This is probably the most misunderstood and prevalent myth out there. We are probably all familiar with the properties of conductors and materials used for them. Materials such as gold, silver, aluminum, copper, and the ferrous metals are all excellent conductors of electricity. Most other materials around us have some resistance to electrical current flow of one degree or another.

Materials with a high resistance to electrical current are called insulators, or insulating material. Examples are plastic, rubber, fiberglass, wood, and glass. Materials manufactured and designed with electrical insulating qualities in mind, could have insulating properties measured in thousands of volts.

However, we need to understand that no material is effective at insulating someone from electrical current at any voltage. All dedicated insulators have a voltage limit to resisting electrical current flow. There is no insulating material that will protect you from a sufficiently high voltage. Remember, voltage is the pressure of the electron flow, and that pressure is exerted against the insulating material outwardly, as the electrical flow passes. Therefore, you will find that insulating materials have a voltage rating. The most common voltage rating for a electrical cords, power tools, and appliances is 600 V. Just as you can imagine what would happen if you put 6000 V on a 600 V cord. The same thing applies to any insulating material if a sufficiently high voltage is plied to it. Sometimes the only insulating protection is simply distance.

Myth #2 – Electricity seeks the best path to ground

It is important to recognize that electrical flow is from a high potential source or level to a lower potential level. Electricity will always flow when a path is available from a higher potential to a lower potential. Since common electrical power distribution is tied or referenced to the earth, we typically refer to voltage as voltage-to-ground. Therefore, if a power tool or a cord is abraded or somehow there is a path available to ground, the current flow will seek any available path to ground-all at the same time. You could be holding a power tool connected to a perfectly good grounded extension cord, and if you are touching a grounded pipe or cabinet, or kneeling in wet grass, you can also become a path to ground in a short-circuit condition. Workers have been injured or killed with a perfectly good grounded system. The common grounding system, while typically effective may still allow a fatal amount of electrical (as little as 1/20th of amp) flow through the worker when a short-circuit occurs.

Myth #3 – You don’t need GFCI’s at all times

While technically correct according to OSHA, not using a GFCI circuit for work with the power tools and extension cords, is simply foolhardy. Ground fault circuit interrupters are designed specifically to shut off the power extremely quick and at an extremely low current flow, typically 1/10 of the amount it would take for heart fibrillation to occur. Not using a GFCI can simply increase your chances of a fatal shock in the event of a short-circuit. Most construction companies require 100% GFCI circuit protection on their projects.

Myth #4 – An assured grounding equipment conductor program can be used in lieu of a GFCI

This is perhaps the most dangerous myth the law. OSHA is assured grounding conductor program, or AEGCP is allowed to be used in lieu of a GFCI. I recommend never ever to use an AEGCP in lieu of a GFCI circuit. An assured equipment grounding conductor program is a method to simply verify the ground continuity of power tools and extension cords on a periodic (usually three month) basis. The problem is simply using a good quality extension cord with a ground is still not completely effective at preventing electrocution, especially if the worker is well grounded. The AEGCP is fine to use: but only in addition to or as an adjunct to a proper GFCI – faithful program.

Myth #5 – Fiberglass and wood ladders will protect you from electrical shock

This is mostly true, however, one needs to be careful about this belief. Electricity can still flow through wet and or dirty fiberglass and wood ladders. Clean and dry fiberglass and wood ladders are effective at insulating a worker from electrical shock, but only for low voltage (under 600 V) conditions. Even then, other protective measures need to be taken, such as: insulated tools, gloves, and boots. Of course, the absolute best method is to simply work with deenergized circuits.

Electrocution hazards can be generalized into four categories: Working around power lines, working around power tools and extension cords, locking out and tagging out electrical equipment, and demolition work.

Electrocution from powerline contact is the leading cause of electrocutions for construction workers.  While OSHA requires a minimum of 10 foot separation from any construction activity and power lines, all powerline contacts result from encroaching on this distance.  Typically, powerline contact results when activity (hoist line, material, worker) is within a few inches of the powerline.  Simply maintaining the 10 foot clearance is the most important thing you can do.  The new cranes and derricks regulation requires certain actions to take place.  When any construction activity is possible within 20 feet of power lines, from the 20 foot mark to the 10 foot mark, a pre-activity meeting is required and an observer is required when activity is ongoing in this buffer area.

Effective power tools and extension cords can be a source of electrocution, however with the advent of GFCI protection, there’s cause of electrocution has been reduced significantly.  Always use GFCI protection, whatever you’re using power tools and extension cords, and always inspect your power tools and extension cords for defects.  Electrical power tools and extension cords cannot be repaired by your typical construction worker.  They may only be repaired by a qualified person (i.e. an electrician or electrical maintenance worker).

Many workers are killed when working on electrical equipment that they thought was deenergized.  A methodical, comprehensive lockout tag out program is required when working on equipment that can be potentially energized.  One of the most important tools a construction worker can have it in their toolbox is their own personal lock with a tag having their picture on it.

When performing demolition work around potentially energized circuits, workers need to ensure circuits are deenergized before cutting into walls.  There is a variety of electrical test equipment on the market that can ensure that where you are cutting will only have dead circuits.  If you are forced to keep some circuits energized, then a slow methodical approach to demolition needs to be performed.

A comprehensive health and safety program will list various conditions were electrocution hazards exist, and which countermeasures to employ.  A safety and health plan will have countermeasures for working around powerllines, with power tools and extension cords, with locked out equipment, and demolition work around energized circuits.

OSHA has significantly changed it’s treatment of powerlines with its new subpart 1926.1407-1411.  In the past there was little to no discussion until personnel or equipment got within 10 feet of an overhead powerline.

Now, before assembly or disassembly of a crane, the employer must determine if it could come within 20 feet of a power line. If so, the employer must either confirm with the power company that the line is de-energized and visibly grounded at the worksite, make sure no part gets within 20 feet of the power line or follows Table A, which has minimum distances based on voltage.

Now if the line is not de-energized (which is usually the case), the employer must: conduct a meeting with the assembly/disassembly crew to review measures to prevent encroachment; they must use only nonconductive tag lines; and they must use a dedicated spotter, an elevated warning line/barrier in view of the operator, or an alarm/ automatic control system.

Cranes cannot be assembled or disassembled below an energized power line or within the minimum distances referenced in Table A of a power line. And if Table A is used, the owner/utility must provide the voltage to the employer within 2 days of a request.  Power lines must be assumed to be energized until they are confirmed to be de-energized and visibly grounded. Warnings about electrocution hazards must be posted conspicuously in the cab (in view of the operator) and outside the cab (except for overhead gantry and tower cranes).

The work zones around equipment must be marked 360 degrees around the equipment to prevent encroachments within 20 feet of a power line. If the line is not de-energized, a meeting must also be held with the crew before operations begin to review the location of the lines and procedures to prevent encroachment.

Measures similar to those required during assembly/disassembly must be taken to prevent encroachment.  An insulating link between the load line and load is also an option.

Now it probably goes with out saying, but operators and crew members must now be trained in several items: on the procedures to follow in the event of a contact; that power lines must be presumed to be energized until confirmed and visibly grounded, that power lines are presumed un-insulated until otherwise confirmed by the owner or a qualified person, on the limits of insulating links and other devices, and on proper grounding procedures and their limitations.  Spotters must also get training as applicable to their work and responsibilities..

The minimum clearance distances are specified in Table A as:

Voltage (kV)                                                 Minimum clearance distance (ft)

Up to 50                                                                                 10

>50 to 200                                                                             15

> 200 to 350                                                                          20

>350 to 500                                                                           25*

>500 to 750                                                                           35*

>750 to 1,000                                                                        45*

> 1,000                                               determined by the utility/owner

* According to 1926.1409, for power lines over 350 to 1,000 kV, the minimum distance is presumed to be 50 feet. Over 1,000 kV, the utility/owner or a registered engineer must establish the minimum distance.

Over 350 to 1,000 kV, the minimum distance is presumed to be 50 feet. Over 1,000 kV, the utility/owner or a registered engineer must establish it.

If work has to operate closer than the Table A values, then the following precautions must be taken:

• The employer must show that Table A is infeasible and that it is infeasible to de-energize and ground or relocate the line;
• Safe distances must be determined by the owner/operator of the line or a registered professional engineer who is a qualified person;
• A planning meeting must be held;
• Automatic reenergizing devices must be inoperative;
• A dedicated spotter must be assigned;
• An elevated warning line/barricade or an insulating link must be installed between the line and the load (additional provisions kick in one to three years after the effective date);
• Non-conductive rigging must be used;
• A range of motion limiting device must be used;
• Non-conductive tag lines must be used;
• Barricades at least 10 feet from the equipment (where feasible) must be established;
• Equipment must be properly grounded;
• Workers must be kept from touching the line above the insulating link;
• The owner and user must meet with the equipment operator and other workers to review procedures;
• One person must be identified who will implement the plan and can stop work if necessary; and
• Documentation of these procedures must be immediately available on site.

Equipment traveling under or near a power line must have a lowered boom/mast and support system, and must obey minimum clearance distances set in Table T,  It’s also important to reduce speeds to minimize breaching, Also, use a dedicated spotter if closer than 20 feet, and illuminate or identify the power lines at night and finally identify and use a safe path of travel.

Table T – Minimum Clearance Distances While Traveling with No Load

Up to 0.75 kV                                                            4 ft

>0.75 to 50 kV                                                           6 ft

>50 to 345 kV                                                            10 ft

>345 to 750 kV                                                         16 ft

>750 to 1,000 kV                                                      20 ft

> 1,000 kV                             established by owner or registered professional engineer/qualified person

Before any work can begin, OSHA requires a thorough assessment of the area to determine what parts are energized, the condition of poles, hardware, and equipment. This survey shall include any affected peripherals such as fire alarm, phone, or cable TV lines.

Workers then approaching a work area must maintain minimum clear distances from energized parts with a phase-to phase potential of 2,100 volts or higher. This applies to any workers who are not completely isolated, and includes workers using “hot sticks” or other similar devices that are insulated. For instance, the minimum clear distance for energized parts from 2,100 volts to 15,000 volts is 2 ft. This distance increases slightly to 2 ft. 4 in. for voltages from 15,001 volts to 35,000 volts, and increases incrementally thereafter.

Workers will first usually put on their personal protective equipment. OSHA does require that all rubber equipment and live-line tools be visually inspected prior to use. In addition, rubber gloves in particular shall be “air-tested” prior to use.

Lines and equipment that are deenergized to be worked on can, in most cases, visually show that it’s disconnected from energized portions of the system. In cases where an item is not visibly open or visibly locked out, special care needs to be taken.

First, the line needs to be identified and declared deenergized by a designated worker. All switches that can supply power to the deenergized section shall be plainly tagged that men are working on the section. If switches can be locked out, or have their handles removed (or other similar action) this shall be done to assure the switches cannot be turned on. After all the above work is performed, the section shall be final tested to verify the section is deenergized. At that point protective grounds shall be installed, and then work may start. When attaching ground leads, start by attaching the lead to the ground point, then connect the other end with insulating tools or similar devices. Reversal of the above process is performed when reenergizing the section.

OSHA has a few general regulations for equipment use. For instance, a visual inspection and test of brakes and operating systems shall performed on all equipment at the start of the workshift. Hydraulic fluids used in Aerial lifts or similar equipment shall be of the insulating type- with fire-resistant characteristics of this fluid being exempted for this type of high voltage work. Arial lifts used near energized lines or equipment are required to be either grounded or barricaded. Equipment (such as cranes) without a voltage rating shall be kept clear of high voltage lines and equipment by 10 ft. (for 50,000 volts and less). Also OSHA prohibits line work under adverse weather conditions (especially high winds) except during emergencies.

There are many regulations OSHA has for line-stringing operations, however most of these regulations are covered by normal company work rules. OSHA does, however, require a briefing to be held before work starts which discusses the following topics:

• The type of equipment to be used.
• The grounding devices and procedures to be used.
• The crossover methods to be used.
• The clearance authorization(s) required.

When stringing operations are parallel to existing, energized lines, a competent determination needs to be made to ascertain if dangerous, induced voltage buildups can occur, especially during switching and ground fault conditions. If this is the case, the entire stringing operations require grounding until conductor installation is complete. The normal OSHA regulations also apply as to inspecting all equipment and line stringing accessories, etc. prior to use.

Working on live-line bare-hand work is a specialty in itself. OSHA requires any worker attempting this type of work to be thoroughly training prior to working on any energized circuits. Before working on live-line bare-hand work, the following items need to be determined:

• The voltage rating of the circuit on which work will be performed.
• The clearances to ground or other phases on which work will be performed.
• The voltage limitations of the aerial-lift equipment to be used.

All equipment used for this type of work shall be designed, tested and intended for live-line bare-hand work. One of the keys to this work is the insulating capacity of the aerial bucket arm. The ability of the aerial bucket to be completely isolated from any other voltage potential make this type of live-line bare-hand work possible. Before the start of the workday, when higher voltages are worked during the day, or any other factors develop that may change voltage conditions, the aerial bucket arm shall be physically tested. This test consists of placing the bucket arm in contact for three minutes with the voltage to be encountered during the work. Leakage tests shall be made during the three minutes. If more than 1 microampere/ kilovolt rating (between phases) is found, the bucket arm fails the test and shall not be used until repairs are made.

Once the aerial lift passes the test, work may then proceed only with personal supervision by a person trained and qualified in live-line bare-hand work. Again, this may be standard procedure to those familiar with live-line work, but OSHA does require the conductive aerial bucket liner to be bonded to the energized line being worked before the line is worked on. The worker is also similarly bonded to the liner with conductive shoes, or leg clips. This ensures the worker (isolated from ground or other phases) is at exactly the same voltage potential as the line, thereby making the live line safe to perform work on.

A careful assessment of the applicable regulations should be reviewed with your own safety procedures to assure compliance with OSHA regulations.