads? The rule reads as follows: “(i) The employer shall ensure that devices used by employees to open circuits under load conditions are designed to interrupt the current involved. (ii) The employer shall ensure that devices used by employees to close circuits under load conditions are designed to safely carry the current involved.”

A: This rule often is mischaracterized as prohibiting opening or closing under load using a non-load-break switch or a bare hot-line clamp. The rule does prohibit opening or closing a switch or hot-line clamp (“device”) under load if the employee performing the task could be injured by the act. If the employee can safely perform the act, there is no violation. To explain, there are two keys to properly interpreting this rule. One is the location of the rule; it is found in 1910.269(l), “Working on or near exposed energized parts.” The purpose of the paragraph is protection of employees, as stated in the section following the title: “This paragraph applies to work on exposed live parts, or near enough to them to expose the employee to any hazard they present.”

When OSHA reviews potential violations of the standard, they typically consider three issues: if there was a rule in place, if the employer knew about the rule and if an employee was exposed to danger by violating the rule. OSHA also will review consensus standards and best practices, as well as unadopted consensus standards, which sometimes are used in de minimis conditions and General Duty Clause violations. We know this because when we read public notice citations, we find unadopted consensus standard language used in the notice of violation without reference to the unadopted standard.

Q: I understand OSHA has made a final announcement on minimum approach distances. Can you explain the latest information?

A: On December 22, 2016, OSHA issued a memorandum to regional administrators regarding the enforcement of minimum approach distance requirements in 29 CFR 1910.269 and 1926 Subpart V (see www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=INTERPRETATIONS&p_id=31079). The memorandum had an effective date of July 1, 2017. Readers will recall that concerns about the rising risks of transient over-voltages were the basis for the increased minimum approach distances published by OSHA in 2014. The bottom line is that OSHA has accepted an industry engineering analysis – an IEEE paper titled “Practical Approaches to Reducing Transient Overvoltages Factors for Live Work” that was delivered at IEEE’s 2016 ESMO conference – as a basis for the final guidance of the memorandum. The guidance for enforcement is simple, but it is divided for above and below 72 kV. Following are the choices spelled out in the memorandum.

New Transient Table
The IEEE paper established a new Table A with standard transient multipliers based on voltage. The employer may still calculate their own minimum approach distances utilizing an engineering analysis approved by the standard using transients published in the new Table A.

Q: We have gotten mixed advice from our colleagues at other utilities and can’t decide whether or not civil workers digging a foundation by hand in a hot substation should be required to wear arc protective clothing. They are inside the fence but in a new area approximately 20 feet from the nearest distribution structure. Where do we find the requirements or OSHA guidance?

A: That depends. Sometimes it depends on the criteria in the statutes, and sometimes it depends on compliance with company policy. Normally, following the guidelines of OSHA 29 CFR 1910.269(l)(8) – which establish the criteria for arc flash protection – excavation in a substation would not produce the type of work exposure you described that could create an arc flash. The location of the work and the type of work would not bring a worker within any distance of an energized bus or apparatus that would be a threat. If that’s the case, there would not be a requirement for arc-rated clothing for civil workers in a substation.

We are aware that there are utilities that require all workers, no matter what their craft or task is, to wear arc flash protective shirts while in a substation because it’s a company policy. But in regard to your question, it’s all about exposure. No exposure, no requirement for shirts. It is obvious that it’s not quite that simple for policymakers and risk analysts, who often are the people who make these decisions. Utilities must decide how to protect employees, protect the company and comply with the standards. That goal sometimes results in a blanket requirement as opposed to writing detailed criteria for when workers must suit up. The rules held by some utilities raise this question: If workers must wear arc-rated shirts, why don’t they have to wear arc-rated face protection? In fact, most of the inquiries we’ve made would seem to indicate the decision to require arc protective clothing in substations is more about gut response to the spirit of arc flash protection for contractors and employees than the result of arc flash analysis. Processes and knowledge are still expanding in the industry. As most would say, it doesn’t hurt for civil workers to wear arc protective shirts unless there is an unacceptable heat stress factor involved. In fact, there are some pretty lightweight pullover tees in Cat 2 that may help relieve both arc flash and heat stress.

Q: We are a contractor and were recently working in a manhole with live primary cables running through it. We were cited in an audit by a client’s safety team for not having our people in the manhole tied off to rescue lines. We had a tripod up and a winch ready for the three workers inside. What did we miss?

A: This question has come up occasionally, and it’s usually a matter of misunderstanding the OSHA regulations. The latest revision of the rule has modified the language, but following is the relevant regulation. Look for the phrases “safe work practices,” “safe rescue” and “enclosed space.”

1910.269(e)(1)
Safe work practices. The employer shall ensure the use of safe work practices for entry into, and work in, enclosed spaces and for rescue of employees from such spaces.

1910.269(e)(2)
Training. Each employee who enters an enclosed space or who serves as an attendant shall be trained in the hazards of enclosed-space entry, in enclosed-space entry procedures, and in enclosed-space rescue procedures.

1910.269(e)(3)
Rescue equipment. Employers shall provide equipment to ensure the prompt and safe rescue of employees from the enclosed space.

This rule deals with enclosed spaces, not other spaces referenced in 29 CFR 1910.269(t), “Underground electrical installations.” Enclosed spaces are not, as many think, spaces with energized cables inside. In fact, the definition of an enclosed space has no mention of energized cables. What it does have is the single criterion for an enclosed space: Under normal conditions, it does not contain a hazardous atmosphere, but it may contain a hazardous atmosphere under abnormal conditions.

Q: We have a group reviewing our personal protective grounding procedures, and they are asking if we should be grinding the galvanized coating off towers when we install the phase grounding connections. What are your thoughts?

A: In addition to your question, we also recently received another question about connecting to steel for bonding, so we’ll address both questions in this installment of the Q&A. Your question is about the effectiveness of grounding to towers, and the other question is about the effectiveness of EPZs created on steel towers. We’ll discuss the grounding question first and then move on to the EPZ question.

As to grounding effectiveness, we have two thoughts here – one simple and one that likely will raise more questions than we can resolve in these pages.

The simple thought is this: Consider grounding to the circuit static. It’s difficult to reach but doing so makes it easier to create an electrical connection. Using the system static shares current with adjacent structures and reduces current on the structure being worked. Dividing current among adjacent structures also reduces ground potential’s risks to workers at the foot of the tower. See the following Q&A regarding EPZ if you are grounding to the static.

As to connecting to the tower, grinding off the galvanized coating opens the underlying steel to corrosion and would need to be replaced after the operation. We have asked how utilities make connections and found that most use a flat clamp to a brushed plate or insulator bracket, or a C-clamp to a brushed bolt or step. Either method is a good one. Others follow one of the recommendations in IEEE 1048, “IEEE Guide for Protective Grounding of Power Lines,” 9.2.1.1 for lattice using a ground cluster. The cluster serves two purposes: providing a clamping connection and keeping the clamps close together.

Fortunately, the structure connection can be installed by hand, making the cleaning and mechanical security of the connection pretty reliable. There are several considerations to discuss that should be part of the training provided to lineworkers who make these connections.

Q: Our plant safety committee has a longtime rule requiring electrical hazard safety shoes for our electricians. We were recently told by an auditor that we have to pay for those shoes if we require employees to wear them. We found the OSHA rule requiring payment, but now we wonder if we are really required to use the shoes. Can you help us figure it out?

A: Sure, we can help. But first, please note that Incident Prevention and the consultants who have reviewed this Q&A are not criticizing a rule or recommending a rule change for any employer. What we do in these pages is explain background, intent and compliance issues for workers and employers in the workplace.

You mentioned a longtime rule that probably dates back to the early OSHA rules that required electrical hazard boots for electricians. We can’t remember exactly when, but there was a letter to administrators in the early 1990s and subsequent rule-making that changed the language on the use of electrical hazard shoes. Your auditor is right; if you require employees to wear them, you are required to pay for them because unlike regular safety shoes, the electrical hazard criterion makes the safety shoe a specialty shoe. Specialty shoes must be provided at no cost to the employee (see www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=INTERPRETATIONS&p_id=29825).

Now let’s address the question, are the shoes required? Employers are required to perform a workplace hazard assessment and then use engineering or procedural controls to eliminate hazards. If a hazard cannot be eliminated by procedures or engineering, PPE is required. OSHA agrees throughout current literature that electrical hazard shoes are to be employed as part of a system of protection based on the hierarchy of controls. If you read the rule closely, you will see that the language is very particular. OSHA 29 CFR 1910.136(a) – edited here for clarity and space – states that the “employer shall ensure that each affected employee uses protective footwear … when the use of protective footwear will protect the affected employee from an electrical hazard, such as … electric-shock hazard, that remains after the employer takes other necessary protective measures.” Those other measures are the hierarchy first, PPE last.

Q: We are a small, distribution-only municipal utility that has been looking into human performance. We are having some trouble understanding it all and how it could benefit us. Most of the training resources are pretty expensive. Can you help us sort it out?

A: We can. Human performance management (HPM) has been around in various forms and focuses since before the 1950s. Throughout the ’50s and ’60s, it seems the focus was on companies performing functional analysis and correcting issues that created losses, thereby promoting more efficient and error-resistant operations. In the ’60s and ’70s, much of the literature on HPM seemed to surround the nuclear power industry, and indeed the introduction of HPM into the transmission/distribution side of the utility industry appears to have come through the generation side. In the ’70s, researchers began to experiment and write about more closely analyzing the knowledge and skills of the performer. It took a while to sink in, but the safety industry began to research HPM as a culture analysis and risk prevention tool. It makes sense. Human performance – in particular knowledge, skills modes, decision-making modes and performance – affects all of every enterprise whether you have an HPM program or not. Organizations are made of people. HPM has identified and categorized commonalities in types of personalities that predict how people make decisions and perform tasks. Studying human performance also can help identify safety culture issues and risk behaviors. It’s not a big or expensive step to train your workforce on problem-solving and decision-making characteristics of the human mind. Soon they will understand their own processes and the limitations of the way they naturally think, allowing them to make adjustments toward better performance. So if we can take advantage of HPM to prevent incidents, why not do it? Most organizations start small. Pick a few key people to begin training on the basics of HPM, and then look at your organization to see where the initial undertakings can do the most good. There are several experts associated with Incident Prevention who will be glad to help should you need it. Additionally, on the iP website (www.incident-prevention.com) you can find numerous HPM articles in the iP archives as well as information and training sessions from past iP Utility Safety Conferences. HPM works. We hope you will pursue it.

Q: We hear lots of opinions on whether a lineworker can lift a hot-line clamp that has a load on it. There is a rule that says disconnects must be rated for the load they are to break. We’ve been doing it forever. Are we breaking an OSHA rule or not?

A: Incident Prevention has answered this question before, but it won’t hurt to revisit it and use the opportunity to explain how OSHA analyzes a scenario to see if it’s a violation. Most objections to operating a hot-line clamp (HLC) under load are based on OSHA 29 CFR 1910.269(l)(12)(i), which states that the “employer shall ensure that devices used by employees to open circuits under load conditions are designed to interrupt the current involved.” There are some utilities that prohibit operating HLCs energized, and there’s nothing wrong with that. Our purpose at iP is not to judge an employer’s operational rules but to enlighten and educate the industry.

On its face, the rule seems to prohibit use of an HLC to break load. Anybody could also argue, then, that any operation of an HLC must be dead-break since HLC manufacturers offer no load-break value at all. However, there are several facets to analyze in this scenario. First, if a non-rated HLC cannot be lifted under load, how about a drop-out switch? We operate those thousands of times a day without injury to the employee, although sometimes an ill-advised operation does smoke a pole top. There is nothing in the rules that prohibits an employer from making an engineering-based decision establishing criteria or protocols for operating HLCs or drop-outs under certain load conditions. Primarily, the employer’s determination would be based on risk to the employee and risk to the equipment. For OSHA, the primary consideration would be risk to the employee. Just as in the working alone rule, if the device is operated by a hot stick from a position that prevented injury to the employee, there would be no violation. Second, what would be the solution in the scenario? If the solution required installing a mechanical jumper and installing a load-break switch, would such an operation add risk exposure to the crew, and would adding the switch really enhance the safety of the operation? At the very worst case, the scenario – operating the HLC under load – could be ruled a de minimis violation. De minimis is the level of violation where OSHA recognizes that a direct rule was violated, but there was no other way, or no safer way, of executing the required task, and there was no risk to the employee.

Q: What is meant by the phrase “circulating current” as it pertains to transmission towers? Does it have something to do with the fact that there is no neutral?

A: We’re glad you asked the question because it gives us an opportunity to discuss one of the basic principles of the hazard of induction. More and more trainers are teaching with a focus on principles instead of procedures, and we often overlook some of these basic definitions. The concept of circulation is associated with what happens in any interconnected electrical system. Refer to the basic definition for parallel paths: Current flows in every available path inversely proportional to the resistance of the path. That means that current flows through every path, and the path with the least resistance has the most current flowing in it. Inversely, the path with the most resistance has the least current flowing in it.

When you ground a circuit to the structure, you are making an electrical connection to the tower. Current will flow in every available path. If there is any source for current, including induction, there will be current flow. The greater part of the current will flow in the lower-resistance pathways. If the tower is well grounded, the majority of the current will flow in the tower to ground. In a distribution system, the majority of the neutral current flows in the neutral. Pole bonds to ground rods have much higher resistance and therefore lower current that usually can’t be measured by a typical clamp current meter, so some people think there is no current flowing in them. There is, and under the right conditions – such as a fault or open in the neutral – the level of current flowing in a pole bond can be deadly.