This Electrical Safety Hazards Handbook was developed for general education purposes only and Use the information within this Handbook at your own risk. Chapter 2. Electrical Safety Equipment. Introduction / Glossary / General Inspection and Testing Requirements for Electrical. Safety Equipment / ELECTRICAL SAFETY HAZARDS HANDBOOK The World's Leading Provider of Circuit Protection Solutions Littelfuse is the global leader in circuit protection A.
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Abstract: Covering every major electrical standard, including NEC, NESC, NFPA, 70E, IEEE , and OSHA, Electrical Safety Handbook, Fourth Edition is a. Electrical Workers' Safety Handbook. 4. CONTENTS. 6 About This Handbook. 8 Conduct and Professionalism. OSHA Guidelines for a Safe Workplace. This DOE Electrical Safety Handbook replaces the DOE Electrical Safety other electrical codes and standards utilized in this handbook include: 29 CFR
Answers to these questions and other criteria will Unlike fuses, Circuit Protection Checklist help to determine the type of overcurrent protective circuit breakers device to use for optimum safety and reliability.
What is the normal or average current expected? What is the maximum continuous three hours or more current expected? What inrush or temporary surge currents can be expected?
Are the overcurrent protective devices able to distinguish between expected inrush and surge currents and open under sustained overloads and fault conditions? The low relative beneits and dangers of Direct Current of electricity and its effects have been known DC vs.
Alternating Current AC. Thus began the need to commissioned the development of the electric much current regulate electrical installations to protect people chair for their capital punishment program. Even and equipment from its unintended effects. Thomas Edison is said to using AC. In , Edison in Chicago. Obviously, Edison was proven power station in New York City. It produced wrong regarding the safe application of AC.
In , Edison was issued the irst generating and distributing electrical energy fuse patent. Ever since, controlling electricity over long distances at higher voltages and then and protecting wires from ire has become transforming it to lower useable voltages. In an effort to increase began the need for increased electrical www. In some cases. Many electric generating plants and transmission lines were built and installed in the US in the early 20th Century.
Construction and safety standards were quickly developed. The presence of low voltages can be determined by tasting. The method is feasible only where the Underwriters Laboratories published the irst pressure is but a few volts and hence is fuse standard.
If voltage the presence of voltage, etc.
The taste is due to Circuit-Breakers. Electricians often test for the presence of voltage by touching the conductors with the fingers. It that may burn. Electrical which deals speciically with the practical safety standards and practices needed to safeguarding of electrical workers at their keep pace with the ever-increasing growth workplaces. In the year in the Workplace.
It an expanded section on Arc-Flash hazards. Also in , the IEEE Institute of was asked to research and provide guidelines for Electronic and Electrical Engineers published electrical safety in the workplace. Raphael Lee opened the irst burn center in Chicago dedicated to the care and treatment of electrical burns. Electric Arc Blast Burns. It remains today as one of the For more information: Standards and safety organizations include: Subpart worker.
Together, OSHA the workplace. One of is the group that addresses power distribution their objectives is to minimize the hazards of in industrial and similar facilities.
There are electricity through standards that specify safe numerous sub-committees that meet regularly design characteristics and work practices for to research, publish, and update standards electrical equipment and systems. Many of the and guidelines for the testing, evaluation, standards and codes are not only accepted in and application of their particular industry the United States, but throughout the world.
Although there are other methods of determining Arc-Flash The primary organization in the U. It also requires an electrical hazard tories, Inc. NFPA 70E deines and establishes conformance to accepted standards.
Work- shock and Arc-Flash approach boundaries to ing with industry associations, manufacturers, energized equipment and addresses how to experts, insurance companies, and government For more information: If the product meets or exceeds the standards, UL The American National Standards Institute lists the product in their guides and permits ANSI is a private, non-proit organization manufacturers to display the UL label on the that administers and coordinates the U.
Protective devices such as fuses and voluntary standardization and conformity circuit breakers must meet rigid standards such assessment system. Equipment that has been modiied ASTM American Society of Testing and may require new evaluation and manufacturers Materials , ANSI coordinates and adopts routinely submit their products to UL for re- these various industry consensus standards evaluation to maintain their listing.
NEMA has American Society for Testing and Materials, is a developed and published hundreds of standards voluntary standards development organization jointly developed by its member companies.
American National Standards. They have also developed Used in Commercial and Industrial Applications; electrical safety standards with emphasis and FU Low-voltage Cartridge Fuses, on their members. In many cases, these while others address safety issues such standards are being adopted by ANSI.
Except for OSHA regulations most standards do not Live parts to which an employee might be exposed shall be put into an standards have automatically become law. However, they are often electrically safe work condition before adopted by governmental bodies and become law; an employee works on or near them, been developed to enforced by the Authority Having Jurisdiction AHJ.
Whether law or additional or increased hazards or is not, applicable standards should be followed to infeasible due to equipment design improve safety and reduce potential hazards. How to establish an electrically safe Live parts to which an employee may work condition be exposed shall be deenergized before the employee works on or near them, Equipment that has been deenergized and unless the employer can demonstrate veriied as such is said to be in an electrically that deenergizing introduces additional safe work condition.
Live parts that operate electrically safe work condition. They are: To demonstrate the close relationship between 1. This reprinted material is not the complete and official position of the NFPA on the referenced subject, www. Check applicable Although the best practice is to always up-to-date drawings, diagrams, work on deenergized equipment, OSHA and identification tags. After properly interrupting the load hazard or be infeasible to deenergize. Such accordance with a documented work practices shall protect employees and established policy.
Use an adequately rated voltage of their body or indirectly through detector to test each phase some other conductive object…. Test each Electrical tasks such as troubleshooting and phase conductor or circuit part testing for the presence of voltage, current, both phase-to-phase and phase- etc.
Before and after each is energized. Other exceptions that allow 6. Where the possibility of induced work on energized equipment include: A mistake often made is confusing infeasibility It is important to note that a safe work with inconvenience. For example, meeting condition does not exist until all 6 steps are a manufacturing production schedule does complete.
During the process of creating not qualify as infeasible. It may be very the electrically safe work condition, the inconvenient but it still does not authorize appropriate PPE must also be utilized. In addition to being trained some tasks and un- and the speciic equipment to be serviced.
Knowing the difference may even save your life. Training is the key in determining who methods but still be considered unqualiied is considered a qualiied worker.
All personnel for others. Unqualiied persons must also who may be exposed to electrical hazards MUST be trained in the risks they are exposed to receive documented training in order to become and the procedures that are necessary to qualiied. Such persons shall be capable of working safely on energized Before work is performed on energized circuits and shall be familiar with the equipment, NFPA 70E states: The objective is to training on the hazards involved.
This reprinted material is not the For more information: The location and description of involved so they will be less likely to approve equipment to be serviced work on energized components. In essence, 2. Justification why circuit this shifts the decision to work on energized cannot be deenergized equipment from the worker to management. Results of the shock hazard analysis permits can also be written to cover a certain length of time for routine tasks provided the 5.
Determination of the shock worker is trained and qualiied. Other tasks that protection boundaries are not routine should generate a work permit as needed to insure the worker is trained and 6. Results of the flash hazard analysis qualiied for the task.
Exceptions to the written 7. The Flash Protection Boundary work permit include testing, troubleshooting, and voltage measuring by qualiied workers. Description of PPE to be used 9. However, Evidence of job briefing it should contain the following 11 elements: Signature of Manufacturing Manager Date equipment.
Together energized equipment. Together they must develop Safety Program. Current may also and sound energies cause an erratic heartbeat known as ventricular ibrillation. If ibrillation occurs even briely and Secondary hazards may include burns, the goes untreated, the effects are usually fatal.
Unexpected events can When personnel cause startled workers to lose their balance A clear understanding of how electric current come in contact and fall from ladders or jerk their muscles travels through the body can help minimize possibly causing whiplash or other injuries.
The table below with energized outlines the effects that various values of conductors they electrical current have on the human body. Signs of internal current through the body. Any person 1 In a touch potential contact, current experiencing any kind of electrical shock should travels from one hand through the seek immediate medical attention.
Using heart and out through the other hand. Arc-Flash and Arc Blasts 2 In a step potential contact, current travels from one foot through the legs, and out An Arc-Flash is an unexpected sudden release of the other foot.
The heart is not in the of heat and light energy produced by electricity direct path of current but the leg muscles traveling through air, usually caused by may contract, causing the victim to col- accidental contact between live conductors. The Since energy equals power multiplied by time, air and gases surrounding the arc are instantly and power wattage is volts X amps, we can heated and the conductors are vaporized see that calories are directly related to amperes, causing a pressure wave called an Arc Blast.
The higher the current, voltage and time, the more calories produced. Personnel directly exposed to an Arc-Flash and Arc-Blast events are subject to third To deine the magnitude of an Arc-Flash and degree burns, possible blindness, shock, blast the associated hazards, some basic terms have effects and hearing loss. Even relatively small been established: The amount of instantaneous arcs can cause severe injury. The secondary heat energy released by an Arc-Flash is generally effect of arcs includes toxic gases, airborne called incident energy.
The high deined as the heat energy impressed on an temperatures of the arc and the molten and area measuring one square centimeter cm2. If we place instruments that measure incident Any energized electrical conductor that makes energy at varying distances from a controlled accidental contact with another conductor or Arc-Flash, we would learn that the amount with ground will produce an Arc-Flash.
The arcing of incident energy varies with the distance current will continue to low until the overcurrent from the arc. It decreases approximately as Incident energy is protective device used upstream opens the the square of the distance in feet. Just like the instantaneous circuit or until something else causes the current walking into a room with a ireplace, the to stop lowing. The arc current can vary up to closer we are, the greater the heat energy.
Tests have indicated that an incident energy an Arc-Flash and is of only 1. Arc-Flash, we need to understand some basic For the purpose of understanding the potential terms. An Arc-Flash produces intense heat at effects of an Arc-Flash, you must determine the point of the arc.
The part. Most measurements or calculations are following data provides a basis for measuring made at a working distance of 18 inches. This heat energy: High current and longer circuit breaker. It is important to remember that it only takes 1. Studies have shown that many What determines the severity of existing molded case circuit breakers take up an Arc Flash? Refer to the Several groups and organizations have table on page 31 showing the typical opening developed formulas to determine the times for various overcurrent protective devices.
In all cases, the severity of the Arc-Flash depends on Arc Blast Effect one or more of the following criteria: Even large objects such as switchboard conductors. Faulty electrical equipment can doors, bus bars, or other components can also produce a hazard while being operated.
In some cases, bus bars have shock and Arc-Flash can also be caused by: For The severity and causes of electrical hazards are comparison, OSHA states that decibel levels varied, but the best protection is to deenergize Circuit breakers exceeding 85 dB require hearing protection.
No one has can take up to ever been killed or injured from an Arc-Flash while working on deenergized equipment. It is important to remember than current- weariness, pressure to restore power, or over- that proper selection and application of conidence can cause an electrical worker to overcurrent protective devices OCPD will limiting fuses.
The analysis must include all from shock. A boundary distance is electrical system electrical hazards: To enter this speciically requires Electrical Hazard Analysis boundary, unqualified persons must be volts or higher.
The results of the use PPE. Electrical Hazard Analysis will determine the work practices, protection boundaries, personal protective equipment, and other procedures Restricted Approach Boundary required to protect employees from Arc-Flash The Restricted Approach Boundary is an or contact with energized conductors. A boundary distance is established from an energized part Shock Hazard Analysis based on system voltage.
Work in this boundary is PPE required to minimize shock hazards. NFPA 70E has established three shock protection boundaries: Approach Boundary distances may range from an inch to several feet. The discussion and examples that tions are based on contain a Flash Hazard Analysis. For other conditions or point in the electrical system. This includes all under engineering supervision, calculations components contained in the electrical system.
In part, Arc-Flash hazard calculations are based on the The following data is required to available fault current and the opening time of complete the Flash Hazards Analysis: In order is important to remember that although voltage to determine the potential Arc-Flash hazard, levels may be higher at the service entrance, Flash Protection Boundaries must be calculated secondary power distribution transformers can produce much higher current levels and Arc- For more information: This reprinted material is not the available fault current at the service entrance TEC-FUSE complete and official position of the NFPA on the referenced subject, which is represented only by the standard in its entirety.
Hand calculations or www. The results can vary drastically depending on the speciic system parameters. An arcing fault will also produce very Arc-Flash Calculations different incident energy levels depending on if the arc is in open air or conined in a cubic box.
If the maximum available fault current at a The formula in Table B estimates the incident particular location is known, then an analysis of the energy for a fault occurring in a 20 inch cubic upstream overcurrent protective device OCPD box with one side open. This estimate simulates will determine how fast the device will clear the the potential effect of an arc-lash while working circuit at the fault current.
If these two factors in equipment and switchgear enclosures. During arcing faults the arc impedance resistance reduces arc current. If the bolted fault current Isc is not total arc energy.
Studies have shown that known, it can be calculated based on the MVA the minimum self-sustainable arc in volt rating and impedance of the source transformer.
Table A provides a basic formula both maximum and minimum fault currents. The formula in Table B only applies to systems where the available short circuit current is in the range of 16kA to 50kA.
Transformer secondary substation. Transformer secondary protected with current-limiting fuses. Calculate MVAbf: Calculate DC: Calculate Isc: Isc 43, A Calculate F: Calculate EMB: In this particular comparison, the required level of PPE would also be quite different between the Step 1 fuse and circuit breaker. The above calculations can also be performed using commercially Collect the system and installation data available software programs.
Refer to Annex D of this handbook for more details on the steps Depending on whether you are doing a required to complete the hand calculations. In order to calculate the bolted fault developing these methods. Included in are spreadsheet power source and the area you are concerned programs that simplify the calculation of with. Next, you must record the size, type, incident energy and lash-protection boundaries.
All For more information: If the fuse manufacturer Determine the system modes of operation or circuit breaker manufacturer publishes maximum and minimum clearing times, it is Most installations have only one mode of important to use the maximum clearing time operation with one utility connection. However, possible for the predicted arc fault current. This step can be omitted if the more transformers, or co-generators running overcurrent protective devices are those in parallel.
Each mode can be very complex already tested and listed in the IEEE and require a detailed hazard analysis. See Section 4.
Step 3 Step 6 Determine the bolted fault currents Document the system voltages and classes of equipment You can perform hand calculations or use commercially available software programs such Make sure you document the system voltages as the Littelfuse EDR software to calculate the and class of equipment such as 15kV switchgear, bolted fault currents at all points between the 5kV switchgear, low-voltage switchgear, low- utility and the distribution or control equipment voltage MCCs and panelboards, or cable runs.
It will be necessary to plug in all of the data you have recorded about the transformers, cable sizes and lengths, and Step 7 type of conduit, etc. As previously discussed, incident energy of determining Determine the arc fault currents calculations and Hazard Risk Categories will incident energy depend on the working distances selected.
The predicted arc fault current will be to use NFPA for system voltages under 1kV depends on the Determine the incident energy for bolted fault current, system voltage, arc gap, all equipment 70E equations and and whether the arc would most likely occur in calculations.
This distance must be established Step 1 Flash Hazard and will vary based on system parameters. However, Software programs automatically calculate Once the equipment is identiied where work the distance based on the arc fault current, is to be performed, review the up-to-date one a complete analysis system voltage, arc gap, and arc duration. If the one line If the overcurrent protective devices OCPD drawing is not up to date or the available short are something other than those covered circuit is not known, it must be determined.
If the desired task to Protection Boundary and incident energy be performed is not listed, the Table Method must be calculated by another method. Risk Categories and required PPE.
All footnotes listed at the end of the corresponding notes in Table For systems V and below, using one of the other calculation methods. Design a safer system. When designing a safer system the following occur every day There are many practices that will help reduce goals and factors should be considered: Use and upgrade to current-limiting Arc-Flash hazards. Implement an Electrical Safety Program. Observe safe work practices.
Use Warning Labels. Use an Energized Electrical Work Permit. Achieve or Increase Selective Coordination. Often the selection of the overcurrent protective devices or equipment can be easily devices that best meet those goals can be repaired rather than face time-con- determined. What is the best choice for your suming and costly replacement.
Factors to consider include: After a fault, will the units be usable or will they require replacement? That means you are up and running dardized at , , and once the cause of the fault is removed. Use and upgrade to current-limiting ages and are often mis-applied. Circuit is allowed to low. Within their current-limiting breaker interrupting ratings may range range, current-limiting devices reduce the peak from 10kA to kA, but the interrupt- fault current.
In recent years, the community has begun to recognize that in addition to fire and electro- cution, arc-flash and arc-blast hazards also result in injury. The knowledge base about these hazards is expanding but is not yet complete. The community knows that as the distance between a worker and an electrical hazard decreases, the degree of exposure increases.
Workers must understand that they are exposed to these hazards until an electrically safe work condition has been established, as explained in this handbook. When a failure occurs, a worker is expected to identify the problem, repair the problem, and restore the equipment to normal service. Although the electrical energy sometimes is removed before a worker begins a maintenance task, those tasks often are executed while the source of electricity is energized.
Short-term employees may be expected to work in an environment that includes exposure to energized electrical circuits and components. Consultant and service employees are frequently exposed to energized electrical equipment and circuits. In many cases, the worker might troubleshoot while the circuit is energized.
They must also understand how to select and use work practices that minimize or eliminate risk of injury and how to select and wear protective equipment that will minimize or eliminate that risk.
Employees must be trained to understand the concepts discussed in each chapter. The authors of this handbook are warriors in the fight for electrical safe workplaces. This new edition provides critical, up-to-date information for employers about how to avoid injury. All of the information is here in the handbook, and work practices, procedures, and the overall electrical safety program should embody the ideas discussed herein.
I highly recommend this valuable resource to employers as they join the growing effort to ensure that their workers remain safe. Providing a safe work place is not only an economical asset, it is the right thing to do.
He or she is responsible for assuring each person's qualifications, and will assign one person to do the work and the other to be the backup. Extension Cords Damaged and improperly used extension cords cause thousands of electrical fires and injuries in homes and workplaces every year. Before using extension cords, inspect them for cracks, ripped insulation, and damaged or missing grounding prongs. Do not bend back or break off grounding prongs: they are important safety features that receive harmful stray currents.
To prevent overheating or possible electrical shock, choose cords rated for current levels that exceed your needs by a safe margin. Never run extension cords through walls, windows, or doorways or behind walls, ceilings, or floors. Never connect extension cords in a series or splice them together. Remove the extension cord when you are finished. Extension cords are not to become permanent fixtures for regular use. Gloves may be required however, do not wear gloves when you are operating a revolving tool, such as a drill or saw.
Safety glasses prescription and non-prescription and boots or shoes of many types are also available with download orders from the business office. Wear appropriate personal protective equipment when you are working with power tools, electricity of 50 volts or greater, or heavy equipment.
Remember that watches and rings can cause fatal injury by acting as conductors. Remove all jewelry when you are working with power tools or near electrical hazards. Collapse Know Your Equipment Know Your Equipment Before beginning electrical work, check that your diagnostic equipment is in good working order, is properly calibrated, and covers the range necessary for the job.
A small, hand-held digital voltage meter DVM is commonly used, but you must check the rating on the front of the DVM to ensure that the voltage with which you are working is under the meter's maximum rating. It is dangerous to use a meter on voltages that exceed its maximum rating. Use proper testing equipment and accessories when repairing AC or DC powered equipment.
Choose probes and modules carefully because they are rated for different peak voltages. Remember that peak AC voltage is about one and a half times the normally quoted RMS root mean square voltage. If you are unsure of which probe to choose for the equipment you are planning to work on, then you should use a DVM with a rating higher than the highest possible voltage in the equipment you are working on to measure the voltage first.