Safety
Assume everything is energized
Electrical hazard awareness (EHAP)
Reading utility infrastructure, estimating voltage from insulators, minimum approach distances, and the hazards that injure tree workers who never touch a wire.
The rule that comes first
- Treat every conductor, every guy, every unidentified line as energized until the utility says otherwise in person.
- Only a qualified line-clearance arborist — trained, and authorized by the utility — may work inside the reduced approach distances.
- Everyone else is a non-qualified tree worker and stays at least 10 ft (3.05 m) from any energized conductor, including with tools, limbs, ropes and the tree itself.
- No contact means no contact by anything: a wet rope, a green limb and an aluminium pole all conduct.
- If a line clearance job is beyond your qualification, the correct action is to stop and call the utility.
Electrocution remains a leading cause of death in tree work, and most victims never intended to go near the wire.
Reading the pole: what is up there
Utility poles are stacked in a consistent order — highest voltage at the top, communications at the bottom.
| Position | What it is | How to recognize it |
|---|---|---|
| Top of pole | Primary distribution conductors | Highest wires, spaced apart, each supported on its own insulator. One wire = single-phase; two = two-phase/open-delta; three = three-phase. |
| Below primary | Neutral conductor | Usually a single bare wire mounted close to the pole with little or no insulator; it is bonded and grounded but never treated as safe. |
| Mid pole | Open-wire secondary | Two or three separate bare or lightly covered wires at 120/240 V feeding older services. |
| Mid pole | Triplex service drop | Two insulated conductors twisted around a bare neutral messenger, running from the pole to a house. |
| Lowest, below the safety space | Communications: telephone, CATV, fibre | Bundled, often in a cable with a messenger, frequently with slack and loops. Still never treated as safe — cross-contacts happen. |
| Diagonal to ground / anchor | Guy wire | Steel, sometimes with an insulator link. Can become energized in a fault. |
Transformers, capacitors, reclosers and cutouts on the pole all indicate primary voltage above them.
Insulators and estimating voltage
Insulator type and the number of discs give a rough voltage class. It is an estimate for planning your distance — never a clearance calculation.
- Pin-type insulator: a single bell mounted on a pin on the crossarm, common on distribution up to about 34.5 kV.
- Post insulator: a rigid column bolted to pole or crossarm, used on distribution and sub-transmission.
- Bell / suspension insulator strings: discs hanging in a chain, used from sub-transmission upward. More discs means more voltage.
- Rough rule: count roughly 10–15 kV per disc in a suspension string. One or two discs is distribution; four to six suggests sub-transmission; ten or more means high-voltage transmission.
- Bigger, longer and more numerous insulators always mean more voltage and a larger required distance.
- When the count is ambiguous, assume the higher tier and increase your distance.
Voltage tiers
| Tier | Typical voltages | Clues |
|---|---|---|
| Service / secondary | 120 V – 480 V | Triplex drops and open-wire secondary to buildings; still lethal. |
| Distribution | 4 kV – 34.5 kV | Top-of-pole primaries on pin or post insulators, pole transformers, cutouts. |
| Sub-transmission | ~69 kV | Larger poles or light steel structures, insulator strings of several discs, no house services. |
| Transmission | 115 kV – 500 kV+ | Lattice steel towers or tall monopoles, long insulator strings, bundled conductors, wide right-of-way. |
Actual voltages vary by utility. Ask the utility rather than guessing when the work is close.
Minimum approach distance (MAD)
ANSI Z133 sets minimum approach distances by voltage and by whether the worker is qualified. These are the shortest distances anything — worker, tool, rope, limb — may come to an energized conductor.
| Worker | Voltage | Minimum approach distance |
|---|---|---|
| Non-qualified tree worker | Up to 50 kV | 10 ft (3.05 m) from any energized conductor |
| Non-qualified tree worker | Over 50 kV | 10 ft plus 4 in for every additional 10 kV over 50 kV |
| Qualified line-clearance arborist | Up to 750 V | Avoid contact — insulating gloves and utility-authorized procedures |
| Qualified line-clearance arborist | 751 V – 15 kV | Roughly 2 ft 2 in (0.66 m) |
| Qualified line-clearance arborist | 15.1 kV – 36 kV | Roughly 2 ft 7 in (0.79 m) |
| Qualified line-clearance arborist | 36.1 kV – 46 kV | Roughly 2 ft 10 in (0.86 m) |
| Qualified line-clearance arborist | 46.1 kV – 72.5 kV | Roughly 3 ft 6 in (1.07 m) |
Approximate values for awareness only. Always work from the current ANSI Z133 tables and the distances the utility specifies for the job.
Worked example: a 115 kV line is 65 kV over 50 kV, so a non-qualified worker adds about 26 in — roughly 12 ft from the conductor.
Hazards beyond direct contact
- Touch potential: touching an energized object — or a tree, ladder or truck in contact with one — while your body provides a path to ground.
- Step potential: current spreading through the ground from a downed conductor creates a voltage difference between your feet. If a line drops, shuffle away with small steps, feet together, and keep everyone back.
- Conductor sag and sway: lines sag with heat and load, and swing in wind. The gap you measured at 7 am is not the gap at 3 pm in a gust.
- Induced voltage: a de-energized conductor running parallel to an energized one can carry dangerous voltage. Only the utility's grounding makes a line safe.
- Tools and equipment: use non-conductive aerial tools — dielectric-tested poles and pole saws, fibreglass ladders, insulated boom sections — kept clean and dry, and tested on schedule.
- Aerial devices and cranes: booms, cables and load lines need the same clearance as your body, and the vehicle itself becomes energized on contact. If contact occurs, stay in the vehicle unless fire forces you out, then jump clear without touching vehicle and ground at once.
- Weather: rain, ice, and wet ropes and wood all raise the risk. Stop electrical-proximity work in storms.
Before the job starts
- Walk the site and identify every line, its position, and what voltage class it appears to be.
- Put the electrical assessment and the approach distance in the job briefing, out loud, with the whole crew.
- Confirm who is qualified for what, and where the stop line is on the ground.
- Notify the utility when work needs clearance, de-energizing, covering or a standby.
- Plan the drop zone so no piece, rope or brush swings toward a conductor.
- Formal EHAP training through TCIA is the standard way to certify this awareness — see the certifications hub in the app.
Cautions
- This is awareness material, not a line-clearance qualification. Only utility-authorized qualified line-clearance arborists work inside reduced approach distances.
- Distances quoted here are approximate; the current ANSI Z133 tables, OSHA rules and the utility's own instructions govern the work.
- If a conductor is down, damaged or in the tree, clear everyone back and call the utility and emergency services. Do not attempt to move it.