overhead and underground power lines worker safety

P bar Y Safety Consultants Alberta Canada

Overhead and Underground Power Lines Worker Safety

High Voltage Power Line Safety is not about just power lines “IT IS ABOUT WHAT AROUND IT LIKE

YOUR WORKERS AND EQUIPMENT”.


You the supervisor them the worker

As the onsite or on duty SUPERVISOR in your daily safety meeting minutes and tool box talks are you telling people more than the words look up and live. Do they know the risks and associated risks and as the supervisor do you ?DO YOU KNOW THE MINIMUM DISTANCE UNDER LEGISLATION TO APPROACH LINES!


Usual is not UsualThe key word is usually; are you willing to risk it what safety have you covered with workers and staff. Overhead high-voltage conductors are usually installed at the top of utility poles. If there is more than one conductor, they are usually placed side by side on a crossarm. If there is a transformer on the pole, the high-voltage conductors are mounted above it. The Zap Zone isn’t just the power line itself: it’s also the surrounding air space (measured in metres) which insulates the line. Of course you know better than to touch a power line. But operating equipment too close to a power line is risky too.• https://www.youtube.com/watch?v=QCOuVoIQuuw Man gets

electrocuted on power lines

http://www.youtube.com/watch?v=QCOuVoIQuuw


A warning sticker is not protecting the paint it is designed to protect you!


How the current works

When an electric current passes through the body, it generates heat and can extensively damage internal tissues. In some cases, the entry and exit wounds are so severe that a foot or hand has to be amputated. The electric current can also stop the heart. https://www.youtube.com/watch?v=K4jZBy5DMX8

http://www.youtube.com/watch?v=K4jZBy5DMX8

http://www.youtube.com/watch?v=K4jZBy5DMX8


Look up Look around Look Everywhere


Background

• Power lines transmit electricity• Electrical current exposes workers

to serious hazards– Most common hazard is

electrocution– Most workers are unaware of

potential electrical hazards • Power lines can be

– Overhead– Underground

Power lines and transmission towers

Underground Utility Work


Background (cont)• Some activities may cause

interference with power lines– Overhead power lines

• Operation of a crane, forklift, and other construction equipment

• Changing street lights• Tree trimming

– Underground power lines• Excavation Caution: Look out for

overhead power lines when operating equipment


Types of Electrical Lines• Electrical Cables

– High Voltage, Low Voltage– Supervisory and Signaling Cables– Cathodic protection (cabinets, cables, earthing

conductors, cable shrouds)• Communication Cables

– Phone lines– Coaxial cables (e.g. data cables)– Broadband cables– Tram traction cables and trolley wires– Railway supply cables and traction wires


Power Line HazardsWho is at risk?• Almost everyone working

near power lines• Common hazards:

– Electrocution• Injuries are typically fatal

– Electrical shock– Fires– Falls

• As a result of contact with electricity Fire may be caused after

overhead power lines are hit

When unloading materials, watch out for overhead power lines


Common Misconceptions• Birds land on power

lines, so they must be safe to touch - NO– Main objective of

electricity is to reach the ground using the most direct route

– Birds do not get electrocuted when they land on wires because they do not represent a path to the ground

The power lines are safe for perching, but not when struck


Common Misconceptions• Power lines are insulated, so they are safe to touch - NO

– They are not always insulated• Insulation deals with placing nonconductive material around the wire • Insulation is a material that offers high electric resistance making it

suitable for covering wires to prevent the possible future contact of adjacent conductors resulting in a short circuit

– Just because a wire is weather protected does not mean that it is insulated

• Weather protection prevents water and snow from reaching the wire (and insulation, if used)


Common Misconceptions (Cont)• Nonmetallic ladders are safe around power

lines - NO– Wet ladders can be a conducting medium for

electricity• If power lines are not touched, they are safe -

NO– Electricity can jump

Maintain a safe distance from the Danger Zone

(10 foot radius from the power line)


Hazard Identification• Conduct site investigation to identify

existing conditions of:– Voltages of lines and equipment– Presence of hazardous, induced voltages– Presence and condition of protective grounds

and equipment grounding conductors– Locations of electrical circuits and equipment – Maximum switching transient voltages


Think before you get zapped

• Even power lines carrying less than 750 volts can kill. Avoid touching them or coming too close. • Avoid storing material or equipment under power lines. If it must be stored there, hang warning signs to prevent other workers from using hoisting-equipment to move or lift it. • Before moving ladders, rolling scaffolds or elevating work platforms, always check for overhead lines.


Dump truck operators should use caution when unloading materials near overhead power lines


Injury Prevention Techniques

• Stay away from power lines while working

• Maintain a safe distance– OH&S “10-Foot Circle of

Safety” rule– Increase safe distance

near higher voltage power lines

Maintain a safe distance from the

Danger Zone (10 foot radius from the power line)


Nominal Voltage Minimum Required Distance (Feet)

0 to 50,000 10

Over 50,000 10+0.4 inch for each 1,000 volt

Operation Clearances for Energized Overhead Lines

Nominal Voltage Minimum Required Distance (Feet)

0 to 50,000 4

50,000 to 345,000 10

Over 345,000 to 750,000

16

“In Transit” Clearances for Energized Overhead Lines


Injury Prevention Techniques• Recognize high voltage

power lines– If unknown, the

appropriate agency should be contacted

• Inform others about high-voltage power lines

Be aware of nearby high-voltage power lines


It will seek you outElectricity seeks all paths to the ground. That path might include a tree, mobile equipment, or the human body. If a part of the equipment you are operating contacts a live power line, then anything in contact with your equipment will also become energized. The earth itself could become energized for some distance around your unit. Similarly, the ground could become energized if a tree makes contact with a power line or if a broken power line falls to the ground. When the electrical flow reaches the ground, it spreads out like ripples in a pool of water. The voltage is very high where electrical contact is made with the ground; farther away from this point, the voltage gradually drops off. Wet ground will extend the distance and the danger. The voltage at the contact point is approximately the same as the line voltage. With power lines up to and including 60 kV (60,000 V), the voltage drops to zero about 10 metres (33 ft.) away from the contact point with the ground. With higher voltages, such as those carried by the lines along transmission rights-of-way, the voltage might not drop to zero until you are as far away as 32 metres (105 ft.).


Touching very Touching

Touch potential is another danger that comes from the difference in voltage. It occurs when you touch something that is energized while standing on the lower voltage ground. For example, if a tree or some equipment is in contact with a power line, it will be energized to the same voltage as the power line; the surrounding ground will be energized to a lower voltage. If you touch the energized equipment or tree at the same time as you touch the ground with your feet, electricity will flow through your body from the higher voltage tree or equipment to the lower voltage ground.


Injury Prevention Techniques• Examine the site

– Be mindful of power lines• Search carefully around the site• Look for lines not seen due to

obstructions• Alert others at the pre-job briefing• Assume all lines are energized and

potentially dangerous• Make a safety clearance boundary

– Portable safety barriers

HAZARD:

Safe distance has not been maintained


Injury Prevention• Use a spotter

– Equipment operators have limited visibility

– Get spotter’s help to stay clear of overhead power lines

• Spotter’s job should only require spotting and NOT guiding

– Guiders may be at risk of electrical shock

• Especially when using a tag line

A spotter guiding heavy equipment operator


Injury Prevention

• When working with tall and long equipment– Carefully plan and organize work

with heavy equipment– Keep vehicles clear of power lines– Watch out for long objects– Adjust the position of equipment to

maintain a safe distance from power lines

Working with tall equipment


Injury Prevention• In cases of fallen

power lines– Stay away– Call for help– Shuffle with your feet

together and on the ground to minimize electrical shock

– Encourage others to do the same Down power lines are

dangerous


Injury Prevention• Fallen power lines can cause fires

• If a co-worker makes contact with a power line– Stay away– Protect yourself

• You could be shocked too if you touch someone who is in contact with electricity

Fire caused by fallen power line


Injury Prevention

• If you hit a power line– In case of no immediate

danger• Move the equipment away• Have someone call 911• Stay on the equipment until you

know it is safe.• Warn others to stay away

– If you MUST get off the equipment, jump clear Crane hitting a power line


Underground Power Lines• Hitting a buried power, gas or communications

line can cause– Injury– Excessive cost of repair

• Plan the work ahead• Call the utility company

With proper planning, these types of mistakes can be avoided


Underground Power Lines• Locate and mark the perimeter

of underground lines• Exercise caution when

excavating near power lines- Some manual excavation may be

required• Stay away from pad mount

transformers– Green metal box

Underground utility line that has been hit


Tree Trimming

• Trees that grow into power lines can cause unnecessary power outages

• Trees planted under or near power lines are potentially dangerous hazards

• Before tree trimming, check for the power lines

• Use proper equipment and trained personnel Tree trimming may be dangerous

if power lines are hidden in the foliage


So follow the rules

1. 10 METRES TO SAFETY Stay back at least 10 metres (33 ft.) from any downed power line, exposed underground cable, or where there is contact with an overhead power line. Depending on voltage, this distance may increase up to 32 metres (105 ft.). 2. LOOK UP AND LIVE All workers who operate machinery or equipment that could come in contact with power lines should look up and check for overhead power lines before beginning work.


So follow the rules3. KNOW YOUR LIMITS When operating machinery or equipment in close proximity to power lines, always maintain the limits of approach: 3–6 metres (10–20 ft.), depending on the voltage. For proper safe working distances, see the current occupational health and safety regulations or contact the owner of the power system or the WCB. Where any portion of a machine or equipment may come closer than the minimum distance prescribed, a form must be completed before work begins. This allows the owner of the power system to provide some form of protection. 4. DON’T HANG AROUND OPERATING EQUIPMENT On the ground stay at least 10 metres (33 ft.) away from operating equipment because if it contacts an energized line the electricity will go to ground. The operator should be on the vehicle with everyone else clear of the vehicle when the boom is in motion. If you must approach, ensure the equipment is not operating.


So follow the rules5. SHUFFLE OR HOP, DON’T STEP If the machinery you are operating contacts an energized line, move it away from the line to break contact. If this can’t be done, remain on the machine. If there is an uncontrollable fire, jump off the machine keeping your feet together. Never contact the machine and the ground at the same time. Once clear of the machine, shuffle away, never allowing the heel of one foot to move beyond the toe of the other. OR, hop with both feet together to a minimum distance of 10 metres (33 ft.).

6. CALL BEFORE YOU DIG Whenever digging or drilling is to occur, the location of all underground services in the area must be accurately determined. Call the owner of the power system before you dig. If a cable is accidentally dug up, call the power utility immediately. Move the digger bucket clear of the cable and stay out of the trench. If the machine can’t be moved, keep workers 10 metres (33 ft.) away and have the operator remain on the vehicle. If the operator must leave the vehicle because of fire, the operator should follow the “Shuffle or Hop, Don’t Step” rule.


So follow the rules

7. DON’T BECOME A VICTIM Always call your local emergency services when someone is injured in an electrical accident. If they are still in contact with the electrical source and you touch them, you could be seriously injured or killed. Keep everyone back a minimum distance of 10 metres (33 ft.), and have someone call for help immediately


Summary of the Training

• Working in proximity of overhead and underground power lines is hazardous– Most common hazard is electrocution

• Workers should be aware of such hazards• Several injury prevention techniques should be

exercised to prevent injuries and fatalities– Need sufficient training to understand the hazards and

practices for injury prevention– One of the best ways of hazard elimination is maintain a

minimum safe distance• Properly locate underground power lines before

starting of work

overhead and underground power lines worker safety

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