Part 6: Work Practices Near an Electrical Hazard

Part 1 of Chapter 4, Safe Work Practices (TCI Magazine, March 2024), covered the job hazard analysis (JHA), work plan and job briefing. This article, Part 2 of Chapter 4, Safe Work Practices, focuses on arboricultural operations near overhead power and communication lines.

Personal protective equipment

Personal protective equipment (PPE) – helmet, eye protection, hearing protection and appropriate footwear – are requirements for arboricultural operations. Cut-resistant leg protection – pants or chaps – also is required PPE for arborists operating chain saws on the ground. Arborists often treat their PPE casually, not properly caring for it or wearing it incorrectly – if wearing it at all.

Class E helmets provide only a measure of protection.
Class E helmets provide only a measure of protection. All photos courtesy of John Ball.

Hearing protection performs its function every day in the field. Hearing loss is often gradual, the accumulation of years of noise exposure. But the protection afforded by helmets, safety glasses and cut-resistant pants or chaps is often immediate.

The cut branch stub falls and ricochets off the helmet of a ground worker; a branch with a thorn whips back, grazing the lens of the safety glasses on a climber; or the chain-saw bar and chain kick back into the fabric of the chaps. We forget that the one time we need this PPE is when everything else has failed – it is your last defense from an injury.

When working in proximity with overhead power lines, the climber or aerial-lift operator must wear a Class E helmet (ANSI Z89.1). This means whenever working within 10 feet of energized conductors, either secondary or primary overhead power lines. Class E helmets protect against impact injuries but also against electrical shock. A Class E helmet is rated at 20,000 volts. This rating is a measure of protection from electrical shock, not immunity from injury.

Indirect contact through a conductive pole tool is one of the most common electric-shock incidents.
Indirect contact through a conductive pole tool is one of the most common electric-shock incidents.

Qualified employees

The PPE arborists do not wear while working near overhead power lines is rubber insulating gloves or sleeves and overshoes/rubber boots. While these are PPE for line personnel, arborists – even qualified line-clearance arborists – are not considered qualified employees under OSHA Standard 29 CFR Section 1910.269. A qualified employee is defined by OSHA as “one who is knowledgeable in the construction and operation of the electric-power generation, transmission and distribution equipment.”

Arborists who have the appropriate training and skills may work in the proximity of overhead power lines, but they are not qualified to work on the lines. There is no need or requirement for them to wear insulating boots, overshoes or gloves. And, if an arborist does wear them, it does not change what they are allowed to do or their minimum approach distance to overhead power lines.

Arborists do not have a clothing requirement for working near power lines, but remember, the most common injuries from electrical contact are burns. Synthetic fabrics are comfortable on hot, humid days, but nylon, polyester and related materials can melt upon ignition and adhere to skin. This does not mean cotton is “safe.” Heavy cotton, as in jeans, once ignited, can burn for a long time.

Finally, clothing choices do not reduce the chances of an electrical incident, just possibly the severity.

Manual tree felling and electrical hazards

We often associate electrical-contact incidents with climbing and aerial-device operations, not ground operations. While it is true that many fatal electrical incidents involve climbers – slightly fewer than half – ground workers account for about another quarter of arboricultural-operation electrocutions.

The greatest risk in manual tree felling is being struck by the cut tree as it falls, or by a limb that detaches during the fall or on impact. But we do see electrocution incidents during manual tree-felling operations. These typically happen when the falling tree strikes a primary line, either detaching it from the pole or poles or having the tree held by sagging lines. These down or sagging lines may strike a ground worker.

There is one major difference between climbers and ground workers in the outcome of direct-contact incidents with an overhead power line. The contact is most often quickly broken for the climber due to the sudden and forceful spasms of the body as muscles contract. While they may suffer severe burns, they may survive. In the case of ground workers, they may have the line draped over their body, resulting in continual contact, which always results in death.

Climbers must maintain minimum approach distance (MAD) at all times.
Climbers must maintain minimum approach distance (MAD) at all times.

Tree felling

Electrical-contact incidents also occur to chain-saw operators during felling. The operator fells the tree into the power line and it remains hung up on the line. When the chain-saw operator touches the trunk with their hands, i.e., to roll it off the power line, or touches it with the saw to cut it free, they suffer electrical shock or are electrocuted. A tree that falls into one conductor – one phase line – may not draw enough current to cause the fuse to open, but may still draw enough current to cause fatal touch potential.

While there are multiple causal agents for these electrical-contact incidents, there are two common ones. The direction of fall was not the intended path, or the crew misjudged the height of the tree. The notch determines the direction of fall. The fall path is now destined and cannot be changed, including by angling the back of the hinge – a technique called holding the corner.

Trees should be felled away from, not toward, overhead power lines. Only fall trees toward the lines if it is the safest direction. There must be enough distance between the line and the tree that there is no possibility of a line strike as the tree falls or breaks apart on impact. Also consider other trees that may be knocked over in domino fashion by the tree being felled.

Keep workers away

No uninvolved workers can be standing within a distance equivalent to two times the height of the tree, and involved workers – those tending pull lines, for example – can be no closer than 1.5 times the tree’s height. The workers tending pull lines should not be standing under or beyond the overhead power lines. There have been incidents where a pull-crew member received an electric shock or was electrocuted when the pull line contacted a primary overhead power line.

While being positioned at least two times the tree height away from the tree being felled is a measure of protection, it is not complete. There was an incident where the ground worker was electrocuted when the cut tree fell in an unintended direction, striking a power line and causing the line to land on a chain-link fence. The ground worker was leaning on the fence, but more than 80 feet away, yet was killed by the electric shock.

Climbing operations and electrical hazards.

Climbers are the tree workers most at risk for electric-shock injuries. The two most common incidents are either the climber touching a metal pole saw or chain saw to the overhead power line, or holding a cut branch that touches the line.

Numerous electrocutions occur every year when a climber reaches out with a metal pole saw and it touches an overhead power line. A common factor in these incidents is that the climber was unaware the power line was even passing through or near the tree. Either a job-hazard analysis was not completed or was poorly executed.

Another frequent electrocution incident is that of the climber cutting a branch that deflects into an overhead power line. The distance between the contact point with line and the cut is typically less than 6 feet, but there have been incidents where the branch distance between the line and the cut has been 12 feet or more.

There also are electric-shock incidents where the cut has been completed and the climber is still holding the branch when it touches the overhead power line. One “branch” that is commonly associated with these incidents is a palm frond. The climber is ready to toss a cut frond when it sweeps across a power line, electrocuting the worker.

Climbers must inspect the tree canopy to be certain that the branch they are cutting with conductive tools is outside their minimum approach distance (MAD). There should be no possibility that any deflection of the branch as it is being cut or during its fall could cause it to touch the line. If the branch tip is within the climber’s MAD, the branch must be cut back to outside MAD for the overhead power line, using an insulating tool. The climber also must be qualified to use insulating tools within the MAD. This is the Electrical Level 3 and 4 Arborist for primary voltages.

Direct contact

Climbers directly touching the overhead power line as they climb through the tree are a less-frequent electrical-contact incident. The contact point is typically the upper back, meaning the climber has turned their back to the conductors. Climbers should climb on the side of the tree away from the overhead power line and avoid turning their backs to power lines. Climbing away from the power lines also reduces the chance that the climbing line or lanyard could contact the conductors.

Climbing-line contact

The climbing line has served as the conductive object in climber electrocutions. While these represent a small number of deaths, they do happen when climbers are positioned above the power lines. Sometimes the lanyard touches the power line as the climber moves out on a limb above the power line. Other times the dangling climbing line sweeps the power line as the worker climbs above it.

One of the most unusual, and rare, incidents is ground workers electrocuted when the climber’s line they are tending brushes against an overhead power line. The ground worker is electrocuted, but not the climber.

Only insulated lifts may be used near electrical conductors.
Only insulated lifts may be used near electrical conductors.

Aerial devices and electrical hazards

Not all aerial devices may be used in proximity – within 10 feet – of overhead power lines. Aerial devices that are not insulating are specifically labeled with this warning. This does not mean the labels are read or followed. Every year, tree workers are electrocuted when the basket of an uninsulated telehandler or portable lift touches an overhead power line.

The insulating devices that can be used in proximity to overhead power lines must have the insulating properties of the boom and other equipment – liners, hydraulic hoses and oils – evaluated once a year. This dielectric testing is necessary, as the insulating properties of the equipment are commonly compromised by age, contamination with dirt or oil or by abuse.

Fiberglass and rubber insulating materials will degrade with age and exposure to light. Cuts and gouges in the fiberglass boom can diminish the dielectric properties. Contamination of the insulator surface with chemicals also can lead to deterioration of the insulator. These are all reasons for annual dielectric testing.

While an aerial device with insulating properties may be used in proximity to overhead power lines, the qualification of the operator determines the minimum approach distance of the bucket and boom. If the operator is unqualified – Electrical Level 1 – even an aerial device with insulating properties cannot be used within 10 feet of overhead power lines.

Face the danger

Aerial-lift operators have been electrocuted while operating insulated booms/baskets. These are typically direct contact with the overhead power line touching their back or neck while the operator was looking in the opposite direction. The shocked operator is often within the tree’s canopy, so there is contact with the tree as well as the line, a phase-to-ground contact.

Danger to ground worker

Ground workers also have been electrocuted from touching an aerial device, or merely standing nearby, when an uninsulated part of the lift touched an overhead power line. Ground workers have suffered electrical shock, sometime fatal, while opening a cabinet on the aerial-lift truck on which – at the same instant – the truck’s boom or knuckle touched a power line.

Another potential incident can occur when a ground worker is standing near the truck when it contacts the power line. There is a ground gradient of voltage emanating out from the truck outriggers. It is not the voltage of the ground that is the hazard, but the difference in voltage between the spread of the two feet of the ground worker.

In one instance, the ground worker was acting as a spotter for the aerial-lift operator who was pruning near overhead power lines. When the lower boom touched the line, the spotter, standing 10 feet away from the outriggers, was electrocuted.

When the lift is operating close to and could violate MAD, a spotter must be used. Their job is to pay undivided attention to the separation distance between lift boom(s) and wire(s) and provide timely warning to the lift operator – who may not be able to judge or even see – when MAD is approached.

Tree pruning

The fall path of cut branches must be away from the overhead power lines. Each year, climbers are killed when the cut branch strikes a power line and falls back on the worker. And no batting! A technique occasionally seen is cutting a branch over a conductor with a pole saw, then using the pole as a bat to push it away from the conductor as it falls. This is an unsafe practice! Major league baseball players’ batting average is less than .300, and the only penalty for a series of misses is being traded. An aerial-lift operator missing a swing once with the pole saw could be electrocuted if the branch kicks back.

Rigging a branch may be a safer option, but there are still some electrical risks. The cut branch can swing into the overhead power lines if the rigging blocks are above or near the power lines. The rigging line also may touch the power line. Any rigging system must be set so the rigging lines do not, or the load does not, swing or fall into the power lines.

Ground workers have been electrocuted while tending rigging lines when the load contacts a primary. One ground worker was electrocuted and another suffered burns when the rigging line they were holding was energized as the load – a large limb – swung into a 7.2 kV power line.

Arborists also must consider any sway or sag to the power lines due to temperature, wind or snow/ice loading.

Let the utility do it

Aside from the risks to the climber or aerial-lift operator of an uncontrolled cut branch striking them and a power line, there is a risk to the utility system. A cut branch that falls on two phases of a three-phase system may create a fault, causing a power interruption on the system.

Utilities are not pleased when arborists are responsible for an outage. If there is any doubt in a tree company’s ability to safely do arboricultural operations near overhead power lines, either give the job to another company or contact the utility to see if they can make the operation safer.

Witch’s broom

Previous contact between an overhead power line and a tree may present as a witch’s broom – a dense cluster of stunted shoots – or charred shoot tips. These “electrically pruned” trees have power lines that are directly above them. Lines will stretch during warm days and when there is high demand, so contact may only be on a hot afternoon. The line is not necessarily in the tree while being inspected during the job-hazard assessment.

Trees presenting with symptoms of contact with a power line should be considered energized. Arborists should avoid climbing these trees. Corded electrical tools, such as power drills, must not be used in these trees. Arborists have been electrocuted when drilling into these trees with a corded drill to install bracing rods.


The goal or purpose of this eight-part series is to inform readers about changes to TCIA’s Electrical Hazards Awareness Program (EHAP), being made in an ongoing revision to coincide with the revision of the ANSI Z133 Standard. We will have one or more articles for each of the program’s six chapters. There may be some variation in this series in terminology or content from the actual EHAP revision.

Articles in this series include:
Part 1, Chapter 1: Electricity and the Utility Industry (TCI Magazine, November 2023)

Part 2, Chapter 2, Part 1: Electrical Hardware Recognition: Voltage Management and Protective Devices (TCI Magazine, December 2023)

Part 3, Chapter 2, Part 2: Electrical Hardware Recognition: Other Switching Devices, Support and Other Utility Hardware (TCI Magazine, January 2024)

Part 4, Chapter 3: Recognizing Electrical Hazards (TCI Magazine, February 2024)

Part 5, Chapter 4, Part 1: Work Practices Near Utility Conductors: Different Categories of Tree Workers Relative to Electrical Hazards, Conducting a Job-Site Hazard Assessment and Job Briefing (TCI Magazine, March 2024)

Part 6, Chapter 4, Part 2: Work Practices Near Utility Conductors: Work Practices Near an Electrical Hazard

Part 7, Chapter 5: Emergency Response and Aerial Rescue

Part 8, Chapter 6: Safety Standards

Storm cleanup

Storms take down not only trees and branches but often power lines and poles. Storms or other abnormal conditions may result in wires such as communication lines and even guy wires being energized with sufficient voltage (and amperage) to cause an electrical shock to workers who directly or indirectly contact them.

Any downed power lines must be treated as energized. Even after a line is confirmed as de-energized by the utility, arborists must avoid direct contact with these lines.

Next Up…

This article covers some basic work practices for working in proximity to overhead power lines. Part 7 of this series will cover what to do when things go wrong around electricity – emergency response and aerial rescue.

John Ball, Ph.D., BCMA, CTSP, A-NREMT (Advanced-National Registry of Emergency Medical Technicians), is a professor of forestry at South Dakota State University.

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