In brief
A crane boom, concrete pump arm or tipper truck body approaching an overhead power line can cause a fatal accident through arcing even without touching the line. The Regulation on OHS in Construction Work requires an adequate safety distance that also allows for the swing of conductors in the wind; if the distance cannot be maintained, the line is diverted or de-energised with the approval of the competent authorities. In excavation, the location of underground cables is determined before work begins.
Working near power lines: the danger starts before contact
A medium-voltage line runs along the edge of the site. As the concrete pump operator unfolds the boom, he judges the line to be “far enough away”; the wind swings the conductor, the tip of the boom approaches the line and electricity jumps through the air without contact. The worker holding the hose next to the pump becomes the path by which the current reaches earth. This is the common feature of accidents when working near power lines: the operator usually sees the line but misjudges the distance.
Accept three points from the outset for this work:
- Contact is not necessary. As voltage rises, electricity can arc across to a boom, rope or load approaching the conductor.
- Judging distance by eye is misleading. Looking up from below, the difference in depth between the line and the boom tip cannot be seen.
- The conductor is not fixed. It swings in the wind and sags in the heat; the boom and load also swing as they move.
What does the Regulation on OHS in Construction Work require?
Annex I, item 2.19 of the Regulation on Work Equipment also requires all work equipment to protect employees from direct or indirect electrical contact. Cranes, platforms and concrete pumps fall under this general rule.
How is the overhead line safety distance determined?
OHS legislation does not give a single number for each voltage; it requires an “adequate safety distance”. The correct distance depends on the voltage and type of the line and on conditions on site. So do not estimate the distance on site; obtain it in writing from the owner of the line:
- Find the owner of the line. Distribution lines belong to the regional electricity distribution company; in Bursa, Balıkesir and Yalova, this company is UEDAŞ. High-voltage transmission lines are the responsibility of TEİAŞ (the Turkish electricity transmission company).
- Request the voltage and minimum approach distance in writing. Do not estimate the voltage by looking at the marking on the pole or the number of insulators.
- Calculate the working limit. To the distance given by the authority, add the boom’s most extreme position, the swing of the load and sling, the swing of the conductor and the operator’s reaction margin. Physically mark the limit you arrive at on site.
- If you cannot maintain the limit, there are two options: diverting the line or cutting the power for the duration of the work. Both are done with the approval of the distribution company and under its own procedure. That the power has been cut is never assumed without written confirmation.
| Situation on site | Measure to apply |
|---|---|
| Line outside the work area but within reach of the machine | Barrier and warning sign, working limit marked on the ground, operator briefing |
| Crane boom or load could approach the line | Written distance, boom slew and height limiter, continuous spotter |
| Vehicles must pass under the line | Height-limiting gateways on both sides of the line, rule of passing with tipper and boom lowered |
| Concrete pump to be set up near the line | Choose a set-up location outside the line’s reach; if not possible, power cut or diversion |
| Distance cannot be maintained by any method | Diversion or power cut with the distribution company’s approval; work does not start until then |
Wind increases both conductor swing and load sway. We explained when crane work should be stopped in strong winds in our article on cranes and work at height in strong winds.
Crane contact with power lines and construction machinery near lines: before starting work
Crane contact with power lines and accidents involving construction machinery near power lines usually happen during set-up, repositioning or short “one-off” jobs. Follow this sequence for every job near a line:
- Survey: Mark overhead lines, poles and known underground lines on the site plan. Do not forget a line running through a neighbouring plot.
- Written work plan and permit to work: Issue a permit for lifting, pumping and platform work near the line that states the distance, the spotter and the method of communication. For the framework, see our article on permit-to-work systems.
- Physical limitation: Use barriers rather than tape, slew and height limiters on cranes, and height-limiting gateways at vehicle crossings.
- Spotter: Whenever the operator cannot watch the line and the boom tip at the same time, assign a spotter connected by radio who focuses solely on this task. Our article on crane signallers and slingers gives guidance on signalling rules.
- Conductive materials: Do not use metal ladders, long metal sections or conductive tag lines near the line.
- Briefing: The operator, slinger and ground crew must have been told the line voltage, the limit and what to do in the event of contact before work begins.
You can find detailed set-up rules for concrete pumps and mixers in our article on concrete pumps and mixers, and for tower cranes in our article on tower crane safety.
If contact occurs: the operator and those nearby
For first response to a person who has received a shock, see our article on first response to electric shock, and for general electrical safety principles, our article on the five safety rules in electrical work.
Underground cables in excavation: locate before you dig
An excavator bucket cutting an underground cable carries the risk of both electric shock and arc burns. Before excavation begins:
- Collect utility information. Request line information from the distribution company, the municipality and the natural gas, water and telecommunications providers. Assume that there may be unrecorded lines on the site of old buildings.
- Locate on site. Scan the route with a cable locator and mark it on the ground with paint. The person using the locator must be trained.
- Dig a trial hole. At points near the marked route, verify the actual depth and position of the cable with a hole dug by hand using insulated hand tools.
- Limit mechanical excavation. Continue digging by hand in the area where the cable is exposed; stop when warning tape or protective tiles are seen.
- If damage occurs, do not try to pull the bucket away from the cable; clear the area and notify the owner of the line.
Our article on excavation and trench collapse measures complements this on excavation slopes and shoring.
On construction projects, identifying work near lines during the site survey and turning it into a work plan and permit is part of our OHS specialist service; the findings are entered as actions in the risk assessment document.
Frequently Asked Questions
How many metres should the overhead line safety distance be?
The Regulation on OHS in Construction Work does not give a single number; it requires an adequate distance that also allows for conductor swing. The distance varies with the voltage of the line. Obtain the voltage and minimum approach distance in writing from the distribution or transmission company that owns the line, and add a margin for boom, load and conductor swing.
Can work be done near a line without cutting the power?
Yes, if the safety distance can be maintained with barriers, limiters and a spotter. If it cannot, the regulation requires the line to be diverted or de-energised with the approval of the competent authorities. Do not assume the power has been cut without written confirmation.
What should be done if an unexpected cable is found during excavation?
Excavation is stopped immediately, the cable is not touched and the area is cleared. The owner of the cable is identified and notified; work does not continue until it is clear that the cable is de-energised and how it will be protected.
Who is responsible for work near a line?
Each employer is responsible for its own employees. If the crane, pump or excavation contractor and the principal employer work in the same area, they coordinate measures together under Art. 23 of Law No. 6331; who will check the distance and who will provide the spotter must be written in the work plan.
A certified specialist matched to your hazard class: site inspections, approved logbook, training plan, annual plan and report follow-up.
Bursa SİSTEMER OSGB Technical Team — written from the field experience of our OHS specialists and workplace physicians. Legal information is valid as of the publication/update date; contact us for an assessment specific to your business.