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Course 809: Focus Four - Electrocution Hazards

Safety guides and audits to make your job as a safety professional easier

Protecting Yourself from Electrocution Hazards

Maintain Safe Distance from Overhead Power Lines

Staying away from power lines is the best option. The following table shows the safe power line clearance distance for various line voltages.

Power Line Clearance Distances

Table A - Minimum Clearance Distances
Voltage (nominal, kV, alternating current) Minimum clearance distance (feet)
Up to 50 10
Over 50 to 200 15
Over 200 to 350 20
Over 350 to 500 25
Over 500 to 750 35
Over 750 to 1000 45
Over 1000 (As established by the power line owner/operator or registered professional engineer who is a qualified person with respect to electrical power transmission and distribution)

The following are preventive measures for workers to consider.

General

Before work begins, make sure:

  • equipment/activity is located within a safe working distance from power lines;
  • the utility company has de-energized and visibly grounded the power lines or installed insulated sleeves on power lines;
  • flagged warning lines have been installed to mark horizontal and vertical power line clearance distances; and
  • tools and materials used are nonconductive.

Maintain Safe Distance from Overhead Power Lines (Continued...)

Cranes and other high-reaching equipment

Be sure the utility company has confirmed the voltage and, therefore, the safe working distance from the power lines. Also, if applicable and feasible, use a/an: observer; insulated link; boom cage guard; proximity device.

Mobile heavy equipment

If provided, use installed rider posts under power lines to avoid working too close to the power lines.

Ladders

Use nonconductive ladders and be sure to retract them before moving.

Material storage

  • Ensure no materials are stored under power lines
  • Use caution tape and signs to cordon off area under power lines

Excavations

  • Locate and understand the markings the local underground line locator service has marked before digging
  • Hand dig within three feet of cable location (be aware that more than one underground cable may be buried in area of locator markings)

Maintain Safe Distance from Overhead Power Lines (Continued...)

Let’s review an example of an actual accident:

Crane boom near power lines.
Accident Type: Electrocution
Weather Conditions: Sunny, Clear
Type of Company: Steel Erection
Size of Work Crew: 3
Union or Non-Union: Non-Union
Competent Safety Monitor on Site: Yes-Victim
Safety and Health Program in Effect: No
Was the Worksite Inspected Regularly: Yes
Training and Education Provided: No
Employee Job Title: Steel Erector Foreman
Age & Sex: 43-male
Experience at this Type of Work: 4 Months
Time on Project: 4 Hours

Description of Accident

Employees were moving a steel canopy structure using a "boom crane" truck. The boom cable made contact with a 7200-volt electrical power distribution line electrocuting the operator of the crane; he was the foreman at the site.

Inspection Results

As a result of its investigation OSHA issued citations for four serious violations of its construction standards dealing with training, protective equipment, and working too close to power lines. OSHA's construction safety standards include several requirements that, if they had been followed here might have prevented this fatality.

What would you recommend?

Recommendations

  • Develop and maintain a safety and health program to provide guidance for safe operations (29 CFR1926.20(b)(1))
  • Instruct each employee on how to recognize and avoid unsafe conditions that apply to the work and work areas (29 CFR 1926.21(b)(2))
  • If high voltage lines are not de-energized, visibly grounded, or protected by insulating barriers, equipment operators must maintain a minimum distance of 10 feet between their equipment and the electrical distribution or transmission lines (29 CFR 1926.550(a)(15)(i))

Maintain Safe Distance from Overhead Power Lines (Continued...)

What Must Your Employer do to Protect You?

Before working on overhead power lines, they must be de-energized and grounded by the owner/operator of the lines, or other protective measures must be provided, such as PPE (rubber insulating gloves, hoods, sleeves, matting, blankets, line hose, and industrial protective helmets). Protective measures (such as guarding or insulating the lines) must be designed to prevent contact with the lines.

The three primary methods your employer should control power line hazards are:

  1. maintaining a safe distance from lines;
  2. having the power company de-energize and ground the power line(s) (have a power company representative at the site); and
  3. having the power company install insulated sleeves (also known as “eels”) over power lines.

Your employer should train workers regarding power line hazards and about the available protective measures. Employers need to fully warn workers about what jobs may have electrical hazards, and the measure(s) they will take to control the hazards. Also, workers should be reminded they should always ask questions if they have any doubts about maintaining safe working conditions.

Use ground-fault circuit interrupters (GFCI)

A "GFCI" is a ground fault circuit interrupter designed to protect people from severe and sometimes fatal electrical shock. A GFCI detects ground faults and interrupts the flow of electric current and is designed to protect the worker by limiting the duration of an electrical shock.

A Classic Example of the GFCI at Work

A homeowner is using an old drill with a loose bare wire inside it touching the outer metal housing. With the drill plugged in, the housing is charged with electricity. If it is used outside in the rain and the worker is standing on the ground, there is a path from the hot wire inside the drill through the worker to the ground. If electricity flows from hot to ground through the worker, it could be fatal. The GFCI can sense the current flowing through you because not all of the current is flowing from hot to neutral as it expects -- some of it is flowing through the worker to the ground. As soon as the GFCI senses that, it trips the circuit and cuts off the electricity.

Use ground-fault circuit interrupters (GFCI)(Continued...)

Types of GFCI

Receptacle GFCI: Often found on construction work sites, outdoor areas and other locations where damp conditions do or could exist. The receptacle GFCI fits into the standard outlet box and protects users against ground faults when an electrical product is connected to the GFCI protected outlet.

These should be tested after installation and once a month by:

  • Plug in a test light or power tool and turn “On.”
  • Push the “Test” button on the receptacle; the “Test” button should pop up, and the power to the light or tool should be “Off.”
  • Push “Reset” to restore power to the outlet.
  • If the above steps worked, the GFCI passed the test and is functioning properly; if the GFCI failed the test, remove it from service.

If a light or power tool remains “ON” when the “Test” button is pushed, the GFCI is not working properly or has been incorrectly installed (miswired). If this is the case, a qualified electrician needs to be contacted to properly wire or replace the GFCI device.

Temporary/portable GFCI: A portable GFCI is an extension cord combined with a GFCI. It adds flexibility in using receptacles that are not protected by GFCls. Extension cords with GFCI protection incorporated should be used when permanent protection is unavailable.

These should be tested prior to each and every use by:

  • visually inspecting the device for obvious defects and/or broken parts;
  • plugging in a test light/tool to the extension cord;
  • pushing the “Reset” button on the GFCI device;
  • pushing the “Test” button to verify no voltage at outlet (e.g., the light or tool shuts off); and
  • pushing the “Reset” button to verify the power is restored.

Circuit Breaker GFCI: The GFCI circuit breaker controls an entire circuit and is installed as a replacement for a circuit breaker on the main circuit board. Rather than install multiple GFCI outlets, one GFCI circuit breaker can protect the entire circuit. At sites equipped with circuit breakers, this type of GFCI might be installed in a panel box to give protection to selected circuits.

Circuit breaker GFCIs should be tested monthly. Keep in mind that the test will disconnect power to everything on the circuit.

Use ground-fault circuit interrupters (GFCI) (Continued...)

Let’s review an example of an actual accident:

Ladder on scaffolding
Accident Type: Electrocution
Weather Conditions: Clear/Hot/Humid
Type of Operation: Window Shutter Installers
Size of Work Crew: 2
Collective Bargaining: N/A
Competent Safety Monitor on Site: No
Safety and Health Program in Effect: Partial
Was the Worksite Inspected Regularly: No
Training and Education Provided: Some
Employee Job Title: Helper
Age & Sex: 17-male
Experience at this Type of Work: 1 Month
Time on Project: 1 Month

Description of Accident

One employee was climbing a metal ladder to hand an electric drill to the journeyman installer on a scaffold about five feet above him. When the victim reached the third rung from the bottom of the ladder, he received an electric shock that killed him. The investigation revealed that the extension cord had a missing grounding prong and that a conductor on the green grounding wire was making intermittent contact with the energizing black wire thereby energizing the entire length of the grounding wire and the drill's frame. The drill was not double insulated.

Inspection Results

As a result of its investigation, OSHA issued citations for violations of construction standards.

What would you recommend?

Recommendations

  • Use approved ground fault circuit interrupters (GFCI) or an assured equipment grounding conductor program to protect employees on construction sites [29 CFR 1926.404(b)(1)].
  • Use equipment that provides a permanent and continuous path from circuits, equipment, structures, conduit or enclosures to ground [29 CFR 1926.404(d)(6)].
  • Inspect electrical tools and equipment daily and remove damaged or defective equipment from use until it is repaired [29 CFR 1926.404(b)(iii)(c)].

Use ground-fault circuit interrupters (GFCI) (Continued...)

What Must Your Employer do to Protect You?

Portable GFCI

OSHA ground-fault protection rules and regulations have been determined necessary and appropriate for worker safety and health. It is your employer's responsibility to provide either:

  • GFCI’s on construction sites for receptacle outlets in use and not part of the permanent wiring of the structure; or
  • a scheduled and recorded assured equipment grounding conductor program on construction sites.

GFCI’s must protect receptacles on the ends of extension cords. Also, an employer may use GFCI circuit breakers. These protected circuit breakers are installed on the main circuit board. GFCI circuit breakers protect an entire circuit.

GFCIs monitor the current-to-the load for leakage to ground. When this leakage exceeds 5 mA ± 1 mA, the GFCI interrupts the current. They are rated to trip quickly enough to prevent electrocution.

Assured Equipment Grounding Conductor Program (AEGCP)

The AEGCP covers all cord sets, receptacles that are not a part of the permanent wiring of the building or structure, and equipment connected by cord and plug that are available for use or used by employees. OSHA requires a written description of the employer's AEGCP, including the specific procedures adopted, be kept at the job site. This program should outline the employer's specific procedures for the required equipment inspections, tests, and test schedule.

The required tests must be recorded, and the record maintained until replaced by a more current record. The written program description and the recorded tests must be made available, at the job site, to OSHA and any affected employee upon request. The employer is required to designate one or more competent persons to implement the program.

Electrical equipment noted in the AEGCP must be visually inspected for damage or defects before each day's use. The employee must not use any damaged or defective equipment until it is repaired.

OSHA requires two tests. One is a continuity test to ensure the equipment grounding conductor is electrically continuous. It must be performed on all cord sets, receptacles that are not part of the permanent wiring of the building or structure, and on cord- and plug-connected equipment required to be grounded. This test may be performed using a simple continuity tester, such as a lamp and battery, a bell and battery, an ohmmeter, or a receptacle tester.

Inspect Portable Tools and Extension Cords

Wire size and ampacity

Workers need to inspect extension cords prior to their use for any cuts or abrasion. Extension cords may have damaged insulation. Sometimes the insulation inside an electrical tool or appliance is damaged. When the insulation is damaged, exposed metal parts may become energized if a live wire inside touches them. Electric hand tools that are old, damaged, or misused may have damaged insulation inside. Please click the following links to review toolbox talk 2 and toolbox talk 3.

Flexible cords used with temporary and portable lights shall be designed for hard or extra-hard usage. They shall be marked with usage type designation size and number of conductors. The cord could be marked with a 14/3 meaning the conductor size (AWG) is 14, and the number of conductors is 3.

Wire Size and Ampacity

In terms of conducting electrical current, size matters (the size of the electrical conductor). Take a look at the following table regarding ampacity, the current-carrying capacity of a conductor in amps. You’ll notice two things: the amount of current a wire can safely carry increases as the diameter (and area) of the wire increases and as the number of the wire size decreases.

AWG Copper Wire Table

Copper Wire Size (AWG) Diameter(Mils) Area (Circular mils) Ampacity in Free Air Ampacity as Part of 3-conductor Cable
14 AWG 64.1 4109 20 Amps 15 Amps
12 AWG 80.8 6529 25 Amps 20 Amps
10 AWG 101.9 10,384 40 Amps 30 Amps
8 AWG 128.5 16,512 70 Amps 50 Amps

Notice that a #8 wire is twice the diameter, but four times the area of a #14 wire. There are a couple of practical applications here. For one thing, the gauge of the wire determines the rating of a fuse or circuit breaker in amps. A circuit wired with #14 copper will get a 15 amp circuit breaker. A circuit with #12 copper can get a 20 amp breaker; #10 copper can be 30 amps, and so on.

It is also possible to create a fire hazard by overloading an extension cord. This occurs when too much current is flowing in a conductor that is not heavy enough for the electrical load in amps. A circuit can be properly wired, and its circuit breaker correctly rated, but if too much current flows through an extension cord with wires that are too small, the cord will heat up. Sometimes there is also a voltage drop over a longer extension cord, which could damage your tools.

What must your employer do to protect you?

The OSHA construction standard requires flexible cords to be rated for hard or extra-hard usage. These ratings are derived from the National Electrical Code, and your employer is required to make sure the cord is indelibly marked approximately every foot along the length of the cord. Examples of these codes are S, ST, SO, and STO for hard service, and SJ, SJO, SJT, and SJTO for junior hard service.

Extension cords must be 3-wire type so they may be grounded, and to permit grounding of any tools or equipment connected to them.

Limit exposure of connectors and tools to excessive moisture by using watertight or sealable connectors.

Use Power Tools and Equipment as Designed

Workers using power tools and equipment should follow tool safety tips to avoid misusing equipment.

  • Never carry a tool by the cord.
  • Never yank the cord to disconnect it.
  • Keep cords away from heat, oil, and sharp edges.
  • Disconnect when not in use and when changing accessories such as blades and bits.
  • Avoid accidental starting (do not hold fingers on the switch button while carrying a plugged-in tool).
  • Use gloves and appropriate footwear.
  • Store tools in a dry place when not using.
  • Don’t use tools in wet/damp environments.
  • Keep working areas well lit.
  • Ensure cords do not cause a tripping hazard.
  • Remove damaged tools from use.
  • Use double-insulated tools.

Common Examples of Misused Equipment

  • using multi-receptacle boxes designed to be mounted by fitting them with a power cord and placing them on the floor
  • fabricating extension cords with ROMEX wire
  • using equipment outdoors that is labeled for use only in dry, indoor locations
  • attaching ungrounded, two-prong adapter plugs to three-prong cords and tools
  • using circuit breakers or fuses with the wrong rating for over-current protection (e.g., using a 30-amp breaker in a system with 15 or 20 amp receptacles -- protection is lost because it will not trip when the system’s load has been exceeded)
  • using modified cords or tools (i.e., ground prongs removed, face plates, insulation, etc.)
  • using cords or tools with worn insulation or exposed wires

Workers need to know even when the power system is properly grounded, electrical equipment can instantly change from safe to hazardous because of extreme conditions and rough treatment.

What Must Your Employer do to Protect You?

Your employer needs to ensure all power tools and equipment are maintained in a safe condition to:

  • ground power supply systems, electrical circuits, and electrical equipment
  • frequently inspect electrical systems to ensure path to ground is continuous
  • ensure workers understand to inspect electrical equipment prior to use
  • ensure ground prongs are not removed from tools or extension cords
  • ground exposed metal parts of equipment

Follow Lockout/Tagout Procedures

LOTO tag on electrical box.

Lockout/tagout is an essential safety procedure to protect workers from injury while working on or near electrical circuits and equipment. In addition, lockout/tagout prevents contact with operating equipment parts such as blades, gears, shafts, etc. Also, lockout/tagout prevents the unexpected release of hazardous gases, fluids, or solid matter in areas where workers are present.

To protect against being electrocuted, workers need to follow lockout/tagout procedures. If performing lockout/tagout on circuits and equipment, you may use the following checklist.

  • Identify all sources of electrical energy for the equipment or circuits in question.
  • Disable backup energy sources such as generators and batteries.
  • Identify all shut-offs for each energy source.
  • Notify all personnel equipment and circuitry must be shut off, locked out, and tagged out (simply turning a switch off is not enough).
  • Shut off energy sources and lock switch gear in the OFF position. Each worker should apply his/her individual lock and keys kept with the worker.
  • A qualified person must test equipment and circuitry to make sure they are de-energized.
  • Deplete stored energy (for example, in capacitors) by bleeding, blocking, grounding, etc.
  • Apply a lock or tag to alert other workers that an energy source or piece of equipment has been locked or tagged out.
  • Make sure all workers are safe and accounted for before equipment and circuits are unlocked and turned back on. Only a qualified person may determine when it is safe to re-energize circuits.

Only qualified persons may work on electric circuit parts or equipment that has not been de-energized. Such persons must be capable of working safely on energized circuits and must be familiar with the proper use of special precautionary techniques, PPE, insulating and shielding materials, and insulated tools.

What Must Your Employer do to Protect You?

Your employer must enforce LOTO safety-related work practices by ensuring:

  • controls that are to be deactivated during the course of work on energized or de-energized equipment or circuits are locked out, tagged or both;
  • equipment or circuits that are de-energized shall be rendered inoperative and post tags attached at all points where such equipment or circuits can be energized;
  • tags are placed to plainly identify the equipment or circuits being worked on; and
  • all circuits used to energize equipment are locked out/tagged out if any worker is exposed to contact with parts of fixed electric equipment that has been de-energized.

Follow Lockout/Tagout Procedures (Continued...)

Let’s review an example of an actual accident:

Lightpole with electrical maintenance cover open.
Accident Type: Electrocution
Weather Conditions: Raining
Type of Operation: Electrical Contractor
Size of Work Crew: 2
Collective Bargaining: No
Competent Safety Monitor on Site: Yes
Safety and Health Program in Effect: Inadequate
Was the Worksite Inspected Regularly: Yes
Training and Education Provided: No
Employee Job Title: Journeyman Electrician
Age & Sex: 39-male
Experience at this Type of Work: 16 Years
Time on Project: 1 Day

Description of Accident

An electrician was removing metal fish tape (a fish tape is used to pull wire through a conduit run) from a hole at the base of a metal light pole. The fish tape became energized, electrocuting him.

Inspection Results

As a result of its inspection, OSHA issued a citation for three serious violations of the agency's construction standards. Had requirements for de-energizing energy sources been followed, the electrocution might have been prevented.

What would you recommend?

Recommendations

  • Ensure all circuits are de-energized before beginning work - 29 CFR 1926.416(a)(3).
  • Controls to be deactivated during the course of work on energized or de-energized equipment or circuits must be tagged - 29 CFR 1926.417(a).
  • Employees must be instructed to recognize and avoid unsafe conditions associated with their work - 29 CFR 1926.21(b)(2).

Is There Anything Else My Employer Must do to Protect Me?

Your employer must also ensure equipment is guarded appropriately, electrical parts are isolated appropriately, and that employees are properly trained about electrocution hazards at their worksite.

Isolate Electrical Parts

Electrical parts, conductors entering boxes, cabinets, or fittings are to be protected from abrasion. Openings through which conductors enter are to be effectively closed. Unused openings in cabinets, boxes, and fittings also need to be effectively closed.

All pull boxes, junction boxes, and fittings must have covers. Metal covers need to be grounded. In energized installations, each outlet box needs to have a cover, faceplate, or fixture canopy. Covers of outlet boxes having holes through which flexible cord pendants pass shall be provided with bushings designed for the purpose or shall have smooth, well-rounded surfaces on which the cords may rest.

Ensure Proper Guarding

Guarding involves locating or enclosing electrical equipment to ensure workers do not accidentally come into contact with its live parts. Effective guarding requires equipment with exposed parts operating at 50 volts or more to be placed where they are accessible only to authorized people qualified to work with/on the equipment. Recommended locations are a:

  • room, vault, or similar enclosure;
  • balcony, gallery, or elevated platform; or
  • site elevated 8 feet or more above the floor.

Sturdy, permanent screens can also serve as effective guards.

Train Employees

Workers need be trained in and familiar with the safety-related work practices that pertain to their respective job assignments. Employers should train their employees to:

  • de-energize electric equipment before inspecting or repairing;
  • use cords, cables, and electric tools that are in good repair;
  • know and understand lockout/tagout recognition and procedures; and
  • use appropriate protective equipment.

Is There Anything Else My Employer Must do to Protect Me?

Let’s review an example of an actual accident:

Powerline near fence
Accident Type: Electrocution
Weather Conditions: Sunny/Clear
Type of Operation: Fence Construction
Size of Work Crew: 5
Collective Bargaining: No
Competent Safety Monitor on Site: No
Safety and Health Program in Effect: Yes
Was the Worksite Inspected Regularly: No
Training and Education Provided: No
Employee Job Title: Laborer
Age & Sex: 25-male
Experience at this Type of Work: 3 Months
Time on Project: 1 Day

Description of Accident

Five employees were constructing a chain link fence in front of a house and directly below a 7200-volt energized power line. They were installing 21-foot sections of metal top rail on the fence. One employee picked up a 21-foot section of top rail and held it up vertically. The top rail contacted the 7200-volt line, and the employee was electrocuted.

Inspection Results

Following its inspection, OSHA determined the employee who was killed had never received any safety training from his employer nor any specific instruction in avoiding the hazards posed by overhead power lines. The agency issued two serious citations for the training deficiencies.

What would you recommend?

Recommendations

  1. Employers must instruct employees to recognize and avoid unsafe conditions applicable to their work environment - 29 CFR 1926.21(b)(2).
  2. Employers must not permit employees to work in proximity to any part of an electrical power circuit when the employee could contact it during the course of work, unless the employee is protected against electric shock by de-energizing the circuit and grounding it or by guarding it effectively by insulation or other means - 29 CFR 1910.416(a)(1).

Instructions

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1. A ground fault circuit interrupter (GFCI) _____.

2. To protect yourself from being electrocuted by contact with overhead power lines, you should always keep yourself and equipment at least ____ away from power lines up to 50kV.

3. When a power system is properly grounded, workers need to be aware that _____.

4. _____ involves locating or enclosing electrical equipment to ensure workers do not accidentally come into contact with its live parts.

5. To protect their employees, employers must ensure extension cords are _____ so they may be grounded.


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