Course 812 Module 8 OSHA Focus Four Hazards: Electrocution

Electrocution Hazards Protective Measures

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)
Crane near powerlines
Everyone needs to be aware of the safe distances from power lines.

Safe Practices Working Near Powerlines

The following are preventive measures for workers.

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.

1. Before working near power lines, each of the following is necessary, EXCEPT _____.

a. work is within safe working distances
b. flagged warning lines are installed
c. tools and equipment are semi-conductive
d. the power lines have been grounded and de-energized

Safe Practices Working Near Powerlines (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.

A worker carrying a ladder.
This worker retracted the ladder before moving it.

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)

2. What should be done after using extension ladders while working around power lines?

a. Fully retract the ladder.
b. Carry the ladder using the two-point method.
c. Place the ladder against the power line pole.
d. Lean the ladder before carrying.

Safe Practices Working Near Powerlines (Continued)

Employer Responsibilities

Before working on overhead power lines, employers must make sure they are de-energized and grounded by the owner/operator of the power lines, or other protective measures provided.

Employers must provide other protective measures, 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.

Lineman working on powerlines
Power company installing sleeves over power 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.

3. Which of the following is one of the three primary methods to ensure employees are safe working around power lines?

a. Coordinate power line work with local OSHA offices
b. Make sure employees buy proper personal protective equipment
c. Ensure utility companies de-energize and ground power lines
d. Make sure workers install rubber sleeves around poles

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.

4. How does a ground fault circuit interrupter (GFCI) sense the current flowing through a person?

a. It senses a change in voltage
b. It senses an increase in resistance
c. It senses a decrease in resistance
d. It senses a decrease in expected current
Receptacle GFCI
Receptacle GFCI

Types of GFCIs

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.
Portable GFCI
Portable GFCI

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 GFCIs. 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
  • Test light/tool
    Test light/tool
  • 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.

5. Rather than install multiple GFCI outlets, one _____ can protect the entire circuit.

a. receptacle GFCI
b. portable in-line GFCI
c. GFCI circuit breaker
d. Magnetic type circuit breaker

GFCIs (Continued)

What Must Your Employer do to Protect You?

Portable GFCI
GFCIs should be inspected and tested monthly.

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:

  • GFCIs 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.

GFCIs 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. The should be inspected and tested monthly.

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.

Portable GFCI
Employers need to ensure electrical equipment is visually inspected for damage before each day’s use.

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:

  1. Continuity Test: The continuity test ensures that the equipment grounding conductor is electrically continuous. Perform this test on all cord sets, receptacles that are not part of a building or structure's permanent wiring, and cord- and plug-connected equipment required to be grounded. This test can be accomplished with various test equipment.
  2. Terminal Connection Test: The terminal connection test ensures that the equipment grounding conductor is connected to its proper terminal at receptacles and cord plugs. Perform this test with the same equipment used in the first test, or for receptacles use receptacle testers.

The required tests must be recorded, and the record maintained until replaced by a more current record.

6. Under the Assured Equipment Grounding Conductor Program (AEGCP), electrical equipment noted in the program must be _____.

a. inspected before each day's use
b. listed in the approved UL equipment list
c. designed with the latest technology available
d. less than five years old

Inspect Portable Tools and Extension Cords

Cords
Electrical wires of various gage sizes.

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.

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.

American Wire Gauge (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. The gauge of the wire determines the rating of a fuse or circuit breaker in amps. For example, a circuit wired with #14 copper will get a 15 amp circuit breaker and a circuit with #12 copper can get a 20 amp breaker.

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.

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.

7. As the American Wire Gauge (AWG) wire size _____, the ampacity of the wire, as part of a 3-conductor cable _____.

a. decreases, increases
b. decreases, remains the same
c. increases, remains the same
d. decreases, decreases

Use Power Tools and Equipment as Designed

Power cords laying all over the floor of a house under construction.
Are these cords a tripping hazard?

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.
Power cord missing the ground prong.
The ground prong must never be removed from the plug.

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
  • using modified cords or tools
  • 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 employee are properly trained and that all power tools, systems, and equipment are inspected and maintained in a safe condition.

8. Which of the following is a example of safe electrical equipment use?

a. Using cords and equipment in damp locations
b. Placing plugs with missing ground prongs out of service
c. Fabricating extension cords with ROMEX® sire
d. Modifying cords or electrical-powered tools

Follow Lockout/Tagout Procedures

Lockout/Tagout image
Always follow formal lockout/tagout procedures.

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. You can learn more about using lockout/tagout procedures in course 710 Energy Control Program (Lockout/Tagout).

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.

Energized circuits: Only qualified persons may work on electric circuit parts or equipment that has not been de-energized. Qualified 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.

9. Who is allowed to work on energized circuits?

a. Authorized persons
b. Competent persons
c. Qualified persons
d. Designated persons

Protecting Workers

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.

Wire protruding from a wall under construction.
Do you think this electrical wire is protected from abrasion?

Isolate Electrical Parts

Electrical parts, conductors entering boxes, cabinets, or fittings must be protected from abrasion. Openings, whether used or not, through which conductors enter must 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.

10. Effective guarding requires equipment with exposed parts operating at _____ to be placed where they are accessible only to authorized people qualified to work with/on the equipment.

a. 10 volts or higher
b. 50 volts or more
c. in excess of 120 volts
d. between 120 volts and 240 volts

Check your Work

Click on the "Check Quiz Answers" button to grade your quiz and see your score. You will receive a message if you forgot to answer one of the questions. After clicking the button, the questions you missed will be listed below. You can correct any missed questions and check your answers again.

Final Exam
 

Optional Exercise: Accident Scenario

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).

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