NETA Handbook Series I, Arc-Flash Vol 2-PDF

Arc-Flash Safety Handbook Volume 2 Patent Pending UL and CUL Rated

Remote Racking Solutions The CBS ArcSafe Remote Racking System

Distance Is Safety®

CBS ArcSafe Remote Switching Options There are numerous CBS ArcSafe remote switch actuators which enable the system to be used with circuit breakers, motor controls, and other electrical equipment which use a variety of: • Pistol-grip switches • Pushbutton switches • Lever or toggle style control switches • Charge, close and/or tripping

940-382-4411 1-877-4 SAFETY (1-877-472-3389)

PO Box 550 • Argyle, TX 76226 • www.DistanceisSafety.com • [email protected]

Published by InterNational Electrical Testing Association

• Use with low and medium voltage circuit breakers produced by all the major switchgear manufacturers • Use with horizontal and vertical types of air, SF6 and vacuum circuit breakers • Remote operation places operator outside the arc flash protection boundary • Height and angle of the drive is easily adjusted • Quick release drive shafts and couplings simplify setup • Over-racking protection is provided • Battery operated with built-in charger

Published by InterNational Electrical Testing Association

Arc Flash Safety Handbook Volume 2

Published by InterNational Electrical Testing Association

quick-trip™ arc flash reduction switch

DATA SHEET Providing a safer working environment for people working on energized electrical equipment as required by 2011 NEC Article 240.87.

Since arc flash potential is directly related to breaker clearing time, the QUICK-TRIP system provides an easy and safe method to reduce faultclearing time without opening a cubicle door to reprogram the trip unit. The QUICK-TRIP system is activated by means of a padlockable selector switch. When enabled, two additional settings are activated in the AC-PRO trip unit to provide enhanced protection: ❏ QT Instantaneous

System Features

❏ Ground Fault

The QUICK-TRIP system is as easy to use as it is to install, with the additional personnel safety features:

The two individually programmable settings are designed to provide faster clearing times in the event of a fault.

❏ Installation uses standard punches. ❏ Wires in minutes without cutting into existing wiring harness. ❏ QT settings are only active when the selector switch is in the ON position (during maintenance).

Practical Example A technician needs to rack out a feeder breaker for maintenance. In so doing, he is the minimum 18” away from any potential arc flash source in the cubicle. As the breaker is being racked out, a 12,000A arcing fault occurs inside the cubicle. The 2000A main breaker sees the fault and trips, subsequently clearing the fault in the feeder breaker cubicle. The two Time-Current-Curves below illustrate the dramatic impact that arc-clearing time has on incident energy levels. Given that: F = 12kA and D = 18 in. TCC 1: QUICK-TRIP: OFF shows the trip time characteristics of the main breaker.

❏ QUICK-TRIP ON LED confirms operation. ❏ SELF-TEST LED verifies trip unit operation. ❏ QUICK-TRIP settings can be reviewed on the external QT-DISPLAY. ❏ Last Trip Data and all settings can be reviewed on the QT-DISPLAY. ❏ 3-phase currents are displayed continuously on the QT-DISPLAY. ❏ The system is fully powered by the trip unit’s CTs. No aux power or batteries.

TCC 2: QUICK-TRIP: ON shows the trip time characteristics of the main breaker.

TCC 1

❏ Padlocking switch can be incorporated into a lock-out tag-out procedure.

❏ PICK-UP LED indicates overcurrent situations.

❏ The AC-PRO will cause the main breaker to clear the 12kA fault in .556 seconds (based on a Short-Time Delay of .20 seconds with I2T ON). The resulting arc duration will be: t = .556 ❏ The resulting incident energy is: EI =25.8022 ❏ The Hazard Risk Category is: 4

❏ The AC-PRO will now cause the main breaker to clear the 12kA fault in .05 seconds (based on the Instantaneous QT or I QT Pick-Up setting of 8000A). The resulting arc duration will be: t = .05 ❏ The resulting incident energy is: EI = 2.3203 ❏ Hazard Risk Category reduced to: 1

❏ Reduction in arc flash incident energy levels may permit lower PPE clothing for maintenance personnel.

❏ Extra contacts on the selector switch are available for external annunciation.

Call Toll Free: 888.289.2864 For additional information visit our website:

w w w. u t i l i t y r e l a y. c o m

URC Utility Relay Company TCC 2

10100 Queens Way, Chagrin Falls, OH 44023 Phone: 440-708-1000 Fax: 440-708-1177

Arc-Flash Safety Handbook Volume 2

Table of Contents How Do I Perform Arc Flash Labeling to Comply with NFPA 70E? .................................1 Lynn Hamrick

Determining PPE Requirements Using the NFPA 70E Tables ........................................5 Ron Widup and Jim White

Arc Flash vs. Arc Blast “Know The Difference” ............................................................7 Paul Hartman

Practical Implications of Electrical Arc Flash Safety if There Is No Arc Flash Hazard Assessment .............................................................11 Daniel Doan, P.E.

Electrical Safety and Maintenance Training .............................................................15 Dennis K. Neitzel, C.P.E.

Hand Protection for Shock and Arc Flash — How Do I Apply OSHA and NFPA 70E Requirements? .......................................................................................18 Lynn Hamrick

Arc Flash Labels — Why Bother? ..............................................................................22 Ron Widup and Jim White

Layered Clothing — Why It Makes Sense ..................................................................25 Ron Widup and Jim White

So, You Think You’re Qualified? ...............................................................................27 Jim White

The Challenge of High Impedance Faults – Setting and Testing Dilemmas ..................31 Helmut G. Brosz and Peter J.E. Brosz

Tables, Labels, and HRCs ........................................................................................33 Ron Widup and Jim White

Published by

InterNational Electrical Testing Association 3050 Old Centre Avenue, Suite 102, Portage, Michigan 49024

269.488.6382

www.netaworld.org

Arc-Flash Safety Handbook Volume 2

Table of Contents (continued) Methods of Inspection to Determine the Presence of Potential Arc Flash Incidents .....36 Mark Goodman

What Is All This 70E Business? ................................................................................41 Ron Widup and Jim White

Electrical Equipment Performance and the Impact to Personnel ................................46 Kerry Heid and Ron Widup

Application of Existing Technologies to Reduce Arc Flash Hazards ..............................49 Jim Buff and Karl Zimmerman

Arc Flash Protection Utilizing Light Sensing .............................................................58 Chris Gingras

Tripping with the Speed of Light: Arc Flash Protection ..............................................62 Robert A. Wilson P.E., Rainer Harju, Juha Keisala, and Sethuraman Ganesan

NOTICE AND DISCLAIMER NETA Technical Papers and Articles are published by the InterNational Electrical Testing Association. Opinions, views, and conclusions expressed in articles herein are those of the authors and not necessarily those of NETA. Publication herein does not constitute or imply any endorsement of any opinion, product, or service by NETA, its directors, officers, members, employees, or agents (hereinafter “NETA”). All technical data in this publication reflects the experience of individuals using specific tools, products equipment, and components under specific conditions and circumstances which may or may not be fully reported and over which NETA has neither exercised nor reserved control. Such data has not been independently tested or otherwise verified by NETA. NETA makes no endorsement, representation, or warranty as to any opinion, product, or service referenced in this publication. NETA expressly disclaims any and all liability to any consumer, purchaser, or any other person using any product or service referenced herein for any injuries or damages of any kind whatsoever, including, but not limited to, any consequential, special incidental, direct, or indirect damages. NETA further disclaims any and all warranties, express or implied including, but not limited to, any implied warranty or merchantability or any implied warranty of fitness for a particular purpose. Please Note: All biographies of authors and presenters contained herein are reflective of the professional standing of these individuals at the time the articles were originally published. Titles, companies, and other factors may have changed since the original publication date. Copyright © 2009 by InterNational Electrical Testing Association, all rights reserved. No part of this publication may be reproduced in any form or by any means, electronic or mechanical, without permission in writing from the publisher.

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Arc Flash Safety Handbook — Volume 2

How Do I Perform Arc Flash Labeling to Comply with NFPA 70E? NETA World, Winter 2005-2006 Issue by Lynn Hamrick ESCO Energy Services Company

Many industrials have performed arc flash hazard analysis studies for their facilities. However, when they have tried to implement the field labeling associated with results of the arc flash study, they have met with some varying opinions on what is and is not required. This narrative provides information associated with arc flash labeling. It summarizes both current regulations and NFPA 70E criteria. Additionally, it provides recommendations associated with implementing this guidance within the industrial environment. As a starter, excerpts from OSHA requirements, NFPA 70 (NEC), and NFPA 70E are provided below. The requirements and guidance information will be used as the basis for subsequent discussions.

29CFR1910, SubPart S – Electrical “§ 1910.303 General Requirements. (2) Guarding of live parts. 1910.303(2)(iii) states: (iii) Entrances to rooms and other guarded locations containing exposed live parts shall be marked with conspicuous warning signs forbidding unqualified persons to enter.” “§ 1910.335 Safeguards for personnel protection. (b) Alerting techniques.. The following alerting techniques shall be used to warn and protect employees from hazards which could cause injury due to electric shock, burns, or failure of electric equipment parts:

(1) Safety signs and tags. Safety signs, safety symbols, or accident prevention tags shall be used where necessary to warn employees about electrical hazards which may endanger them, as required by 1910.145.

(2) Barricades. Barricades shall be used in conjunction with safety signs where it is necessary to prevent or limit employee access to work areas exposing employees to

uninsulated energized conductors or circuit parts. Conductive barricades may not be used where they might cause an electrical contact hazard. (3) Attendants. If signs and barricades do not provide sufficient warning and protection from electrical hazards, an attendant shall be stationed to warn and protect employees.”

NFPA 70, National Electric Code – 2005 Article 110.16 Flash Protection. Switchboards, panelboards, industrial control panels, meter socket enclosures, and motor control centers that are in other than dwelling occupancies and are likely to require examination, adjustment, servicing, or maintenance while energized shall be field marked to warn qualified persons of potential electric arc flash hazards. The marking shall be located so as to be clearly visible to qualified persons before examination, adjustment, servicing, or maintenance of the equipment. FPN No. 1: NFPA 70E-2004, Standard for Electrical Safety in the Workplace, provides assistance in determining severity of potential exposure, planning safe work practices, and selecting personal protective equipment.

FPN No. 2: ANSI Z535.4-1998, Product Safety Signs and Labels, provides guidelines for the design of safety signs and labels for application to products.” Article 110.27 Guarding of Live Parts. (C) Warning Signs. Entrances to rooms and other guarded locations that contain exposed live parts shall be marked with conspicuous warning signs forbidding unqualified persons to enter.”

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Arc Flash Safety Handbook — Volume 2 ment or a specific work method and be trained to recognize and avoid the electric hazards that might be present with respect to that equipment or work method.

NFPA 70E, Standard for Electrical Safety in the Workplace – 2004 Edition Article 110.6 Training Requirements (D) Employee Training. (1) Qualified Person. A qualified person shall be trained and knowledgeable of the construction and operation of equip-

Figure 1

Figure 2

(a) Such persons shall also be familiar with the proper use of the special precautionary techniques, personal protective equipment, including arc flash, insulating and shielding materials, and insulated tools and test equip-

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Arc Flash Safety Handbook — Volume 2 ment. A person can be considered qualified with respect to certain equipment and methods but still unqualified for others.

(b) An employee who is undergoing on-the-job training and who, in the course of such training, has demonstrated an ability to perform duties safely at his or her level of training and who is under the direction supervision of a qualified person shall be considered to be a qualified person for the performance of those duties.” Article 130.3 Flash Hazard Analysis. A flash hazard analysis shall be done in order to protect personnel from the possibility of being injured by an arc flash. The analysis shall determine the Flash Protection Boundary and the personal protective equipment that people within the Flash Protection Boundary shall use.”

Article 130.3(B) Protective Clothing and Personal Protective Equipment for Application with a Flash Hazard Analysis. Where it has been determined that work will be performed within the Flash Protection Boundary …., the flash hazard analysis shall determine, and the employer shall document, the incident energy exposure of the worker (in calories per square centimeter). The incident energy exposure level shall be based on the working distance of the employee’s face and chest areas from the prospective arc source for the specific task to be performed. Flameresistant (FR)…

Article 130.7(E) Alerting Techniques. (1) Safety Signs and Tags. Safety sign, safety symbols, or accident prevention tags shall be used where necessary to warn employees about electrical hazards that might endanger them. Such signs and tags shall meet the requirements of ANSI Standard Z535 given in Table 130.7(F).

analyses, it will become obvious that working distances are very important in selecting PPE. NFPA 70E has provided the following tables (Figure 1 and Figure 2) for use in making PPE decisions. Remember to include review of the information provided in the table notes, including current Tentative Interim Amendments (TIAs), to ensure appropriate application of the tables. To summarize the discussion so far, the following objectives should be considered while implementing arc flash labeling in a facility: 1. Field marking is required to warn employees of arc flash hazards.

2. Qualified electrical workers should have access to analytical information such as the FPB, working distance, and incident energy so that they can adequately ascertain the level of risk and the appropriate PPE.

Implementation Recommendations There are many ways to implement the labeling requirements. Some implementation recommendations are provided below for typical options being implemented in industrial environments. All of these recommendations meet the labeling requirements discussed above.

Detailed Arc Flash Labeling On Each Component One approach is to provide detailed labeling on each component within the electrical infrastructure of a facility where energized circuits may be exposed to workers.

Discussion From Article 110.16 of the NEC, it is evident that arc flash labels, or field marking, should be provided any place there is a potential for exposing a worker to energized circuitry greater than 50 volts. This field marking should be provided in accordance with the requirements of ANSI Z535. Supporting requirements are provided in the NEC and OSHA standards associated with providing signage to warn employees about the electrical hazards. These requirements are also parroted within applicable NFPA 70E guidance. What is not specifically stated is what should be on the labels. There is some guidance within NFPA 70E as to what information should be made available to assist qualified employees in ascertaining electrical hazards. For arc flash hazards, this guidance includes performing an analysis to determine the Flash Protection Boundary (FPB) and appropriate personal protective equipment (PPE). Also important in selecting PPE is a determination of working distance for the activity to be performed. As one becomes more familiar with dealing with the results of arc flash

Commercially available software programs for electrical systems are available for performing the hazard analysis and for printing the labels to a file. One advantage to implementing this type of process is that the analytical information associated with the arc–flash hazard is on the label, and, with this detailed information, the qualified personnel can make decisions on how to mitigate the hazard. A disadvantage is

4 that the development of the analytical model required for performing this effort can be costly, and, with an infrastructure change, the labels may need to be replaced.

Generic Arc Flash Labeling On Each Component Another approach is to provide generic labeling on each component within the electrical infrastructure of a facility where energized circuits may be exposed to workers.

The advantage to implementing this type of process is that with any infrastructure change, the label need not be replaced. The disadvantage is that the analytical information associated with arc flash hazard that is required for qualified personnel to make decisions about the hazard is not readily available within the label: therefore, another mechanism for providing that information to the worker will be required. Some industrial facilities have procedurally resolved this issue by requiring an energized work permit which requires that the information be provided within the permit. Others have prepared task assessment sheets for each electrical distribution panel and posted them on or near the panels. With either an energized work permit or the task assessment sheets, the needed information is provided for the worker to assist them in selecting appropriate PPE. This application of work task assessment sheets for each panel may also delineate different PPE requirements, similar to Tables 130.7(C)(9)(a) of NFPA 70E, for different work tasks on the panels.

Detailed and Generic Arc Flash Labeling Components The approach which seems to be implemented most of the time is to provide generic labeling for components having a Hazard Risk Category (HRC) of “0” and detailed labeling for components having a HRC of “1” or greater. With this approach, labeling is provided for each component within the electrical infrastructure for a facility where energized circuits may be exposed to workers. The analytical information associated with the arc flash hazard for most conditions is readily available within the label. A disadvantage to this approach is that with some infrastructure changes some of the labels may still need to be replaced. With each implementation recommendation above, there should also be a program of electrical safety training with specific emphasis on identifying and mitigating the arc flash hazard. Additionally, other guidance within NFPA 70E includes recommendations associated with the use of job briefings, planning, and energized work permits. The use of prepared task assessment sheets, as discussed above, should

Arc Flash Safety Handbook — Volume 2 also be considered for each electrical distribution panel. All of these activities should be performed to control, mitigate, or remove the potential effects of electrical hazards in the workplace. As Operations Manager of ESCO Energy Services Company, Lynn brings over 25 years of working knowledge in design, permitting, construction, and startup of mechanical, electrical, and instrumentation and controls projects as well as experience in the operation and maintenance of facilities.Lynn is a Professional Engineer, Certified Energy Manager and has a BS in Nuclear Engineering from the University of Tennessee.

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Arc Flash Safety Handbook — Volume 2

Determining PPE Requirements Using the NFPA 70E Tables NETA World, Winter 2005-2006 Issue by Ron Widup and Jim White Shermco Industries

Some of the additions to the 2000 edition of the NFPA 70E were the tables for determining what personal protective equipment (PPE) to use for the arc flash hazard. Those tables have been carried over into the 2004 edition with a few changes. One of the subjects most often discussed during training sessions is how to properly use the tables. When applying the tables, it is not enough to just look up a task and the assigned hazard/risk category and flip over to the PPE matrix and look up the minimum required PPE.. Some common sense must be applied to the specific task being performed. The following scenario is used as an example: The task required is to operate a 480-volt circuit breaker with the panel closed and latched. With the equipment in this configuration, there are no exposed, energized conductors. The key words in that last sentence are exposed and energized. If the circuits or parts are behind a properly latched door, there are no exposed, energized components and, therefore, 70E would consider them guarded with no hazard. No PPE would be required in this situation. However, if there were open vents facing the operator, such as is common in older 480-volt switchgear, there may not be a shock hazard, but there certainly could be an arc flash hazard. One such installation we recently visited had had an arc flash study performed and the equipment was labeled. So far so good. Unfortunately, the door of the main switch had expanded-metal vents directly facing the door of the room. The Flash Protection Boundary, according to the label, was 24 feet, not inches, but feet. There was an approximate distance of eight feet from the vents to the door. When discussing this with the customer, he was stunned to find out that there was a hazard, especially since there was no mention of it in the final report. It was recommended that the door be locked and labeled, with access only to qualified personnel, and then only if they had appropriate PPE on.

This installation is outside of what the 70E Committee had in mind when putting the tables together. This is not an isolated incident caused by equipment not being made to the standards and regulations of its day. Rather it is topof-the-line switchgear built by an American manufacturer in the 1950’s and 1960’s, and there is a lot of this type of equipment still in service. Times have changed, and the state-of-the-art in equipment design has also changed. We can look at many areas in electrical substations and switchgear rooms around us and find instances of equipment and installations that would not be considered acceptable today. However, they met the NEC or NESC at the time of installation, and they do not have to be updated unless there are major renovations taking place. Safety-wise, it might be worthwhile to review such installations and try to modify them so the arc flash exposure is reduced. Why the open vents? Many manufacturers used vents as a method to control internal pressures that could build up during and arc flash incident as well as temperature rise that may occur under normal loading. Our understanding of the arc flash hazard has emphasized the weaknesses of some of the old standard methods of construction and installation. So, what can be done to reduce the hazard? Blanking off the vents may not be an acceptable option, unless studies are conducted to determine that the switchgear can withstand the internal fault pressures generated by a full, three-phase arcing fault and the elevated temperatures within the switchgear enclosure. It is likely that the example installation could have the vents blanked off, but you would need to do some engineering to determine the impact of such an action. There may be a possibility of reventing the switchgear so that vents are in the rear of the switchgear instead of the front, but there would still be an arc blast hazard, which

6 could travel around the switchgear along with the heat of the arc flash. In this type of installation, where the incident energy is so great and the clearances so close, arc resistant switchgear could provide relief. Retrofitting existing switchgear to have arc resistant properties may be an option.

Summary Keep in mind when choosing PPE, all factors and hazards must be considered. Just choosing a task from Table 130.7(C)(9)(a) and assuming it fits your needs is not adequate. What additional factors do your workers have to face when performing a “standard” task? Is the system available short circuit energy above 35 kA for 0.5 second (for 600-volt systems)? If it is above that rating, the tables in the 70E are not applicable. and an engineering study should be performed. It is important to plan out the work, determine the hazards and what PPE will be required, set up safety barriers to keep unqualified persons from injury, and wear the PPE and equipment properly. You know — Be Safe. Ron A. Widup and Jim White are NETA’s representatives to NFPA Technical Committee 70E (Electrical Safety Requirements for Employee Workplaces). Jim White is nationally recognized for technical skills and safety training in the electrical power systems industry. He is currently the Training Director for Shermco Industries, a NETA Accredited Company. Jim has spent the last twenty years directly involved in technical skills and safety training for electrical power system technicians.

Arc Flash Safety Handbook — Volume 2

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Arc Flash Safety Handbook — Volume 2

Arc Flash vs. Arc Blast “Know The Difference” PowerTest 2006 (NETA Annual Technical Conference) Paul Hartman Power Testing and Energization

Introduction Electric arc flash safety has been the focus of many a safety meeting, presentation and discussion. There are standards, formulas and classes taught by qualified instructors that provide valuable information to further the understanding of this hazardous phenomenon. Another facet of the arc flash hazard is the arc blast factor. Ballistics is a study of the motion of a projectile during its three phases, interior, exterior and terminal. If this is beginning to sound like a study in firearms ballistics that is because there are a lot of similarities between Electric Arc Blast and the firing of a bullet. The electric arc flash hazard is similar to the muzzle blast from a large weapon. For instance the surge of hot air and gases that burst from a muzzle can cause serious injury or death. This is best represented by the powder blast from a device that is firing blank ammunition.

Types of Blast Injury Primary blast injury: Due to the shock wave traveling through the body. Secondary blast injury: Associated with being hit by flying projectiles. Tertiary blast injury: Associated with the body impacting a stationary object after being accelerated by the pressure wave.

Interior Ballistics Bullet ballistics are as follows: 1) Firing pin hits the primer 2) Powder begins to burn

3) Heat and pressure builds up 4) Bullet is expelled 5) Bullet possesses energy created by the burning powder 6) Projectile transmits energy to the person Arc blast interior ballistics also deals with the temperature, volume and pressure of the gases as a result of the energy released from an electrical arc. For instance when an arc first starts there is a build-up of heat which proceeds to create pressure by either the expansion of hot gasses or the creation of gasses from a solid element. It is possible that the energy, in the form of pressure, can launch pieces and parts (projectile) at a high rate of speed. And of course any person in the path will absorb the projectile energy.

Exterior Ballistics Here is where the similarities between firearms and arc blast projectiles differ greatly. The firearms projectile can be designed to travel fast and accurate as in a jacketed slug. They can also be designed to travel slow and broad as in a shotgun or even change its characteristics upon colliding with an object as in hollow-point bullets. Arc-blast projectiles vary in size, shape and weight. There path is not nearly as predictable In some cases a person educated in the nuances of arc blast may be able to predict a probable path based on the design and construction of the electrical equipment. The difficulty in predicting a projectiles path during an arc blast is clearly represented in photos #1 and #2. These two photos were taken at a large high voltage substation that experienced a severe arc blast. Photo #1 shows the projectile, a piece of porcelain. The penny placed in the center of the one inch thick, six ounce projectile shows its relative size.

8

Arc Flash Safety Handbook — Volume 2 Not all blasts are sever enough to create as much havoc as the one mentioned above. The switchgear fault in photo #3 was contained inside the equipment with relatively little exterior damage. The maintenance engineer at this facility had smelled smoke in this electrical room the day before but could not find the source. The failure of the fused switch and the subsequent smoke it created made it quite easy to locate the source of the problem.

Photo #1: Six ounce porcelain projectile

In this particular failure the 500 kV arc blast occurred at an elevation of fifteen feet above the substation gravel bed. The extreme pressures generated where not confined or focused in any one direction. For all practical purposes it was a 360 degree explosion. This was quite evident in the pattern created by the hundreds of pieces of debris scattered in a 100 foot plus radius around the failed PT and bushing. Photo #2 illustrates the exterior ballistics of the six ounce porcelain projectile. This substation chain link fence is located seventy feet from the failed equipment. The hole in the fence was made by the projectile in photo #1. The faulted equipment can bee seen in the lower portion of photo #2, off in the distance.

Photo #3: Slow developing blast that did only minor damage to the exterior of the switchboard

Terminal Ballistics

Photo #2: Fence damage by arc blast projectile

Once an object in motion reaches its target, or in this case worker, the science of terminal ballistics is applicable. The variables associated with this study include quantity of projectiles, size, velocity and spatial distribution of fragments. A moving projectile possesses kinetic energy. As this projectile travels into or through the body it transfers the kinetic energy to the tissue of the body. Two factors that

9

Arc Flash Safety Handbook — Volume 2 directly effect the amount of deliverable kinetic energy are mass and velocity. In general neither mass nor velocity actually produce harmful injuries. It is the high acceleration of a body that has been struck by the mass with velocity that is dangerous. The same is true for high deceleration. For instance in a car crash the sudden deceleration of the body can cause severe damage. In both the acceleration and deceleration of the human body there are two different motions to contend with. The first is the sudden movement of the body, the second the crashing of the body’s internal organs. When an arc blast occurs the forces of the blast hit the body and cause acceleration away from the blast. The g forces at this point can be strong enough to severely distort the human body. Meanwhile the internal organs of the body have not yet achieved the same speed as the outer body and are now crashing into each other. This type of internal organ movement can be sever enough to cause damage such as pulling the pulmonary artery away from the heart or bruising the brain against the inside of the skull. Each body part has a different density and therefore some organs are more susceptible to g forces than others. The average male adult has over nineteen square feet of surface area. If a quarter of that area, say five square feet were exposed to the forces of a large arc blast the g forces could cause severe damage. Photo #4 illustrates the acceleration and deceleration principle. The blast forces inside the switchgear caused this door to accelerate in such a manner that it ripped the door right off of its hinges. From there the door flew into a light pole and the deceleration effect wrapped it around the pole.

Physical Damage The most common human injuries from a severe blast are: Ruptured ear (high-pressure wave) Crushed chest wall Collapsed lungs Damaged abdominal wall Damaged internal organs Through high speed photographic techniques scientists have been able to improve their studies of high-pressure shock waves and their effects.

Conclusion Arc flash/blast hazards can range from the extreme worst case scenario to the more common lower level faults. Photos #5 and #6 are from a 480V circuit breaker that failed during closing. The steel frame of the breaker is shown in photo #5 with the corresponding holes in the circuit breaker cubicle door shown in photo #6. The damage appears to be minimal however the worker was injured by the molten metal that burned through his polyester coat. Obviously the lack of proper safety equipment contributed to this accident. Through education and the use of proper safety equipment and techniques the potential hazards of arc flash/blast can be minimized.

Photo #5: Circuit breaker frame

Photo #4: Switchgear door that was blown off and wrapped around a light pole

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Arc Flash Safety Handbook — Volume 2

Photo #6: Circuit breaker cubicle door.

Paul Hartman has over 18 years experience in start-up, commissioning, maintenance, and training in power generation, including international projects in Pakistan, Indonesia, Thailand, Brazil, and Korea. He has been an instructor for state certified continuing education programs. Paul is currently Project Manager for Power Testing and Energization. He is a regular contributor to NETA World and a frequent speaker at NETA’s Annual Technical Conference.

quick-trip™ arc flash reduction switch

DATA SHEET Providing a safer working environment for people working on energized electrical equipment as required by 2011 NEC Article 240.87.

Since arc flash potential is directly related to breaker clearing time, the QUICK-TRIP system provides an easy and safe method to reduce faultclearing time without opening a cubicle door to reprogram the trip unit. The QUICK-TRIP system is activated by means of a padlockable selector switch. When enabled, two additional settings are activated in the AC-PRO trip unit to provide enhanced protection: ❏ QT Instantaneous

System Features

❏ Ground Fault

The QUICK-TRIP system is as easy to use as it is to install, with the additional personnel safety features:

The two individually programmable settings are designed to provide faster clearing times in the event of a fault.

❏ Installation uses standard punches. ❏ Wires in minutes without cutting into existing wiring harness. ❏ QT settings are only active when the selector switch is in the ON position (during maintenance).

Practical Example A technician needs to rack out a feeder breaker for maintenance. In so doing, he is the minimum 18” away from any potential arc flash source in the cubicle. As the breaker is being racked out, a 12,000A arcing fault occurs inside the cubicle. The 2000A main breaker sees the fault and trips, subsequently clearing the fault in the feeder breaker cubicle. The two Time-Current-Curves below illustrate the dramatic impact that arc-clearing time has on incident energy levels. Given that: F = 12kA and D = 18 in. TCC 1: QUICK-TRIP: OFF shows the trip time characteristics of the main breaker.

❏ QUICK-TRIP ON LED confirms operation. ❏ SELF-TEST LED verifies trip unit operation. ❏ QUICK-TRIP settings can be reviewed on the external QT-DISPLAY. ❏ Last Trip Data and all settings can be reviewed on the QT-DISPLAY. ❏ 3-phase currents are displayed continuously on the QT-DISPLAY. ❏ The system is fully powered by the trip unit’s CTs. No aux power or batteries.

TCC 2: QUICK-TRIP: ON shows the trip time characteristics of the main breaker.

TCC 1

❏ Padlocking switch can be incorporated into a lock-out tag-out procedure.

❏ PICK-UP LED indicates overcurrent situations.

❏ The AC-PRO will cause the main breaker to clear the 12kA fault in .556 seconds (based on a Short-Time Delay of .20 seconds with I2T ON). The resulting arc duration will be: t = .556 ❏ The resulting incident energy is: EI =25.8022 ❏ The Hazard Risk Category is: 4

❏ The AC-PRO will now cause the main breaker to clear the 12kA fault in .05 seconds (based on the Instantaneous QT or I QT Pick-Up setting of 8000A). The resulting arc duration will be: t = .05 ❏ The resulting incident energy is: EI = 2.3203 ❏ Hazard Risk Category reduced to: 1

❏ Reduction in arc flash incident energy levels may permit lower PPE clothing for maintenance personnel.

❏ Extra contacts on the selector switch are available for external annunciation.

Call Toll Free: 888.289.2864 For additional information visit our website:

w w w. u t i l i t y r e l a y. c o m

URC Utility Relay Company TCC 2

10100 Queens Way, Chagrin Falls, OH 44023 Phone: 440-708-1000 Fax: 440-708-1177

11

Arc Flash Safety Handbook — Volume 2

Practical Implications of Electrical Arc Flash Safety if There Is No Arc Flash Hazard Assessment PowerTest 2006 (NETA Annual Technical Conference) Daniel Doan, P.E. DuPont

Abstract: OSHA and NFPA 70E require an arc flash hazard assessment to determine the arc flash boundary and personal protective equipment (PPE) requirements for electrical work. During the course of your work, you may be asked to approach equipment where no assessment has been done. You or your workers can be exposed to arc flash hazards that are more intense than you expect. Based on findings from many assessments, this session will give you an understanding of typical arc flash hazard assessment results, the limitations and safety factors of tables that are often used to determine PPE requirements, and some clues to look for to determine when high energy exposures are possible. You will learn some questions to ask your host or customer before doing your test work, and questions to ask about special cases where high energy exposures may exist.

A. Introduction to the Electrical Arc Flash Hazard The electrical arc flash hazard has been described increasingly in the past few years. OSHA [1] and NFPA70E[2] have described the need for understanding and mitigating this hazard. The best defense, as shown in those documents, is to only work on de-energized electrical equipment. Unfortunately, there is always a chance that the equipment is not turned off – it may be that the switches are mislabeled, or the switch didn’t open properly. Also, switching the system off in the first place can expose the worker to this hazard. At these times, the worst imaginable accident can occur – an electrical arc with high thermal energy can blast out from the equipment to engulf the worker in a fireball. Burning clothing and skin can be the result, with months and even years of rehabilitation and medical care in the victim’s future.

A National Institute of Occupational Safety and Health (NIOSH) paper [3] listed the injury statistics of electrical arc flash. In the USA, from 1992 to 1998, there were over 12,500 arc flash incidents with one or more injuries. This is the basis for the NFPA 70E and OSHA requirements – to try to reduce these injuries by helping our workers understand the hazards, and to ensure that they use proper PPE and work practices. An IEEE paper [4] discusses arc flash incident data for a large chemical company. The typical ratio of arc flash incidents with potential for injury to OSHA recordable injuries is 1 in 200. That is, for every 200 OSHA recordable injuries, companies can expect one arc flash incident with a potential for injury. It is a good policy to understand the safety record and statistics of any company you visit; this will help you understand what to watch for to keep yourself safe. Reducing this hazard and providing a safe working environment is our goal, and there are many resources for finding methods to mitigate this hazard. The NFPA 70E “Standard for Electrical Safety In the Workplace” is a good place to start. This standard discusses the need for an electrically safe work condition, training, planning the work, and the use of protective equipment. Other resources include the IEEE1584 “Guide for Arc Flash Hazard Calculations” [5], and the IEEE/IAS Electrical Safety Workshop. http://www.ewh.ieee.org/cmte/ias-esw/ There have been many technical papers and articles published on the subject, and a search at IEEE’s Xplore website will provide many references. http://ieeexplore.ieee.org/Xplore/dynhome.jsp

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Arc Flash Safety Handbook — Volume 2

B. Results of Industrial Studies

D. No Hazard Assessment?

An IEEE paper [6] summarized the results from arc flash hazard assessments at 33 industrial sites for a large chemical company. Nearly 10,000 pieces of equipment were studied, and the distribution of arc flash incident energy values at different levels is shown in Figure 1. For any arc flash hazard over 1.2 calories per square centimeter (cal/sqcm), flame-resistant (FR) clothing is required by OSHA and NFPA70E. An incident energy value of 1.2 cal/sqcm is the point where the skin of the worker would have the onset of a second degree burn, and would require medical attention. One cal/sqcm is roughly equivalent to holding the tip of the finger in a lighter flame for one second. Arc flash energy values over 40 cal/sqcm, as you can imagine, are very high and would give a worker a very serious injury. About 10% of the equipment had arc flash hazards above the 40 cal/sqcm maximum exposure addressed in NFPA 70E, Table 130.7(C)(11) “Protective Clothing Characteristics.” Protective clothing with higher arc flash ratings are available, but the user should realize that higher energy exposures may also expose the worker to other hazards such as noise, blast, and projectiles. If the typical exposures for normal industrial work are taken into account, the estimated exposures of workers to these hazards has a different distribution than is shown in Figure 1. This is because workers are more likely to be switching or troubleshooting the lower energy equipment, such as motor control centers or panelboards. Higher energy equipment is switched less frequently. The estimated exposures for the same company’s equipment is shown in Figure 2. About 2% of the exposures are over 40 cal/sqcm.

Many companies have not completed the arc flash hazard assessment for their facilities as described in NFPA 70E. If this hasn’t been completed, and the equipment is not labeled, then the worker has no way to determine what level of FR clothing is needed to properly protect from the hazard. I am often asked these questions: What PPE should I wear? Can you give me a simple chart to show me the right PPE? Unfortunately, there are no easy answers. There are many variables that determine the right PPE. There is no way to determine just by looking at the equipment. Two pieces of equipment that look identical could be fed from different sources, with different fuses. This could change the arc flash energy significantly. Why don’t they have an assessment completed? It is often the case that the owner of the facility doesn’t understand the need for arc flash assessment. Perhaps they have started but not completed the study. Or they may have completed the study, but not yet labeled the equipment. Some companies are using the task tables in NFPA 70E to determine their PPE requirements. These tables can be very useful, but they also can be misapplied. The fine-print notes below the table show that the electrical system must have certain specifications for the table to be applied. For some tasks, the system must have a short circuit current below 25kA, with a fault clearing time of 0.03 seconds (2 cycles). For other tasks, there are other system requirements. The user must be sure that their electrical system meets these requirements, and in many cases some basic amount of electrical system study will be required to ensure that the requirements in the notes are met. Another way to make a PPE list is to study a lot of equipment, and use the worst case arc flash energy values found. Based on the statistics in the study mentioned previously [6], Table 1 is a list of PPE that would be adequate to protect against the arc flash energy of 98% of the exposures found. This can be a starting point for determining the PPE required before an assessment is complete. In the table, Working Distance is the distance between the worker’s body and the possible arcing point. CLF means “current limiting fuse,” and shows that circuits protected by current limited fuses usually have lower arc flash energy.

C. Typical Field Tasks with Hazard Exposure All types of testing can expose the worker to arc flash hazards. Infrared (thermal) imaging, voltage and harmonics testing, and other types of on-line measurements must often be completed when the system is energized. These may have varying working distance from energized conductors, so they will have different arc flash energy values. Switching of equipment to create a safe de-energized working condition is also a task where the worker can be exposed to arc flash hazard. The order of switching can significantly change the arc flash energy. For example, when connecting two 1500kVA substation transformers together during an online transfer, the energy will be higher. If other switching is done during the transfer, those tasks would have a higher energy than if they were done before or after the transfer. A hazard that is sometimes unexpected is when others nearby cause an arc flash. Even a bystander can be exposed to the hazard in this case. Figure 3 depicts the situation in one incident where several workers were exposed to an arc flash hazard, and were classified as lost-workday cases. The workers in positions 1, 2, and 3 were injured; the worker in position 4 was not injured due to good body position.

Table 1. Basic PPE requirements for work when assessment/label not complete Equipment

Working Distance

HV and MV (over 1kV) HV and MV LV Switchgear (under 1kV) LV MCCs/Panels LV MCCs Protected by CLF

36 inches 20 feet 24 inches 18 inches 18 inches

PPE Rating Recommended

100 cal/sqcm 4 cal/sqcm 100 cal/sqcm 20 cal/sqcm 4 cal/sqcm

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Arc Flash Safety Handbook — Volume 2 E. Ask questions before starting the work Before doing any work where you are exposed to the arc flash hazard, and especially at those locations where an arc flash hazard assessment has not been completed, it is important to ask the right questions, to learn if there are any special conditions that would increase the hazard. The first thing to ask is “Can this work be done de-energized?” If so, it minimizes the exposure to the worker. Next, ask about the existence of any tie conditions. Some substations and distribution equipment can be switched to allow two different sources at once to feed a switchgear or panel. In these cases, the fault current can be higher than expected. Also, the current is flowing through two protective devices in parallel, and so can those devices will take longer to open. This can result in very high energy. Another question to ask is about the fuses and/or circuit breakers protecting the equipment. Are the fuses current limiting? If not, then they may take longer to open than current limiting fuses. Have they been changed out to larger fuses? If so, they may take longer to open. Are the circuit breaker trip units set to the proper settings? If they have been changed without the knowledge of the owner, then the breaker may take longer to open, or may not open at all in an arcing condition. Has the equipment been well maintained? If not, circuit breakers and relays may operate more slowly or not at all, and increase the arc flash energy. Also you should ask about the switching procedures which are in place for the equipment. It is possible that the switching plan has more switching steps than are really required. Additional switching exposures will increase the risk to the worker. Review the job plan and do everything possible to reduce the risk of being exposed to a hazard. For example, suppose the existing job plan calls for turning off all switches in a motor control center (MCC) and then opening the substation feeder breaker to the MCC. Instead, it may be possible to leave the MCC switches closed, and open the substation feeder breaker to shutdown the power to the MCC. When it is de-energized, the MCC switches could be opened. This could eliminate many arc flash exposures for a large MCC. Another question is “Can I increase my working distance?” If you can do the job at a larger distance from the electrical equipment, then you can reduce the flash hazard.

F. Conclusion Electrical arc flash hazards can be understood and mitigated with study, assessment, and good attention to safe work practices. There are many resources to use to ensure that your workers are properly protected from these hazards during their work. A preliminary PPE table, based on statistical analysis of nearly 10,000 pieces of electrical equipment, is available for reference if there has been no arc flash hazard assessment. Ask questions and make sure you understand the hazards before you do any work where you are exposed to the electrical arc flash.

References: [1] OSHA 29 CFR 1910.132, “Personal Protective Equipment for General Industry (PPE)” [2] NFPA 70E, Standard for Electrical Safety in the Workplace, National Fire Protection Association, Boston, MA 02210

[3] J.C. Cawley and G.T.Homce (NIOSH), “Occupational electrical injuries in the United States, 1992– 1998, and recommendations for safety research”, Journal of Safety Research, Vol. 34 (2003), pp 241– 248

[4] D.R. Doan, H.L. Floyd, and T.E. Neal, “Comparison of methods for selecting personal protective equipment for arc flash hazards”, IEEE Transactions on Industry Applications, Vol 40, Issue 4, July/Aug 2004, pp 963 – 969 [5] IEEE 1584, “Guide for Arc Flash Hazard Calculations”

[6] D.R. Doan and R.A. Sweigart, “A Summary of Arc Flash Hazard Calculations”, IEEE Transactions on Industry Applications, Volume 39, Issue 4, July-Aug. 2003, Page(s):1200 – 1204

3000 2500 2000 1500 1000 500 0 0 (0-1.2)

1 (to 4)

2 (to 8)

3 (to 25)

4 5 >5 (to 40) (to 100) (>100)

Figure 1. Pieces of Equipment with Assessed Arc Flash Hazard Levels (cal/sqcm)

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Arc Flash Safety Handbook — Volume 2

400000

300000

200000

100000

0

0 (0-1.2)

1 (to 4)

2 (to 8)

3 4 5 >5 (to 25) (to 40) (to 100) (>100)

Figure 2. Estimated Exposures at Assessed Arc Flash Hazard Levels (cal/sqcm)

Figure 3. Bystanders Exposed to Arc Flash Hazard

Daniel R. Doan is a Consultant for DuPont in Wilmington, Delaware. Dan received the BSEE and MSEE degrees from the Massachusetts Institute of Technology. He has co-authored IEEE papers at IAS/PCIC and Pulp & Paper on subjects ranging from electrical safety to electrical system reliability and operations. He has co-authored PCIC tutorials on Electrical System Reliability and Arc Flash Hazard Analysis, and has participated in many IAS Electrical Safety Workshops and other conferences as author and presenter. Dan is a senior member of the IEEE, a member of the IEEE 1584 Guide for Arc Flash Calculations Working Group, a member of the IEEE/NFPA Research and Testing Planning Committee, and is a Registered Professional Engineer in Pennsylvania.

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Arc Flash Safety Handbook — Volume 2

Electrical Safety and Maintenance Training NETA World, Spring 2006 Issue by Dennis K. Neitzel, C.P.E.

There is nothing more important to an electrical safety program than to have a staff of technicians who have been properly trained and who are qualified to do their jobs efficiently and safely. Here are a few questions to think about: How do I know that all of my technicians are qualified? Have job/task analysis and hazards analysis been conducted? Do my technicians know what the hazards of electricity are and how to protect themselves? Have I conducted a needs assessment? Do I have a current job description for each of the crafts? So many questions; do you have any answers? You might be asking at this point, where do I start? Before any significant training can take place, an assessment must be conducted to determine what is needed. The needs assessment involves relevant company personnel who are aware of the job requirements and all applicable codes, standards, and regulations. Information that is collected will provide insights into any past or present performance problems that must be addressed in the training program. This process can also be used to determine whether or not training is the solution to any problems that may exist. There may be other factors that might affect performance that must be recognized and considered. These other factors could include the quality of procedures, human factors, management style, and work environment. Any one or all of these factors may affect job performance and safety.

You might be asking the question: Why do I need to do all of this? My technicians know what they are doing because they have many years of field experience. The answer to this is found in NFPA 70E-2004, Article 205, “General Maintenance Requirements”, Section 205.1, “Qualified Persons”, which states: “Employees who perform maintenance on electrical equipment and installations shall be qualified persons as required in Chapter 1 and shall be trained in, and familiar with, the specific maintenance procedures and tests required.” Chapter 1, Article 100 defines a qualified person as: “One who has skills and knowledge related to the construction and operation of the electrical equipment and installations and has received safety training on the hazards involved.” When evaluating the qualification level of employees, remember there is a difference between ten years of experience and one year of experience repeated ten times. What classroom and on-the-job training have they received? Was the effectiveness of the training measured to ensure comprehension? Were they required to demonstrate proficiency in the work practices involved? The quality and extent of the training program is extremely important. Studies in retention indicate that the average person will retain:

Training and Qualification Analysis

• 20 percent of what they hear (lecture)

The results of the needs assessment should provide a good starting point for the job/task and hazards analyses and ultimately the design, development, implementation, and evaluation of the training program that will be needed in order to qualify your technicians. Another benefit to all this is that you will have a well defined job description for your technicians. This can also be extremely beneficial when it comes time to hire additional technicians because you have also developed a job description for posting an ad for employment.

• 10 percent of what they read (books and other written course materials) • 30 percent of what they see (illustrations – “a picture is worth a thousand words”)

• 50 percent of what they see and hear (demonstrations and/or video)

• 70 percent of what they say (discussion – two-way communication) • 90 percent of what they do and say (hands-on training – demonstrate proficiency)

16 The more extensive the training program the better qualified the employee. As can be seen by the percentages above, the most effective training programs include a combination of lecture, demonstration, and hands-on instruction. As an example, an employee attends a class on circuit breaker maintenance and testing using the following agenda: (1) the instructor explains, in lecture and discussion, all of the maintenance and testing techniques; (2) the instructor then demonstrates those techniques on a circuit breaker; and (3) the employee performs hands-on maintenance and testing of the circuit breaker using the techniques that were presented, discussed, and demonstrated. In this example, employees, on average, would retain at least 90 percent of what they were taught. This method of training has proven to be the most effective means for qualifying employees. All this takes us back to the job/task and hazards analyses. The only way to really know whether or not an employee has been properly trained and qualified is to perform a job/task analysis as well as a hazards analysis. To do this, carefully study and record each step of a job, identify the tasks and elements that make up the job, identify existing or potential job hazards, and determine the best way to perform the job along with reducing or eliminating the hazards. The job hazards analysis can accomplish a great deal toward reducing accidents and injuries in the workplace, but it is only effective if it is reviewed and updated periodically. Even if no changes have been made in a job, hazards that were missed in an earlier analysis may be identified while performing the individual tasks. Any time a job/task or hazards analysis is revised, training in the new job methods or protective measures must be provided to all employees affected by the changes. Job/task and hazards analyses can also be used to train new employees on job steps and hazards.

The Hazards of Electricity In order to fully comprehend the requirements for an effective technician training and qualification program, we must first have an understanding of the hazards of electricity. All of the studies reviewed have revealed three major hazards of electricity which are electrical shock, electrical arc flash, and electrical arc blast. Each of these hazards will be addressed as to the physiological effect on the human body. Electrical shock It takes a very low value of current flowing through the human body to cause death or serious physical harm. Many studies have been performed in this area with different values of current that causes each effect. The following chart shows average values of current and the effects as taken from the published studies:

Arc Flash Safety Handbook — Volume 2 Current

Effect

1-3 mA

Perception threshold (most cases)

9-25 mA

Muscular contractions (can’t let go)

1 mA

Barely perceptible

3-9 mA

25-60 mA

60 mA or more 4 A or more 5 A or more

Painful sensations

Respiratory paralysis (may be fatal)

Ventricular fibrillation (probably fatal) Heart paralysis (fatal)

Tissue burning (fatal if vital organ)

Physiological Effects of AC Current on the Body

Electrical arc flash There are two different issues with this hazard, the arc temperature and the incident energy. The main concern with the arc temperature is the flash flame and ignition of 0 0 clothing. At approximately 203 F (96 C) for one-tenth of a second (6 cycles), the skin is rendered incurable or in other words a third-degree burn. Onset of a second-degree 2 burn occurs with only 1.2 cal/cm of incident energy It does not take a very high temperature or very much energy to cause extreme pain and discomfort or even death to the employee.

Electrical arc blast The pressures developed by an electrical arc can be extremely high. One study noted that copper, when vaporized, expands at a factor of 67,000 times, which one expert estimated was the same expansion as that produced by dynamite. Doors or covers must be securely latched before operating a switch or circuit breaker. Technicians or operators must place their body in the safest position possible before operating the equipment. Never stand directly in front of electrical equipment when it is being operated, racked-in, or racked-out.

Regulatory Requirements Although proper training and qualification of employees is the right thing to do, many employers have stated that training is just too expensive or that their employees know what they are doing and therefore don’t need any additional training. These same employers have also stated that they will do it only if they have to. OSHA has provided strict guidelines for safety training that go hand-in-hand with the qualification of an employee. Training is an OSHA mandate for all employees who are required to work on or near exposed energized circuits and parts of electrical equipment, operating at 50 volts to ground or more. The following quotes are provided in order to inform the reader that training is not an option, and to assist in gaining a better understanding of these mandates:

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Arc Flash Safety Handbook — Volume 2 OSHA 29 CFR 1910.269(a)(2) Training. (i) Employees shall be trained in and familiar with the safety-related work practices, safety procedures, and other safety requirements in this section that pertain to their respective job assignments. OSHA continues with this requirement by requiring qualified employees to be trained and competent in:

• The skills and techniques necessary to distinguish exposed live parts from other parts of the equipment • The skills and techniques necessary to determine the nominal voltage of the circuits and equipment

• The minimum safe approach distances to exposed live parts • The proper use of:

• Special precautionary techniques

• Insulating and shielding materials

• Insulated tools and test equipment • Job planning

In addition to this, OSHA states that a person must have this training in order to be considered a qualified person. The employer is also required, through regular supervision and annual inspections, to verify that employees are complying with the safety-related work practices. Additional training or retraining may be required for any of the following:

• The supervision or annual inspection indicates noncompliance with or lack of understanding of the work practices • New technology

• New types of equipment are installed • Changes in procedures

• Employee is required to use work practices that they normally do not use

OSHA also considers tasks that are performed less often than once per year to necessitate retraining before the performance of the work practices involved. This retraining may be as simple as a detailed job briefing prior to the commencement of the work or it may require more in-depth classroom instruction along with on-the-job training. Note the statement above that requires the employee to demonstrate proficiency in the work practices involved. The best way that the employee can demonstrate proficiency is to actually do the work after receiving the training or as part of the training. Hands-on training would be required in order to accomplish this OSHA requirement.

Hands-On Training The OSHA Electrical Safety-Related Work Practices regulation, 29 CFR 1910.331-.335, Electric Power Generation, Transmission, and Distribution.29 CFR 1910.269, and NFPA 70E-2004, Section 110.6. all have similar requirements for training. As can be seen by the above statements, proper training is a vital part of the worker’s safety and proficiency as well as being a mandated OSHA requirement.

Conclusion Electrical power systems today are often very complex. Protective devices, controls, instrumentation, and interlock systems demand that technicians be trained and qualified at a high technical skill level. Safety and operating procedures utilized in working on these systems are equally as complex, requiring technicians to be expertly trained in all safety practices and procedures. OSHA Regulations require employers to document that employees have demonstrated proficiency in electrical tasks. Employers must certify that their employees are qualified and that this certification is maintained for the duration of the employee’s employment. Dennis K. Neitzel, C.P.E., is the Director of AVO Training Institute, Inc., Dallas, Texas and is a Principle Committee Member for the NFPA 70E, Standard for Electrical Safety in the Workplace. He is also co-author of the Electrical Safety Handbook, McGraw-Hill Publishers.

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Arc Flash Safety Handbook — Volume 2

Hand Protection for Shock and Arc Flash —

How Do I Apply OSHA and NFPA 70E Requirements? NETA World, Summer 2006 Issue by Lynn Hamrick ESCO Energy Services Company

This narrative provides information associated with hand protection. It summarizes both current regulations and NFPA 70E. Additionally, it provides recommendations associated with implementing these regulations in the industrial environment. As a starter, excerpts from OSHA requirements and NFPA 70E are provided below as a basis for further discussion.

(vii) Protector gloves shall be worn over insulating gloves, except as follows: (A) Protector gloves need not be used with Class 0 gloves, under limited-use conditions, where small equipment and parts manipulation necessitate unusually high finger dexterity. Note: Extra care is needed in the visual examination of the glove and in the avoidance of handling sharp objects. (B) Any other class of glove may be used for similar work without protector gloves if the employer can demonstrate that the possibility of physical damage to the gloves is small and if the class of

29CFR1910, SubPart I – Personal Protective Equipment § 1910.137 Electrical protective equipment (b) In-service care and use. (2) The following specific requirements apply to insulating blankets, covers, line hose, gloves, and sleeves made of rubber: (i) Maximum use voltages shall conform to those listed in Table I-5. (ii) Insulating equipment shall be inspected for damage before each day’s use and immediately following any incident that can reasonably be suspected of having caused damage. Insulating gloves shall be given an air test, along with the inspection. (iv) Insulating equipment found to have other defects that might affect its insulating properties shall be removed from service and returned for testing…. (vi) Insulating equipment shall be stored in such a location and in such a manner as to protect it from light, temperature extremes, excessive humidity, ozone, and other injurious substances and conditions.

Table I-5 – Rubber Insulating Equipment Voltage Requirements Class of Equipment

Maximum use voltage(1) a-c - rms

Retest voltage(2) a-c - rms

Retest voltage(2) d-c - avg

0

1,000

5,000

20,000

1

7,500

10,000

40,000

2

17,000

20,000

50,000

3

26,500

30,000

60,000

4

36,000

40,000

70,000

1. The maximum use voltage is the a-c voltage (rms) classification of the protective equipment that designates the maximum nominal design voltage of the energized system that may be safely worked. The nominal design voltage is equal to the phase-to-phase voltage on multiphase circuits. However, the phase-to-ground potential is considered to be the nominal design voltage: (1) If there is no multiphase exposure in a system area and if the voltage exposure is limited to the phase-to-ground potential, or (2) If the electrical equipment and devices are insulated or isolated or both so that the multiphase exposure on a grounded wye circuit is removed. 2. The proof-test voltage shall be applied continuously for at least 1 minute, but no more than 3 minutes,

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Arc Flash Safety Handbook — Volume 2 glove is one class higher than that required for the voltage involved. Insulating gloves that have been used without protector gloves may not be used at a higher voltage until they have been tested …. (viii) Electrical protective equipment shall be subjected to periodic electrical tests. Test voltages and the maximum intervals between tests shall be in accordance with Table I-5 and Table I-6. Table I-6 – Rubber Insulating Equipment Test Intervals Type of Equipment

When to test

Rubber insulating line hose Rubber insulating covers Rubber insulating blankets Rubber insulating gloves Rubber insulating sleeves

Upon indication that insulating value is suspect. Upon indication that insulating value is suspect. 1 Before first issue and every 12 months thereafter. Before first issue and every 6 months thereafter.1 Before first issue and every 12 months thereafter.1

1

If the insulating equipment has been electrically testing but not issued for service, it may not be placed into service unless it has been electrically tested within the previous 12 months.

29CFR1910, SubPart S — Electrical § 1910.333 Selection and use of work practices. (a) General. Safety-related work practices shall be employed to prevent electric shock or other injuries resulting from either direct or indirect electrical contacts… (2) Energized parts. If the exposed live parts are not deenergized (i.e., for reasons of increased or additional hazards or infeasibility), other safety-related work practices shall be used to protect employees who may be exposed to the electrical hazards involved. Such work practices shall protect employees against contact with energized circuit parts directly with any part of their body or indirectly through some other conductive object. …. Specific work practice requirements are detailed in paragraph (c) of this section (c) Working on or near exposed energized parts. (2) Work on energized equipment. Only qualified persons may work on electric circuit parts or equipment that have not been deenergized under the procedures of paragraph (b) of this section. Such persons shall be capable of working safely on energized circuits and shall be familiar with the proper use of special precautionary techniques, personal protective equipment, insulating and shielding materials, and insulated tools. (ii) Qualified persons. When a qualified person is working in the vicinity of overhead lines, whether in an elevated position or on the ground, the person may not approach or take any conductive object without an approved insulating handle closer to exposed energized parts than shown in Table S-5 unless:

Table S-5 – Approach Distances for Qualified Employees Alternating Current Voltage Range (phase-to-phase) 300V and less Over 300V, not over 750V Over 750V, not over 2kV Over 2kV, not over 15kV Over 15kV, not over 37kV Over 37kV, not over 87.5kV Over 87.5kV, not over 121kV Over 121kV, not over 140kV

Minimum approach distance Avoid Contact 1 ft. 0 in. (30.5 cm). 1 ft. 6 in. (46 cm). 2 ft. 0 in. (61 cm). 3 ft. 0 in. (91 cm). 3 ft. 6 in. (107 cm). 4 ft. 0 in. (122 cm). 4 ft. 6 in. (137 cm).

(A) The person is insulated from the energized part (gloves, with sleeves if necessary, rated for the voltage involved are considered to be insulation of the person from the energized part on which work is performed), or (B) The energized part is insulated both from all other conductive objects at a different potential and from the person, or (C) The person is insulated from all conductive objects at a potential different from that of the energized part.

§ 1910.335 Safeguards for personnel protection. (a) Use of protective equipment. (1) Personal protective equipment. (i) Employees working in areas where there are potential electrical hazards shall be provided with, and shall use, electrical protective equipment that is appropriate for the specific parts of the body to be protected and for the work to be performed. Note: Personal protective equipment requirements are contained in subpart I of this part. (ii) Protective equipment shall be maintained in a safe, reliable condition and shall be periodically inspected or tested, as required by 1910.137. (iii) If the insulating capability of protective equipment may be subject to damage during use, the insulating material shall be protected. (For example, an outer covering of leather is sometimes used for the protection of rubber insulating material.)

NFPA 70E, Standard for Electrical Safety in the Workplace — 2004 130.2(C) Approach to Exposed Live Parts Operating at 50 Volts or More. No qualified person shall approach or take any conductive object closer to exposed live parts operating at 50 volts or more than the Restricted Approach Boundary set forth in Table 130.2(C), unless any of the following apply:

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Arc Flash Safety Handbook — Volume 2

NFPA 70E Table 130.2(C) Approach Boundaries to Live Parts for Shock Protection (All dimensions are distance form live part to employee.) (1)

(2)

(3)

(4)

(5)

Prohibited Approach Boundary (1)

Exposable Movable Conductor

Exposed Fixed Circuit Part

Restricted Approach Boundary (1); Includes Inadvertent Movement Adder

0 to 50 51 to 300 301 to 750

Not Specified 10 ft. 0 in. 10 ft. 0 in.

Not Specified 3 ft. 6 in. 3 ft. 6 in.

Not Specified Avoid Contact 1 ft. 0 in.

Not Specified Avoid Contact 0 ft. 1 in.

751 to 15 kV 15.1 kV to 36 kV 36.1 kV to 46 kV

10 ft. 0 in. 10 ft. 0 in. 10 ft. 0 in.

5 ft. 0 in. 6 ft. 0 in. 8 ft. 0 in.

2 ft. 2 in. 2 ft. 7 in. 2 ft. 9 in.

0 ft. 7 in. 0 ft. 10 in. 1 ft. 5 in.

46.1 kV to 72.5 kV 72.6 kV to 121 kV 138 kV to 145 kV

10 ft. 0 in. 10 ft. 8 in. 11 ft. 0 in.

8 ft. 0 in. 8 ft. 0 in. 10 ft. 0 in.

3 ft. 3 in. 3 ft. 2 in. 3 ft. 7 in.

2 ft. 1 in. 2 ft. 8 in. 3 ft. 1 in.

161 kV to 169 kV 230 kV to 242 kV 345 kV to 362 kV

11 ft. 8 in. 13 ft. 0 in. 15 ft. 4 in.

11 ft. 8 in. 13 ft. 0 in. 15 ft. 4 in.

4 ft. 0 in. 5 ft. 3 in. 8 ft. 6 in.

3 ft. 6 in. 4 ft. 9 in. 8 ft. 0 in.

500 kV to 550 kV 765 kV to 800 kV

19 ft. 0 in. 23 ft. 9 in.

19 ft. 0 in. 23 ft. 9 in.

11 ft. 3 in. 14 ft. 11 in.

10 ft. 9 in. 14 ft. 5 in.

Nominal System Voltage Range, Phase to Phase

Limited Approach Boundary (1)

Notes: For SI units 1 in. = 25.4 mm 1 ft. = 0.3048 m For flash protection boundary see 130.3(A) (1) See definitions in Article 100 and text in 130.2(D)(2) and Annex C for elaboration.

(1) The qualified person is insulated or guarded from the live parts operating at 50 volts or more (insulating gloves or insulating gloves and sleeves are considered insulation only with regard to the energized parts upon which the work is being performed), and no uninsulated part of the qualified person’s body crosses the Prohibited Approach Boundary set forth in Table 130.2(C). (2) The live part operating at 50 volts or more is insulated from the qualified person and from any other conductive object at a different potential. (3) The qualified person is insulated from any other conductive object as during live-line, bare-hand work. 130.7(C)(6) Hand and Arm Protection. Employees shall wear rubber insulating gloves where there is danger of hand and arm injury from electric shock due to contact with live parts. Hand and arm protection shall be worn where there is possible exposure to arc flash burn. The apparel described in 130.7(C)(13)(c) shall be required for protection of hands from burns. Arm protection shall be accomplished by apparel described in 130.7(C)(5). 130.7(C)(13)(c) Hand Protection. Leather or FR gloves shall be worn where required for arc flash protection. Where insulating rubber gloves are used for shock protection, leather protectors shall be worn over the rubber gloves.

FPN: Insulating rubber gloves and gloves made from layers of flame-resistant material provide hand protection against the arc flash hazard. Heavy-duty leather 2 (e.g., greater than 12 oz/yd ) gloves provide protection suitable up to Hazard/Risk Category 2. The leather protectors worn over insulating rubber gloves provide additional arc flash protection for the hands. During high arc flash exposures leather can shrink and cause a decrease in protection.

Discussion From Section 1910.333 of the OSHA requirements, it is stated that rubber insulating gloves should be worn as personal protective equipment (PPE) whenever a qualified person is working inside of the clearance distance provided in Table S-4. NFPA 70E specifies that rubber insulating gloves should be worn when a qualified person breaches the Restricted Approach Boundary, as defined in Table 130.2(C). If one closely examines these tables, one would recognize some slight discrepancies in the associated distances. It is suggested that the NFPA 70E table be used since it is more restrictive. It should be noted that only qualified persons are allowed inside these boundaries. Further, it should be noted that these requirements are associated with shock protection only.

Arc Flash Safety Handbook — Volume 2 With respect to arc flash protection, NFPA 70E requires both unqualified and qualified persons, to wear leather or FR gloves whenever they breach the Flash Protection Boundary. This requirement suggests that leather covers should always be worn when rubber insulating gloves are being worn. OSHA requirements in 1910.137 also require that protective covers be worn with rubber insulating gloves, but these requirements include exceptions to wearing the covers, particularly when high finger dexterity becomes an issue. Unfortunately, the more recent guidance of NFPA 70E supersede these exceptions due to arc flash requirements; therefore, leather covers should always be used where rubber insulating gloves are required for shock protection. To summarize the discussion so far, the following requirements apply to wearing protective gloves: 1. Rubber insulating gloves should be worn whenever a worker breaches the Restricted Approach Boundary. 2. Leather or FR gloves should be worn whenever a worker breaches the Flash Protection Boundary. 3. Leather protective covers should be worn over the rubber insulating gloves whenever the worker will be breaching both the Restricted Approach Boundary and the Flash Protection Boundary.

From 1910.137, other requirements are provided associated with the use of rubber insulating gloves. The gloves should be inspected and air tested every time they are used. Further, rubber insulating gloves should be proof-tested every six months. These activities should minimize the potential for the gloves not protecting the worker when used in the workplace. The worker should also be cognizant of the difference between the testing voltage and the use voltage. The glove classification and the testing voltage are required to be identified on the cuff of the glove. This could provide the worker with a false sense of security if the testing voltage is mistaken for the use voltage. It is the responsibility of the qualified worker to know the difference and to apply them correctly. Since 1910.137 has been published, a Class 00 glove has been approved for use. This glove classification has a use voltage of 500 volts with a testing voltage of 2,500 volts.

In addition to observing the previously discussed requirements, one should always use gloves that fit properly. This will minimize the chaffing and hand fatigue. When selecting a glove size, measure the circumference around the palm. Allow for additional room if fabric or thermal glove liners are to be worn.

21 When purchasing gloves, purchase the matching leather covers at the same time and always retain the canvas bag that come with the gloves. The leather covers should be shorter than the rubber insulating gloves to minimize the potential for electrical tracking when in use. Also, exposure to sunlight and fluorescent lighting will greatly reduce the useful life of rubber insulating gloves. When the gloves are not being used, they should be stored in a dark place. The canvas bags are an ideal storage container. As Operations Manager of ESCO Energy Services Company, Lynn brings over 25 years of working knowledge in design, permitting, construction, and startup of mechanical, electrical, and instrumentation and controls projects as well as experience in the operation and maintenance of facilities. Lynn is a Professional Engineer, Certified Energy Manager and has a BS in Nuclear Engineering from the University of Tennessee.

Arc-Flash Safety Handbook Volume 2 Patent Pending UL and CUL Rated

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• Use with low and medium voltage circuit breakers produced by all the major switchgear manufacturers • Use with horizontal and vertical types of air, SF6 and vacuum circuit breakers • Remote operation places operator outside the arc flash protection boundary • Height and angle of the drive is easily adjusted • Quick release drive shafts and couplings simplify setup • Over-racking protection is provided • Battery operated with built-in charger

Published by InterNational Electrical Testing Association

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Arc Flash Safety Handbook — Volume 2

Arc Flash Labels — Why Bother? NETA World, Summer 2006 Issue by Ron Widup and Jim White Shermco Industries

Often times the question comes up, “Do we have to put arc flash labels on our equipment?” This is a fair question. To answer it is helpful to know how the wording for Article 110.16 of the National Electrical Code (NEC) came about. The NFPA 70E Committee introduced a proposal to the NFPA 70 Committee (NEC) to require arc flash hazard labels on all newly-installed electrical equipment that may require servicing or maintenance while energized. After much deliberation, the NEC Committee decided that the information pertaining to the circuits could change over time, leaving the technician underprotected and relying on outdated information. A requirement was accepted that all new (2002 and later) equipment must be field-marked warning a qualified worker about the hazards of arc flash and shock if covers are removed. Field-marked indicates that the installer must ensure the labels are applied and correctly oriented so they are clearly visible to anyone who may be involved in servicing or maintenance. Figure 1 shows such a label. It is basically a hazard reminder, without giving the worker specific information to help him assess the electrical hazards involved.

Figure 1 — Mandated Warning Label

Quite often we have seen an approach to hazard identification by labeling all of the electrical power devices, whether they were recently installed or had been in place for several years, without verifying the actual data associated with a particular piece of equipment or providing equipment specific data. When the facility has hundreds, or even thousands, of generic warning labels, the effectiveness of those labels are very low. At the recent PowerTest Conference, one of the participants in the electrical safety panel discussions asked, “I’ve done the Arc Flash Study – why have the need to label?” The answer can be summed up in two words, liability and responsibility. OSHA’s Multi-Employer Worksite Policy (CPL2-0.124) ensures that whether a worker is contracted or a permanent employee, the host employer is responsible, at least in part, for the worker’s safety. The best reason to label is responsibility. OSHA 29 CFR 1910.132(d)(1) states, “The employer shall assess the workplace to determine if hazards are present, or are likely to be present, which necessitate the use of personal protective equipment (PPE). If such hazards are present, or likely to be present, the employer shall: Select, and have each affected employee use, the types of PPE that will protect the affected employee from the hazards identified in the hazard assessment;” [29 CFR 1910.132(d)(1)(i)]. If you employ qualified workers engaged in the servicing and maintenance of energized electrical equipment you have the responsibility to assess the hazard, select the correct PPE to protect them based on the hazard, supply that PPE to the employees and ensure it is used properly. Due to the abovereferenced OSHA policy, you also have the responsibility to see that contracted employees select and use the proper PPE. If you conduct an Arc Flash Study and don’t install the labels, you haven’t really discharged the responsibility to the employees or contracted employees.

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Arc Flash Safety Handbook — Volume 2 NEC Article 110.16 Flash Protection Switchboards, panelboards, industrial control panels, meter socket enclosures, and motor control centers that are in other than dwelling occupancies and are likely to require examination, adjustment, servicing, or maintenance while energized shall be field marked to warn qualified persons of potential electric arc flash hazards. The marking shall be located so as to be clearly visible to qualified persons before examination, adjustment, servicing, or maintenance of the equipment. FPN No. 1: NFPA 70E-2004, Standard for Electrical Safety in the Workplace, provides assistance in determining severity of potential exposure, planning safe work practices, and selecting personal protective equipment. FPN No. 2: ANSI Z535.4-1998, Product Safety Signs and Labels, provides guidelines for the design of safety signs and labels for application to products. Performing the assessment required by 1910.132(d) is important, but communicating that information to employees, both in-house and contracted, is equally important. Having the information safely tucked away in a file cabinet somewhere on site is not going to prevent one from being injured or killed. Arc Flash labels ensure that all persons who need that information have it available to them. Will it prevent someone from ignoring the labels and injuring themselves? Of course not! There will always be a segment of the population that does not follow procedure and ignores warnings, but when the equipment is properly labeled (in addition to a properly administered safety program) and a good-faith-effort is shown, it not only puts your company in a legally-defensible position but more importantly, it helps establish a culture of electrical safety and communication which ultimately should help reduce electrical injuries and incidents. This works much better than saying, “They should have been qualified; that’s why I contracted them.” OSHA wants you to be proactive, not reactive. There are various styles of labels and the information on them can be customized to meet a company’s specific needs. Figures 2 and 3 show different approaches that are being used for labeling of equipment.

Figure 2 — Arc Flash Hazard Label

Figure 3 — Arc Flash Hazard Label

24 Don’t forget that once these labels are placed on the equipment they must be updated when needed. Significant changes to your power system such as up-sizing transformers or cables, changes in relay settings, and utility fault-current contribution changes, can drastically change the amount of short-circuit current that may be available in segments of your electrical power distribution system. The physical properties of the Arc Flash labels must be monitored as well. They fade, especially when used outdoors. They peal and they are damaged by wear or accident. Replace them when they no longer convey the needed information or cannot be easily identified.

Summary In today’s litigious society, people are quick to seek redress for any accident and are reluctant to accept responsibility for their actions (or mistakes). The owners of electrical equipment must do all they can to show good-faith effort and protect their workers. Even if you win a lawsuit, you still lose. Time, money and resource are diverted from the goals of the company and everyone suffers. Ron A. Widup and Jim White are NETA’s representatives to NFPA Technical Committee 70E (Electrical Safety Requirements for Employee Workplaces). Jim White is nationally recognized for technical skills and safety training in the electrical power systems industry. He is currently the Training Director for Shermco Industries, a NETA Accredited Company. Jim has spent the last twenty years directly involved in technical skills and safety training for electrical power system technicians.

Arc Flash Safety Handbook — Volume 2

Arc Flash Safety Handbook — Volume 2

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Layered Clothing — Why It Makes Sense NETA World, Fall 2006 Issue by Ron Widup and Jim White Shermco Industries

A number of manufacturers have recently been touting the benefits of their new layered arc flash protective equipment. This aspect of arc flash PPE really gets to the heart of protecting people. It has been recognized for some time that wearing layers of clothing will increase the ability of the PPE system to dissipate the heat from an arc flash. The word “system” is emphasized because we must view PPE and arc-rated clothing as a system of individual articles of clothing and equipment that, when used together properly, greatly improve their performance over that when used individually. Below is an arc flash label from one manufacturer’s clothing, Figure 1. Note that it states that when this arc flash PPE is worn without underlayers the probability of

a second-degree burn through the fabric is 50 percent if it were to be exposed to its rated incident energy for 6 cycles (1/10th second). The PPE system also includes items such as hearing protection, UV-rated safety glasses or goggles, heavy leather safety shoes, and underlayers. Underlayers, as the name implies, is the clothing worn under the arc flash protective clothing. Wearing the improper type of underlayers greatly increases the chances of a residual burn from an arc flash. Spandex® is a synthetic fiber that can melt at temperatures as low as 1800F. When an arc flash hits the outer layer of clothing, even arc-rated clothing, it heats up tremendously. Some of this heat is transferred through the fabric. (Think of pulling your jeans out of a hot dryer and putting them on.) Enough heat can be transferred through the arc-rated cloth1 2 ARC 15 – Arc Rating (ATPV) 15 cal/cm ing to melt the underlayers. This would be 2 nd a very painful burn, especially for female Probability of 2 ARC 15 Suit Over 4.5 2 ARC 15 Suit Over 2 technicians wearing synthetic lingerie. Degree Burn ARC 15 Suit oz/yd FR Daily Work 2 4.5 oz/yd FR Electrical workers must be trained in this or FR Fabric Wear and Cotton No Underlayers Daily Workwear2,3 2, 3, 4 type of hazard, as most people would not Break-Open Longjohns generally think of it. Cotton underlayers 50% ATPV50 15 ATPV50 24 E8050 46 are recommended in most circumstances, although increased protection can be pro40% ATPV40 14 ATPV40 23 E8040 46 vided by FR underlayers. The rule-of-thumb we are often quoted 30% ATPV30 14 ATPV30 22 E8030 45 is that for every layer of clothing worn under arc-rated clothing, the heat drops 20% ATPV20 14 ATPV20 21 E8020 44 by 50 percent. By wearing FR dailywear and cotton underlayers, the heat will 10% ATPV10 14 ATPV10 20 E8010 43 drop by 50 percent for each layer, at least 5% ATPV5 14 ATPV5 19 E805 42 on those areas that are covered. The air between the layers of clothing increases ATPV1 17 E801 40 1% ATPV1 13 the ability of the arc-rated clothing to dissipate heat, much like a down jacket is Figure 1 — Arc Energy Ratings for Example FR Clothing warmer due to the air pockets around the Courtesy Oberon Company feathers. One protest often heard is that

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Arc Flash Safety Handbook — Volume 2 Typical System Weights for a Range of Arc Ratings System Rating cal/cm

2

1st Generation FR Cotton & Hybrids

2nd Generation Aramid Systems

15 to 20

13 oz/yd

2

8.8 oz/yd2

25 to 31

17 oz/yd2

9.7 oz/yd2

40 to 50

24 oz/yd2

12.1 oz/yd2

65 to 76

34 oz/yd2

15.5 oz/yd2

100

41 oz/yd2

24.5 oz/yd2

Figure 2 — Fabric Weights for FR Clothing Systems

From “Arc Flash Improvement Update and Worker Heat Stress Analysis for Arc Flash PPE” Dr. Tomas Neal, 13th Annual IEEE Electrical Safety Workshop

wearing a tee-shirt as required by the NFPA 70E Table 130.7(C)(10) is too hot and uncomfortable in the summer. Actually, a person wearing a tee-shirt will stay cooler, since the tee-shirt wicks moisture from the body, allowing it to evaporate more effectively. The tee-shirt also provides an air layer which is so important to dissipate heat, at least on the areas covered by it. Note in Figure 1 that wearing just the arc-rated FR clothing provides a 50 percent probability of a second-degree burn at 15 cal/cm2. Wearing FR dailywear clothing underneath increases that rating to 24 cal/cm2. Adding underlayers such as the longjohns will increase that rating to 46 cal/cm2. The preceding numbers are for a 50 percent probability of a second-degree burn. I am not advocating wearing longjohns in Texas during the summer, or almost any other time, but any areas covered by underlayers reap the benefit of increased heat dissipation. Figure 2 shows another aspect of layering. Newer, layered FR clothing outperforms single-layer systems and is much lighter in fabric weight. This is one of the reasons the NFPA 70E Committee voted to eliminate the weights of fabrics from Table 130.7(C)(11). At Shermco, we issue our field service technicians 65 cal/cm2 arc-rated PPE. We don’t expect them to work at that level, but we often have to work on or near electrical systems whose previous maintenance history is questionable. If there is an extra arc rating for the FR clothing system, it theoretically will provide a cushion if something should go wrong. Note in Figure 2 that an older single-layer 65 calorie arc flash suit weighs 34oz/yd2. This is very uncomfortable and restricts movement to a degree that most tasks are not practical, at least for many people. Multilayer, arc-rated clothing and PPE in the newer systems weigh in at 15.5 oz/yd2, a reduction of more than half ! This is the type of weight reduction that can improve wearability and reduce heat stress.

Summary Electrical safety, especially around arc flash hazards, is a critical aspect of employee safety. Understanding the importance of a layered system of protective clothing and PPE is part of being a qualified electrical worker as well as providing protection in the case of an electrical incident. Layering clothing provides extended performance of arcrated clothing and offers a method to minimize burns due to heat transfer during an arc flash. Be safe out there – and remember “If you turn it off, you don’t have to worry about it.” Ron A. Widup and Jim White are NETA’s representatives to NFPA Technical Committee 70E (Electrical Safety Requirements for Employee Workplaces). Jim White is nationally recognized for technical skills and safety training in the electrical power systems industry. He is currently the Training Director for Shermco Industries, a NETA Accredited Company. Jim has spent the last twenty years directly involved in technical skills and safety training for electrical power system technicians.

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Arc Flash Safety Handbook — Volume 2

So, You Think You’re Qualified? PowerTest 2007 (NETA Annual Technical Conference) Jim White Shermco Industries

Of Course I’m Qualified, I’m a Master Electrician!! This paper first appeared in the “Safety Corner” column in the NEC Digest on December, 2005 (part 1) and February, 2006 (part 2) Have you ever talked to someone who is a Journeyman or Master Electrician about whether or not they are qualified? You would think you insulted their mother! Many companies hire only electrical workers who have a Journeyman’s or Master’s license or have a two-year degree from a technical school thinking that these people will be fully qualified. The problem with this seemingly good logic is that the term “QUALIFIED” is not completely dependent upon a person’s knowledge or expertise, although that is certainly an important part. Qualified is an involved term requiring expertise and knowledge in many areas that are not typically addressed in apprenticeship, technical schools or on the licensing tests. Construction and maintenance activities have little to do with each other from a job task standpoint. Most electrical workers on construction sites rarely, if ever, get involved in maintenance or testing activities. Looking at the definition of a qualified electrical worker from both OSHA and the NFPA 70E makes it clear that just because we have years of experience, it does not mean we are qualified to do all electrical work. I like to point out to the students in my classes that I’m qualified for working on substation equipment, such as transformers, protective relays and circuit breakers, but not qualified when working on motors, PLC’s or VFD’s. If I work on a PLC or VFD, one of us could get hurt! Maintenance involves primarily testing and troubleshooting, with some repair or replacement of equipment, while construction involves primarily installation of electrical

systems to the requirements of the NEC. In construction (except for temporary circuits), the energized work comes after months of working with deenergized systems. There are some very real differences in the way a worker needs to approach these job tasks. I would like to point out that the hazards faced by both groups are the same; that is shock, arc flash and arc blast. Whether involved in construction or maintenance activities, the NFPA 70E requirements will protect the worker.

And Your Point Is………….. What does OSHA expect for a person to be a considered a qualified electrical worker? First of all, a qualified electrical worker must meet the OSHA definition as stated in 29CFR1910.399, “Qualified person.” One familiar with the construction and operation of the equipment and the hazards involved. Note 1: Whether an employee is considered to be a “qualified person” will depend upon various circumstances in the workplace. It is possible and, in fact, likely for an individual to be considered qualified” with regard to certain equipment in the workplace, but “unqualified” as to other equipment. (See 1910.332(b)(3) for training requirements that specifically apply to qualified persons.) The NFPA 70E states this definition in stronger terms, “Qualified person.” One who has the skills and knowledge related to the construction and operation of the electrical equipment and installations and has received safety training on the hazards involved.” This definition is expanded on in Article 110.6(D)(1) where it states, “A qualified person shall be trained and knowledgeable of the construction and operation of equipment or a specific work method and be trained to recognize and avoid the electrical hazards that might be present with respect to that equipment or work method.”

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Arc Flash Safety Handbook — Volume 2

The intent in both definitions is not that the person be an “expert” at say, designing or tearing down a circuit breaker, but that he understands how circuit breakers are constructed and how they are operated. Different voltage classes of circuit breakers may require additional training to ensure an understanding of the differences, both in construction, operation and also whatever hazards may be present. A worker who has had training on the construction, operation and hazards associated with a low-voltage moldedcase circuit breaker could be considered qualified with regard to those devices. However, he would not be qualified to work on a 15kV air-magnetic circuit breaker, a vacuum circuit breaker, an oil circuit breaker or a gas breaker. Even though the basic construction and operation of the two air breakers are similar, there are substantial differences in construction, operation and especially where potential hazards are concerned. So, if we use a plant-type electrician who works on low-voltage circuit breakers and then is tasked with working on medium-voltage metal-clad switchgear, what can be done to qualify that person? Figure 1 shows a worker racking a vacuum circuit breaker in while his safety backup observes. Note the PPE required for this task. Figure 2 shows the PPE typically needed to work on a molded-case type circuit breaker with a 22,000A interrupting rating.

Options include On-The-Job (OJT) training, formal classroom training and a combination of the two. OJT is a double-edged sword; the price is right, but there are some inherent problems. If the person conducting the OJT is well-qualified and has good work practices, that is what will be passed on. I’ve had some very good OJT training when I was in the field. The problem comes up when the person conducting the OJT training has bad habits or has an incomplete understanding of what he is teaching, which has also happened to me. Years ago when I was first learning how to calibrate protective relays I was taught that directional overcurrent relays are tested by jumping out the directional unit contact and testing as an overcurrent relay. Not good, since if the directional unit fails, the relay is nonfunctional. I later was taught how to properly calibrate those relays, but in the ensuing period of time I “calibrated” many of these relays incorrectly. Another issue that I see consistently with companies that train by OJT is a lack of recordskeeping. They conduct the training, but there’s either no documentation or very poor documentation. Either way the company is now open to citations and fines from OSHA since they can’t prove the worker had that training. Formal training can be very good, especially if it has hands-on labs included in the curriculum. The problems with formal training are: 1. Cost. Typically high when people have to be sent out of town, mostly due to travel costs. This can be made much more reasonable if training at your job-site is performed, as opposed to sending everyone out. Instead of paying for 5, 7 or 10 people’s travel expenses you pay for one (the instructor’s). If only three or four people are being trained, it’s pretty much a toss up how you go.

Figure 1 — Racking a 15kV Vacuum Circuit Breaker

2. Use It or Lose It. You can’t send someone to a technical-skills training course, wait five years and then expect them to remember what was learned. OSHA 29CFR19 10.269(a)(2)(iv)(C) Note states, “OSHA would consider tasks that are performed less often than once per year to necessitate retraining before the performance of the work practices involved.” The reason for this is simple, you use it or you lose it. The best practice is to have a program consisting of both OJT and formal training. Formal training to ensure full understanding is achieved is a great way to bring people up to speed quickly. When these classes are conducted at your site, they can be customized to your equipment and incorporate your procedures. OJT follows, having the trainee perform work on that type of equipment or device in a plant environment, participating in shut downs or other maintenance activities in order to keep their skills up.

And Now, For The Rest Of The Story Figure 2 — Installing a Molded-Case Circuit Breaker

Meeting the base definition of a Qualified Person is only part of the story. The rest of the requirements come from 29CFR1910.332 and .333. 1910.332 states, “Qualified

29

Arc Flash Safety Handbook — Volume 2 persons (i.e. those permitted to work on or near exposed energized parts) shall, at a minimum, be trained in and familiar with the following: 1. The skills and techniques necessary to distinguish exposed live parts from other parts of electric equipment. 2. The skills and techniques necessary to determine the nominal voltage of exposed live parts, and

3. The clearance distances specified in 1910.333(c) and the corresponding voltages to which the qualified person will be exposed.

Note 1: For the purposes of 1910.331 through 1910.335, a person must have the training required by paragraph (b)(3) of this section in order to be considered a qualified person.” In the .269 regulation, a qualified person has to demonstrate proficiency in these areas. That means there has to be some show-and-tell in the training or documented on the jobsite to ensure the person can do it, not just talk about it. In order to able to comply with Number 1 above, a worker must be able to choose the correct voltage detector or tester, be able to inspect it to ensure it is safe to use and then be able to use it properly and safely. This would include the Live-Dead-Live method of testing, mandated by OSHA when voltages are above 600V. At Shermco we recommend it to our technicians, students at our training courses and our field service customers, as well. E.I. DuPont has a program called, “Test Before Touch” (TBT) that covers everything a person needs to put an electrical system in an electrically-safe work condition and is easy to remember, using signs placed on electrical equipment as a reminder and issuing wallet cards to their employees. Photos 1 and 2 are front and back examples of such a wallet card. DuPont has no copyright on this material and encourages people to use the program.

Photo 1 TBT Wallet Card – Front

Photo 2 TBT Wallet Card – Rear

The determination of nominal voltages (Number 2) is fairly easy. Checking dataplates, nameplates or single-line diagrams would provide that information. What a lot of people don’t seem to understand is the use of the word “nominal” in this context. Many of the students in my training programs seem to think that they should determine the actual voltage. The manner in which the word “nominal” is used means “system design voltage”. This is to allow the worker to choose PPE and their test devices without making contact with an energized electrical system before they know what they may make contact with. Checking dataplates and single-lines would achieve this goal. The clearance distances in Number 3 above are the “Safe Approach Distances for Qualified Persons” in 29CFR1910.333(c). Since the .269 regulation was issued voltages above 750V are covered by that document, rather than .333. This is because .269 became law four years after the .333 regulations. Table 130.2 in the NFPA 70E reflects this change in the column titled “Restricted Approach Distances”. These distances are the closest a qualified electrical worker can approach an exposed, energized conductor or circuit part and then must wear appropriate rubber insulating PPE, or have that conductor or circuit part insulated for the voltage, or use live line or insulated tools or be in an insulated bucket truck, depending on the voltage. This is only looking at the shock hazard, however, and arc flash PPE may also be required. 1910.333 states, “Only qualified persons may work on electric circuit parts or equipment that have not been deenergized under the procedures of paragraph (b) of this section. Such persons shall be capable of working safely on energized circuits and shall be familiar with the proper use of special precautionary techniques, personal protective equipment, insulating and shielding materials, and insulated tools.” This paragraph requires that if a circuit is not in an electrically-safe work condition, it must be worked as if it were energized. One of the first requirements specified is that a person be “capable of working safely”. This sounds a little strange at first glance. If a worker is not able to work safely,

30 why is he working as a qualified electrical worker at all? This requirement reflects the reality that there are times when all of us may not be capable of working safely, at least on a temporary basis. If we are ill, or fatigued our responses and decision-making processes are similar to someone who is intoxicated. If we are taking medications, whether over-thecounter or prescription, we may be impaired. Several states have cited drivers for DUI due to the effects medications may have had on their ability to operate a motor vehicle. Lastly, what if we are undergoing severe mental or emotional stress? Unfaithful spouses, children taking drugs, etc can impair our ability to concentrate at the task at hand, which if it is working on energized electrical systems; we need all the faculties we can muster. We are not capable of working safely. The “use of special precautionary techniques” requirement refers to using safety barrier or tape to cordon off a safe work zone when working energized. There are two hazards that can be quantified; arc flash and shock. The arc blast hazard is being studied and hopefully we will soon be able to quantify its limits in the same way we do for the other two hazards. The Limited Approach Boundary listed in the 70E can be defined as the closest an unqualified person can get to an exposed, energized conductor or circuit part. The Flash Protection Boundary is the distance from an exposed, energized conductor or circuit part where a worker would receive the on-set of a second-degree burn on unprotected skin. Whichever of these boundaries if furthest from the exposed, energized circuit or part is where the barriers, signs or attendants need to be placed. The “use of personal protective equipment, insulating and shielding materials, and insulated tools” requirement also requires the proper selection of such tools, PPE and insulating and shielding materials, inspection and safe use of these items. Are the materials and tools being used appropriate for the voltage, conditions of use and do they meet ASTM and NFPA 70E standards? Are the properly marked? Is there any damage to arc flash PPE that could cause them to be unsafe, such as holes or grease spots? Are the PPE and equipment being worn properly? Are there gaps in the seals that could allow heat to enter when wearing arc flash PPE? Is the clothing the right size? If you look like sausage boy in your arc flash coveralls, the incident energy could be transferred right through the clothing and you’ll receive a severe burn. One additional requirement that Joe Rachford of Gallatin Steel uses that I really like is that “the person must be mature enough to handle the responsibilities of the work”. The old saying, “The only difference between a man and a boy is the cost of his toys” is not too far from the mark at times. Do you have someone who engages in horseplay while on the job? Do they make bad decisions that could affect other workers or themselves? This may not be the person you want working on hazardous systems. The decision-making process is extremely important to electrical safety. If a

Arc Flash Safety Handbook — Volume 2 person cannot plan and prepare for an energized electrical project, using common sense and intelligence, they are not capable of working safely, either. Qualified. It’s not your father’s definition.

Summary Having qualified electrical workers is at the crux of a safe work environment. It is the people working on the power system that make for a safe work environment. That being said, the systems we have (or don’t have) in place, our work culture and the work environment all have a tremendous impact on safety in the workplace. People, of course, control most of these factors, so people require training and safe, reliable systems to manage this hazardous substance we call electricity. Jim White is the Director of Training for Shermco Industries, a NETA Accredited Testing Company and is nationally recognized for technical skills and safety training in the electrical power systems industry. Jim is a NETA Certified Level IV Technician, and serves as the alternative NETA representative on the NFPA 70E Committee. He is the NETA representative on the newly-formed IEEE/NFPA Arc Flash Hazard Work Group (RPTC). Additionally he serves as the secretary for the 2006 IEEE Electrical Safety Work Shop, is an authorized OSHA Outreach instructor, the Vice Chair of the Doble Transformer Field Processing Subcommittee and a member of the Asset Maintenance Management Committee and Circuit Breaker Committee. Jim is an associate IEEE member and Inspector member of the International Association of Electrical Inspectors (IAEI).

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Arc Flash Safety Handbook — Volume 2

The Challenge of High Impedance Faults – Setting and Testing Dilemmas PowerTest 2007 (NETA Annual Technical Conference) Helmut G. Brosz and Peter J.E. Brosz Brosz and Associates

High Impedance faults results when an energized primary conductor comes into contact with a quasi insulating object. Typically, a high impedance fault exhibits arcing and flashing at the point of contact. The significance of these hard to detect faults is that they represent a serious public safety hazard as well as a risk of arcing ignition of fires. High impedance fault detection has been a major concern of protective relaying for a long time. The vast majority of these faults are ground faults. This presentation discusses some of the field trials that have been conducted by manufacturers performing stagedfault testing at different utilities and protective relays that manufacturer’s have brought to market. A conventional protection system based on overcurrent and impedance are suitable only for relatively large fault currents. However, as small percentage of the ground faults have very large impedance, often comparable to load impedance and consequently have very little fault component of current. Although these high impedance faults do not create imminent danger to power system equipment, they are a considerable threat to humans and property. DEFINITION: The IEEE power system relay committee working group on high impedance fault detection technology, defines high impedance faults as those that do not produce enough current to be detectable by convention over current relays or fuses. High impedance fault detection has been a major concern for relaying engineers for a long time and have been challenged to develop a suitable technique that will detect high impedance faults with a reasonable degree of

reliability, while being secure against false detection. Utilities have public safety in mind. However, high impedance fault detection has not been possible in the past and realistic detection algorithms are not anticipated that can detect 100% of all downed conductors, while having 100% security against misoperation. Utilities need an affordable/cost effective economic solution and a system that can reliably detect high impedance faults. Various Utilities and Labs tested a number of high impedance fault detection systems. The most significant result was that the higher frequencies of high impedance fault signatures played an important role in high impedance fault detection and in distinguishing high impedance faults from other types of faults, or normal arcing operations. Some High impedance fault detection uses three algorithms based on 1. Higher order statistics 2. Wavelets and neural networks. 3. Decision logic The acquired data is filtered using a band pass filter. The energy is then calculated and the calculated energy is compared to a threshold to determine if a high impedance fault has occurred. The first neural network investigated used one thousand input nodes to the network. The network was trained with 600 input/target cases, (300 high impedance fault data, and 300 load data), and had a sum-squared error of 1.4 after completion of learning (one misdetection and 0 false alarms) The network achieved a detection rate of 70.83 percent with a 22 percent false alarm rate. A second neural network design used fast Fourier transforms

32 truncated at the thirteenth harmonic and out of 600 cases had 8 misdetections and 4 false alarms according to one manufacturer. The third neural network architecture was a combination of the two previous networks operating in parallel. If the output of both networks was greater that 0.5 then a positive detection was indicated. If the two networks disagreed, the output was summed and a variable threshold was used to make the decision according to one manufacturer.

Laboratory Test Results Field tests were done with bare conductor connected to one terminal of test transformer to simulate a downed transmission line. The other terminal was connected to a copper plate buried in soil, thereby simulating the ground electrode and the earth. The bare conductor was dropped on a variety of soil surfaces to investigate differences in resulting currents. The current signatures were collected using a data acquisition system. Each trial case was conducted for 50 second duration. This data acquisition scheme was also used to collect signatures for currents for single phase non linear loads ( e.g. TV, fluorescent lamp, PC, bridge rectifier, phase controlled motor drive, and arc welder). The higher order statistics based algorithms tested indicate a probability of detection of about 97% with a zero false alarm rate. The wavelet based algorithm delivers about 80% detection with a 0.5 false alarm rate. Helmut G. Brosz, P. Eng., Adjunct Assistant Professor at University of Toronto, CEO of Brosz and Associates, and Director of the Institute of Forensic Electro-Pathology, graduated from the University of Toronto in electrical engineering in 1966 and in business administration in 1970. A consultant on electrical maintenance practices, insurance losses and loss prevention, he has investigated over 4400 major electrical failures for insurance companies, law firms, industry, etc. He has testified in property damage, personal injury, safety, product liability cases, and many others. Peter J. E. Brosz, Dipl. Elec. Tech., B.Eng., graduated from George Brown College in Electrical Engineering Technology in 1995. He then went on to earn a degree in electrical engineering from Ryerson University, graduating in 2000. During the seven summer breaks, he worked at Dynaway Electric, Electrical Testing Instruments, Rybka Smith and Ginsler, Tamini Transformatori, FGH Mannheim. After graduating from Ryerson University, he worked at Canadian Standards Association for one evaluating and testing IT equipment for safety and fire certification. Presently, he works at Brosz and Associates as a project engineer.

Arc Flash Safety Handbook — Volume 2

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Arc Flash Safety Handbook — Volume 2

Tables, Labels, and HRCs NETA World, Spring 2007 Issue by Ron Widup and Jim White Shermco Industries

When using the NFPA 70E, do you understand the tables in Article 130 and how they are intended to be used? Do you apply the parameters of the tables properly? Let’s discuss the tables, the labels, and the Hazard/Risk Categories (HRCs). There are two factors in the tables to consider, the hazard and the risk.

The Hazard When using the tables in 70E the hazard is the estimated incident energy. This is expected to fall within certain range based on the maximum short-circuit current and the maximum total clearing time of the protective device. In Table 130.7(C)(9)(a), the notes provide the limitations of the table for each type of task and equipment category. If the available short-circuit current or clearing time of the protective device is greater than that specified in the table notes, the table cannot be used. As an example, Note 1 applies to the equipment category, “Panelboards Rated 240 V and Below – Notes 1 & 3.” Note 1 states, “25 kA short circuit current available, 0.03 second (2 cycle) fault clearing time.” If the equipment being worked on exceeds those limits, the table cannot be used to determine Hazard/Risk Categories for those tasks listed. So then how is the arc flash PPE and clothing chosen if the tables cannot be used? The NFPA 70E directs us to perform a detailed arc flash study, document 2, the incident exposure to the worker in cal/cm and choose PPE and clothing based on the incident energy. Article 130.3(B) states (B) Protective Clothing and Personal Protective Equipment for Application with a Flash Hazard Analysis. Where it has been determined that work will be performed within the Flash Protection Boundary by 130.3(A), the flash hazard analysis shall determine, and the employer shall document, the incident energy exposure of the worker (in calories per square centimeter). The incident energy exposure level shall be based on the working distance of the employee’s face and

chest areas from a prospective arc source for the specific task to be performed. Flame-resistant (FR) clothing and personal protective equipment (PPE) shall be used by the employee based on the incident energy exposure associated with the specific task. Recognizing that incident energy increases as the distance from the arc flash decreases, additional PPE shall be used for any parts of the body that are closer than the distance at which the incident energy was determined. As an alternative, the PPE requirements of 130.7(C)(9) shall be permitted to be used in lieu of the detailed flash hazard analysis approach described in 130.3(A). FPN: For information on estimating the incident energy, see Annex D.

The Risk When you look at a specific task in Table 130.7(C)(9)(a), the hazard and the risk are addressed. When assessing the risk associated with a task, some of the issues that need to be considered are: • The condition of the equipment being worked on. • The age of the equipment and its general design. Does it have venting that would direct hot gases towards personnel? Can it be racked with the door closed, or does it have to be open? Can it be racked, or does it have a lever device? • The maintenance history. Have there been problems and breakdowns with this piece of equipment? Is there a problem with it now? Have there been technical bulletins issued by the manufacturer? • The loading of the equipment. Is it heavily loaded or lightly loaded? Do you have to close a tie breaker before you trip the one you are working on? • The design of the power system. Is it a ring bus, radial bus, or double-ended substation? When it is isolated, what does that really mean?

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Arc Flash Safety Handbook — Volume 2

• The skill level of the personnel doing the work. Are they highly experienced, well-qualified? Has it been a while since anyone has done this task? Have they familiarized themselves with the manufacturer’s instructions for operating the equipment or are they “figuring it out as they go”?

The Tables The NFPA 70E standard is back in the review cycle and there are several proposals concerning the tables in Article 130 [130.7(C)(9)(a), 130.7(C)(10) and 130.7(C)(11)]. Of the 579 proposals submitted to the NFPA for this review cycle, there are 189 proposals that deal specifically with the tables and each one of them has to be considered and discussed, and action has to be taken by the 70E committee. A Task Group was formed to specifically look at the proposals associated with the tables, and during the recent review sessions the Task Group had some very interesting conversations regarding not just the tables, but their intent and purpose. One discussion revolved around Table 130.7(C)(9)(a) and the Hazard/Risk Categories. It was one of the basic principles of using the tables that both factors, equally important, are an integral part of the table usage. The hazard, as stated earlier, is typically quantified in calories per square centimeter and is the estimated incident energy exposure associated with the task. The risk, which is the element of the equation that becomes very subjective, is the probability of causing or being involved in an arc flash incident based on the task being performed. The NFPA 70E assumes the electrical devices have been properly engineered, designed, installed and maintained — and if not, 70E is not going to help. These factors are also considerations in a risk assessment. Also, one must be cognizant of the purposes of the PPErelated tables in Article 130: Table (C)(9)(a) (C)(10) (C)(11)

Description Deals with specific tasks while working on energized equipment Lists the PPE required after the Hazard Risk Category has been determined Lists examples of protective clothing systems and typical characteristics

An important point to note is that you cannot apply the HR categories of Table (C)(9)(a) unless you are performing the same task as listed within the Table and you meet all of the requirements of the notes. If your particular situation is not the same as listed in the Table or does not meet the requirements of the notes then you cannot use the Table, and you must perform a detailed flash-hazard analysis.

WARNING

!

Arc Flash and Shock Hazard Appropriate PPE Required 252 inch 38.2 cal/cm 2 Class 4 480 VAC 00 42 Inch 12 Inch 1 Inch

Flash Hazard Boundary Flash Hazard at 24 Inches Cotton Underwear + FR Shirt & Pant + Multi Layer Flash Suit Shock Hazard when cover is removed Glove Class Limited Approach Restricted Approach Prohibited Approach

Bus: 3USS 480 V BUS Prot: 3USS MAIN Figure 1 — Arc Flash Warning Label

If you have not performed a flash-hazard analysis, be aware that you cannot use the Hazard/Risk Categories listed in Table (C)(9)(a) and work backwards into Table (C)(11) by selecting a task that has a particular Hazard Risk Category indicated in (C)(9)(a). For example, you have a task to rack out a 480-volt circuit breaker in 600 V class switchgear with the door open (shown in (C)(9)(a) as a Hazard/Risk Category 3) and you don’t know or haven’t met the requirements of the table notes. You cannot assume the task of racking out all 480-volt circuit breakers to be a HRC 3 task and apply the clothing system with a minimum arc rating of 25 calories per square centimeter as indicated in Table (C)(11). You must perform a complete flash-hazard analysis and quantify the hazard to verify the required level of PPE.

The Labels When using the arc flash warning labels, be aware that they typically state the level of hazard in calories per square centimeter and a defined working distance, but they do not take into account the risk. That’s one reason why the tables and the labels should not be mixed together. The tables are task-based; the labels are hazard-based. See Figure 1 for an example of an arc flash label. When using the labels, it may be possible to lower the amount of PPE based on risk, if that is what the risk assessment indicates. Performing a thermographic infrared scan is one example where the hazard may be high, but the risk may potentially be low. Typically it is noninvasive and can often be performed three or more feet away from the equipment being scanned, and except for during the removal of panels the plane of the switchgear is not typically broken. For example, a piece of equipment has a label that indicates an incident energy exposure of 8.2 calories at an 18 inch working distance. This would be classified as an HRC 3 situation (8.1 – 25 calories) so because of the working distances involved in the IR task,

Arc Flash Safety Handbook — Volume 2 reducing the level of PPE for the camera operator could be an option, based on the risk assessment. The personnel removing panels, however, would have a higher level of risk as they would be closer to the exposed part and using tools that could possibly drop into the equipment. Many programs and companies performing arc flash hazard analysis put the Hazard/Risk category on their labels in an attempt to guide workers to the correct PPE and clothing; however, one should be careful not to mix the two concepts, tables and labels. Whether the tables or arc flash warning labels are used, always perform a risk assessment based on the overall equipment condition, personnel, and specific tasks to be performed under the conditions that you have at that moment in time. While there are other factors to be considered as well, performing a risk assessment is critical to worker safety, regardless of whether the tables are used or an arc flash analysis is performed. Be safe out there and keep your workers informed and safe! Ron A. Widup and Jim White are NETA’s representatives to NFPA Technical Committee 70E (Electrical Safety Requirements for Employee Workplaces). Jim White is nationally recognized for technical skills and safety training in the electrical power systems industry. He is currently the Training Director for Shermco Industries, a NETA Accredited Company. Jim has spent the last twenty years directly involved in technical skills and safety training for electrical power system technicians.

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Arc Flash Safety Handbook — Volume 2

Methods of Inspection to Determine the Presence of Potential Arc Flash Incidents NETA World, Spring 2007 Issue by Mark Goodman UE Systems, Inc.

Arc flash can kill. Arc flash can be considered as a short circuit through the air. It produces tremendous energy that will travel outward from electrical equipment. An arc flash o produces temperatures as high as 35,000 F, which is hotter than the surface of the sun and produces a force that is equivalent to being hit by a hand grenade. The impact is so high it can cause hearing loss and memory loss. If it doesn’t kill you, it will severely burn or injure you. In addition, the conditions that produce an arc flash, even when no arc flash occurs, will also lead to damage to electrical equipment causing unplanned outages and costly downtime. Statistics show that five to ten arc flash explosions occur in electric 1 equipment daily within the US . Unreported instances are reputed to be several times greater. Many of these victims are so badly burned they require treatment at special burn centers. In the US, the Occupational Safety and Health Administration (OSHA) has become aggressive in their attempts to reduce arc flash incidents and has begun to use the National Fire Protection Association NFPA 70E Standard for Electrical Safety Requirements for Employee Workplaces, 2 2004 edition , as the guide for compliance for worker safety. There are standards for arc flash assessment, various types of PPE (Personal Protective Equipment), working around energized equipment, and opening enclosed equipment to name a few. All are geared for worker safety. There are many causes of arc flash. It can occur in any electrical equipment regardless of voltage. Arc-flash incidents can happen from poor work habits, dropping of tools, or accidental contact with energized equipment. However, there are conditions that produce the potential for arc flash within enclosed cabinets that can be detected before creating flashover or arc flash incidents. These conditions are arcing, tracking, and corona.

While infrared thermography will detect heat generated by arcing and in most instances tracking, it will not sense corona. If cabinets are enclosed, unless there is an IR test port, it is highly unlikely that infrared will detect the presence of these emissions. In addition, to view components within enclosed electrical cabinets, it is necessary to conform to NFPA standards with regard to PPE; therefore, in many situations IR inspectors must wear cumbersome clothing and hoods and perform the required procedure to open cabinets for inspection. This can be very time consuming and, in hot weather, very uncomfortable. An integrated approach incorporating infrared and ultrasound is recommended for the detection of the potential for arc flash. Arcing, tracking, and corona emissions produce ionization. Ionization is a process by which a neutral atom or molecule loses or gains an electron(s), thereby acquiring a net charge, becoming an ion. Ionization has by-products: ozone and nitrogen oxides. These combine with moisture to produce nitric acid, which is destructive to most dielectrics and certain metallic compositions, resulting in corrosion. The object of electric condition monitoring is to detect the presence of these events before flashover occurs or before they produce an arc flash incident when a cabinet is opened. Ultrasound technology is ideally suited for detecting these emissions since the ionization process produces frequencies in the ultrasonic region. Ultrasonic instruments sense between 20-100 kHz and use heterodyning to translate the ultrasonic emissions into the audible range. These portable instruments provide information via headphones for the audio signal and on a meter to display intensity readings, usually in decibels. These hand-held devices usually contain two sensing heads containing piezoelectric transducers: a scanning module for airborne sounds and a contact probe/ wave-guide for structure borne signals.

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Arc Flash Safety Handbook — Volume 2 How Portable Instruments Are Used to Detect Potential Failure and Arc Flash Conditions Typically an operator will scan around the door seams and air vents of enclosed electrical cabinets with the scanning module while listening through headphones and observing a display panel. Arcing, tracking and corona all have distinct sound qualities that can be heard. If there are no air paths, the inspector will use the waveguide to probe around the cabinet wall. Due to a possible change in wave characteristics as the ultrasound moves from airborne to structure borne, the operator will change the frequency from 40 kHz (effective for airborne scans) to 25 kHz. Should there be a need to analyze these patterns further, the sounds can be recorded and played back on spectral analysis software. Voltage will play a role in the diagnosis since corona will only occur at 1,000 volts and higher. There may be instances where it is difficult to determine the type of problem heard through the headphones. In these situations, a sound recording of the condition can be made (some instruments have on-board sound recording capability) and viewed on spectral analysis software. The sounds may be heard in real time as they are viewed on a fast Fourier transform (FFT) or time series screen for analysis. This enables inspectors to observe subtle problems that might be missed by just viewing a screen without sound. As an example, the following screen shows a transformer that had a typical transformer hum. By just observing the screen, the condition of loose windings might have been overlooked. The sound sample, showing a buildup and drop-off of the sound along with movement on the screen highlighted this condition.

Transformer Winding Time Series:

Transformer Winding Vibration Spectrum:

If any of these conditions are detected, the potential for arc flash exists and operators will be prepared to follow the correct procedures to safely open the equipment and repair the condition. Infrared scans can be taken to confirm the diagnosis and to identify any additional problems that would generate heat but not sound. We are often asked at which voltages and on what type of equipment is ultrasound most effective. The answer is not simple since it often depends on the individual asking the question. First of all, determining the definition of low, medium, and high voltages is relative. Those in the power distribution arena will look at 12 kV as medium voltage, those who work in a typical manufacturing plant will look on 440 volts as high voltage. The main electric problems detected ultrasonically are partial discharge, arcing, tracking, and corona. Ultrasound detects the ionization of air as it produces turbulence. This can be from corona, tracking or arcing. Heat is produced when there is either resistance due to corrosion or from tracking and arcing. Since heat is produced by the flow of current through corrosion or resistance, you can have a hot spot detectable with IR, and have no ultrasound because there would be no ionization.

Low-Voltage Equipment The main concern for ultrasound detection in low voltage equipment is arcing, since low voltage equipment rarely produces corona or tracking. Typically 110-, 220- and 440volt systems are inspected with infrared imaging and/or spot radiometers for temperature changes. Hot spots, usually an indication of increased resistance, can be indicative of a potential for equipment failure or they could indicate a possible fire hazard. When arcing occurs, it is often accompanied by heat. However, it is not always possible to detect a hot spot if the equipment is covered. Ultrasound will hear arcing in circuit breakers, switches, contacts, and relays. In most instances, a quick scan of a door seal or vent will detect the ultrasound emission. Listening for internal arcing in circuit breakers and switches can be accomplished with the contact probe. For example, touch a circuit breaker switch with the contact probe to listen for internally generated arcing.

38 The most effective method of low-voltage inspection will be to combine infrared imaging with an ultrasonic probe. Please keep in mind that since air cannot be a conductor of electricity below 1000 volts, corona cannot exist. Any “buzzing” sounds are either loose components vibrating at 60 (or 50) Hz or tracking.

Medium- and High-Voltage Equipment Higher voltages often produce more potential for equipment failure. Problems such as arcing, tracking (sometimes referred to as “baby arcing”), and corona as well as partial discharge (PD) and mechanical looseness all produce detectable ultrasound that warn of impending failure. Detecting these emissions are relatively easy with ultrasound. The acoustic difference among these potentially destructive events is the sound pattern. Arcing produces erratic bursts with sudden starts and stops of energy, while corona is a steady buzzing sound. Tracking has a buildup and drop-off of energy resulting in a buzzing sound accompanied by subtle popping noises. While scanning for these emissions, use a parabolic reflector. These accessories can more than double the detection distance of the standard scanning modules. PD, which occurs inside electrical components such as in transformers and insulated bus bars, is another problem that can be detected with ultrasound. Partial discharge can be quite destructive. It is both effected by and causes deterioration of insulation. This is heard as a combination of buzzing and popping noises. The contact probe is employed for PD detection. If your test instrument has frequency tuning, try 20 kHz.

Analysis of Recorded Signals While it is relatively easy to determine arcing, tracking, or corona by the sound pattern, there can be occasions where it may prove confusing. It may be possible that a strong buzzing sound thought to be corona might, in fact, be nothing more than mechanical looseness. Spectral and time-domain analysis can be useful tools in analyzing electric emissions. Since many test instruments heterodyne ultrasound down into the audible range, they used to record audible sounds. You must use a recording device that has a suitable bandwidth in the lower frequencies. Digital voice recorders are not acceptable as they only can record signals above 300 Hz, which is not low enough to be useful for the 50 or 60 Hz peaks. Laptop computers, MP3 recorders or quality cassette recorders work well for recording the signals in the field. When recording the signals, make certain that the signal is not distorted. On the analogue instruments, do not let the signal go over 50% of full scale on the signal strength indicator. On the digital instruments, try to maintain the signal strength between four and six segments of the bar graph. These sounds can then be downloaded to a PC with a sound card and viewed as a spectrum or time-series for analysis. It is necessary to examine both the spectrum and the time-domain images when you are trying to evaluate

Arc Flash Safety Handbook — Volume 2 the source of the sound. The main harmonic of an electrical emission (60 Hz in the US, 50 Hz elsewhere) will be most prevalent in corona. As the condition becomes more severe, there will be fewer and fewer 60 Hz harmonics observed. As an example, arcing has very few 60-cycle components. Mechanical looseness will be rich in 60 Hz harmonics, will have little frequency content between the 60 Hz peaks, and will also demonstrate harmonics other than 60 Hz. Examining the time-domain image can also be of help. In the case of corona, you will have a uniform band of signal with very few peaks that extend above the average band. With tracking, you will begin to see the peaks created by the discharges extend above the average band. With arcing, you will see several bursts of energy which correspond to the discharges. In all cases, both the spectrum and the time-domain images should be examined before the final determination is made. Below are examples of both the spectrum and time-domain views for the varying degrees of severity of discharge to atmosphere.

Corona:

Arc Flash Safety Handbook — Volume 2 Minor Tracking:

Extreme Tracking:

Arcing:

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40 Loose or Vibrating Component: New On-Line Condition Monitors

Arc Flash Safety Handbook — Volume 2 1. “Preventing Arc Flash Incidents in the Workplace,” George Greggory: EC&M June 2003 2. National Fire Protection Association, 1 Batterymarch Park, Quincy, MA 02269-9101

Mark Goodman has served as the Vice President of Engineering of UE SYSTEMS since 1975, where he has been responsible for the designing the Ultrasound Detection and Monitoring Equipment. Mark is a member of ASME, ASNT, ASTM, IEEE, ISO and ISA. He CoAuthored the Ultrasound Section of ASNT LEAK TESTING NDT HANDBOOK, and sits on the Leak Detection Committees for both ASNT and ASTM. Mr Goodman is also Convener of the ISO Committee: Condition Monitoring and Diagnostics of Machines - Using Airborne/Structure Borne Ultrasound.

While a great majority of the inspections around energized electrical equipment incorporate portable instruments, these inspections are limited in their ability to protect equipment from failure or from an arc flash potential going undetected. The limitations are time based. If an inspector is testing at the time any of these incidents is occurring, there is a good chance they will be detected and reported for corrective action. But, unlike mechanical conditions which are usually detected first and then trended to specific action levels, once arcing, tracking, or corona are present, there is a potential for failure and arc flash that can occur at any time. Therefore, there is need for continuous on-line monitoring of enclosed electrical equipment. An electrical cabinet monitor is mounted on the internal side of a door or wall facing the components. Utilizing an airborne scanner, a threshold level is set. Should an event of arcing, tracking, or corona occur, the sound level will be above the ambient threshold and be detected. A 4-20 mA or 0-10 Vdc output can be selected to carry the signal to an alarm mechanism or red light alert. In addition, these units should contain a heterodyned signal to provide recording capability for record keeping and analysis purposes. The advantage of on-line monitoring is obvious; it is not operator dependent and will continuously monitor. Whenever a condition occurs to produce the potential for arc flash or flashover, it will be sensed and alarmed instantly.

Conclusion Ultrasound inspection is an effective screening tool for detecting the potential for arc flash incidents. When handheld ultrasonic instruments are used to scan enclosed electrical apparatus the procedure is fast, accurate, and simple. It can help inspectors by eliminating the need for wearing cumbersome, uncomfortable PPE during a preliminary survey. On-line continuous monitors can warn personnel of the presence of arcing, tracking, and corona in advance of an inspection.

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Arc Flash Safety Handbook — Volume 2

What Is All This 70E Business? NETA World, Fall 2007 Issue by Ron Widup and Jim White Shermco Industries

Foreword We thought it might be advantageous to go through a general description of the 70E document and try to illustrate some of the important aspects and dynamics that the standard is creating within our industry. Undoubtedly, you have heard of (or know quite a bit about) the national consensus electrical safety standard entitled NFPA 70E, Standard for Electrical Safety in the Workplace. This very important electrical safety standard gives us guidance and assistance in our quest to keep our workplace safe and our employees free from injury. In 2006, Jane G. Jones produced a document entitled Electrical Safety Champions which detailed personal stories from industry professionals and how they became interested in electrical safety. From Jane’s writings, OSHA’s David Wallis states, “NFPA 70E has had a major impact on industry. Subpart S really came from 70E. It’s one of the few places where safe work practices are part of an OSHA standard. 70E is very unique in that aspect. ...Protection requirements in 70E are detailed and extensive, and they provide a good resource and also encouragement for industry to use PPE to protect their workers…” So what is all this 70E business? Why is it important? What does it have to do with OSHA? What does the future hold for industry and the 70E? We will attempt to answer these questions and more as we go through the 70E journey.

The Beginning and More In 1976, the U.S. Occupational Safety and Health Administration (OSHA) approached the National Fire Protection Association (NFPA) for help in developing a standard that could be used as the basis for their electrical safety regulations. The NFPA responded by using their consensus standards developing methodology, and in 1979 the first edition of NFPA 70E was published. This version of the

70E was really no more than the safety-related portions of the National Electrical Code (NEC NFPA 70) which today is Chapter Four of the 70E. There were no safety-related work practices developed at that time. In 1995 the fifth edition was published, and it included major revisions to Part I (Installation Safety Requirements) based on the 1993 National Electrical Code. The concept of limits of approach was introduced, and a Flash Protection Boundary was established. In 2000, the sixth edition introduced the tables which contained task-based risk analysis and hazard class identification. With the 2000 edition introduction of the tables (now 130.7), this gave the user the first easy-to-use (sort of ) method for determining PPE requirements for the arc flash hazard. Also a significant move forward to hazard awareness was the 1999 NEC, which contained Article 110.16 calling for the marking of electrical equipment that may require servicing while energized.

“Subpart S Citations: 80% of OSHA’s citations were for electrical installation violations; however, 91% of the accidents were caused by unsafe work practices…” Interest has grown in the 70E as people have learned more about the arc flash hazard or have been exposed or seen coworkers exposed to it. The 70E, though, is not a onetrick pony. There is a wealth of information inside its covers, especially in the annexes, where explanatory information is contained.

42 Oh, By the Way According to a paper presented at the 2006 IEEE Electrical Safety Workshop, in a national comparison of OSHA’s 1910 Subpart S citations versus accidents and fatalities from a period of October 1, 2003 through September 30, 2004 (one year), Ken Mastrullo reported that OSHA writes 80 percent of their citations for electrical installation violations, but 91 percent of accidents are caused by unsafe work practices. It is our understanding that one of the ways OSHA is attempting to rectify this situation is by training their field safety compliance officers on how to use and understand the 70E – to help support their enforcement efforts. When attending the OSHA Institute two years ago, we noted that when OSHA cites the General Duty clause in court, they lose approximately 50 percent of those cases. However, when OSHA uses the 70E as justification for the General Duty clause citation they win 100 percent of the cases. It seems that understanding the 70E would be a smart thing to do!

The 70E — A Living Document While the OSHA regulations are pretty static, the 70E is a standard that is at the leading edge of electrical safety, both in safe work practices as well as PPE. The NFPA uses a consensus approach to developing their standards, which means that members of the affected industries and trade associations, people who are directly involved in using the standards, are solicited to be on committees or panels. To prevent the committee from being biased by manufacturers, utilities, or any other trade group or organization, the NFPA requires that the committee be composed of members from specific interested parties such as users, manufacturers, unions, and so on. A listing of these committee members and their alternates is contained in the front of the 70E. NETA has been an active participant on the 70E committee since the mid 1990’s. There are several stages that the standards-making process goes through. In the beginning or the proposal stage, proposals are solicited from the general public (although many proposals come from the committee members). These proposals are numbered, compiled, categorized, and sent to the committee members for review. A meeting is held, usually three to five days in length, and they are discussed, deliberated, argued and nit-picked by the full committee until they are accepted as written, accepted with changes, or rejected. Often, as in the current cycle, proposals are grouped by subject matter and task groups are formed to review all proposals on a given topic or section in order to have a coherent approach to the subject. During the current 70E cycle, a good example of task group activity is proposals related to the tables in section 130.7 which had well over 100 proposals specific to the tables. The Tables Task Group spent several long hours and days reviewing each proposal and then making proposed changes to the tables based on their deliberations. These changes were then presented to the full committee for discussion and a vote.

Arc Flash Safety Handbook — Volume 2 The result of the meeting is published as a Report on Proposals (ROP), which is sent out for public comment. The proposals are available for review on the NFPA website, although committee members receive written copies. The next stage is the comment period which lasts a few months, so all interested parties have the opportunity to comment on the proposals and recommended committee actions or statements. All comments are then collected and a second committee meeting is held to discuss and have a final vote on the proposals, previous committee actions, and the comments received. A lot can change from the proposal stage until the proposals and comments are given the final vote. For example, during the last cycle the committee reversed itself on several proposals due to the comments received. It is a very open process and there is always a willingness to consider input. We encourage members of the public to attend these meetings and provide an opportunity for them to explain their reasoning behind their proposals or comments. A Report on Comments (ROC), which contains the results of the committee deliberations and vote, is published after the second meeting. At this point the ROC is distributed to the committee members and the NFPA Technical Correlating Committee (TCC). The TCC reviews the committee actions and they vote on the final committee actions. Once approved, the NFPA staff reviews the document for errors, omissions, and other issues. The 70E is then published as a new standard. The next (eighth edition) of the 70E is due to be published in October 2008 as a 2009 standard. This may seem as though it is a very drawn-out, overly tedious process, but this process is critical in developing the best standard possible. As mentioned earlier, often new information or views will cause the committee to reconsider previous actions – and the longer time frame allows for us to fully consider everything that has taken place. There may also be additional task groups to look at specific issues, such as the “words and phrases task group” which is currently trying to harmonize live and energized and other associated wording. These terms are used in different ways throughout the document and as such have caused some confusion, even among committee members.

The 70E – By the Numbers Article numbers, that is. Most people we talk with really don’t know what the 70E has inside its covers. They look at Article 130, maybe Article 120, and skip the rest of the standard. Many misunderstandings people have about the 70E could be corrected simply by reading and understanding the definitions, Article 100. During training sessions, we have had students dissect every word in Article 130 and come to some seriously wrong conclusions, simply because they didn’t know a defined term. Words have meaning and if the meaning is misinterpreted, off you go on a rabbit trail, becoming more and more confused as you go. Article 100 is at the beginning not just because it’s numbered sequentially but because definitions are so critical to understanding the intent of the 70E, so it’s a great place to start.

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Arc Flash Safety Handbook — Volume 2 Article 110 is a general overview of the requirements of the standard. There are also specific requirements in Article 110 that are not found any place else in the 70E. A good example is 110.4 Multiemployer Relationship. This section details the requirements for a pre-job safety meeting between all groups or companies that are working at a site so that hazardous conditions can be planned for and avoided. One example we use is where one company may be working inside a switch while another company is testing the cable connected to the switch. In order to prevent this type of situation from occurring, it is important that every company meet, discuss possible hazardous conditions and work, determine what PPE is necessary, determine what work practices should be used, and coordinate the work to prevent possible accidents. This meeting is to be documented. This requirement is needed due to OSHA’s Multiemployer Worksite Policy and is found only in Article 110. Article 110 also contains overall requirements for an Energized Electrical Work Permit, training requirements for qualified and unqualified workers, and a safety program. Article 120 covers all things about placing equipment in an electrically-safe work condition. There are several suggested procedures for accomplishing lockout/tagout (LOTO) on electrical equipment, and Article 120 also goes into detail about the equipment required, training, and coordination of other procedures.

Article 130 is where people spend most of their time. Really, if everyone read and understood Article 120, Article 130 wouldn’t be nearly as important as it is. Article 130.1, “Justification for Work,” starts out by emphasizing that “Live parts to which an employee might be exposed shall be placed in an electrically-safe work condition before an employee works on or near them.” This is essentially the same wording that OSHA uses in 1910.333 and is often overlooked. Make no mistake: the 70E committee and OSHA both agree that the very first choice for working on electrical systems should be to de-energize it! Article 130 provides details on the use of an Energized Electrical Work Permit and exceptions to its use. Didn’t know there were exceptions? You really need to read this section. Shock Approach and Flash Protection Boundaries are discussed (but you need to read the definitions to understand them) as well as the need for shock and arc flash hazard analysis. Article 130 contains the infamous tables, of course, but also has information on requirements for PPE and arc flash protective equipment and that workers need to understand in selecting PPE. There’s a lot of information here.

Chapter 2 contains safety-related maintenance requirements. Didn’t know about that? You’re in good company. This is one of those chapters most people just don’t get to. This section is full of information on how and what to inspect on various types of electrical equipment for substations, switchgear, MCC’s, circuit breakers, rotating equipment. Most anything in an electrical system is covered in this chapter.

Chapter 3 covers safety requirements for special types of equipment including power electronics, electrolytic cell lines (no, these aren’t batteries), and batteries and battery rooms.

Chapter 4 consists of safety-related excerpts from the NEC. The 70E was held back by one year, partially so that it could incorporate the changes that are made each cycle from the newest edition of the NEC, rather than having Chapter 4 one cycle behind. This causes the 70E to have a four-year cycle this time, but allows it to be better positioned now to use the latest NEC as its base. From time to time (every cycle) there are proposals to remove the information in Chapter 4 from the 70E, but it is of use to OSHA compliance officers in the field, since they would only need one document (the 70E) rather than two (70E plus the NEC). The new revision to Subpart S (Part II) is taken from the 2000 edition of the 70E and the 2002 NEC.

Annex This….. Information contained in the annexes of 70E is informational and not mandatory. When the phrase “not mandatory” is used, a lot of people automatically think they can ignore that part. To ignore the annexes in the 70E means some of the best information available will be ignored. Annex A contains a list of referenced publications. When reading the 70E you might have a question as to where information came from or what standard it came from. Annex A answers those questions. It’s pretty amazing how many different resources there are for people who want the details. Annex B contains a listing of informational resources, similar to the information in Annex A. Annex C covers Limits of Approach and provides detailed information on the shock approach boundaries, how the distances were determined, and what requirements are for crossing the boundaries. This section can clear up many misunderstandings people may have about the Limited, Restricted, and Prohibited Approach Boundaries. Want to test your technicians or electrical personnel? Ask them at the next safety meeting what the three shock approach boundary distances are for 480 volts. The silence will be deafening. (By the way, it is one inch [prohibited], 12 inches [restricted], and 42 inches [limited].) Annex D is quite lengthy, as it contains calculations for determining the flash protection boundary, utilizing several methods and examples, including the written portion of IEEE 1584-2002, “Guide for Performing Arc Flash Hazard Calculations.” Everything from the equations to the rationale behind 1584 is contained in Annex D. Equations for calculating the Flash Protection Boundary are also contained in Annex D. Looking for a place to use your math skills? Check out Annex D. Annex E covers additional requirements for an Electrical Safety Program (ESP). This is a concise, bulleted guide to setting up an ESP and can be very helpful if you don’t already have one.

44 Annex F is the hazard/risk evaluation procedure. A flow chart of the decision-making process is contained here. One-page long, it is a very concise method to determine the level of risk associated with a task. We have found that when discussing the hazard/risk analysis process with personnel, often they understand the hazard part of the assessment but don’t seem to understand the importance of assessing the risk as well. There may be times when the level of PPE can be reduced due to the very low risk factor involved with the task. For example, the Tables Task Group had many discussions about this when we reviewed proposals for performing infrared scans. The hazard was there, but once the covers were removed the risk has moved to something that was [arguably] quite small.

Annex G provides detailed information on lockout/tagout. Multiple methods are discussed and options are provided, depending on the particular situation you may be working in. Annex G, 3.0, “Preparation for Lockout (Tagout)” is one section that everyone needs to read and understand, as it covers the steps necessary to perform safe LOTO and the placing of equipment in an electrically-safe work condition. Also important to point out is Annex G, 4.0, “Individual Employee Control Procedure,” is meant for equipment such as motor control centers where the disconnecting means is immediately available at all times. This is a section that can cause some confusion if applied to other types and locations of equipment. Annex H is used by many companies to simplify the use of arc-rated (FR) protective clothing and PPE. Rather than have arc-rated clothing and PPE for each and every level of hazard, the simplified two-category approach provides a cost-effective and protection-effective methodology to providing appropriate PPE. OSHA uses the word appropriate in 1910.335 in the requirements for providing PPE to protect personnel from electrical hazards.

Annex I is a one-page Job Briefing and Planning Checklist. Modify this as needed. It is a simple check off to ensure various topics were discussed and/or considered during the required job briefing. Another one-pager is Annex J, Energized Electrical Work Permit. This is a very nice piece of work that really is useful. Broken into three sections, the work permit ensures that the work is properly authorized, planned out, and reviewed by both the qualified persons doing the work and by management. As managers, we know how it can get when managers are asked to sign a document like this one. The upside is that it allows management to control what energized work is being performed, who does that work, and why it is being performed energized to begin with. Since the company (and its managers) are responsible if anything should go wrong, this is very much a self-defense document. Annex K provides a brief description of the three recognized electrical hazards: shock, arc flash, and arc blast.

Arc Flash Safety Handbook — Volume 2 Annex L is of special interest to those working in a cell line working zone as it covers the typical safeguards for that type of work.

Annex M can be helpful if you are familiar with the 2000 edition of the 70E and have difficulty finding where things were moved to in the 2004 edition. Typically, most people who use the 70E are beyond the need for this, but people who use the standard only occasionally will find this beneficial.

But Wait, There’s More!! For whatever reason, quite often utilities, municipalities, local and state governments, universities, and others who are exempt from OSHA regulation seem to think that the 70E does not apply to them. So ask yourself since when do safe work practices not apply to workers just because they are government or utility-based? One argument often heard is that utilities have their own safety document, ANSI C2, the National Electrical Safety Code. In fact, C2 does have some information on safe work practices, but it is very superficial and primarily covers overhead line work. Power plants, indoor and outdoor substations, warehouses, and other support facilities have exactly the type of work environment the 70E is best suited for. What is the difference between the switchgear in a generating facility and an industrial facility? There is no difference. There are proposals being considered by the 70E committee that would remove the exemption for utilities due to the nature of the hazards involved with the work. The question people should be asking is, “Why not do what is in the best interest of the worker’s safety?” rather than ask, “Why should I do this if I am not forced to?” Why would anyone want to be responsible, even partially responsible, for someone else being crippled, disfigured, or killed on the job when using the 70E could prevent it? How this all plays out in the coming months remains to be seen, but what is certain is that the 70E will continue to gain acceptance by the electrical industry and will be adopted by many of the companies who are currently resisting its use. What we need to change is the culture of the electrical industry. When we first began working in the field, people were still using their fingers to test for the absence of voltage. Today we look at that type of behavior and laugh about it, but that reflects a change in our culture. What was acceptable then may no longer be seen as acceptable today and, in fact, may be considered stupid. So the question is, can we change our culture fast enough to save lives and worker’s livelihood? Like it or not, OSHA will continue in its diligence towards electrical safety compliance. As the 70E becomes woven more and more into the fabric of industry its use and understanding will continue to grow. If you don’t have a copy, get one today. If you have a copy, read it from cover to cover a few times. The people you may save or protect are all around you.

Arc Flash Safety Handbook — Volume 2 Be careful, be safe, turn it off, and test before touch. Electrical equipment is very toxic. Safe work practices are a must. Ron A. Widup and Jim White are NETA’s representatives to NFPA Technical Committee 70E (Standard for Electrical Safety in the Workplace.) Jim also served as the NETA representative on the IEEE/NFPA Research Testing and Planning working group committee (RTPC). Additionally he is the Chairman for the 2008 IEEE Industry Applications Society Electrical Safety Work Shop, is an authorized OSHA Outreach instructor and, the Vice Chair of the Doble Transformer Field Processing Subcommittee. Ron Widup, Executive Vice President/General Manager of Shermco Industries has over 25 years of experience in the low-, medium-, and high-voltage switchgear and substation market. He is a principal member of the NEC Code Panel 11, a member of the NFPA 70B committee, past president of NETA and currently a member of the NETA Board of Directors and Standards Review Council. Both Ron and Jim are certified NETA Level IV Test Technicians.

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Arc Flash Safety Handbook — Volume 2

Electrical Equipment Performance and the Impact to Personnel PowerTest 2008 (NETA Annual Technical Conference) Kerry Heid, Magna Electric Corp. and Ron Widup, Shermco Industries

Abstract The proper performance of electrical power equipment is paramount if calculated values of incident energies are to be accurate and the correct application of personal protective equipment is to be accomplished. A national survey was conducted on the performance of service-aged electrical equipment and the results of the survey, along with common electrical equipment failure modes impacting electrical safety of personnel, were examined. How these failure modes affect personnel in the workplace along with methodologies to effectively mitigate the failures based on electrical equipment reliability, condition, and criticality will be explained. Understanding these key areas of performance, the dilemma it creates with arc flash incident energy exposures, and the overall impact of the performance to personnel will help the owners and users of the electrical equipment provide for a safer workplace. Index Terms — arc flash, arc flash, arc flash study, circuit breaker, electrical maintenance, electrical safety, field testing, IEEE 493, IEEE 902, InterNational Electrical Testing Association, low-voltage circuit breaker, lubrication, maintenance, medium-voltage circuit breaker, NFPA 70E, protective devices, personal protective equipment, PPE

Introduction Proper performance of electrical power equipment is paramount if calculated values of incident energies are to be accurate. A national survey of field performance on approximately 340,000 protective devices was reviewed, and the results of those findings are included in this paper. The results of the findings illustrate that proper personnel pro-

tection and PPE assessment cannot be performed without accurate and reliable data, including properly functioning protective devices.

Protective Device Safety-Related Operation The ability of protective devices to operate in such a manner as to clear electrical fault conditions requires that the devices are maintained properly and are tested as appropriate for the conditions and environment they are subjected to. Guidance on this subject can be found in national consensus standards. National Fire Protection Association (NFPA) consensus standard NFPA 70E; Standard for Electrical Safety in the Workplace; 2004 Edition, (NFPA 70E) Article 210.5 states: “Protective Devices. Protective devices shall be maintained to adequately withstand or interrupt available fault current.” NFPA 70E Article 225.3 states: “Circuit Breaker Testing. Circuit breakers that interrupt faults approaching their ratings shall be inspected and tested in accordance with the manufacturer’s instructions.” NFPA 70E Article 200.1(3) states: “…maintenance shall be defined as preserving or restoring the condition of electrical equipment and installations, or parts of either, for the safety of employees who work on, near, or with such equipment.”

47

Arc Flash Safety Handbook — Volume 2 Additionally, the Institute of Electrical and Electronic Engineers, Inc. (IEEE) Standard 493-2007; Design of Reliable Industrial and Commercial Power Systems (the Gold Book) states: “Of the many factors involved in reliability, electrical preventive maintenance often receives meager emphasis in the design phase and operation of electrical distribution systems when it is a key factor in high reliability.” IEEE Standard 902-1998; Guide for Maintenance, Operation, and Safety of Industrial and Commercial Power Systems states: “The integrity of electrical equipment shall be maintained with particular emphasis on enclosures, insulation, operating mechanisms, grounding, and circuit protective devices.” From the guidance suggested within these standards, it becomes clear that safety-related performance of protective devices is defined by the proper maintenance and testing of the devices. Without proper maintenance equipment reliability and performance cannot be assured.

Field Testing Survey of Performance A survey was conducted of field testing results for low- and medium-voltage circuit breakers and related components. The results were obtained from InterNational Electrical Testing Association (NETA) accredited companies in the United States and Canada. The results yielded data of approximately 340,000 electrical protective devices under field test. A series of 17 questions were asked. Specifically:

1. Number of years of experience testing low- and medium-voltage circuit breakers in the field

2. Number of low- and medium-voltage circuit breakers tested 3. Percentage of breakers tested with issues affecting overall performance

4. Percentage of breakers tested that did not function at all 5. Of those with performance issues, what percentage were related to mechanical issues 6. Of those with mechanical issues, what percentage failed due to lubrication issues 7. Of those with mechanical issues, what percentage failed due to worn or broken parts 8. Of those with mechanical issues, what percentage failed due to cell fit or alignment 9. The overall percentage of failures related to electrical diagnostic issues

10. Of those with electrical diagnostic issues, what percentage failed due to the failure of a trip unit/protective device 11. Of those with electrical diagnostic issues, what percentage failed due to low insulation resistance 12. Of those with electrical diagnostic issues, what percentage failed due to high contact resistance 13. Of those with electrical diagnostic issues, what percentage failed due to auxiliary trip device issues 14. Of those with electrical diagnostic issues, what percentage failed due to high insulation power factor issues

15. Of the percentage of circuit breakers with failure of the trip unit/protective device, what percentage was due to a malfunctioning series trip unit or electro-mechanical relay

16. Of the percentage of circuit breakers with failure of the trip unit/protective device, what percentage was due to a malfunctioning solid state programmer or relay

17. Of the percentage of circuit breakers with failure of the trip unit/protective device, what percentage was due to a malfunctioning primary trip device (magnetic latch, flux shifter, trip coil, etc.) Based on the results of the survey, approximately 22% of the circuit breakers tested (Question No. 3) had an issue affecting the protective device operation. This data closely correlates with failure data presented in IEEE Std. 493-2007, Table 5-1 in the “fair” (18.1%) to “poor” (32.8%) maintenance quality category. With percentages in these ranges, approximately one in five of the devices in the field will not operate as indicated on the arc flash studies. The actual overall impact to personnel in the field is not known, but it can be reasonably assumed that incident energies will significantly increase on the defective equipment. Another alarming statistic was the fact that on average 10.5% of the devices did not function at all when tested. If a fault were to occur, a no-trip condition would severely impact personnel safety when working on or near that particular piece of equipment. Of the units with issues affecting performance, 42.8% were mechanical issues, and 26.7% had issues related to electrical diagnostic testing. Lubrication issues were the predominant mechanical failures at 51.4%. This has been a long-standing problem within industry and is often vetted during preventive maintenance operations.

Impact to Personnel If protective equipment does not function as designed or intended, the results can be disastrous, as the results of engineering studies for protective device clearing times as well as safety-related data such as arc flash studies become invalidated, as clearing times become an unknown element.

48 It is common for facilities to perform a flash hazard analysis using commercially produced software, relying on the published trip times of the protective devices. When possible, often times after the initial analysis protective device settings are modified (lowered) to decrease incident energies and hazard labels are applied to indicate the circuit parameters. If electrical protective devices do not function as designed, the arc flash study is not valid and severe increases in incident energies can be obtained, which could render the PPE assessment as inadequate.

Conclusions Electrical devices must be properly maintained. Field test data shows that lack of or improper maintenance severely affects protective device operation, thus affecting the overall arc flash data. Arc flash studies, incident energy calculations, and PPE assessment become invalidated with improper operation of protective devices.

References [1] NFPA 70E, 2004 Standard for Electrical Safety in the Workplace, Quincy, MA: NFPA.

[2] IEEE Std. 493-2007, Design of Reliable Industrial and Commercial Power Systems, New York, NY: IEEE. [3] IEEE Std. 902-1998, Guide for Maintenance, Operation, and Safety of Industrial and Commercial Power Systems, New York, NY: IEEE.

Kerry D. Heid, A.Sc.T., is currently President and General Manager of Magna Electric Corporation. He has been with the Magna Group seven years and previously worked eight years with Westinghouse Services Division. Kerry is experienced in power transformers up to 230 kV, switchgear, relay testing, and substation commissioning and maintenance. He is an electrical engineering technologist and NETA Level IV Certified Technician. Kerry has provided extensive training on the NETA Maintenance & Acceptance Testing Specifications throughout Canada Ron. A. Widup, Executive Vice President/General Manager of Shermco Industries has over 20 years of experience in the low-, medium-, and high-voltage switchgear and substation market. He is a principal member of NFPA Technical Committee 70E Standard for Electrical Safety in the Workplace and a member of NEC Code Panel 11. He is past president of NETA and currently a member of the Board of Directors and Standards Review Council. He is certified as a NETA Level IV Test Technician.

Arc Flash Safety Handbook — Volume 2

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Arc Flash Safety Handbook — Volume 2

Application of Existing Technologies to Reduce Arc Flash Hazards PowerTest 2008 (NETA Annual Technical Conference) Jim Buff and Karl Zimmerman Schweitzer Engineering Laboratories, Inc.

Introduction Protective relay engineers have long been concerned with protecting power systems and all of the equipment associated with those systems. We routinely apply relays to limit damage to apparatus (e.g., transmission and distribution lines, power transformers, buses, generators, motors, etc.) and protect against, or reduce, the impact of electrical disturbances on the larger power system (e.g., shedding load for frequency or voltage variations). Safety for personnel has always been a concern, but in the past several years there is a heightened awareness of the importance of safety around electrical apparatus, as reflected in recent regulations and standards [1] [2]. In particular, industry and utilities alike recognize that arc flash events can cause dangerous and potentially fatal levels of heat, ultraviolet radiation, blast pressure, flying shrapnel, and deafening sound waves. The existing standards mainly deal with the heat energy from the arc flash. The energy produced by an arc flash event is proportional to voltage, current, and the duration of the event (V•I•t). Design engineers have a few options to reduce system voltage or fault currents (e.g., grounding practices and application of current-limiting fuses), but the best and most direct ways to reduce arc flash hazards are to reduce fault-clearing times and use wireless communications to reduce the need for technicians to be in harms way. In most cases, clearing times are reduced via more complete use of microprocessor relays features and other technologies already available. Similarly, digital relay communications and secure wireless communications devices allow engineers and technicians to converse with relays from a safe distance. In this paper, we include some important industry definitions of arc flash and ways of measuring arc flash hazards. We then examine the use of existing technologies, including

digital relays and communications capabilities, to implement reduced trip times using instantaneous overcurrent relays, a fast bus-trip scheme, and differential schemes. We use a typical industrial switchgear lineup as an example of how to implement these schemes. Finally, we quantify the levels to which we can reduce arc flash energy and its impact on safety.

Definitions What is an arc flash? How do we measure the energy so as to quantify improvement? Some important definitions of arc flash and related issues can be found in IEEE 15842002, “IEEE Guide for Performing Arc Flash Hazard Calculations.” Similar definitions are found in NFPA 70E, “Standard for Electrical Safety in the Workplace, 2004 Edition.” Arc Flash Hazard. A dangerous condition associated with the release of energy caused by an electric arc. Flash Hazard Analysis. A method to determine the risk of personal injury as a result of exposure to incident energy from an electrical arc flash.

Flash Protection Boundary. An approach limit at a distance from live parts that are insulated or exposed within which a person could receive a second-degree burn.

Working Distance. The dimension between the possible arc point and the head and the body of the worker positioned in place to perform the assigned task [1].

50 Measuring Arc Flash and the Effects of Arc Flash There are several methods for calculating incident energy due to an arc flash event. These include a table-based method in NFPA 70E-2004, a theory-based model for applications over 15 kV (Lee method), empirically derived models based on a curve-fitting program, and a physical model-based method with some verification testing. Within the last few years, IEEE 1584 was published, and an empirically derived model based on statistical analysis was developed as part of this effort [1]. IEEE 1584 includes several spreadsheets to assist the engineer in arc flash studies. We will use this method for our analysis in this paper. Incident energy is typically quantified in cal/cm2 or Joules/cm2. The incident energy determines the personal protective equipment (PPE) required to provide adequate protection based on recommendations in NFPA 70E. Incident energy calculations also provide the basis for the flash protection boundary.

Protection Considerations for Arc Flash

Arc Flash Safety Handbook — Volume 2 Determine the Arc Fault Currents The arc-fault current is typically slightly less than boltedfault current due to arc impedance.

Determine the Protective Relay/Device Operate Times One subtle aspect of calculating arc flash incident energy is that a lower fault current (e.g., further downstream fault) may not decrease the energy if the protection used is an inverse time-current characteristic (fuse or 51 device). The lower fault current could (and often does) result in increased energy because of the increased trip times. So, the incident energy analysis is typically performed at 100% and 85% of maximum arcing current. Also, if no intentional time delay is used, the operate time for “instantaneous” relaying is still taken into account. Thus we must always consider breaker operate times.

Document System Voltages, Equipment Class, and Working Distances

IEEE 1584-2002 concluded that arc time has a linear effect on incident energy, i.e., reducing fault-clearing times proportionately reduces arc flash. Also, IEEE 1584-2002 states that the system X/R ratio had “little or no effect” on arc current and incident energy and was, thus, neglected. All of the formulas for arc current and incident energy calculations assume a 200 ms arc duration and use symmetrical fault current. For the analysis in this paper, no “weight” factor was added due to asymmetrical current, but it seems possible that faster clearing times (< 100 ms) might increase incident energy due to higher dc offset currents. Further study, beyond the scope of this paper, would be required to analyze this issue.

IEEE 1584-2002 includes tables that provide the typical bus gaps and working distances for 15 kV, 5 kV, and low-voltage switchgear, low-voltage motor control centers, panel boards, and cable.

Steps in Calculating Arc Flash Energy and Its Effects

How Arc Flash Energy Affects Personal Protective Equipment (PPE)

Collect the System Data and Modes of Operation In short, we need an accurate one-line diagram including system source, line, and transformer impedances. We also need to know the modes of operation, if additional feeders and generators may be in service, and how this impacts fault currents and trip times. The goal is to establish the conditions that produce the maximum fault currents.

Determine the Bolted Fault Currents Next, we calculate the maximum three-phase fault current based on short-circuit programs, fault studies, or the method shown in the “Example System to Analyze Arc Flash” section.

Determine the Incident Energy Use one of the methods discussed earlier to calculate incident energy. IEEE 1584-2002 includes the equations and reference spreadsheets that can be used for this task.

Determine the Flash Protection Boundary Based on the incident energy, a flash boundary can be calculated.

NFPA 70E defines five levels of arc hazard. Table 1 shows the hazard/risk category levels and the calculated incident energy at the working distance. The table lists typical clothing and layer counts for the torso. In short, this is the level of clothing that should be worn to limit incident energy damage to a second-degree burn. Put another way, this guide is designed to protect the worker from heat to prevent a second-degree burn.

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Arc Flash Safety Handbook — Volume 2 Table 1

Determine the Bolted Fault Currents

Personal Protective Equipment (PPE) to Limit Burns Hazard/Risk Category 0

Clothing Description (Typical clothing layers in parentheses)

Requiring Minimum Arc Rating of PPE cal/cm2 N/A

Fire retardant (FR) shirt and pants or FR coverall (1) Cotton undergarments plus FR shirt and pants (1 or 2) Cotton undergarments plus FR shirt and pants, plus FR coverall, or plus two FR coveralls (2 or 3)

1 2 3

4

(1)

25

Where: %Z

40

[3]

Example System to Analyze Arc Flash Steps to Calculate Arc Flash on an Example System The system shown in Figure 1 is used to help analyze these issues.

Utility

583 MVA X/R = 15

2.4 ohms

2000/5

2000/5

13.8/4.16 kV 10.5/12.5 MVA Z = 4.1%

2000/5

NO

NC

4.16 kV Bus B

kVu

= Utility voltage base

MVAu

= Utility fault MVA

X/R

= Utility X/R ratio

kVt

MVAt

= Transformer voltage base

= Transformer MVA base

The conversion gives the following result:

(2)

24.7 kA 29 cal/cm2 24 Meter Boundary Category 4 Protection Required 3500 HP

Figure 1 — Example System

The example shows switchgear and has no cable impedance to add to the total impedance to the bus. We must add the transformer impedance, which is listed as 4.1%. If we assume that the transformer impedance is all inductive, then the total impedance to the bus is:

To calculate the fault current, we use (3): 600/5

600/5

2400/120

MTR

= Utility impedance in percent based on transformer base

583 MVA X/R = 15 Utility

2.4 ohms

NC 4.16 kV Bus A

To convert this to a percent impedance based on the transformer MVA and kV, we use (1):

8

Cotton undergarments plus FR shirt and pants plus multilayer flash suit (3 or more)

4

The first step in calculating an arc flash number is to calculate the maximum available three-phase fault current. The utility may give a number based on fault MVA and an X/R ratio. As shown in (2), the utility has given the available source fault MVA as 583 and the X/R ratio as 15.

XFMR 4160/480 1.5/2.0 MVA Z = 8.7%

(3) Where: If

= Maximum bus fault current

MVAt

= Transformer MVA base

kVt

= Transformer voltage base

%Ztotal = Total impedance on transformer base to bus in percent

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Arc Flash Safety Handbook — Volume 2

The fault current for this example is as follows:

Time Current Curves 10000.00

Determine the Arc-Fault Currents After calculating the maximum three-phase fault current, we calculate arcing current. The arc-fault current is typically lower than the bolted-fault current due to the arc impedance. In this example, the arcing fault current is 23.6 kA.

Time (Seconds)

1000.00

100.00

TIE RELAY

1.00

0.10 100

Ia

1000

10000

= Maximum bus fault current in kA

= Maximum arcing current in kA

The arcing current for this example is as follows:

We also want 85% of this value to see how the lower fault current impacts trip times (which may in fact increase energy). The 85% value is 20 kA.

Determine the Protective Relay/Device Operate Times The relay coordination for this system is shown in Figure 2. The breaker time of five cycles was added to obtain the total trip time. For the 23.6 kA current, the bus relay trip time is:

Figure 2 — Example System Relay Coordination

Document the System Voltages, Equipment Class, and Working Distances IEEE 1584-2002 includes tables that provide typical bus gaps and working distances for 15 kV, 5 kV, and low-voltage switchgear, low-voltage motor control centers, panel boards, and cable. Also included are spreadsheets, which perform calculations based on selected parameters. For 5 kV switchgear, the gap between conductors is assumed to be 102 mm and the working distance is assumed to be 910 mm. Other factors, like the configuration of the switchgear, cable, or box, and the system grounding, are taken into account.

Determine the Incident Energy The empirically-derived model presented in IEEE 1584 provides two equations to calculate the incident arc flash energy. The first is the normalized incident energy. The second is the incident energy with specific parameters. The normalized incident energy assumes a “typical working distance” of 610 mm and an arc duration of 0.2 s. The equation for this example is:

0.69 + 5/60 = 0.77 s

(5)

For the 20.0 kA current, the bus relay trip time is: 0.88 + 5/60 = 0.96 s

100000

Current (Amps Primary)

(4)

Ibf

START CURVE

10.00

BUS RELAY

Equation (4) is used to calculate the arcing current:

Where:

MTR RELAY

Where: En

= Normalized incident energy in J/cm2

K2

= 0.0 for a resistance-grounded system

K1

Ia

G

= –0.555 for a box configuration

= Maximum arcing current in kA

= Gap between conductors = 102 mm

Thus the normalized incident energy for the 23.6 kA arc current in this example is as follows:

53

Arc Flash Safety Handbook — Volume 2 Determine the Flash Protection Boundary The flash boundary is calculated from (7):

The normalized incident energy for the 20 kA arc current in this example is as follows:

(7) Where: Eb Cf

Next, we vary the parameters to calculate incident energy for our specific example system. For 5 kV switchgear, we use a working distance of 910 mm and then we calculate incident energy for different operate times (0.77 s and 0.96 s): (6) Where: E

= Incident energy in J/cm2

Cf

= 1.0 for voltages above 1.0 kV

En

= 1.0 for voltages above 1.0 kV

t

= Arcing time in s

x

= Distance exponent = 0.973 for 5.0 kV switchgear

Db = Distance of the boundary from the arcing point in mm

En

= Normalized incident energy in J/cm2

For this system, the flash boundary is:

= Normalized incident energy in J/cm2

t

= Arcing time in seconds

x

= Distance exponent = 0.973 for 5.0 kV switchgear

D

= Incident energy at the boundary in J/cm2 = 5.0 for bare skin

= Distance from the possible arc point = 910 mm

For this system, the incident energy is:

Note the 85% current actually has more incident energy due to the longer trip time delay from the bus relay. Next, we convert the arc energy into cal/cm2 using the conversion: 2 2 5.0 J/cm = 1.2 cal/cm Thus the arc flash energy at the bus is:

This indicates that within 24 meters of the arc flash, any unprotected person could sustain second-degree burns from the fault incident energy. From this we also see that a worker must use Level 4 PPE to perform live work on this switchgear.

What Can Be Done to Reduce Arc Flash Nearly all distribution, utility or industrial, uses fuse and/ or time-overcurrent protection. Using common practices and coordination techniques, trip times are higher closest to the source transformer or switchgear. In short, the hazard is the greatest where personnel are most likely to be in or near the switchgear. As discussed earlier, the energy produced by an arc flash event is proportional to Energy = V•I•t. By performing arc flash analysis on each system, it is often possible to reduce time-coordination intervals to achieve lower trip times and thus, lower incident energy.

Nonrelaying Approaches On low-voltage systems (1000V In the case of a system whose voltage is greater then 1000 volts, the arcing current is only slightly less then the bolted fault current. In the case of a low voltage system, which is defined as a system 1-5

Cf is a calculation factor

1.0 for voltages above 1kV

1.5 for voltages at or below 1kV

t

D x

is the arcing time (seconds)

is the distance from the possible arc point to the person (mm). See Table 1 for typical working distances. is the distance exponent from Table 2

Ibf is the bolted fault current for three-phase faults (symmetrical RMS)(kA) V

>5-15

is the system voltage

TABLE 1 – Typical working distances [1] Classes of Equipment

Typical Working Distance

15 kV switchgear

910 mm (36 in.)

5 kV switchgear

910 mm (36 in.)

Low-voltage switchgear

610 mm (24 in.)

Low-voltage MCCs & panelboards

455 mm (18 in.)

Cable

455 mm (18 in.)

Other

Determined in the field

Equipment Type

Typical conductor gap (mm)

Distance x Factor

Open Air

10-40

2.000

Switchgear

32

1.473

MCC and panels

25

1.641

Cable

13

2.000

Open Air

102

2.000

Switchgear

13-102

0.973

Cable

13

2.000

Open Air

13-153

2.000

Switchgear

153

0.973

Cable

13

2.000

II. Hazard Levels NFPA 70E assigns relative hazard risk levels depending on the calculated incident energy levels. NFPA 70E also lists an example of typical PPE (Personal Protective Equipment) clothing appropriate to each hazard category. For actual applications, the calculated incident energy must be compared to specific PPE combinations used at the facility being evaluated. The example given in NFPA is shown below in Table 3:

TABLE 3 – PPE Characteristics [2] Hazard Risk Category 0 1 2 3 4

Typical Protective Clothing Systems Non-melting, flammable materials (natural or treated materials with at least 4.5 oz/yd2) FR pants and FR shirt, or FR coverall Cotton Underwear, plus FR shirt and FR pants Cotton Underwear, plus FR shirt and FR pants and FR coverall Cotton Underwear, plus FR shirt and FR pants and multi-layer flash suit

Required Minimum PPE Arc Rating (cal/cm2) N/A (1.2) 4 8 25 40

Note that the highest defined hazard category is level 4 2 having an upper limit of 40 cal/cm . While PPE is certainly 2 available in ratings well above 40 cal/cm , working near 2 exposed energized equipment above 40 cal/cm is discouraged. NFPA 70E notes that “greater than normal emphasis should be placed on de-energizing the equipment” (Annex D.8 FPN) at such high incident energy levels [2]. One possible reason is that PPE is primarily intended for thermal protection. Other factors including physical trauma are

64 very dangerous above 40 cal/cm2 and must be considered. At such high incident energy levels, the concussion forces of the pressure wave can be as dangerous as the radiated thermal energy.

III. Mitigating Strategies The three most obvious arc flash mitigating strategies are: Reduce the fault current (If ) Increase the working distance (D) Reduce the clearing time (t)

A. Reducing the fault current Some protective devices are current limiting by design. Current limiting fuses, for example, are capable of both limiting the magnitude of fault current and duration provided the fault current is within their current limiting range (typically 10-15 times the device rating) [3]. Fault currents below this range must be analyzed like non-current limiting devices (based on the time-current characteristics). Lower level arcing currents can easily result in higher incident energy because the current falls outside the current limiting range and resulting in a clearing time that is much longer compared to a higher current within the current limiting range. Current limiting reactors (CLR) may also be used to limit the available fault current. The disadvantage of a CLR is that it also introduces impedance in the circuit and its associated undesirable voltage drop [4]. In some cases, the cost of a pyrotechnic-operated high-current fault limiter with interrupting ratings exceeding 200kA can be justified [5].

B. Increasing the working distance Increasing the working distance has a dramatic effect on the incident energy. From equations (1) and (2), it is also apparent that the incident energy level decreases exponentially with increasing working distance. Examples of this strategy include remote racking and the use of extension tools (i.e. hotsticks). However, many tasks may not be able to be accomplished remotely and remote racking devices may not operate as desired.

C. Reducing the clearing time Referring to equations (1) and (2), it is also evident that the incident energy is directly proportional to the arcing time. The arcing time represents the total fault clearing time. Where a circuit breaker is involved, this time consists of the relay operating time plus the breaker opening time. According to IEEE Standard 1584™, breaker operating times vary from 1.5 cycles to 8 cycles depending on the class of breaker involved. Table 4 lists the typical operating times referenced in this standard.

Arc Flash Safety Handbook — Volume 2 TABLE 4 – Power circuit breaker operating times [1] Circuit breaker rating, type Low voltage (molded case) (