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.
Before work begins, make sure:
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.
If provided, use installed rider posts under power lines to avoid working too close to the power lines.
Use nonconductive ladders and be sure to retract them before moving.
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.
The three primary methods your employer should control power line hazards are:
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.
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.
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:
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:
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.
What Must Your Employer do to Protect You?
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 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.
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:
The required tests must be recorded, and the record maintained until replaced by a more current record.
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.
Workers using power tools and equipment should follow tool safety tips to avoid misusing equipment.
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.
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.
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).
Your employer must enforce LOTO safety-related work practices by ensuring:
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.
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.
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.
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:
Sturdy, permanent screens can also serve as effective guards.
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:
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Let’s review an example of an actual accident:
|Type of Operation:||Electrical Contractor|
|Size of Work Crew:||2|
|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.
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?