Handbook for Electrical Safety

Edition 2

Includes new information for calculating and reducing arc-flash hazards

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Safety BASICsHandbook for Electrical Safety

(Bussmann Awareness of Safety Issues Campaign)

This is an unproven compilation of technical materials that has been assembled by the developers for the benefit of training othersabout electrical safety, including electrical arc-flash hazards. It is being presented to illustrate the critical nature of electrical safetypractices. While not the only method(s) or answer(s), or perhaps not even the best method(s) or answer(s), in the opinion of thedevelopers/presenters the content is an accurate, acceptable, and positive way to present the subject material. The National FireProtection Associations NFPA 70E, Standard for Electrical Safety in the Workplace, introduces safe work practices to mitigate thehazards identified by this work. By creating awareness of the potential hazards and describing workable solutions by which the hazards can be controlled, minimized or eliminated, it is hoped that injury will be reduced and lives will be saved.

Use of the information contained in the Safety BASICs program material is at your own risk.

Those seeking permission to reproduce portions of this document must contact Cooper Bussmann, Inc. for appropriate license.

Edition 2

I. Introduction ....................................................7

II. Consensus Standards ....................................7A. Types of standards ......................................8B. NFPA 70 (National Electrical Code)............8C. OSHA standards ..........................................8D. NFPA 70E ....................................................9E OSHA and NFPA 70E ..................................9F. Other standards and resources..................10

III. Establishing an Electrical Safety Program..............................................11

IV. Electrical Safety Program ............................11A. Safety program principles ..........................11B. Safety program controls ............................12C. Safety program procedures........................13D. Hazard/Risk evaluation ..............................13E. Job briefing ................................................13F. Incident and injury prevention ....................13G. Designing electrical system

for safety ....................................................14

V. Electrical Hazards ........................................14A. Electrical shock ..........................................14B. Arcing faults: arc-flash and arc-blast..........16

1. Arc fault basics ......................................162. Arc-flash and arc-blast ..........................173. Effects on humans ................................17

VI. The Role of Overcurrent Protective Devices In Electrical Safety ........................18- Staged arc-flash tests ..................................19

VII. Attending to Electrical Incident Victims ....21A. Preparedness ............................................21B. Effects of electrical incidents......................21C. Enhancement of chances for recovery ......21

VIII. Whos Responsible for Safety? ..................22

IX. Electrical Incident and Hazard Prevention 23A. Not working on or near ..............................23B. Electrically safe work condition ..................23

C. Shock hazard and flash hazard analysis ............................................24

D. Approach boundaries for shock protection ........................................25

E. Flash hazard analysis ................................27Method 1: NFPA 70E tables ......................27Method 2 NFPA 70E formulae ..................28Method 3 IEEE 1584 ................................29Example 1: method 1 ................................30Example 2: method 2 ................................31Example 3: method 3 ................................33Arcing fault currents in the long time characteristic of overcurrent protective devices ......................................34Other considerations ..................................34

F. Personal protective equipment (PPE) ........35G. Lockout/Tagout ..........................................37H. Stored energy systems ..............................38I. IP2X (finger-safe) ratings ..........................38J. Grounding and GFCIs ................................39K. Voltage testing 1,000V and below..............40

X. Suggestions for Limiting Arc-flash and Shock Hazards ............................................42

A. Avoidance is surest safety measure ..........42B. Avoidance: Energized Work Permit ..........42C. Voltage testing work practices & PPE........43D. NEC 110.16 arc-flash warning label ........43E. Worker qualified for the task ......................44F. Resetting circuit breakers or

replacing fuses ..........................................44G. Follow procedures for fuses and circuit

breakers after interrupting a fault ..............44H. Testing fuses ..............................................45I. Properly test knife-blade fuses ..................45J. Good housekeeping ..................................46K. Keep equipment doors closed....................46L. Keep people outside the flash

protection boundary....................................46M. Overcurrent protection reliability,

maintenance requirements, and the effect maintenance has on arc-flash hazards........................................46

N. Designing systems overcurrent protective device selection ........................471. Non current-limiting ................................472. Current-limiting ......................................48

O. Specify switches that shunt-trip when a fuse opens ....................................49

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Table of Contents

P. Improving existing fusible systems that have Class H, R, J, CC, or L fuse clips, upgrade to LOW-PEAK fuses ....................................49

Q. Type 2 (no damage) protection for motor controllers ..................50

R. Finger-safe products and terminal covers ..........................................51

S. In-sight motor disconnects ........................51T. Isolate the circuit: selective coordination ..52U. High impedance-grounded wye systems ..52V. Do not use short-time delay

settings on circuit breakers ........................52W. Specify a main on a service ......................53X. Cable limiters on service conductors ........53Y. Break up large loads into smaller

circuits ........................................................53Z. If using circuit breakers, specify

zone-selective interlocking ........................54AA. Smart equipment ................................54BB. Utilize arc resistant MV switchgear ......54

CC. Retrofit existing feeders with LOW-PEAK fuses ........................54

DD. Retrofit under-utilized circuits with lower-amp rated LOW-PEAK fuses ................................54

EE. Proper interrupting rating ......................55

XI. Costs Associated with Safety ......................56

XII. References ....................................................57

XIII. Glossary of Terms ........................................57

Notes Pages ............................................59-60

XIV. AnnexesA. Checklist for victims of electrical

incidents ....................................................61B. Sources of information ..............................62C. OSHA & other standards for protective

equipment ..................................................63D. Listing of IEEE standards: color books ......64E. Safety BASICsawareness quiz ..........65F. 3 Short-circuit calculation method ..........67G. Arc-flash incident energy & FPB

calculator table & notes..............................69

LOW-PEAK Upgrade ....................back-cover

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Safety BASICs - Bussmann Awareness of Safety Issues Campaign Copyright 2004 Cooper Bussmann All Rights Reserved Printed in the U.S.A

Acknowledgement

Special thanks go to Ray A. Jones, PE, and Jane G. Jones, with Electrical SafetyConsulting Services, Inc., (ESCS, Inc.), who provided consultation services for the Safety BASICs program material.

Ray is a professional engineer with more than 40 years of experience in developing and operating electrical safety systems and processes in industrial units. Ray retired from the DuPont Company in 1998, where he held the position of Principal Consultant,concentrating on electrical safety systems and processes as well as codes and stan-dards. Ray chairs the technical committee for NFPA 70E, Standard for Electrical Safetyin the Workplace. He is a senior member of the Institute of Electrical and ElectronicEngineers (IEEE). Ray has authored or co-authored many technical papers covering safety systems andprocesses, several of which have been published in IEEE Transactions on IndustryApplications, and earned awards from IEEE. He is a frequent lecturer and contributor at the IEEE-IAS Petroleum and Chemical Industry Committee Electrical Safety Workshop and other IEEE tutorials.

Jane has worked as a book and journal editor, newspaper reporter, author, and technical writer. In addition to serving as a writing consultant and editor for many technical papers, she has coauthored and edited numerous technical journal articles.Specializing in electrical safety, Jane helps to develop and formulate procedures andstandards for industrial plants.

Ray and Jane wrote the book Electrical Safety in the Workplace, published by NFPA in2000, and coauthored The Electrical Safety Program Book with Ken Mastrullo in 2003.

To learn more about services offered by ESCS, Inc., contact Ray Jones at 919-557-7711,ray.jones@ieee.org, or jandrjones@worldnet.att.net.

I. Introduction An increasing number of organizations are actively promoting electrical safety for employees. The NationalFire Protection Associations NFPA 70E, Standard forElectrical Safety in the Workplace, an AmericanNational Standard, is updated on a three-year cycle.The Institute of Electrical and Electronics Engineers(IEEE) publishes the Yellow Book, the IEEE Guide for Maintenance, Operation, and Safety of Industrialand Commercial Power Systems, and IEEE 1584,the IEEE Guide for Performing Arc-flash HazardCalculations. Cooper Bussmann makes available anArc-flash Calculator Guide, see Annex G and an arc-flash calculator on its website (www.bussmann.com).The University of Chicago Trauma Center has a unitthat specializes in electrical burns and related injuries.Its interests are not only on improving treatment meth-ods but also in providing insight into electrical injuriesand awareness of how to avoid electrical hazards.Major manufacturers and entire industries are seeingbenefits of becoming more involved in promotingemployee safety awareness programs.

The purpose of this Safety BASICs handbook is todo the following:

Increase awareness of safety issues for individualswho work on or near electrical equipment as well as system operators and equipmentdesigners/specifiers.

Provide safety principles to be used for protectingindividuals from potential injuries and even deathcaused by electrical hazards.

Provide some means to perform flash hazard analysis.

Provide some design, system upgrades and workpractice suggestions that enhance electrical safety in the workplace.

This material is designed to provide the reader with an overview of hazards associated with exposure toelectrical energy. It highlights standards and standardorganizations, and offers guidance on safety proce-dures and a number of key principles that can help tominimize exposure to electrical hazards. Knowing howto minimize the exposure to electrical hazards orreducing the hazard itself can help to reduce futureinjuries and even deaths. The Safety BASICs program is for the supervisor,manager, electrician, engineer, and the designer/spec-ifier of equipment used in the electrical system. TheIEEE makes it very clear that, Engineers engaged in the design and operation of electrical systems protection should familiarize themselves with the most recent OSHA regulations and all other applicable regulations related to human safety. To the IEEE, providing adequate safety means going beyond theminimum requirements of consensus standards.

Perhaps a statement in the IEEE Buff Book says itbest: Safety has priority over service continuity,equipment damage or economics.

II. Consensus StandardsConsensus standards are seen as generally acceptedengineering practices and can be used for litigationpurposes when entered as evidence in a legal pro-ceeding. In case of an incident where litigation isinvolved, the design and safety practices used arecompared with these standards. In some cases, thistype of enforcement is more critical than if the govern-ment were the enforcing agent.

In the United States, consensus standards are normally written by volunteers and published by stan-dards-developing organizations (SDOs). The contentof consensus standards is the result of work done bya blue-ribbon panel of experts and defines the indus-trys best generally available knowledge. Consensusstandards fall into several different classes. Someconsensus standards are product oriented; othersdefine testing requirements, cover installation ordesign issues, or are people oriented. Many becomelegally mandated by governmental organizations.

Whether a national consensus standard is mandatedand enforced by governmental action or not, the judi-cial system tends to use these standards as generallyrecognized and accepted engineering practices for litigation purposes. To understand the significance ofthis point, consider the text used in the OSH Act: the(Labor) Secretary shall...by rule promulgate as anoccupational safety or health standard any nationalconsensus standard.... The legal profession uses relevant national consensus standards in court cases,where the standard is entered into evidence.

Each SDO and standard has a principle objective. To correctly apply any individual consensus standard,both the SDO objective and the standard objectiveshould be clearly understood. The standard thenshould be applied with this understanding in mind. For instance, the National Fire Protection Association(NFPA) is primarily concerned with fire protection andpersonal safety. Therefore, NFPA standards should beembraced when these objectives are consideredimportant. Some NFPA standards are product ori-ented; others are installation oriented. These stan-dards should be applied as discussed in the scope of the document.

The NFPA publishes two critical standards. One isNFPA 70, otherwise known as the NationalElectrical Code (NEC), and the other isthe Standard for Electrical Safety in theWorkplace (NFPA 70E). The NFPA hasmany other standards, but these are two ofthe most important electrical standards.

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The premier standards publishing organization in theU.S. is the American National Standards Institute(ANSI). ANSI is authorized by the U.S. government asthe organization with the authority to identify AmericanNational Standards (ANS). No standard is written byANSI; instead, ANSI identifies requirements for boththe SDO and the standard. Among these is a require-ment that each standard be produced by peopleknowledgeable in the area being addressed. EachANSI standard, then, is ensured to have had broad,knowledgeable input as well as a consensus by thecommunity covered by the standard.

Most consensus standards define minimum require-ments necessary to accomplish the prime objectiveunder normal operating or functioning conditions. Ofcourse, in most cases, a standard tends to definesome protective measures. However, defined protec-tive measures are intended to protect the equipmentfrom destruction in case of a failure. Generally, con-sideration for the people factor is missing from thestandards puzzle, even though actions of peopleaccount for more than 75 percent of all incidents thatresult in injury. A. Types of standards At this point in time, more than 22,000 national consensus standards exist in the U.S. Standardsdeveloping organizations (SDOs) that address electri-cal safety include the:

American National Standards Institute (ANSI) National Fire Protection Association (NFPA) Institute of Electrical and Electronic Engineers

(IEEE) Underwriters Laboratories (UL) U.S. Occupational Safety and Health

Administration (OSHA) National Electrical Contractors Association (NECA) National Electrical Manufacturers Association

(NEMA) Note that these SDOs mostly are based in the U.S.and primarily have a U.S. focus.

Each of these SDOs writes and publishes standardsthat address various electrical safety issues. As statedearlier, some standards are intended for adoption bygovernmental organizations. However, national SDO-developed consensus standards not adopted by gov-ernmental organizations can still be used in a court of law.

B. NFPA 70 (the National Electrical Code NEC)

NFPA 70 commonly is called the National ElectricalCode, or the NEC. The NEC is currently adopted bymore than 1,800 different governmental organizationsin the U.S. and by several Latin American countries.These organizations include city, county, or state gov-ernments. Some adopt the NEC as it is published byNFPA; others add or subtract requirements.

The NEC is the document related to installation ofpremises wiring. Premises wiring involves interiorand exterior wiring, including power, lighting, controland signal circuits, along with all associated hardware.This wiring extends from the service point from theutility or separately derived system to the outlet(s). The focus of the NEC is to identify requirements usedto control the probability of electrical fires and providesafe installation when the system or equipment isoperating normally. By itself, the NEC is a standardwith advisory information offered for use in law and forregulatory purposes. The NEC is reviewed andrevised on a three-year cycle.

Keep in mind, however, that the NEC is offered as aminimum standard and, therefore, its requirementssometimes must be exceeded to meet functionalnecessities, sound engineering judgment, andimproved safety.

C. OSHA standards The U.S. Occupational Safety and HealthAdministration was authorized by the Williams-Steigeract of 1970. The OSHA Act passed both Houses ofCongress. Signed into public law, it became known asThe Act. The Act provides for several very importantelements:

Establishes OSHA as an arm of the U.S.Department of Labor

Mandates that an employer provide a safe work-place for employees

Defines national consensus standards as the starting point for a safe workplace

Provides for an inspection and enforcementprocess

Provides for a due process Provides for specific standards related to personal

safety requirements Provides for public input to the process

OSHA standards are published in the U.S. FederalRegister and made available to the general publiconline at www.osha.gov and in hard copy from theU.S. Government Printing Office.

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The U.S. Department of Labor has written the OSHAregulations under Title 29 of the Code of FederalRegulations (CFR), establishing them as requirementsfor electrical installations and electrically safe prac-tices. In the Standard 29 CFR, Part 1910 covers general industry, while Part 1926 covers the construc-tion industry (see Table II(C)). Each Part is subdividedinto Subparts. Each Subpart is further subdivided into Paragraphs.

Table II(C). OSHA Standards for Electrical WorkOSHAStandard Title Addresses1910.7 Nationally Recognized NRTLs

Testing Laboratories

1910.137 Electrical Personal Voltage-rated Protective Equipment protective products

1910.147 Control of Hazardous Lockout/tagout1910.333(b)(2) Energy

1910.269 Power Generation, Overhead andTransmission and underground Distribution distribution

1910.300-399 Electrical Safety General industryRequirements

1926.400-449 Electrical Safety ConstructionRequirements

General industry tasks (for electrical energy) are covered in 29 CFR 1910.7, 1910.137, 1910.147,1910.269, and 1910.300-399. Construction tasks arelocated in section 1926.400-449. OSHA standards(rules) and requirements also contain definitions.These definitions generally are related to tasks ratherthan employers or even industries. Employers shouldtherefore pay close attention to the type of tasks beingperformed.

It is important to note that OSHA law enforcementincludes fines. While many fines may be small, it isnot unusual for fines of up to $70,000 to be assessedper instance, per exposed employee. OSHA fines easily can escalate to more than a million dollars. Inaddition to fines, OSHA violations can result in crimi-nal indictment. It is also becoming more common foran employer to be held personally accountable. Insome situations, the employer, or even the plant man-ager, can be held criminally liable and sent to jail. D. NFPA 70E NFPA 70E is the Standard for Electrical SafetyRequirements in the Workplace. This standardfocuses on protecting people and identifies require-ments that are considered necessary to provide aworkplace that is generally free from electrical haz-ards. NFPA 70E is intended to address conditions thatexist, or might exist, and abnormal conditions wherepeople can become involved.

NFPA 70E suggests the following: Electrical hazards include shock, arc-flash, and

arc-blast. The best way to avoid injury or incident is to

establish an electrically safe work condition beforebeginning the work.

Procedures and training are extremely important ifinjury is to be avoided.

When OSHAs electrical standards were first devel-oped, they were based on the National ElectricalCode. As OSHA focused more on all aspects of electrical safety, OSHA recognized the need for a consensus document of electrical safety requirementsto protect individuals working on, or near, electricalequipment.

The first edition of NFPA 70E was published in 1979.Although NFPA 70E may not yet have the sameextensive recognition as the NEC, it provides the latest thinking on the subject of electrical safety, particularly in the area of safe work practices. Manyparts of the current OSHA regulations 29 CFR 1910Subpart S were derived from NFPA 70E.

NFPA 70E identifies the requirements for enhancedpersonal safety. It is growing in recognition as anextremely important national consensus standard that defines the requirements for an overall electricalsafety program. It is being adopted widely by organi-zations across the U.S. National consensus stan-dards, like NFPA 70E, may be entered into evidence in a court of law.

E. OSHA and NFPA 70EFor electrical safety in the workplace, some peopledescribe the relationship between the OSHA regula-tions and NFPA 70E as OSHA is the shall and NFPA 70E is the how. OSHA regulations, which are Federal law and shall be followed, are often written in performance-oriented language (does notstate how to comply). NFPA 70E is recognized as the tool that illustrates how an employer might accomplish the objective defined by the OSHAperformance-oriented language.

For electrical citations, OSHA commonly uses thegeneral duty clause and then as an alternative(means to comply) OSHA uses NFPA 70E.General Duty Clause: Section 5(a)(1) of theOccupational Safety and Health Act requires anemployer to furnish to its employees: employment anda place of employment which are free from recognizedhazards that are causing or are likely to cause death orserious physical harm to his employees

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The following is an excerpt from an OSHA Letter ofInterpretation dated July 25, 2003 signed by RussellB. Swanson, Director, Directorate of Construction:

The following is another excerpt from the OSHA Letterof Interpretation dated July 25, 2003 signed byRussell B. Swanson, Director, Directorate ofConstruction:

Another approach by OSHA is to investigate whetherelectrical work meets 1910.333(a)(1) which requiresworkers not to work on or near exposed live partsexcept for two demonstrable reasons (see Section IX(A) in this book). If the work can be justified for a workerto work on or near while energized, then OSHA will useNFPA 70E as an alternative or means to comply. That is

OSHA uses NFPA 70E as the how.

As an example of progressive safety initia-tives, the National Electrical ContractorsAssociation (NECA) Central Ohio Chapterin partnership with the International

Brotherhood of Electrical Workers (IBEW) Locals 683and 1105 and with OSHA Region V Columbus AreaOffice have an agreement to work as partners toachieve improvements in electrical worker safety. Aspart of the agreement there is a standard checklistthat must be used when working energized circuits;this is based on NFPA 70E.

In 2000, a major industrial was cited by OSHA foralleged serious and repeated safety violations includ-ing failing to de-energize live electrical parts beforeworking on or near them, failing to require employ-ees to wear protective clothing, gloves, and face protection when working on or near electrical parts,and failing to certify that a hazard assessment hadbeen conducted. In the settlement between the company and OSHA, it was agreed the companydevelop hazard analyses in accordance with specificNFPA 70E requirements.

F. Other standards and resources The National Electrical Safety Code (NESC) is an ANSIstandard that is written and published by the IEEE. Thisstandard is intended to identify requirements that applyto outdoor electrical transmission, distribution, and com-munication systems, equipment, and associated workpractices, as opposed to premises wiring, which isaddressed in the NEC. The NESC is the base standardthat provided the starting point for OSHA when 29 CFR1910.269 was being written.

NFPA 70B, Recommended Practices for ElectricalEquipment Maintenance, is a document whose purpose is to reduce hazards to life and property that can result from failure or malfunction of industrialand commercial electrical systems and equipment.Along with its maintenance guidance, it alsoaddresses electrical safety.

The National Electrical Manufacturers Association(NEMA) has many standards on electrical productsand systems. NEMA standards often have served as a basis for Underwriter Laboratories (UL) safety stan-dards. Both NEMA and UL standards are designed asconsensus standards and are considered as minimalrequirements.

The Color Book Series by the Institute of Electricaland Electronic Engineers (IEEE) provides recom-mended practices and guidelines that go beyond theminimum requirements of the NEC, NEMA, and ULstandards. When designing electrical power systemsfor industrial and commercial facilities, considerationshould be given to the design and safety requirementsof the IEEE color books listed in Annex D.

The need for unified international standards was identified many years ago. The U.S. standards systemis essentially voluntary. In some parts of the world,governments essentially mandate adherence to the

Question (2): I note that OSHA has not incorporated thepersonal protective equipment portions of NFPA 70E byreference in 1910.132 (personal protective equipment,general requirements) or 1910.335 (safeguards for per-sonal protection). Does an employer have an obligationunder the General Duty Clause to ensure that its ownemployees comply with personal protective equipmentrequirements in NFPA 70E?

Answer (partially reprinted)These provisions are written in general terms, requiring,for example, that personal protective equipment be provided where necessary by reason of hazards...(1910.132(a)), and requiring the employer to selectequipment that will protect the affected employee fromthe hazards.... (1910.132(d)(1)). Also, 1910.132(c)requires the equipment to be of safe design and con-struction for the work performed.

Similarly, 1910.335 contains requirements such as the provision and use of electrical protective equipmentthat is appropriate for the specific parts of the body to be protected and the work to be performed(1910.335(a)(i)). Industry consensus standards, such as NFPA 70E, can be used by employers as guides to making theassessments and equipment selections required by the standard. Similarly, in OSHA enforcement actions,they can be used as evidence of whether the employeracted reasonably.

Industry Consensus Standard NFPA 70EWith respect to the General Duty Clause, industry consensus standards may be evidence that a hazard isrecognized and that there is a feasible means of correcting such a hazard.

Industry consensus standards, such as NFPA 70E, can beused by employers as guides to making the assessmentsand equipment selections required by the standard.Similarly, in OSHA enforcement actions, they can be usedas evidence of whether the employer acted reasonably.

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standards system that is in place. The InternationalElectrotechnical Commission (IEC) standards are anattempt within international communities to reach aconsensus on standard requirements. Significantprogress is being achieved with this objective. Manyof the European governments have mandated stan-dards systems. The European Union (EU) encouragesfurther consensus among affected nations.

In many instances, protection schemes embraced inthe IEC differ from those in the U.S. For example, inthe U.S., nationally recognized testing laboratories are used to perform standardized third party producttesting. Products meeting the testing standard aremarked, identifying the testing laboratory. Many prod-ucts meeting international safety requirements forinstallation in Europe require certification to testingstandards and must bear a CE mark. The CE markapplies to certain directives within European Unioncountries. The intent is to provide a safe product thatis acceptable to all of the EU countries.

With regard to personnel safety, the IEC standardsaddress protection from electrical shock more directlythan U.S. standards. For instance, IEC standards generally recognize that degrees of exposure vary.This idea will be discussed further in the section on IP finger-safe ratings.

III. Establishing an Electrical Safety Program

Reducing and even eliminating exposure to electricalhazards requires continuous attention. An overall elec-trical safety program must be implemented thatemphasizes specific areas of concern. The programmust be well thought out. People who are well versedin safety standards and procedures must write theprogram. Program authors should include safety pro-fessionals, technical professionals, and practitioners.And the program must be published and readily avail-able to all employees. The following are three goodreasons for practicing electrical safety:

Personal reasons, which affect us as caring indi-viduals and employers

Business reasons, because safety makes goodbusiness sense

Regulatory and legal reasons, because violationscan result in fines and/or imprisonment

An essential element in an effective electrical safetyprogram is training. From both a legal and effectivepoint of view, training records are important. Trainingshould be based on the program and procedures inplace within an organization. The training should focusfirst on increasing knowledge and understanding ofelectrical hazards and second on how to avoid expo-sure to these hazards. As a person completes a spe-

cific segment of training, a record should be estab-lished and maintained.

An electrical safety program should accomplish thefollowing objectives:

Make personnel aware of the rules, responsibili-ties, and procedures for working safely in an electrical environment.

Demonstrate the employers intention to complyfully with federal law.

Document general requirements and guidelines toprovide workplace facilities free from unauthorizedexposure to electrical hazards.

Document general requirements and guidelines to direct the activities of personnel, who could beeither deliberately or accidentally exposed to electrical hazards.

Encourage and make it easier for each employeeto be responsible for his or her own electricalsafety self-discipline.

IV. Electrical Safety ProgramAn electrical safety program is vital in establishing anelectrically safe work place and is required:

To reduce electrical hazards, each hazard must beaddressed, as the work is being assigned and planned.An overview of electrical safety requirements can befound in OSHA 29 CFR 1910.3311910.335, Safety-Related Work Practices. These requirements containinformation on qualified vs. unqualified persons, trainingrequirements, work practice selection, use of electricalequipment, and safeguards for personnel protection. Inaddition, NFPA 70E addresses all the key aspects ofelectrical safety and electrical safe work practices. Ifthese requirements are followed completely, injuries and deaths can be prevented.

A. Electrical safety program principles The following principles, when implemented, can helpensure safer work places: 1. Identify and minimize the hazards in electrical

systems. For new systems, designersshould address minimizing hazards inthe electrical system design stage. Forexisting systems, implement upgradesor retrofits that reduce the hazards.

NFPA 70E 110.7 Electrical Safety Program.

(A) General. The employer shall implement an overallelectrical safety program that directs activity appropriatefor the voltage, energy level, and circuit conditions.

FPN: Safety-related work practices are just one compo-nent of an overall electrical safety program.

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2. Plan every job. Most incidents occur when some-thing unexpected happens. Take time to prepare aplan that considers all possible eventualities.Before you start the job, think about each stepand try to visualize the potential for a hazard. Ifneeded, conduct a flash hazard and shock hazardanalysis; NFPA 70E 110.8(B)(1)(a) & (b) haverequirements for these analyses.

3. If possible, put circuit or equipment in an elec-trically safe work condition. An electrically safework condition is an important principle. If theindustry only worked on equipment or circuits thatare in an electrically safe work condition, therewould be far fewer injuries and deaths of an elec-trical origin. For more on electrically safe workcondition, refer to Electrical Incident and HazardPrevention Section.

4. Anticipate unexpected results. When thinkingabout a job, break each task into small steps.Understand that plans can change, so be ready tomodify the plan if necessary. Make sure thateveryone involved in the job is working accordingto the same plan. Whenever work is required nearan electrical hazard, a written plan is needed tooutline the scope of the job.

5. Identify and minimize the hazards for each job.After your work plan is complete, review eachstep. Consider that the equipment might be per-fectly safe under normal conditions and veryunsafe when systems are not working properly.Also consider potential hazards that might beunrelated to electrical energy. If it is impossible toestablish an electrically safe work condition, besure to shut down every possible energy source.Understand that sometimes a de-energized circuitcan become re-energized, and do something tolessen the risk.

6. Assess a workers abilities. Make sure that anyperson assigned to tasks associated with electri-cal energy is qualified and trained for the job athand. He or she must be able to identify electricalhazards, avoid exposure to those hazards, andunderstand the potential results of all action taken.Dont forget to include yourself in this analysis.And dont forget to establish and maintain trainingrecords.

7. Use the right tool for the job. Use the appropri-ate tools for the job at hand, keeping them acces-sible and in good working condition. Using ascrewdriver for a job that requires a fuse puller isan invitation to an incident. Unless the componentis listed for the purpose, fuses must never be

installed or removed when the circuit isenergized.

8. Isolate the equipment. The best way to avoid anincident is to reduce exposure to hazards. Keepdoors closed. Keep barricades in place. Installtemporary voltage-rated blankets coveringexposed live parts.

9. Protect the person. Use appropriate PPE for thejob. This equipment might include safety glasses orface shield, head protection, voltage-rated gloves,safety belts and harness, or flame-resistant clothing.

10. Inspect/evaluate the electrical equipment. Besure the equipment is suitable for its use, where itis applied, and in good working condition.

11. Maintain the electrical equipments insulationand enclosure integrity. As an example, ifrepairs or changes must be made, use compo-nents meeting the original specifications.

12. Audit these principles. A principle is somethingyou believe in enough to be willing to do. Are youwilling to take the steps necessary to avoid injury?Review these principles often. Add to them whennecessary.

B. Electrical safety program controlsControls can ensure the electrical safety program is implemented properly. Some controls include thefollowing:1. Implement an Energized Work Permit procedure

and culture.2. All conductors or equipment are considered

energized until verified otherwise.3. No bare-hand work on exposed conductors or

circuits above 50V to ground that have not beenplaced in an electrically safe work condition,unless the bare-hand method is necessary andproperly used.

4. The tasks while de-energizing and putting aconductor or circuit in an electrically safework condition are in themselves hazardous.Take proper precautions and wear the appropriatePPE while putting circuits in an electrically safework condition.

5. Responsibilities: employers develop programsand training, and the employees apply them.

6. Use procedures as tools. Procedures are thebest way to help you prepare, execute, and com-plete the job. Like any tools, make sure your pro-cedures are maintained.

7. Train employees to qualify them for working inan environment influenced by the presence ofelectrical energy.

8. Hazard determination: use a logical approach todetermine the potential hazards associated withdoing tasks.

9. Precautions: identify and use precautions appro-priate to the working environment.

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C. Electrical safety program procedures All electrical work should be planned before the workbegins, and the work should be done to approved procedures that comply with safe work practices. Fornon-hazardous electrical work, the plan is typicallyunwritten. Jobs that are done repeatedly should havea written procedure, which is followed each time thework is performed. Written or not, all plans must con-sider all hazards and guard against them. A qualifiedperson who understands the work to be done andhazards involved as well as is familiar with the equip-ment being worked on, should prepare written proce-dures. Written procedures must include a step-by-stepoutline of the work to be performed and a single-linediagram or other appropriate drawings that can beused to discuss the job. Procedures for work per-formed should be reviewed with the appropriate individuals responsible.

Procedures typically come in two varieties: those writ-ten specifically to plan a particular job or more generalprocedures that include a checklist or a simple verbalplan. Procedures can include:

Purpose of task Number of workers and their qualifications Hazardous nature and extent of task Shock approach boundaries and flash protection

boundaries Safe work practices to be utilized Personal protective equipment required Insulating materials and tools required Special precautionary techniques Electrical diagrams and one-line diagrams Equipment details Sketches of unique features Reference data

D. Hazard risk evaluationEvery electrical safety program must include a proce-dure for analyzing the risks and hazards associatedwith each job. This analysis must include an evalua-tion of hazards, work procedures, special precautions,energy source controls, and PPE requirements. If thework tasks include working on or near exposed elec-trical parts that have not been put in an electricallysafe work condition, then 70E-110.8(B)(1) requires anelectrical hazard analysis. This includes a shock haz-ard analysis and flash hazard analysis. If necessary,these analyses will determine the appropriate shockapproach boundaries, flash protection boundaries,personal protective equipment, and tools required forspecific tasks. The analyses should be documentedand retained.

The hazard/risk analysis can only be performed afterthe task planning process is complete. In concept,each step of a task should be analyzed in accordancewith a defined protocol. Each step of the protocolshould take a step closer to understanding if a risk isassociated with the task. In performing a hazard/riskanalysis, analyzing the exposure to electrical hazardsmust be the main focus.

Identifying the necessary PPE is also important toprotect the person should there be an accidentalrelease of energy. For instance, the first step shouldbe to determine if the equipment or service mustremain energized while the task is executed. Whenthe questions are answered, the task is defined interms of the amount of voltage and energy availablein the system while the work is executed.

Note: The preferred work practice is to establish anelectrically safe work condition prior to execut-ing the task. PPE is necessary until the electri-cally safe work condition is established.

NFPA 70E has a sample risk/hazard analysis flow dia-gram in Annex G.

E. Job briefingNFPA 70E 110.7(G) requires that prior to the start of a job the involved workers shall be briefed on suchtopics as hazards associated with the job, work proce-dures, special precautions, energy source controls,and PPE required. If the days work is repetitive orsimilar, a job briefing shall be conducted prior to thefirst job of the day. Contractors typically do a tailgatebriefing at the beginning of the day. During the courseof the days work, if there are significant changes,additional briefing(s) shall be conducted. If the work is routine, then the briefing can be short. A more in-depth briefing is required if the work is complicated,hazardous, or the workers cannot be expected to rec-ognize the hazards involved. See NFPA 70E Annex I,Job Briefing and Planning Checklist.

F. Incident and injury prevention The following actions should be undertaken in everyelectrical safety program:

Review programs for the inspection and/or repairof portable electrical equipment for completenessand effectiveness.

Review policies concerning work permits on ener-gized circuits with a goal of reducing the frequencyof such work.

Emphasize electrical worker training inthe following areas: Lockout/tagout practices Use of protective equipment

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Use of insulated tools Minimum approach distances Meter selection/testing/use Electrical rescue/CPR

Include a pre-task review of the following forsupervision of selected electrical work: Goals of the task Task methodology (energized vs. lockout/tagout) Qualifications of assigned personnel proper

instrumentation/tools Adequate protective equipment and usage Methods of preventing a fall should a shock occur

Perform an inventory of energized electrical circuits with a goal of disconnecting unused circuits from the source and removing the wiring.

Employees must be provided training that includesinformation about electrical risks, such as inadequategrounding, reverse polarity, and probable electricshock-producing equipment, including extensioncords, plugs, and portable power tools. The dangersof energized and unattended appliances should bestressed in this training as well as the theory behindlockout and tagout procedures. Employees workingwith electricity must also be informed on how to rec-ognize electric shock victims, safe methods of rescue,and cardiopulmonary resuscitation.

G. Designing an electrical system for safety It is advisable that the electrical safety programincludes a process to consider improvements to exist-ing electrical systems and better designs for workersafety for new systems. There are numerous electricalsystem and equipment design considerations that canimprove safety for workers. Some ideas for systemdesign and system upgrades are presented inSuggestions for Limiting the Arc-flash and ShockHazards, Section X.

V. Electrical Hazards Electricity has become such an integral part of our society that it often is taken for granted. Yet, electricityremains a very dangerous hazard for people working onor near it. Many electrical circuits do not directly poseserious shock or burn hazards by themselves. However,many of these circuits are found adjacent to circuits withpotentially lethal levels of energy. Even a minor shockcan cause a worker to rebound into a lethal circuit orcause the worker to drop a tool into the circuit.

Involuntary reaction to a shock might alsoresult in bruises, bone fractures, and evendeath from collisions or falls.

The following are recognized as commonelectrical hazards that can cause injury, and

even death, while a person works on or near electricalequipment and systems:

Electrical shock Electrical burns from contact (current) and flash

(radiant) Arc-blast impact from expanding air and vaporized

materials

In the next several sections, electrical shock, arc-flash, and arc-blast will be discussed in more depth. In addition, a section on the term electrically safework condition explains the steps necessary toachieve this condition. NFPA 70E 110.8(B)(1) requires an electrical hazard analysis if workers will be exposed to electrical parts that have not beenplaced in an electrically safe work condition. This shallinclude a Shock Hazard Analysis and Flash HazardAnalysis, which will also be covered in other sections.

A. Electrical shock More than 30,000 non-fatal electrical shock incidentsare estimated to occur each year. The National SafetyCouncil estimates that from 600 to 1,000 people dieevery year from electrocution. Of those killed with voltages less than 600V, nearly half were working onexposed energized circuits at the time the fatal injuryoccurred. Electrocution continues to rank as the fourthhighest cause of industrial fatalities (behind traffic, violence/homicide, and construction incidents). Most personnel are aware of the danger of electricalshock, even electrocution. It is the one electrical hazardaround which most electrical safety standards havebeen built. However, few really understand just how littlecurrent is required to cause injury, even death. Actually,the current drawn by a 7 W, 120V lamp, passing acrossthe chest, from hand-to-hand or hand-to-foot, is enough to cause fatal electrocution.

The effects of electric current on the human bodydepend on the following:

Circuit characteristics (current, resistance, frequency, and voltage)

Contact resistance and internal resistance of the body The currents pathway through the body, determined

by contact location and internal body chemistry Duration of the contact Environmental conditions that affect the bodys

contact resistance

OSHA 1910 Subpart S - 1910.333(a)Safety-related work practices shall be employed to prevent electric shock or other injuries resulting fromeither direct or indirect electrical contacts, when work isperformed near or on equipment or circuits which are ormay be energized. The specific safety-related work prac-tices shall be consistent with the nature and extent ofthe associated electrical hazards

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To understand the currents possible in the human body,it is important to understand the contact resistance ofskin (see Table V(A)(1)). The skins resistance canchange as a function of the moisture present in its exter-nal and internal layers, with changes due to such factorsas ambient temperatures, humidity, fright, and anxiety.

Table V(A)(1). Human Resistance Values for Skin-Contact Conditions*

Resistance (ohms)

Condition Dry Wet

Finger touch 40,000 to 1,000 4,000 to 15,000

Hand holding wire 15,000 to 50,000 3,000 to 6,000

Finger-thumb grasp 10,000 to 30,000 2,000 to 5,000

Hand holding pliers 5,000 to 10,000 1,000 to 3,000

Palm touch 3,000 to 8,000 1,000 to 2,000

Hand around 1,000 to 3,000 500 to 1,5001 inch pipe

Two hands around 500 to 1,500 250 to 7501 inch pipe

Hand immersed 200 to 500

Foot immersed 100 to 300

Human body, internal, 200 to 1,000excluding skin

*This table was compiled from data developed by Kouwenhoven and Milnor.

Body tissue, vital organs, blood vessels and nerve (non-fat) tissue in the human body contain water andelectrolytes, and are highly conductive with limitedresistance to alternating electrical current. As the resist-ance of the skin is broken down by electrical current,resistance drops and current levels increase.

The human body could be considered as a resistor withhand-to-hand resistance (R) of only 1,000 Ohms. Thevoltage (V) determines the amount of current passingthrough the body.

While 1,000 Ohms might appear to be low, even lowerlevels can be approached by a person with sweat-soaked cloth gloves on both hands and a full-handgrasp of a large, energized conductor and a groundedpipe or conduit. Moreover, cuts, abrasions or blisters onhands can negate skin resistance, leaving only internalbody resistance to oppose current flow. A circuit in therange of 50V could be dangerous in this instance.

Ohms Law: I (amps) = V (volts) / R (ohms) Example 1: I = 480 / 1000 = 480mA (or 0.480A) Product standards consider 4 to 6mA to be the safeupper limit for children and adults (hence the reason a5-milliamp-rated GFCI circuit). Note: GFCIs do not protect against a line-to-neutral or a

line-to-line shock.

Electrical currents can cause muscles to lock up, result-ing in an inability of a person to release his or her grip

from the current source. This is known as the let-gothreshold current. This current level varies with the frequency (see Table V(A)(2)). DC currents usuallycause a single twitch and are considered less danger-ous at lower voltage levels. Alternating currents in thefrequency range of skeletal muscles (40 to 150Hz) aremore serious (e.g., 60Hz). At 60Hz, most females have a let-go limit of about 6 milliamperes (mA), with an average of 10.5mA. Mostmales have a let-go limit above 9mA, with an averageof 15.5mA. (These limits are based on smaller averagesize of females. Therefore, a small man could have alower limit, or a larger woman a higher limit.)Sensitivity, and potential injury, also increase with time.A victim who cannot let go of a current source is muchmore likely to be electrocuted than someone whosereaction removes them from the circuit more quickly.The victim who is exposed for only a fraction of a sec-ond is less likely to sustain an injury. The most damaging path for electrical current is throughthe chest cavity (see A and D in Figure V(A)) and head.In short, any prolonged exposure to 60Hz current of10mA or more might be fatal. Fatal ventricular fibrillationof the heart (stopping of rhythmic pumping action) canbe initiated by a current flow of as little as several mil-liamps. These injuries can cause fatalities resulting fromeither direct paralysis of the respiratory system, failureof the rhythmic heart pumping action, or immediateheart stoppage.

Table V(A)(2). The Effects of Electrical Current on the Body*

Effects Current (mA)Direct Current Alternating Current

60Hz 10HzMen Women Men Women Men Women

Slight sensation 1 0.6 0.4 0.3 7.0 5.0on handMedian 6.2 3.5 1.1 0.7 12.0 8.0perception thresholdShock-not 9.0 6.0 1.8 1.2 17.0 11.0painful; without loss of muscularcontrolPainful shock- 62.0 41.0 9.0 6.0 55.0 37.0threshold for muscular control loss Painful shock- 76.0 51.0 16.0 10.5 75.0 50median let-go thresholdPainful and 90.0 60.0 23.0 15.0 94.0 63.0severe shock-breathing difficult; loss of muscular control* Modified from Deleterious Effects of Electric Shock by

Charles F. Dalziel.

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During fibrillation, the victim might become uncon-scious. On the other hand, he or she might be con-scious, deny needing help, walk a few feet, and thencollapse. Death could occur within a few minutes ortake hours. Prompt medical attention is needed foranyone receiving electrical shock. Many of these peo-ple can be saved, provided they receive proper med-ical treatment, including cardiopulmonary resuscitation(CPR) quickly.

(A) Touch (B) Step (C and D) Touch/StepPotential Potential Potential

Figure V(A). Current Pathways through the BodyTable V(A)(3). Effects of Electrical Shock (60Hz AC)Response* 60hz, AC Current

Tingling sensation 0.5 to 3mA

Muscle contraction and pain 3 to 10mA

Let-go threshold 10 to 40mA

Respiratory paralysis 30 to 75mA

Heart fibrillation; might clamp tight 100 to 200mA

Tissue and organs burn More than 1,500mA* The degree of injury also depends on the duration and frequency

of the current.

Think of electrical shock injuries as icebergs, wheremost of the injury is unseen, below the surface.Entrance and exit wounds are usually coagulatedareas and might have some charring, or these areasmight be missing, having exploded away from thebody due to the level of energy present. The smallerthe area of contact, the greater the heat produced.For a given current, damage in the limbs might be thegreatest, due to the higher current flux per unit ofcross-sectional area.

Within the body, the current can burn internal bodyparts in its path. This type of injury might be difficult todiagnose, as the only initial signs of injury are theentry and exit wounds. Damage to the internal tissues,while not apparent immediately, might cause delayedinternal tissue swelling and irritation. Prompt medicalattention can minimize possible loss of blood circula-tion and the potential for amputation of the affected

extremity, and can prevent death.

All electrocutions are preventable. A sig-nificant part of the OSHA standard is dedi-cated to electrical safety. It would be anoversimplification to state that everyone

should comply with the standards. However, OSHAstandard compliance is considered a minimumrequirement and seen as a very good place to start for improving the safety of the workplace.

Any time an electrocution occurs, potential for both acivil lawsuit and an OSHA citation exists. It is always agood proactive measure to review internal safety pro-cedures when investigating industrial incidents. Theinvestigator must make sure that he or she has anaccurate set of facts to work with. Incidents arealways costly, and most can be avoided.

Several standards offer guidance regarding safeapproach distances to minimize the possibility ofshock from exposed electrical conductors of differentvoltage levels. The most recent, and probably themost authoritative guidance, is presented in NFPA70E. Safe approach distances to exposed energizedelectrical conductors are discussed in Section IX(D) ofthis handbook.

B. Arcing faults: arc-flash and arc-blast

1. Arc fault basicsFollowing is a graphical model of an arcing fault andthe physical consequences that can occur. The uniqueaspect of an arcing fault is that the fault current flowsthrough the air between conductors or a conductor(s)and a grounded part. The arc has an associated arcvoltage because there is arc impedance. The productof the fault current and arc voltage in a concentratedarea, results in tremendous energy being released inseveral forms.

The resulting energies can be in the form of radiantheat, intense light, and tremendous pressures. Intenseradiant heat from the arcing source travels at thespeed of light. The temperature of the arc terminalscan reach approximately 35,000F, or about four timesas hot as the surface of the sun. No material on earthcan withstand this temperature. The high arc tempera-ture changes the state of conductors from solid to hotmolten metal and to vapor. The immediate vaporiza-tion of the conductors is an explosive change in statefrom solid to vapor. Copper vapor expands to 67,000times the volume of solid copper. Because of theexpansive vaporization of conductive metal, a line-to-line or line-to-ground arcing fault can escalate into athree-phase arcing fault in less than a thousandth of a second.

The extremely high release of thermal energy super-heats the immediate surrounding air. The air alsoexpands in an explosive manner. The rapid vaporiza-tion of conductors and superheating of air result inhigh pressure waves and a conductive plasma cloud,that if large enough, can engulf a person. The thermalshock and pressures can violently destroy circuit com-

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ponents. The pressure waves hurl the destroyed, frag-mented components like shrapnel at high velocity;shrapnel fragments can be expelled in excess of 700miles-per-hour. Molten metal droplets at high tempera-tures typically are blown out from the event due to thepressure waves.

Testing has proven that the arcing fault current magni-tude and time duration are the most critical variablesin determining the energy released. It is important tonote that the predictability of arc-faults and the energyreleased by an arc-fault is subject to significant vari-ance. Some of the variables that affect the outcomeinclude: available bolted short-circuit current, the timethe fault is permitted to flow (speed of the overcurrentprotective device), arc gap spacing, size of the enclo-sure or no enclosure, power factor of fault, systemvoltage, whether the arcing fault can sustain itself,type of system grounding scheme, and distance theworkers body parts are from the arc. Typically, engi-neering data that the industry provides concerningarcing faults is based on specific values of these variables. For instance, for 600V and less systems,much of the data has been gathered from testing onsystems with an arc gap spacing of 1.25 inches andincident energy determined at 18 inches from thepoint of the arc-fault.

2. Arc-flash and arc-blastAs previously discussed an arcing fault releases thermal energies and pressure. The effects of arcingfaults can be broadly categorized as arc-flash andarc-blast. The arc-flash is associated with the releaseof tremendous thermal energies and the arc-blast isassociated with the release of tremendous pressure.The industry is devising ways to quantify the risksassociated with arc-flash hazards. However, there islittle or no information on arc-blast hazard risk assess-ment or on protecting workers due to the arc-blasthazard. Neither NFPA 70E nor the current edition ofIEEE 1584 Guide For Performing Arc-flash HazardCalculations, account for the pressure and shrapnelthat can result due to an arcing fault.

3. How arc-faults can affect humans Nearly everyone is aware that an electrical shock is ahazard that can ultimately lead to death. In fact, whilemany people have experienced minor shocks, fewhave realized any real consequences, making themsomewhat complacent. In contrast, few people areaware of the extreme nature of electrical arc-faults;the potential of severe burns associated from arc-flashand the potential injuries due to high pressures fromarc-blast. But this is starting to change, people arelearning that the effects of an arcing fault can be dev-astating to humans.

In recent years, awareness of arc-flash hazards hasbeen increasing. Recent studies of reported electricalinjuries have indicated that as many as 80 percent ofdocumented injury cases were burns resulting fromexposure to electrical arcs. In addition, each year morethan 2,000 people are admitted to burn centers in theU.S. with severe electrical burns. Electrical burns areconsidered extremely hazardous for a number of rea-sons. One important reason is that contact with the cir-cuit is not necessary to incur a serious, even deadly,burn. Serious or fatal burns can occur at distances ofmore than 10 feet from the source of a flash.

Since burns are such a prevalent consequence ofelectrical incidents, the three basic types are men-tioned below. These can be due to contact (shockhazard) or arc-flash.

Electrical burns due to current flow tissuedamage (whether skin deep or deeper) occursbecause the body is unable to dissipate the heatfrom the current flow through the body. The dam-age to a persons tissue can be internal and ini-tially not obvious from external examination.Typically, electrical burns are slow to heal and frequently result in amputation.

Arc burns by radiant heat caused by electricalarcs. Temperatures generated by electric arcs canburn flesh and ignite clothing at distances of 10 feet or more.

Thermal contact burns normally experiencedfrom skin contact with the hot surfaces of over-heated electric conductors or a persons clothingapparel that ignites due to an arc-flash.

The human body survives in a relatively narrow temperature range around 97.7F. Studies show thatwhen the skin temperature is as low as 110F, thebodys temperature equilibrium begins to break downin about 6 hours. At 158F, only one second durationis sufficient to cause total cell destruction. Human skinat temperatures of 205F for more thanone-tenth of one second can cause incur-able, third-degree burns (see Table V(B)).

Electrical Arc

Copper Vapor:Solid to Vapor

Expands by67,000 times

Intense Light

Hot Air-Rapid Expansion

35,000 F

Pressure Waves

Sound Waves

Molten Metal

Shrapnel

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Table V(B). Skin Temperature Tolerance RelationshipSkin

Temperature Duration Damage Caused

110F 6.0 hours Cell breakdown begins

158F 1.0 second Total cell destruction

176F 0.1 second Curable (second-degree) burn

205F 0.1 second Incurable (third-degree) burn

For evaluating burns, protective proprieties of per-sonal protection equipment, and the thermal energyresulting from an arc-flash, the industry has pro-gressed to utilizing calories/centimeters2 (cal/cm2) as a unit of measure. For instance, the incident energy is a measure of thermal energy at a specific distancefrom an arc-fault; the unit of measure is typically incal/cm2. Another example where cal/cm2 is used as ameasure is for various types of PPE with distinct lev-els of thermal protection capabilities rated in cal/cm2.

1.2 cal/cm2 is considered the threshold for a curable (second-degree) burn.

Note: medical treatment may still be required if bare skin is exposed to this level of flash full recovery would be expected.

In addition to burn injuries, victims of arcing faults can experience damage to their sight, hearing, lungs,skeletal system, respiratory system, muscular system,and nervous system. The speed of an arcing fault eventcan be so rapid that the human system can not reactquickly enough for a worker to take corrective meas-ures. The radiant thermal waves, the high pressurewaves, the spewing of hot molten metal, the intenselight, the hurling shrapnel, and the hot, conductiveplasma cloud can be devastating in a small fraction of asecond. The intense thermal energy released can causesevere burns or ignite flammable clothing. Molten metalblown out can burn skin or ignite flammable clothing.Failure to remove or extinguish burning clothing quicklyenough can cause serious burns over much of the body.A person can gasp and inhale hot air and vaporizedmetal sustaining severe injury to their respiratory sys-tem. The tremendous pressure blast from the vaporiza-tion of conducting materials and superheating of air canfracture ribs, collapse lungs and knock workers off lad-ders or blow them across a room.

What is difficult for people to comprehend is that thetime in which the arcing fault event runs its course mayonly be a small fraction of a second. In a matter of only a thousandth of a second or so, a single phase arcing fault can escalate to a three phase arcing fault.Tremendous energies can be released in a few hun-

dredths of a second. Humans can notdetect, much less comprehend and react to events in these time frames.

There is a greater respect for arcing faultand shock hazards on medium and high

voltage systems. However, injury reports show seriousaccidents are occurring at an alarming rate on systemsof 600V or less (notably 480V systems and to a lesserdegree 208V systems), in part because of the high faultcurrents that are possible. But also, designers, manage-ment and workers mistakenly tend not to take the nec-essary precautions that they take when designing orworking on medium and high voltage systems.

VI. The Role of OvercurrentProtective Devices In Electrical Safety

If an arcing fault occurs while a worker is in closeproximity, the survivability of the worker is mostlydependent upon (1) the characteristics of the overcur-rent protective devices, (2) the arc-fault current, and(3) precautions the worker has taken prior to theevent, such as wearing personal protective equipmentappropriate for the hazard. The selection and perform-ance of overcurrent protective devices play a signifi-cant role in electrical safety. Extensive tests andanalysis by industry have shown that the energyreleased during an arcing fault is related to two characteristics of the overcurrent protective deviceprotecting the affected circuit:

1. The time it takes the overcurrent protectivedevice to open. The faster the fault is cleared bythe overcurrent protective device, the lower theenergy released.

2. The amount of fault current the overcurrent pro-tective device lets through. Current-limiting over-current protective devices may reduce the currentlet-through (when the fault current is within thecurrent-limiting range of the overcurrent protec-tive device) and can reduce the energy released.

Lowering the energy released is better for both workersafety and equipment protection. The photos andrecording sensor readings from actual arcing faulttests (next page) illustrate this point very well. An adhoc electrical safety working group within the IEEEPetroleum and Chemical Industry Committee con-ducted these tests to investigate arc-fault hazards.These tests and others are detailed in Staged TestsIncrease Awareness of Arc-Fault Hazards in ElectricalEquipment, IEEE Petroleum and Chemical IndustryConference Record, September 1997, pp. 313-322.This paper can be found at www.bussmann.comunder Services/Safety BASICs. One finding of thisIEEE paper is that current-limiting overcurrent protec-tive devices reduce damage and arc-fault energy (provided the fault current is within the current-limitingrange). To better assess the benefit of limiting the cur-rent of an arcing fault, it is important to note some keythresholds of injury for humans. Results of these testswere recorded by sensors on mannequins and can becompared to these parameters:

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Thresholds for injury to humans Just Curable Burn Threshold: 80C / 176F (0.1 sec) Incurable Burn Threshold: 96C / 205F (0.1 sec) Eardrum Rupture Threshold: 720 lbs/ft2 Lung Damage Threshold: 1728 - 2160 lbs/ft2 OSHA Required Ear Protection Threshold: 85db

(for sustained time period)*

*An increase of 3db is equivalent to doubling the sound level.

Staged arc-flash testsTest 4, Test 3 and Test 1: General All three of thesetests were conducted on the same electrical circuitset-up with an available bolted three-phase, short-circuit current of 22,600 symmetrical rms amps at480V. In each case, an arcing fault was initiated in aSize 1 combination motor controller enclosure with the door open, as if an electrician were working on the unit while energized or before it was placed in anelectrically safe work condition. Test 4 and Test 3 wereidentical except for the overcurrent protective deviceprotecting the circuit. In Test 4, a 640A circuit breakerwith a short-time delay is protecting the circuit; the cir-cuit was cleared in 6 cycles. In Test 3, KRP-C-601SP,601A, current-limiting fuses (Class L) are protectingthe circuit; they opened the fault current in less than cycle and limited the current. The arcing fault was ini-tiated on the line side of the motor branch circuitdevice in both Test 4 and Test 3. This means the faultis on the feeder circuit but within the controller enclo-sure. In Test 1, the arcing fault is initiated on the loadside of the branch circuit overcurrent protectivedevices, which are LPS-RK 30SP, 30A, current-limit-ing fuses (Class RK1). These fuses limited this faultcurrent to a much lower amount and clear the circuitin approximately cycle or less.

A couple of conclusions can be drawn from this testing:1. Arcing faults can release tremendous amounts of

energy in many forms in a very short period oftime. All the measured values can be compared tokey thresholds of injury for humans given in a pre-vious paragraph. Test 4 was protected by a 640A,non-current-limiting device that opened in 6 cyclesor second (0.1 second).

2. The overcurrent protective devices characteristiccan have a significant impact on the outcome. A601A current-limiting overcurrent protectivedevice, protects the circuit in Test 3. The currentthat flowed was reduced (limited), and the clearingtime was cycle or less. This was a significantreduction compared to Test 4. Compare the Test 3measured values to the key thresholds of injuryfor humans and the Test 4 results. The measuredresults of Test 1 are significantly less than those in

Test 4 and even those in Test 3. The reason isthat Test 1 utilized a much smaller (30A), current-limiting device. Test 3 and Test 1 both show thatthere are benefits of using current-limiting over-current protective devices. Test 1 just proves thepoint that the greater the current-limitation, themore the arcing fault energy may be reduced.Both Test 3 and Test 1 utilized very current-limitingfuses, but the lower amps-rated fuses limit thecurrent more than the larger amps rated fuses. Itis important to note that the fault current must bein the current-limiting range of the overcurrent pro-tective device to receive the benefit of the lowercurrent let-through. See the diagram that depictsthe oscillographs of Test 4, Test 3 and Test 1.

3. The cotton shirt reduced the thermal energy expo-sure on the chest (T3 measured temperatureunder the cotton shirt). This illustrates the benefitof workers wearing protective garments.

Non-Current Limiting

Test 1

Test 4

Test 3 Reduced Fault Currentvia Current-Limitation

Current-Limitation: Arc-Energy ReductionCurrent-Limitation: Arc-Energy ReductionCurrent-Limitation: Arc-Energy Reduction

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Following are the results recorded from the various sensors on the mannequin closest to the arcing fault. T1 and T2 recorded the temperature onthe bare hand and neck respectively. The hand with T1 sensor was very close to the arcing fault. T3 recorded the temperature on the chest underthe cotton shirt. P1 recorded the pressure on the chest. And the sound level was measured at the ear. Some results pegged the meter. That is,the specific measurements were unable to be recorded in some cases because the actual level exceeded the range of the sensor/recorder set-ting. These values are shown as >, which indicates that the actual value exceeded the value given but it is unknown how high of a level the actualvalue attained.

Photos and results Test 4: Staged test protected by circuit breaker with short-time delay (not a current-limiting overcurrent protective device).Short-time delay intentionally delayed opening for six cycles (0.1 second). Note: Unexpectedly, there was an additional fault in the wirewayand the blast caused the cover to hit the mannequin in the head.

Photos and results Test 3: Staged test protected by KRP-C-601SP LOW-PEAK current-limiting fuses (Class L). These fuses were in their cur-rent-limiting range and cleared in less than a cycle (0.0083 seconds).

Photos and results Test 1: Staged test protected by LPS-RK-30SP, LOW-PEAK current-limiting fuses (Class RK1). These fuses were in current-limiting range and cleared in approximately cycle (0.004 seconds).

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1 2 3

4 5 6

1 2 3

4 5 6

1 2 3

4 5 6

VII. Attending to Electrical IncidentVictims

A. Preparedness Site personnel should be trained in CPR and first-aidtechniques to prepare for possible electrical incidents.CPR training and periodic retraining of site personnelmust be carefully planned and documented.

First-aid supplies approved by the consulting physi-cian should be easily accessible when required. Thefirst-aid kit should consist of materials approved bythe consulting physician, in a weatherproof containerwith individually sealed packages for each type ofitem. The contents of the first-aid kit should bechecked weekly to ensure that all supplies are present and in good order.

Plans must be in place for transporting incident vic-tims to a physician or hospital. Recovery of electricalincident victims can be greatly enhanced if they arequickly transported to a burn center or other medicalfacility that specializes in electrical trauma. Employersshould evaluate medical facilities in their area anddetermine in advance where such victims should betaken and how they will be transported. Emergencytelephone numbers and specific instructions should be conspicuously posted. All employees should bethoroughly familiar with the procedures.

Locations of eyewash stations and safety showersmust be posted so that they are easily found to cooland flush the burn victim after an incident.

B. Effects of electrical incidents Electrical incidents and the complexities of the traumathey cause to the human body historically have beensurrounded by mystery and lack of understanding. Asmore knowledge is gained about electrical trauma,strategies for effectively handling the emergency andways to improve hospital treatment of victims becomemore apparent. In addition, research suggests ways inwhich workplace supervisors and responders can helpan incident victims caregivers provide appropriatemedical attention.

In the case of an electrical incident, the extent ofinjury to the victim often is not immediately apparent.Some symptoms might be masked by the more read-ily apparent thermal effects of the injury (burns).Caregivers must be aware of additional possible biological effects of electric shock.

In an arc-flash or arc-blast energy incident, the victims skin, ears, eyes, lungs, internal organs, andnervous, muscular, and skeletal systems can beaffected not only by the direct effects of electrical current, but also by the following:

Radiant heat from an electrical arc that producesextremely high temperatures

Disturbance of the hearts electrical conduction,causing changes in the heart rhythm or possiblecardiac arrest

Barotrauma from the acoustic and vibratory forcesaround arc-blast

Inhaled or deposited vapors released through anarc explosion

Incident victims also are subject to the following typesof injury related to contact with electricity:

Low-voltage contact wounds High-voltage contact wounds of entry and exit of

electrical current Burns Respiratory difficulties (The tongue might swell

and obstruct the airway, or vaporized metal orheated air might have been inhaled.)

Infectious complications Injury to bone through falls, heat necrosis (death

of tissue), and muscle contraction (Shoulder jointinjuries and fracture of bones in the neck are com-mon injuries caused by muscle contraction.)

Injury to the heart, such as ventricular fibrillation,cardiac arrest, or stoppage

Internal organ injuries Neurological (nerve) injury Injury to the eyes (Cataracts from electrical injury

have been reported up to three years after an incident.)

C. Enhancement of chances for recovery In most electrical incidents, the inability to diagnosethe extent of injury at the time of admission to thehospital can delay the patients treatment. Recoverycan be enhanced by more detailed information aboutthe incident, including the system voltage, amount ofavailable current, length of contact with current, andpossibility of arc-flash. Recovery can be maximized bytransporting the victim as quickly as possible to a burncenter or other facility that specializes in treatment ofelectrical trauma.

Procedures In response to an electrical incident, the following procedures should be followed immediately:

Remove the immediate hazard; turn off the power.If you are a witness to an electrical inci-dent, exercise great caution that you do not sustain injury as well. Alwaysassume that the source of electricity isstill energized unless you or another

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qualified person determines that the power hasbeen turned off. Unless you are using insulatedequipment (e.g., voltage-rated gloves, hot sticks,or a rubber blanket) to dislodge a victim, you must delay the rescue effort until the circuit can be interrupted.

Note: Sites must establish a training policy and planto cover electrical rescue methods, approvedrescue devices, and CPR training.

Realize that speed is essential. The victims poten-tial for injury increases with contact time. Theresistance of the body is mostly in the skin. If theskin breaks down electrically, only the low internalbody resistance remains to impede current.

Call for help. Delegate someone else to get help, if possible. Make sure that an ambulance or emer-gency medical service is on the way.

Begin CPR. If the victims pulse or breathing hasstopped, cardiopulmonary resuscitation (CPR) isessential to avoid brain damage, which usuallybegins in four to six minutes. If CPR is needed,make sure assistance is on the way but do notwait for help to arrive. Make sure you and the victim are in a safe zone(not in contact with any electrical source and out of reach of any downed or broken wires). If theperson is unconscious, begin the CPR sequence.

Apply first aid to the victim. If the persons clothing is on fire, remind him/her

to drop and roll, or tackle him/her, if necessary,to smother the flames.

Cool the burn with water or saline for a few min-utes or until the skin returns to normal tempera-ture. (For flash-burn victims, safety showersmight be the best method, due to the possibilityof wide-spread surface burns on the body.) Donot attempt to remove clothing that is stuck to aburn.

Remove constricting items such as shoes, belts,jewelry, and tight collars from the victim.

Elevate burned limbs to reduce swelling. Handle the victim with care, being aware that he

or she might have broken bones or spinalinjuries.

Treat for shock: maintain body temperature, donot give anything by mouth. Administer high concentrations of oxygen, if available.

Keep the victim warm and as comfortable aspossible while awaiting transport to the medical

facility. Cover him or her with clean, drysheets or blankets. Cover burn wound(s)with sterile dressings or clean sheets.

Additional Information

After the victims immediate needs are met, note asmany details of the incident as possible. The detailscan help an incident victims caregivers provide appro-priate medical attention.

It is especially important that hospital personnel knowthe cause of the victims injuries. They need to know ifthe victim had contact with electricity or if arc-flashcaused the injuries.While the victim of electrical contact might suffer somesurface burns where the current entered the body, heor she often suffers additional, less visible (internal)damage because of the path of the current throughthe body.

The flash burn victim is more likely to have greaterevident burn damage on the surface of the body, dueto the extremely high temperatures from arc-flash. Heor she is likely to suffer first, second, and third-degreeburns, especially on the face, wrists, ears, back of thehead, neck, and ankles. Any skin surface that is notcovered adequately by protective clothing or equip-ment is at risk.

In addition to burns to the skin, the flash burn victimalso might have inhaled metal vapor (such as copper)into the lungs or suffered adverse effects (such asdamage to the eardrum) due to the pressure wavecaused by arc-blast.

Advance Help for Incident Victims

Each site should prepare a checklist in advance thatwill provide detailed information about an incident (seethe sample checklist in the Annex A). This list shouldbe a part of a sites emergency response plan forelectrical injuries. This checklist should be readilyavailable on site, and its existence should be commu-nicated to all employees. A completed copy shouldaccompany the victim to the hospital or treatment center, if at all possible.

The information can help to ensure the best possibleevaluation and treatment by initial medical caregivers.

VIII. Who Is Responsible for Safety? In most instances, three distinctly different entities areassociated with a project or site: the employer, theemployee, and the owner. When discussing responsi-bility, it is important to understand the existence ofthese different roles.

The employer can be thought of in terms of a person who represents the company. Theemployer, then, can be the owner of the companyor any member of the line management of theorganization.

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On the other hand, the employee is the electricianor other worker. A first or second line supervisor,then, has two roles. He or she might be a repre-sentative of the company, operating as anemployer, in addition to being an employee.

The term owner has still a different twist. Ratherthan a person, the owner is the entity that ownsthe equipment or facility. The owner has a role and responsibility that is somewhat different fromeither employer or employee.

In The Act, OSHA is chartered to establish require-ments for employers. It has no jurisdiction to assignresponsibilities to employees. Therefore, meetingrequirements defined by OSHA is the responsibility of the employer (management of the company). It isthe employer who must:

provide for a safe workplace establish and implement a safety program establish an enforcement policy to ensure that

employees follow established practices

In the case where a contractor is performing work ona site or facility owned by someone else, some inher-ent responsibilities must be assumed by the owner.Perhaps the most important of those responsibilities isto make sure that the contractor is fully apprised of allhazards existing that might impact the work.

National consensus standards are not similarly con-strained. As a result, NFPA 70E also assigns respon-sibility. Responsibility assigned to the employer is thesame as in 29 CFR 1910, Subpart S. The employersresponsibilities include the development and imple-mentation of an electrical safety program, and thedevelopment of safety procedures and guidelines for an employee safety training program on properimplementation of those procedures.

NFPA 70E suggests that employees are responsiblefor implementing the program and procedures pro-vided by the employer. The standard goes on to suggest that although responsibility of employer andemployee are distinct and clear, the most effectiveprocess is to establish a close working relationshipbetween employer and employee in which each hasvalue for the other as they work together.

IX. Electrical Incident and HazardPrevention

A. Not working on or nearAccording to OSHA 1910.333(a)(1) and NFPA 70E130.1, workers shall not work on or near exposed liveparts except for two demonstrable reasons:1. De-energizing introduces additional or

increased hazards (such as cutting ventilation to a hazardous location) or

2. Infeasible due to equipment design or operationallimitations (such as when performing diagnosticsand testing for startup or troubleshooting and thiswork can only be done when circuits are energized).

So, for circumstances other than the two exceptions, thecircuits/equipment shall be put in an electrically safework condition prior to commencing electrical work.

B. Electrically safe work conditionAn electrically safe work condition is a concept firstintroduced in NFPA 70E. This term is now defined inNFPA 70E Definitions and the steps to put a circuit in an electrically safe work condition are detailed in70E-120.1.

The concept embraces several ideas and suggeststhat six different steps must be taken before an electrical circuit is safe to approach or touch withoutPPE. Electricians and other workers tend to believethat a circuit is safe to approach or touch if it is de-energized. The fact that injuries continue ratherfrequently, based upon this belief, proves that addi-tional steps are needed.

Some people also believe that if a lock and tag areplaced on a labeled disconnecting means, the equip-ment is safe to work on. However, other issues mustbe considered. For example, labels can be markedincorrectly, equipment can be supplied from more than one source, or a temporary conductor could have been installed. It also is feasible that an unrelated energized circuit conductor could contact the conductor leading to the work area.

In other instances, workers outside the area or com-plicated systems can affect the work area. Often it isassumed that if the contact point is tested for absenceof voltage, the point is safe for executing the task. Butthis only proves that no voltage is present at the timeof the voltage test. Voltage could be absent due to aprocess interlock being open, or a second source ofenergy could simply be turned off for the moment.Avoiding incidents and injury requires training, planning, and preparation.

NFPA 70E 120.1 requires a process of six discrete andindependent steps be executed prior to declaring theexistence of an electrically safe work condition. Onlyafter the following steps have been executed can workbegin without possible exposure to an electrical hazard. 1. Determine all possible sources of energy. Review

all reliable and up-to-date drawings, documentation,and identification tags and labels. Drawings mustinclude all energy sources, includingtemporary and back up power sources.

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2. After properly interrupting the load, open all dis-connecting devices for the circuit. At this point, the equipment or circuit is simply de-energized.

3. Where possible, visually verify that all disconnect-ing devices, including drawout circuit breakers,are open. Also check that all disconnectingdevices meet appropriate codes and standards.

4. Apply lockout/tagout devices in accordance withdocumented and established policy. An estab-lished policy is an enforced written proceduremade available to all employees.

5. Use adequately rated voltage testers to verify theabsence of voltage on each point where physicalcontact is expected. Employees are required touse only voltage testing equipment that is rated by a third party.

6. Where the possibility of induced voltage or storedenergy exists, ground the phase conductorsbefore touching them. Where it