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VOLUME 2 ARC-FLASH HANDBOOK
VOLUME 2
SERIES II
ANDBOOK
Published By
Shermco Industries
Sponsored by Published by NETA - The InterNational Electrical Testing Association
RC-FLASH
SERIES II
ARC-FLASH HANDBOOK VOLUME 2
Published by
InterNational Electrical Testing Association
Published by InterNational Electrical Testing Association 3050 Old Centre Avenue, Suite 102, Portage, Michigan 49024 269.488.6382 www.netaworld.org
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 © 2013 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.
ARC-FLASH HANDBOOK VOLUME 2 TABLE OF CONTENTS Arc-Flash Hazard Mitigation through relaying......................................................... 5 Basler Electric Co.
Arc-Resistant Switchgear: Tested to ANSI C37.20.7 & NFPA 70E............................... 9 Jim Bowen, Powell Electrical Manufacturing Company
Hazards of Establishing an Electrically Safe Work Condition.................................. 10 Tony Demaria and Dean Naylor, Tony Demaria Electric, Inc.; Mose Ramieh III, Power and Generation Testing
Novel Arc-Flash Protection System...................................................................... 14 Mark Claper, GE
Update on the IE/NFPA Joint Collaboration Project on the Arc-Flash Hazard............. 19 Jim White and Ron Widup, Shermco Industries
Overhead Lines: The Electrical Danger Above...................................................... 20 Jim White and Ron Widup, Shermco Industries
Significant Changes to 2012 NFPA 70E............................................................... 23 Jim White and Ron Widup, Shermco Industries
Switching 2 Maintenance.................................................................................. 29 Kerry Heid, Magna Electric Corporation
Safer Lock-Out Tag-Out with Permanent Electrical Safety Devices–Electrically Safe Work Conditions Based Upon NFPA 70E and OSHA..................................... 32 Philip B. Allen, Grace Engineering Products
Changes and Enhancements to the 2012 NFPA 70E.............................................. 36 James R. White, Shermco Industries
Published by
InterNational Electrical Testing Association 3050 Old Centre Avenue, Suite 102, Portage, Michigan 49024
269.488.6382
www.netaworld.org
TABLE OF CONTENTS CONTINUED...
A New NFPA Process and a Few Words on the 70E Annexes................................ 40 Jim White and Ron Widup, Shermco Industries
Wearing PPE: Important or Not?........................................................................ 43 Jim White and Ron Widup, Shermco Industries
Arc-Flash Clothing and PPE - What Does NFPA 70E Say?...................................... 46 Jim White and Ron Widup, Shermco Industries
NETA Accredited Companies............................................................................ 49
Published by
InterNational Electrical Testing Association 3050 Old Centre Avenue, Suite 102, Portage, Michigan 49024
269.488.6382
www.netaworld.org
5
Arc-Flash Handbook
ARC-FLASH HAZARD MITIGATION THROUGH RELAYING NETA World, Spring 2011 Issue by Basler Electric Co. Arc-flash hazard awareness is a critical topic for those responsible for the management of electrical power systems. NFPA 70E requires an evaluation of the arc-flash hazard level at each piece of electrical equipment and a listing of the personal protective equipment (PPE) necessary if the equipment is to be worked on while energized. NFPA 70E and IEEE Standard 15842002 provide the means to calculate the hazard level in terms of incident energy of the arc. In the evaluations used in both standards, the hazard level becomes a function of available bolted fault current at the point being evaluated and the time that a fault might be allowed to persist before some portion of the protective system clears the fault. Reducing either the bolted fault current or the clearing time will reduce the arc flash-hazard, and a sufficient reduction of the hazard will allow use of less restrictive PPE. The magnitude of the available fault current is dependent on the configuration of the system, the sources available, and other factors beyond the scope of the protective system. The clearing time, on the other hand, is directly controlled by the protective system. This application note provides suggestions for how to use relaying techniques to reduce clearing time without compromising the existing protection, including selectivity. Figures 1 and 2 show representative one-line and relay connection diagrams to illustrate many of the techniques mentioned. These techniques can be used individually or in combination. The one-line in Figure 1 represents an industrial system, served at medium-voltage from the utility (bus 1 in room 1), that has a second medium voltage switchgear location (bus 2 in room 2), and a transformer stepping down the voltage to 480 V for utilization at bus 3. It is likely that a real-world system would be much larger but would have similar features. Figure 2 illustrates connections among numeric multifunction relays discussed below.
SETTINGS GROUPS Typically, a system using numeric relays has multiple settings groups, and this capability can provide a means for arc-flash mitigation without the need for additional relays. One method for using settings groups for arcflash mitigation is to have one group provide normal, fully coordinated protection with the high hazard level associated with the normal protection. By using switches at the entrance to each switchgear room, the relays can be switched to a different settings group, which can provide faster clearing times and allow work on energized equipment with a lower level of PPE than the normal settings.
The switch would be wired to an input on each relay and used to control which of the two settings groups is active. With the switch in the “normal” settings group position, there would be no change from the settings previously in use. With the switch in the “hot work” settings group position, each relay would have an instantaneous element set no more than 150% of maximum load, with an allowance for any starting inrush currents that might occur while workers are performing hot work. This instantaneous setting will not necessarily coordinate with downstream devices but is only used while energized equipment is being serviced. Ideally, the change in settings groups also would be applied to the relay of the breaker supplying the gear in question, because the reduced hazard only applies for faults beyond the CTs connected to the relay with “hot work” settings applied. If the supply breaker is in the switchgear in question, that section of the gear will not have the same lower hazard level associated with the remainder of the gear. Figures 1 and 2 show an example of this application. In Figure 1, note the location of relays 1, 2, and 3; and, in Figure 2, note the connections to input IN3 of each of these relays. Relay 1 is on the main breaker on the incoming line from the utility to switchgear bus 1 in room 1. Relay 2 is in the same gear as relay 1 and protects the feeder to switchgear bus 2. Relay 3, at switchgear bus 2, is on a feeder supplied by bus 2. A switch at the entrance to switchgear room 1 would activate IN3 on relays 1 and 2 to change the settings
Arc-Flash Handbook
6 groups of these relays. Unfortunately, there is no means to increase the speed of the utility protection ahead of relay 1, so the fast tripping will not apply for faults on the supply side of the main breaker; that section will have a higher incident arc energy than the remainder of the gear. A switch at the entrance to switchgear room 2 controls relay 3 and other relays in that gear, as well as relay 2 in switchgear room 1 on the feeder to switchgear bus 2. To allow the control switches at each room to control relay 2 through the same input, the diodes shown are used to block the signal from traveling beyond the intended relays. That way, when the switch for room 2 is on, relay 3 and the other relays in that room are in the “hot work” settings group as is relay 2 in room 1. The upper diode prevents the signal from reaching relay 1 and other relays on that bus, leaving the coordinated protection active.
Transformer differential relays can be useful in arc-flash hazard mitigation, particularly if the zone of protection is expanded from the usual zone of protection. Often, transformer differential relays are applied with the CTs at the terminals of the transformer, and this limits the zone of protection to the transformer itself. If, on the other hand, the CTs of the transformer differential are installed at the breakers on each side of the transformer, the zone of protection will extend to the switchgear. With the transformer differential CTs on the bus side of the breakers and the bus differential CTs on the line side of the breakers, the zones will overlap and there will not be locations where a fault could persist for longer periods of time while waiting for a time overcurrent element to time out.
One thing to consider when contemplating this approach is how the relay responds to the command to change settings groups. Some relays make the change from one settings group to another between ¼ cycle scans and are never off-line. Other relay manufacturers are known to go off-line during the time the settings groups are changing, and the relay does not provide any protection during that time.
In many industrial installations, lines are short enough that two terminal differential relays can be used for line differential with the CTs at both ends of the line brought to the relay. Used this way, careful analysis of the burden of the CT circuits can help avoid CT saturation. The relay burden is low enough that the burden seen by the CT secondary is essentially the impedance of the conductors to the relay.
Figure 1 shows a BE1-CDS relay around the transformer, with the CTs located at the gear at each end of the circuit.
ADDITIONAL RELAYS In many cases, the greatest reduction in arcflash hazard can be achieved through the use of additional relays, particularly differential relays. The beauty of differential relaying from an arcflash mitigation standpoint is that each differential relay protects a clearly defined zone within the system and does not require any delay to coordinate with protection for other portions of the system. Bus differential protection provides a means to respond to faults on a bus without the need for any delay to coordinate with other portions of the system; trip decisions can be made in less than one cycle from the onset of the fault to the trip contact closing. Adding in breaker time, a bus fault can be cleared in 6 cycles or less (0.10 sec at 60 Hz). This is a vast improvement over conventional overcurrent protection times that can extend into the seconds or even tens of seconds. One caution when using bus differential for arc-flash mitigation with metalclad switchgear is that, with the CTs mounted on the breaker bushings, as is the typical installation method, the zone of protection ends at the CTs and a fault at the line terminals will not be cleared by the bus differential. In Figure 1, a BE1-87B is shown with CTs paralleled from each line in and out switchgear bus 1. Not shown in the diagram is the tripping connection between the relay and the breakers in the gear. Typically, that tripping connection would be through a lockout relay with a trip contact for each breaker. If a bus differential relay were applied at switchgear bus 2, CTs would be needed on the incoming feeder, and the lockout relay for this gear would need to trip the supply breaker associated with relay 2.
If the BE1-CDS relay shown around the transformer were to be connected on the feeder between the two pieces of switchgear, faults on the feeder could be cleared instantaneously.
COMMUNICATIONS Communications between relays can greatly reduce the relay time without the need for additional relays, although it does require the use of numeric relays. In the simplest implementation (see Figure 1), consider two relays on a radial circuit, one upstream of the other. In addition to the normal time and instantaneous overcurrent settings, we will add an additional low set definite time (instantaneous with time delay) setting on each relay. We will
Arc-Flash Handbook also connect an output of the downstream relay to an input of the upstream relay. For each relay, this new setting will be set above load, for example 150% of load, but does not necessarily need to coordinate with inrush or other transient events. The upstream relay may be set less sensitively as it may serve more load than the downstream relay, or they may be set nominally the same if they see the same load, but in no case should the upstream relay be set more sensitively than the downstream relay. To avoid inadvertent lack of coordination, the upstream relay should be set less sensitively than the downstream relay by at least twice the relay/ CT tolerance. The downstream relay logic will be set to activate the output whenever the low set element is picked up. The upstream relay will receive, through its input, a signal that the downstream relay sees something unusual. The NOT of this signal will be ANDed with the trip of the low set element in the upstream relay. Knowing that the fault or other abnormality is beyond the next relay downstream, the upstream relay does not need to trip. If the upstream relay low set element picks up but the blocking signal is not received, it can trip after a delay long enough to allow receipt of the blocking signal, plus some margin, as it will have been determined that the fault is located between the relays. With relays directly connected, the delay time can be three cycles or less; with an interposing relay the delay time can be four cycles. Testing during system commissioning can determine the nominal signal time, and the protection engineer can add the desired margin to arrive at the time setting. With this technique, it is helpful to use a
7
Arc-Flash Handbook
8 very short recognition time and a very long debounce time for the input on the upstream relay. The short recognition time is desired to ensure than the signal is recognized as soon as possible, thereby allowing a shorter delay time. The long debounce time is desired to keep the blocking signal in place until after the element on the upstream relay has dropped out. Making these adjustments to the input processing times increases the security of this scheme. The scheme can be extended to include more relays upstream and downstream of the two considered above. As with the bus differential, if this scheme is used only within one piece of switchgear, there will be very fast clearing for faults on the bus itself, but faults that occur on the cable terminals of outgoing feeders will be beyond the CTs of the downstream relay. Communications from the next switchgear or from the load will extend the scheme and provide complete protection. This scheme is illustrated in the figures with the connections detailed in Figure 2. Starting with relay 3, OUT5 closes whenever the low set picks up. This signal becomes an input to relay 2, shown as IN4 in this example. The signal from OUT5 is paralleled with outputs of other relays at the same level in the system so that any relay can provide the blocking signal. Relay 2 receives the blocking signal from relay 3 and also has sent a blocking signal upstream to relay 1. If a fault occurred on bus 2 (Figure 1), the low set element on relays 1 and 2 would pick up; relay 1 would receive a blocking signal and would not trip. Relay 3 would not see the fault current, so no blocking signal is sent to relay 2 resulting in a high speed trip to clear the fault. The tripping decision would be made in 3 to 4 cycles, significantly less than using coordinated time-overcurrent elements. In Figure 1, the connection shown between the BE1-CDS and the upstream relay can be used similarly. An overcurrent element operating on the CTs on the secondary of the transformer can provide a blocking signal which indicates that the fault has occurred on the 480V system rather than somewhere between the medium-voltage gear and the lowvoltage gear.
CT PLACEMENT In all protection schemes, the boundary of the zone of protection is defined by the location of the CT. Traditionally, switchgear has been designed to allow CT installation on the bushings of the circuit breakers. This provides a convenient location for the installation of the CTs and provides good physical protection of the CTs (See Figure 2). Also, at this location there are no concerns of cable shields interfering with correct measurement of the current. As previously discussed, this location can create the situation of faults within the switchgear being seen as beyond the zone of the switchgear. If the CTs are moved to the cable compartment, the zone of protection can be extended to include the cable terminations. Unfortunately, in this location it will be necessary to provide support for the CTs, run the cable shields back through the CT to cancel any current flowing on the shield, and find a path for the CT secondary circuit from the cable compartment to the control compartment.
BREAKER FAILURE PROTECTION All of the protection ideas discussed to this point assume that the intended breaker will trip at the correct time, but what happens if that assumption is false? The possibility of a breaker failing to trip is accounted for in conventional coordinated time overcurrent settings where each device is backed up by all devices further upstream; failure of one device to clear a fault means that the next device will have an opportunity to clear the fault after the set time delay. The fact that times for this backup protection can get into the seconds becomes a serious issue if failure of one interrupting means is considered when evaluating arc flash hazard. Using the breaker failure protection features of the Basler numeric relays, it is possible to have backup protection operate within a few cycles of a breaker failure rather than a few seconds. In Figure 1, if relay 3 sent a trip signal to its breaker, but the breaker failure logic of the relay indicated that the breaker did not open to interrupt the current, the relay would try to retrip the breaker. Simultaneously, or with a user-selected delay, it also would send a trip signal to the breaker associated with relay 2 to clear the fault at that location. Using breaker failure protection, the breaker at relay 2 will be tripped to clear a fault beyond the faulted breaker at relay 3, and that tripping can occur with a delay of less than 20 cycles after the initial attempt to trip the breaker at relay 3.
SUMMARY Historically, protection systems have relied on time coordinated overcurrent protection for selective clearing of system faults. The need for selectivity has resulted in clearing times that become progressively longer the further upstream in a system the fault occurs. When arc- flash hazards are considered, this increased time results in increased levels of required PPE, until the hazard becomes so great that there is not an adequate level of PPE available. Using the relaying techniques discussed above, it is possible to significantly reduce the clearing time for faults at any location in the system while maintaining full selectivity. It is a realistic goal to achieve primary clearing times of less than 10 cycles and backup clearing times of less than 20 cycles for an entire system while maintaining full selectivity for all primary protection. As published by Basler Application Notes – #PC-ARCFLASH
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Arc-Flash Handbook
ARC-RESISTANT SWITCHGEAR TESTED TO ANSI C37.20.7 & NFPA 70E NETA World, Spring 2011 Issue
by Jim Bowen, Powell Electrical Manufacturing Company
The intent of the 2004 version of NFPA 70E, Standard for Electrical Safety in the Work Place, is to minimize the “at-risk” procedures used by operators of electrical equipment. The first step is to minimize risk by having operators perform work with the equipment only in an electrically safe condition. The second step is to design the hazard out of the normal work procedures, and the third step is to rely on personal protective equipment to minimize the risk to the individual performing the task. Arc-resistant switchgear can assist with the first step effort by providing enhanced safety conditions when the operator task involves energized equipment and possible exposure to an arcing fault. Tasks in this category include: • Racking a medium-voltage circuit breaker to or from the bus connected position • Racking a VT or CPT roll-out to or from the bus connected position • Opening and closing a circuit breaker • Calibrating and troubleshooting devices within the instrument compartment The purpose of arc-resistant switchgear certified to ANSI C37.20.7 is to eliminate the risk from the arc blast and the byproducts (heat, pressure, shrapnel, and molten copper) during normal tasks performed on the equipment. During arc-fault design tests, the energy release by an arcing fault is monitored by mounting racks of a black cotton material in panels covering the surface of the switchgear. This material is similar to 4.5oz/yd untreated t-shirt material identified as Hazard/ Risk Category 0 per NFPA 70E Table 130.7(c) (11). The panels are mounted at 3.9 inches from all possible seams and one of the many acceptance criteria of ANSI C37.20.7 is that none of the cotton indicators ignites during or following a test. While the focus of NFPA 70E is the heat from the arc in mediumvoltage switchgear, it is the pressure wave associated with the arc fault that dictates the design of the switchgear. The switchgear designed for arc-resistant protection requires heavy reinforcing of the entire structure. In conclusion, arc-resistant switchgear designs the hazard out of the tasks and reduces the level of risk for normal tasks to a zone 0 category. The result is a reduced need for PPE. The design focus of arc-resistant switchgear is to provide the necessary
enhanced safety features while requiring no addition maintenance, calibration, or final element tests to assure functionality. Jim Bowen graduated from Texas A&M University in 1976 with a BSEE. He has worked for SIP Engineering as a power engineer and for Exxon in all facets of electrical engineering in the petrochemical process. He held the position of regional engineer for Exxon Chemicals Europe for three years. In January of 1997, Jim joined Powell Electrical Manufacturing Company as Technical Director, providing leadership, training, and mentoring to both internal and external electrical communities.
Arc-Flash Handbook
10
HAZARDS OF ESTABLISHING AN ELECTRICALLY SAFE WORK CONDITION NETA World, Spring 2011 Issue by Tony Demaria and Dean Naylor, Tony Demaria Electric, and Mose Ramieh, II, Power & Generation Testing When working around electrical equipment, the preferred working condition includes the equipment being put in an electrically safe work condition or turned off, locked out, and tagged out. This is stated in both OSHA and NFPA 70E requirements. Unfortunately, there are electrical hazards which must be dealt with while achieving this electrically safe work condition. These hazards could involve switching, equipment racking, voltage testing, and applying grounds to assure an electrically safe work condition. This paper will focus on the safety requirements associated with placing equipment in an electrically safe work condition.
COMMON SENSE As a precursor to this discussion, it has been noted by some that OSHA and NFPA 70E requirements can be confusing and cumbersome. It has been said that “Common sense is the knack of seeing things as they are, and doing things as they ought to be done.” It is time to apply some common sense to electrical hazards. Here are some common sense ideas for electrical safety that are unfortunately, not so common. 1. Distance is your friend. The farther you are away from the hazard, the safer you will be and the less PPE you will be required to wear. 2. Bigger equipment is usually more dangerous. 3. When removing equipment covers, removing a household light switch does not typically require an arc-flash suit for protection but removing the cover from an industrial substation typically does. 4. Shock–related PPE requirements and arcflash related PPE requirements should be determined separately and added together. With regard to electrical safety, to do things as they ought to be done means distancing yourself, and others, from the shock and arcflash hazards while establishing an electrically safe work condition. In order to do this, the whole process needs to be thought through and planned ahead of time. Before equipment is turned off, check the condition of the gear. Are there any panel meters or voltage indicators present? Do they appear to be working properly? Are the correct panel lights lit? In what order should the equipment be shut down? Can the loads be turned off remotely or further upstream or downstream where the hazards may be lower? Are there any additional hazards that could be introduced by turning this equipment off? If an action is likely to cause an arc-flash event, then how do you avoid injury?
Frequently, many people use the last method that should be applied. That method is to suit up in arc-flash protective clothing including leather gloves and face shield or flash-suit hood. PPE should always be a last resort when implementing a safety policy. In any unsafe situation, the goal is to remove the hazard so that the use of PPE is minimized.
DISTANCE When turning equipment on or off, there are several options. There are engineered options such as using computer control to operate breakers from a distant operations center. Mimic panels can be used to operate the equipment from outside of the protection boundaries or outside of the room. There are aftermarket options that attach onto the front of the switchgear and will operate switches while allowing the operator to stand away from the switchgear. When none of these options are available, there is also an old tried and true rope-andpulley system (See Figure 1). This is not known or used by many people. It does not work for all applications but excels in switching load interrupter switches, many medium-voltage starters, and many older style OCBs. Using the rope and pulley system, a rope is attached to the operating handle or pull ring and run through a pulley(s), if necessary. In this way the operator can stand away from, and to the side of, the equipment while operating the equipment. This method is inexpensive, easy to set up, and available to everybody. This can be seen being demonstrated on a motor starter in the Fall 2010 issue of NETA World Magazine in Tony Demaria’s article, Safety and Medium Voltage Starters. If you must stand in front of the equipment to operate it, there are a few other things you can do to mitigate being injured. Stand to one side of the equipment being operated and always wear protective gloves. When wearing a face shield and balaclava instead of a full hood, face the equipment to avoid collecting a fireball inside the shield. Arc-rated blankets can be used to redirect the blast as well.
11
Arc-Flash Handbook SHOCK BOUNDARIES
The next task that must be accomplished is to open covers in order to test for absence of voltage. This seemingly easy task can introduce additional hazards. The cover can slip and fall into the gear. There may be loose hardware that is leaning against the cover that could fall when the cover is moved. PPE will be necessary for this task when crossing the shock or arc-flash boundaries.
Figure 1: Medium-Voltage Load Interrupter Switch Operation with Rope and Pulley System Racking out a breaker before you work on it is strongly advised and usually the only way to provide adequate separation from a hazard and establish an electrically safe work condition. Unfortunately, racking out equipment can be very hazardous. Again, there are many methods that can be used to distance yourself from the hazards. Some equipment may have builtin, electrically-operated racking mechanisms that will allow the operator to rack-in or rack-out the equipment while maintaining a safe distance. There are also many aftermarket products or robots which may be employed to rack breakers either at the end of a long control cord, or remotely via wireless control. Some of the remote racking devices come with a remote camera, or may be fitted with one at a later date. If you must rack the breaker out locally, there are additional things to remember. Use closed door racking whenever possible. Wear the proper arc-flash rated PPE and stand to the side, if at all possible. If using a hand crank, use an extension on the crank handle to increase your distance from the equipment and possible arcing location. You can weld an additional section onto your factory-furnished crank handle (See Figure 2). Even an additional few feet can drastically reduce the incident energy exposure. As an example, a 42 cal/cm2 exposure at 36 inches on medium-voltage switchgear can be reduced to 21 cal/cm2 at 72 inches.
First, a determination of the shock-related PPE requirements should be performed. This involves identifying the voltage to be worked on and the shock boundary to be applied. The shock boundaries are voltage dependent boundaries and vary by system nominal voltage. They are outlined in NFPA 70E, Table 130.2(C) and in IEEE C2, Table 441-1. These are defined as the Limited, Restricted, and Prohibited Approach Boundaries and are considered the distance from exposed, energized conductors. The distances stated in these tables are irregular and may be difficult to memorize. NFPA 70E, Table 130.2(C) lists 14 voltage ranges in five columns, or up to 70 distances. We believe that over 90 percent of the electrical workers in the U.S. and Canada have not studied these standards and could not tell you these distances from memory for every voltage level presented in these tables. Further, they could not tell you the definitions of Limited, Restricted and Prohibited Boundaries. The following is an example of a way that your company can create a safety policy that will cover the great majority of electrical workers for shock protection. It uses common sense, and promotes an easy way to memorize the distances. Keep in mind that this is an example of a safety policy for shock protection only. 1. When working on or near exposed, energized, fixed circuits up to 750 volts, you should wear voltage-rated gloves and use voltage-rated tools, if you are going to get closer than three feet six inches. If there is a possibility that you might fall into the hazard, you should also wear voltage-rated sleeves. No part of the unprotected body should get closer than your arms can reach. A hard hat and electrical face shield should also be used to prevent contact in tight areas. 2. When working on or near exposed, energized circuits over 750 volts to 15 kV, you should wear voltage-rated gloves, voltagerated sleeves and voltage-rated tools if you are going to get closer than five feet. No part of the unprotected body may get closer than your arms can reach. A hard hat with an electrical face shield must be worn. 3. Any other voltages or situations should require specialized personnel who are qualified for the higher voltages.
Figure 2: F actory Racking Handle With Two-Foot Extension Welded On
These distances should apply when the covers are off and before the circuits have been deenergized, locked out, tested, and grounded, if necessary. The arc-flash boundary applies any time there are exposed, energized conductors as well as any time anyone is interacting with the equipment in such a manner that could cause an electric arc. This interaction includes operating and racking breakers, removing covers, voltage testing, and applying grounds.
Arc-Flash Handbook
12 OPENING DOORS & COVERS When opening hinged covers, care should be taken not to position yourself so that you are in the path of the arc flash or blast. Keep the door between yourself and the exposed conductors until the cover has been fully opened with no incident. When removing a cover without hinges, get some help to remove the cover. Suction cups can be very helpful when removing covers without handles. Make sure the suction cups are placed on a clean, dry, flat surface. These cups are very inexpensive and can be used to avoid dropping the cover into the equipment. Lean the cover out slowly at first and listen for any unexpected noises. Any scraping against the cover from loose parts, or the hissing or crackling of ionized air is a warning sign that more trouble could be coming. This should be investigated before continuing with the task.
VOLTAGE TESTING In order to test for voltage, the live-dead-live method should always be employed. Panel meters or auxiliary voltage indicators may be used as additional verification. Do the panel meters that you looked at before de-energizing the equipment show an absence of voltage now? Have the voltage indicators that were lit beforehand been extinguished? Even with these checks, it is necessary to use a tested meter to check the circuit. Shock-related PPE and arcflash related PPE are necessary if crossing the shock or arc-flash boundaries, respectively. When testing medium-voltage equipment, the meter should be attached to a hot stick. As a general recommendation, use a measuring device designed for the job and the voltage level. Do not select test equipment based on price alone. Using a hot stick will allow you to distance yourself from the hazard while performing the test. Always extend the hot stick to the fullest length that is practical. Always test all three phases. Start with the voltage range setting for the expected voltage, then gradually lower the voltage range setting to the minimum range to confirm that there is no voltage present. A contact-making meter should be used even after a proximity tester has indicated an absence of voltage in order to test for trapped charge, since proximity testers do not respond to dc voltage. Always use gloves rated for the full system voltage for this task when crossing either the restricted or prohibited approach boundaries. Test all three phases-to-ground as well as phase-to-phase.
GROUNDING Now that absence of voltage has been verified, grounds may be applied. Grounds should always be used when working on equipment that has high fault current capacity., once again, the goal is to protect yourself and others from the hazard. With this in mind, there is another way to apply grounds remotely. Grounding and test devices have been around for some time, but they are not in common use. They are a common sense approach to applying grounds safely. However, it is imperative that the grounding and test device be tested for insulation integrity and the correct stab position chosen for the ground cables. Some cubicles
may be energized on the top stabs and others on the bottom stabs. This is especially typical in tie breakers. Using a grounding device with the wrong side grounded could lead to catastrophic damage. The grounding device may be inserted into a cubicle and then operated remotely from system controls or mimic panels or, if necessary, from a robot operator. Keep in mind, if it needs to be racked into the cubicle, this should also be done remotely, if possible. If not, follow the same precautions as discussed earlier for racking equipment out. If grounding cables or clusters must be applied manually, use a hot stick. Remember again, distance is your friend. When applying ground sets, assume the circuit is energized even after the circuit has been voltage tested and verified to be de-energized. This means wear the appropriate PPE for the hazard. This is common sense as many an experienced electrician can relate a story of applying grounds and having the unfortunate experience of touching an energized conductor with the ground cluster. Not a pretty picture! The good news is, if the grounding cluster has been sized properly and is being installed correctly, it usually trips the upstream breaker with possible damage to equipment. Once again, use hot sticks at the longest practical lengths and position your body so that you are not in the line of fire. Don’t stand in the path of the hazard!
SUMMARY By thinking through and planning each step, the process of establishing an electrically safe work condition can be done safely and without exposing yourself to unnecessary hazards. Once the equipment is de-energized, locked out, tagged out, tested for voltage, and grounded, if necessary, an electrically safe work condition has been established. Now that this has been done safely and the electrical hazards have been removed, the original work task(s) may begin.
Tony Demaria worked for the Los Angeles Department of Water and Power in substation maintenance prior to starting his own company. He has owned and operated Tony Demaria Electric for over 25 years, specializing in maintenance and testing of switchgear and large motors for industrial facilities. Tony Demaria Electric is a NETA Accredited Company, and Tony serves as the NETA Safety Committee Chair.
Arc-Flash Handbook Dean Naylor completed the NJATC Apprenticeship in Baton Rouge, LA before earning his degree in electrical engineering at the University of Tennessee at Chattanooga. He has 20 years of electrical experience in electrical system operating, installation, maintenance, analysis and testing. He is a member of IEEE 1584 and 1814 Committees as well as a Certified Maintenance and Reliability Professional and a NETA Level III Technician. Mose Ramieh, III has ten years of experience in the electrical power field. He is certified as a Level II Thermographer, a NICET Certified Level III Electrical Testing Technician, and a NETA Certified Level IV Technician. His expertise covers industrial and utility power systems from 480 volts to 161 kV and all controls associated with these systems.
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NOVEL ARC-FLASH PROTECTION SYSTEM NETA World, Spring 2011 Issue by Mark Claper, GE Specification Engineer
INTRODUCTION To address the increasing concerns and standards around arcing faults, GE challenged our Global Research Center to develop a new, “active” method of detecting and removing an arcing fault. The goal was to develop a technology that would, in simple terms, reduce the potential for injury and equipment damage. The result is an innovative product called the Arc Vault™ Protection System. This article will outline some basic arc-flash mitigation techniques and culminate with a description of the new GE technology. It should be noted from the onset that this technology is currently in the prototype phase and that the discussion covers applications of 600 V and below.
factors associated with how we quantify the arcing fault will be considered. With the benefit of this information, mitigation techniques can be outlined and categorized. Figure 1 illustrates some of the basic parameters that factor into an incident energy calculation that in turn leads to the Hazard Risk Category labeling.
ARCING FAULTS – WHY THE INDUSTRY CONCERN? Simply put, the effects may result in serious injury, death, equipment damage, and downtime. Unlike the bolted fault, an arcing fault uses ionized air as the conductor. The cause of the fault normally burns away during the initial flash and the arc is sustained by the establishment of a highly conductive, intensely hot plasma arc. The intense heat vaporizes conductors and barriers and superheats the surrounding air resulting in an explosive volume-metric increase within the space. The consequence is an intense pressure wave, deafening sound, blinding light, toxic gases, molten metal and shrapnel. This is often referred to as the arc blast. Unless action is taken to either quickly remove the fault or redirect the arc blast, the brunt of these items will impact people, equipment, or both. The magnitude of the arcing fault is only 43-57% of a bolted fault, so traditional overcurrent protection may not detect and clear the fault before the full impact of the arc develops and causes damage or injury. To gain a better understanding of how to deal with an arcing fault, let’s consider what the contributing variables are and the corresponding incident energy calculations that help categorize them. A complete discussion on arc-flash calculations can be found in IEEE 1584 – Guide for Performing Arc-Flash Hazard Calculations.
WHAT VARIABLES CONTRIBUTE TO AN ARCING FAULT? There are many items that can initiate an arcing fault. Rather than focusing on what the ignition sources can be, the system
Figure 1: Incident Energy Calculation Clearly, there are many variables that factor into the incident energy calculation. Some are specific to equipment types while others are tied to system parameters or maintenance practices. Each variable plays a particular role in how we categorize the arcflash hazard and each is briefly touched upon below: • Voltage – The ability to sustain the arc. Arcing faults are generally limited to systems where the bus voltage is greater than 120 V. • Available bolted fault current – The punch behind the arc fault magnitude. Recall that the magnitude of a low-voltage arcing fault is approximately 43-57% of the bolted fault value. This implies that systems with significant bolted fault currents will have elevated arcing current levels. The reverse is also true; lower bolted fault levels will lead to lower arcing-fault energies. Items such as system impedance, transformer sizing, utility, motor, and generator contributions establish the available fault current. • Arc clearing time – This includes detection and protective device operating time. It is tied to the operating characteristics of a specific protective device for a given level of arcing current. Reducing clearing time is critical to reducing the impacts of arcing fault. • Conductor gap distance – Defines the distance between conductors that an arc must cross. Varies by equipment type and manufacturer, but is fixed for a specific piece of equipment.
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Arc-Flash Handbook • Working distance – The distance from a potential arc source to a worker’s face and chest. Typically assumed to be 18”. Items such as remote monitoring and racking can be implemented to remove the operator from the flash zone for routine maintenance tasks. • System configuration – Solidly grounded, resistance grounded, etc. This category also takes into consideration whether the arc environment is enclosed or open. Given a basic understanding of what variables contribute to an incident energy calculation, the next logical question is to ask what the engineer can do to reduce this energy or exposure to it? Since energy is a function of current, voltage and time, there are several strategies that can be explored: • Reducing the available fault current • Reducing the arcing time • Transferring the energy into a less damaging form or place quicker than it could otherwise be interrupted The paragraphs that follow will highlight several of these strategies.
METHODS OF LIMITING INCIDENT ENERGY AND THE EXPOSURE TO ARCING FAULTS Over the years, different methods to limit arc flash exposure and incident energy have been introduced and can be divided into two general categories: active and passive. Passive mitigation is defined to be an equipment FEATURE SPRING 2011 option or type that either contains and redirects the arc blast or helps to eliminate the potential of a flash event (i.e., insulated main bus). This type of mitigation does not require any actions or settings by an operator to implement. On the opposite end of the spectrum is active mitigation. Active mitigation takes a proactive approach to reducing both incident energy and the exposure to arcing faults through the active use of technology, design, and maintenance practices. The simplest example of active mitigation is to not approach or work on live electrical equipment. Figure 2 contains a list of passive and active items. One clear distinction between the passive and active methods is that the passive method does nothing in the way of detecting or removing an arcing fault. It is focused solely on containing the arc blast or eliminating a potential starting point for an arc flash via equipment options. One should not employ passive techniques without thinking through items such as thermal scanning. Equipment options like insulated main bus and isolated phase bus are good preventative measures; however, they present an issue to performing thermal scans of items other than load connections. The active methods seek to attack on both fronts, incident energy reduction and reduced exposure. The newest technology on the active side is the GE arc absorber protection system. To highlight the application of this new system the following paragraphs will contrast the active arc absorption system vs. the passive, arc resistant structure. The remaining items are listed for reference and will not be covered in detail.
Figure 2: Arc-Flash Mitigation Techniques
LOW-VOLTAGE METAL ENCLOSED SWITCHGEAR Typical low voltage metal enclosed switchgear is designed and tested to withstand the mechanical forces associated with bolted faults (nonarcing). It is not constructed to contain and re-direct the arc blast away from the operator. The standard construction must be able to withstand (carry) the bolted fault current from the line side of the main breaker through the load terminations on the feeders and is short circuit tested to ensure compliance with the applicable ANSI standards. During a short circuit interruption, there may be some out gassing of arc by-products from the breaker but not to the violent extent of the arcing fault. An arc resistant line of low-voltage switchgear is also designed to withstand and interrupt a bolted fault, however it provides a level of protection to arcing faults that is not incorporated in the standard design. Arc resistant structures have been around for 30 plus years and can trace their roots back to IEC standards. In North America, this type of structure is tested & categorized to ANSI C37.20.7 (Refer to Figure 3.)The term arc resistant implies that no arc-fault emissions/ blast will occur in the areas described by each
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requires consideration and awareness of items that are specific to the construction. Several items are listed below for consideration.
Equipment Damage / Downtime What type of downtime will the owner experience for an arcing fault? It is reasonable to expect some structural damage that will require repair as a result of the arc blast. Bus, doors, and barriers are likely candidates for repair. Are there other mitigation methods that can provide operator protection and help reduce equipment damage at the same time?
Maintenance Requiring Approaching Live Equipment
Figure 3: Arc-Resistant Structure Categories category. For example, with a properly installed Type 1 design, an operator could approach the front of a switchgear lineup and not be exposed to the arc blast if an arcing fault were to occur. If the operator were standing to the side of this design, the same protection would not be provided. To function properly, arc-resistant structures have several distinguishing characteristics not found in traditional gear. • Reinforced construction is used to withstand and contain the pressure wave. Front and rear doors, section barriers, etc., may be reinforced and gasketed depending on the ANSI type. • Exhaust chambers are employed within the structure to safely redirect the arcing fault by products away from the operator and toward the vent flaps. • Vent flaps that open due to increased pressure vent the arc blast, typically out the top. • Figures 4 illustrates the redirection and venting of the arcing fault.
The protection afforded by the arc-resistant structure can be negated if a door is not properly secured or if the maintenance task requires the operator to open a door or compartment. What are the impacts to operator safety, maintenance practices, etc.?
Installation Considerations Where does the effluent go when it is vented from the structure? Does the room size need to be increased? Does a restricted area need to be developed and labeled? Is placement of the structure limited to certain areas?
Cost and Size Impacts What are the cost and size impacts associated with the structure itself? Does the room size need to be increased?
Existing Equipment The arc-resistant structure cannot be retrofit onto existing equipment. The comments above are not meant to disparage the arc resistant design. Rather they are meant to highlight that with all products there are application considerations that must be taken into account. Items such as live maintenance, equipment damage, room size, and venting are real concerns that need to be thought through and contrasted against other mitigation techniques.
HOW IS THE GE ARC ABSORPTION TECHNOLOGY DIFFERENT?
Figure 4: Illustration of Arc-Resistant Venting
CONSIDERATIONS – ARC-RESISTANT STRUCTURES The arc-resistant structure does an excellent job of protecting the operator from an arc-flash event; however, it is not a panacea. As noted earlier, this passive technique seeks only to contain the arc blast, but nothing to reduce incident energy or remove the arcing fault, which can result in substantial equipment damage and downtime. Like all products, the application of arc-resistant structures
The arc absorption is an active mitigation technique and aspires to the same basic goal as the arc-resistant structure; to protect the operator. However it does so in a much different fashion than arcresistant structures. Instead of containing and venting the arc-flash effluent, it seeks to limit incident energy via the identification and removal of an arcing fault before it escalates into the signature arc blast and elevated hazard risk categories. The result is a solution that addresses three key areas: • Reduction of the arc-flash hazard • Improved equipment uptime/ reduced damage • Ability to retrofit existing switchgear
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It is important to note that since this system works at arcing fault current levels, as opposed to bolted fault levels, there is a significant energy reduction. The result is 63% less energy, and considerably less stress on the system, when compared to crowbar type systems. This energy reduction applies to not just the local switchgear but also to other system components like transformers. The prototype of the arc absorber containment dome is about the size of an 800 AF breaker and is rated for applications of 100 kA at 480 volts. The arc absorber protection system will contain an arc fault in less than 8 ms with the circuit breaker compartment doors open during operation and maintenance. The incident energy in accordance with IEEE 1584 at 24” from the arc event will be less than 1.2cal/cm2, which is equivalent to HRC0, for a 480 V HRG system with available fault currents up to 100 kA. In addition to incident energy/HRC reduction, eliminating the arcing fault, reducing equipment damage, and eliminating arcing fault effluent. The arc absorber offers the following benefits not found in traditional arc resistant structures:
New and Retrofit Applications
Figure 5: Architecture The architecture for the absorber is depicted in Figure 5 and consists of a current sensor, a parallel-connected containment dome, light sensors, and a logic controller. The current sensor looks for the signature of an arcing fault while the light sensor looks for a simultaneous optical event. The combination of the two is fed into a logic controller which makes the decision on whether to engage the absorber or not. At this point you may be thinking that this is a crow bar. Rest assured, it is not, please read on. The arc absorber has no moving parts and makes use of a plasma gun and containment chamber. When the logic controller activates the absorber, two simultaneous actions take place. A trip signal is sent to the main breaker, and the absorber is activated. When activated, the absorber triggers the plasma gun to break down the dielectric in the air gap within the absorption chamber. The resulting arc creates a lower impedance, phase-to-phase path than the “in equipment” arcing fault presents to the system. This low impedance path is not a bolted fault and in turn redirects/ absorbs fault current originally flowing towards the arcing fault within the controlled environment of the containment chamber. The arc within the containment chamber is then safely cooled and vented. The open air or “in equipment” arc is extinguished as the bus voltage decreases due to the low impedance path within the absorber. The time required to quench the open-air arc is 8 ms. The event is brought to conclusion when the main protective device opens and eliminates current flow within the absorption chamber.
The arc absorber can be implemented in new or existing lowvoltage switchgear platforms while the arc resistant structure is tied to new installations only.
Reuse The arc absorber will be reusable, with minor maintenance or parts replacement, depending on the available fault currents where it is applied. Arc-resistant structures will in all likelihood sustain some form of damage and require repair to place them back into service.
Maintenance Activities The arc absorber does not depend on doors being closed to provide arc-flash protection. Hence the established Hazard Risk Category does not change whether the doors are open or closed.
No Effluent Ventilation No need for increased ceiling heights or the creation of restricted areas to avoid potential exposure to redirected effluent.
CONCLUSION There are many techniques that can be employed to help mitigate the damaging effects of arcing faults. This article has introduced the concept of the arc absorber as a feasible alternative to arc-resistant structures. It can at minimum offer the same or similar Hazard Risk Category (HRC) protection as the arc resistant structure but far exceeds the structure in the areas of equipment protection, uptime, reuse and others. GE presented this concept on the arc absorber to the IEEE Petroleum and Chemical Conference Technical Conference in September of 2009.
Arc-Flash Handbook
18 REFERENCES IEEE 1584 – Guide for Performing Arc-Flash Hazard Calculations IEEE C37.20.7: “Guide for Testing Medium-Voltage MetalEnclosed Switchgear for Internal Arcing Faults.” Mark Clapper is a Specification Engineer for the Industrial Solutions division of GE Energy. He has 20 years of power distribution experience and holds a degree in electrical engineering from Michigan State University
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UPDATE ON THE IE/NFPA JOINT COLLABORATION PROJECT ON THE ARC-FLASH HAZARD NETA World, Sping 2011 Issue by Jim White and Ron Widup, Shermco Industries
At this year’s NFPA 70E ROC (Report on Comments) meeting, an update on the IEEE/NFPA Joint Collaboration Project was presented by Dr. Wei-Jen Lee of the University of Texas at Arlington. Dr. Wei-Jen Lee is the Project Manager for the IEEE/ NFPA Joint Collaboration Project. NETA is always looking for ways to improve its worker’s safety and is a major contributor to this project. Dr. Lee began by stating the goals of the project, which are to determine the arc-flash effects, including heat, blast pressures, light intensity, and sound intensity. These effects are to be quantified and equations developed through executing approximately 2500 tests. These tests are being conducted at five different test laboratories around the US and Canada. The initial series of tests (Phase 1), which have been completed, were to determine instrument functionality, overall accuracy, repeatability and consistency of the various test laboratories. Six calorimeters will be used for testing, and the electrodes will be placed horizontally for some tests and vertically in others. The horizontal electrode placement was to address concerns raised by Dr. David Sweeting who had written a paper pointing out that his research showed that horizontal electrodes could produce arc jets which produce higher incident energy values than when the electrodes are placed vertically. The equations for IEEE 1584, Guide for Performing Arc-Flash Hazard Calculations, will be updated to reflect the new information from these tests once they are completed and analyzed. Dr. Sweeting is also on the technical committee for this project. IEEE 1584 applies only to 208-volt through 15 kV three-phase systems in enclosures. Higher voltages and single-phase systems are covered using Ralph Lee’s equations (no relation to Dr. Lee). Five series of tests were performed for Phase 1, during both cold and warm weather, to gauge the effects of ambient temperature on the test results. The video recorders being used can capture (depending on the laboratory) between 600 fps to 1900 fps. Calorimeters can capture between 200 to 5K samples/second and the pressure sensors can capture between 20K to 50K samples per second. Sound is captured at 20K samples per second. I often get questioned about the need for hearing protection for HRC 0 and HRC 1 levels. Dr. Lee pointed out that their tests so far have shown sound levels at 120 db to 130 db for a 480-volt, 5 kA fault and between 130 db to 164 db at 480 volts and 20 kA. These are very substantial acoustic values and can cause damage to a
worker’s hearing if he is not protected. As a side note, these sound levels were measured at a distance of 2 to 3 meters from the arc, as the instrument’s sensors were damaged if they were placed closer. This means the actual sound levels were probably greater than that indicated. At this time the project has almost completed the 480 V testing. During the Spring and Summer of 2011, Dr. Lee hopes to complete testing at the 4.16 kV level, complete the 480-volt to 600-volt testing, analyze their data and possibly conduct some testing at the 208-volt level. It will take a considerable amount of time to properly analyze all the data produced by these tests, so don’t expect any usable information to be forthcoming anytime soon. Testing on 7.2 kV and 13.8 kV is scheduled to be conducted during the Fall and Winter of 2011. A question was asked about dc voltages and Dr. Lee replied that they will look at dc voltages depending on funding once all the ac tests have been completed. At this time it appears as though there are no definite plans to conduct dc testing, but there are contingent plans if funding becomes available. James R. White and Ron A. Widup are NETA’S representatives to NFPA Technical Committee 70E (Electrical Safety Requirements for Employee Workplaces). James R. 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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OVERHEAD LINES: THE ELECTRICAL DANGER ABOVE NETA World, Summer 2011 Issue
by Jim White and Ron Widup, Shermco Industries
Do you know what to do around overhead power lines? What if one falls to the ground? What if one falls across your car? Do you know what step potential is? Can you quickly and safely react to a downed power line event?
The goal of this article is to provide you with facts to better understand the hazards of overhead power lines… INTRODUCTION Sadly, many people every year, both on and off the job, are seriously injured or killed from contact with overhead lines, and many times the incidents involve overhead lines that have fallen and are lying on the ground or lying on an object that has become energized. Understanding the hazards associated with overhead lines and knowing what to do (or what NOT to do) can literally mean the difference between life and death.
CASE STUDY: A FAMILY TRAGEDY IN CALIFORNIA On January 14, 2011, three family members were electrocuted in San Bernardino, California—a father (age 44), a mother (age 43), and their son (age 21). Based on information obtained from the Los Angeles Times, the details of the tragedy are: • During high winds, at about 5:45 a.m., they heard a loud “pop” in the backyard. • A 12,000-volt line had fallen to the ground. • Several small fires had started in the back and front yards. • The father and his stepson went to investigate in the back yard. • The mother went to the front yard and heard a loud explosion. • Her husband and son were lying on the ground, deceased. • She reached out to help them and was electrocuted. Knowing about the dangers of overhead power lines, especially downed power lines, can mean the difference between life and death.
OVERHEAD LINES IN THE WORKPLACE NFPA 70E NFPA 70E covers “work within the limited approach boundary of uninsulated overhead lines” in Article 130.5. This is the section of the 70E that deals with many of the hazards associated with work in locations near overhead lines. Everyone should take the time to understand and comply with the requirements and guidance located within Article 130.5. The second leading cause of worker deaths in construction (after falls) is electrocution, and the primary cause for the electrocutions is contact with overhead lines. Many times the incidents involve a nonelectrical person doing tasks such as operating a mobile crane, moving a metal ladder, unloading supplies, or accessing a roof. Ladders can be particularly hazardous, as a NIOSH review of the Bureau of Labor Statistics (BL S) Census of Fatal Occupational Injuries (CFOI) data from 1992–2005 identified at least 154 electrocution deaths that resulted from contacting overhead power lines with portable metal ladders (excluding truck-mounted and aerial ladders) [NIOSH 2007a].
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Arc-Flash Handbook OSHA Regulations Current OSHA regulations require employers to take precautions when cranes and boomed vehicles are operated near overhead power lines. Any overhead power line shall be considered energized unless the owner of the line or the electric utility company indicates that it has been de-energized and it is visibly grounded [29 CFR 1926.550 (a)(15)(vi)]. The OSHA regulations are summarized as follows: Employers shall ensure that overhead power lines are de-energized or separated from the crane and its load by implementing one or more of the following procedures: • De-energize and visibly ground electrical distribution and transmission lines. 29 CFR 1910.333(c)(3); 29 CFR 1926.550(a) (15)
are apart, one foot will be at a higher voltage than the other. If that difference in voltage (potential) is great enough, it could force current through your body. That same electricity can enter into your body if you are walking on the ground near the source and the ground becomes energized. Electricity can flow between your feet and through your body and that flow of electricity can lead to ventricular fibrillation (affecting the heart)…and the results can be deadly. It takes very little current flow through the body to cause problems: muscle contraction, suffocation, heart stoppage - all real possibilities when involved in a downed power line event and step potential becomes a factor. • Use independent insulated barriers to prevent physical contact with the power lines. 29 CFR 1910.333(c)(3); 29 CFR 1926. 550(a)(15)
If you are around a downed power line: DO THE SHUFFLE! Shuffle your feet and keep them close together, and after you are clear, keep everyone away and call 911!
• Maintain minimum clearance between energized power lines and the crane and its load. 29 CFR 1910.333(c)(3)(iii); 29 CFR 1926.550(a)(15)(i), (ii), (iii)
But what if you are involved in a vehicle accident and a power line comes down on or around your vehicle – don’t get out of your car!! Only get out if there is a life-threatening situation if you stayed in your car… and if you do have to get out – JUMP! as far as you can! Don’t touch the car and the ground at the same time and keep your feet close together (remember about step potential).
• Where it is difficult for the crane operator to maintain clearance by visual means, a person shall be designated to observe the clearance between the energized power lines and the crane and its load 29 CFR 1926.550(a)(15)(iv) • The use of cage-type boom guards, insulating links, or proximity warning devices shall not alter the need to follow required precautions. 29 CFR 1926.550 (a)(15)(v)
SUMMARY
You should familiarize yourself with all of the OSHA rules concerning overhead line safety.
ALL of the incidents involving injury from overhead power lines can be prevented if a little education and understanding of the hazards of electricity, along with an awareness of your surroundings, are put into place and followed. Remember – electricity is a very toxic thing – and beware of the overhead line!
STEP POTENTIAL: WHAT IS IT?
PRESENTATION
When power lines fall to the ground you have to be concerned with “step potential.” Think of a rock dropping in a bucket of water and the resulting ripples. The same thing happens with electricity – it flows through the ground like ripples of water. The voltage in the ground near the downed power line will be greatest and will decrease as a person moves away from it. If your feet
If you would like to receive a short PowerPoint presentation entitled Overhead Lines: The Electrical Danger Above to use at work, at school, at Boy Scouts, etc… or even at home with the kids – send an email to
[email protected] and we will send it to you for your use and grant permission to freely distribute the information.
Arc-Flash Handbook
22 James R. White and Ron A. Widup are NETA’S representatives to NFPA Technical Committee 70E (Electrical Safety Requirements for Employee Workplaces). James R. 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.
VOLUME 2 ARC-FLASH HANDBOOK
VOLUME 2
SERIES II
ANDBOOK
Published By
Shermco Industries
Sponsored by Published by NETA - The InterNational Electrical Testing Association
RC-FLASH
SERIES II
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SIGNIFICANT CHANGES TO 2012 NFPA 70E NETA World, Winter 2011-2012 Issue by Jim White and Ron Widup, Shermco Industries
The 2012 edition of NFPA 70E is finalized at last! In addition to the Report on Proposals (504 public and eight committee proposals) and the Report on Comments (433 public and 11 committee), there were 11 NITMAMs (Notice of Intent to Make a Motion) and six appeals (the last gasp to change something). It is actually unusual to see appeals made as they really get no traction, but obviously someone did not like parts of the 2012 edition. And while this article does not contain all of the changes, it does contain some of the more interesting ones to look for, and often times we refer to the differences between the 2009 edition and the 2012 edition. At 103 pages, the 2012 edition is packed full of guidance and direction on how to deal with electrical hazards while on the job, and it should be in the toolbox and back pocket of every electrical worker out there.
a good idea to start saying “Do you have your arcrated PPE?” instead of “Do you have your FR?” Look for the ATPV or EBT rating in clothing as that’s how electrical PPE is designated. (See Figure 1 for an example of arc-rated PPE.)
WHY DO YOU CARE? You probably have several articles on NFPA 70E, and you might ask yourself “Why do I care? I’m not involved in all that regulation and rules stuff; I’m just a [worker, engineer, manager, circus performer, etc.]” Here is the first answer to the question of “Why do I care?”: You just made it through the first 225 words of the article and you are still reading! Here is the second reason why you care: Because whether you are working in, around, on, or near electricity you have the ultimate challenge of doing so without getting hurt or killed. Knowledge of safe work practices and the hazards of electricity are key if you are to lead an injuryfree existence. Do do you cut the blue wire or the red wire? Let’s try to better understand the 2012 edition 70E and see if we can figure it out together.
GLOBAL CHANGES Here are a couple of important terms to understand and use as you go through the day: Fine print notes (FPN) have been changed to informational notes (IN) in order to harmonize with the NEC style manual. When referring to PPE, the term flame-resistant (FR) will be replaced by arc-rated in the standard. It is important to note that all arc-rated clothing is FR, but not all FR is arc-rated. This is important to those of us who want protection from effects of electrical arcs and not just protection from fire and flames. It is
Figure 1:F lame resistant (FR) PPE is now arc-rated PPE. Look for the ATPV or EBT rating.
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Arc-Flash Handbook with the general document than just Article 110 and now serve as an introduction. Article 110 went through many changes. All of 110.8 was moved to Article 130 so that all information relating to electrical hazards or PPE could be in one place. 110.1(C) Relationships with Contractors (Outside Service Personnel, etc), Documentation was added requiring that the meeting between the host and contract employers be documented. This was required in the 2004 edition, but dropped in the 2009. Now it is back – so make sure you document those meetings! 110.2(C) Training Requirements now require that all employees responsible for taking action during an emergency be trained in CPR, methods of release, and a new requirement for annual AED training, if one is at the site. While the source is only known as an old safety manual, see Figure 3 for an old school method of release. This is probably not the way you would do it today. 110.2(D)(1)(f ) Employee Training takes wording very closely from OSHA 29 CFR 1910.269(a)(2)(iii) which states: The employer shall determine, through regular supervision and through inspections conducted on at least an annual basis, that each employee is complying with the safety-related work practices required by this section.
ARTICLE 100 DEFINITIONS A new definition of incident energy analysis was added. It reads: “A component of an arc-flash hazard analysis used to predict the incident energy of an arc flash for a specified set of conditions.” Working On (energized conductor or circuit parts) – the words Intentionally coming in contact with…were added. The intent was to clarify that accidental contact was not working on, it was accidental contact. See the full definition in the call-out box.
ARTICLE 110 GENERAL REQUIREMENTS FOR ELECTRICAL SAFETY-RELATED WORK PRACTICES The previous Sections 110.1 through 110.4 in the 2009 edition were separated into a new Article 105 for 2012 entitled Application of Safety-Related Work Practices. These items had more to do
110.2(D)(1)(f ) of the 70E has essentially the same language, except for one small difference in that: The employer shall determine, through regular supervision or through inspections conducted on at least an annual basis, that each employee is complying with the safety-related work practices required by this standard. 110.2 110.2(D)(3)(d) Employee Training. Retraining for qualified persons must now be conducted at least every three years. This requirement was included because NFPA 70E has a threeyear cycle, and employers that are following its requirements should train their personnel using the current edition. 110.2(E) Employee Training, Qualified Person. The required documentation now includes the content of the training as well as the employee’s name and dates of training. There was a lot of discussion as to the wording (content vs. description). Content means something more than an outline, but not necessarily the handouts and text
Figure 3: Method of Release, Early Electrical Pioneers Figure 2: 110.1(C) Requires a Documented Meeting Between the Host Employer and the Contract Employer
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110.4(C)(2) Test Instruments and Equipment requires the use of GFCI protection for portable electric tools and cord sets supplied by 125 V 15 A, 20 A or 30 A circuits. If the tools are rated for other voltages or currents, an assured grounding program must be implemented.
ARTICLE 130 WORK INVOLVING ELECTRICAL HAZARDS Arguably, Article 130 is one of the most valuable and widelyused sections of the 70E. Providing guidance to management, safety professionals, and electrical workers actually performing the work, Article 130 supplies many answers to the difficult aspect of working on, near, and around electrical equipment. Article 130.1 specifies that all the requirements of Article 130 must be met whether the table method is used or an incident energy analysis (arc-flash study) is performed. So no matter how you get there, you need to follow the requirements of Article 130.
FIGURE 4: T raining of Qualified Persons Must also Include the Content of Training. 110.4(C)(1) Test Instruments and Equipment requires that GFCI protection be provided to employees where required by code, standard or laws. It permits the use of listed cord sets and GFCI protection for portable electric tools.
FIGURE 6: Be familiar with Article 130 when Working on Electrical Equipment. FIGURE 5: GFCI Protection is Required when Outdoors and Operating Portable Tools.
One of the more controversial changes was to Article 130. Per Article 130.2 Electrically Safe Working Conditions, electrical equipment that you are going to work on or might be exposed to must be placed into an electrically safe work condition (turned off ) if: 1. The employee is within the limited approach boundary.
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26 2. The employee interacts with equipment where conductors or circuit parts are not exposed, but an increased risk of injury from an exposure to an arc-flash hazard exists. There is an exception to this which essentially states that equipment that has been properly installed and maintained and is opened or racked out to achieve an electrically safe work condition does not have to be turned off in order to operate it as long as the risk assessment agrees with that thought process. Additionally, there were changes (see underlined text) to Article 130.2(B)(1) Energized Electrical Work Permit: An Energized Electrical Work Permit is required when working within the limited approach boundary or the arc flash boundary of exposed energized electrical conductors or circuit parts that are not placed in an electrically safe work condition. The words arc flash boundary were highlighted because this is a new, and somewhat controversial, change to the 70E. But remember, you are working on an energized piece of equipment with exposed parts – don’t you think you should have plan as to why? 130.3(1) Energized Electrical Conductors and Circuit Parts. “Before an employee works within the Limited Approach Boundary energized electrical conductors and circuit parts to which an employee might be exposed shall be placed in to an electrically safe work condition, unless work on energized components can be justified according to 130.2(A).” 130.5 Arc Flash Hazard Analysis, IN No. 5 – This IN replaces Exception No. 1 that was in 130.3. It points out that an Arc Flash Hazard Analysis may not be necessary for some threephase systems rated less than 240 volts and refers the reader to IEEE 1584, Guide for Performing Arc Flash Hazard Analysis. There is good information in 130.5 that you should read and become familiar with. We could probably write an entire piece on just this article of the standard.
FIGURE 8:You Must Place Turn Off Exposed Equipment when Working within the Limited Approach Boundary unless Allowed by 130.2(A). 130.5(A) Arc Flash Hazard Analysis, Arc Flash Boundary (AFB) eliminates the previously allowed precalculated 4-foot AFB and requires that the AFB be calculated as the distance where a worker would receive 1.2 cal/cm2 incident energy exposure. No more default to a four foot boundary – you need to figure out what it really is.
EQUIPMENT LABELING One of the best ways to communicate to the electrical worker in the field is to put a comprehensive label with pertinent hazard information directly on the equipment he is about to work on. Article 130.5(C) Arc Flash Hazard Analysis, Equipment Labeling uses the wording from NEC Article 110.16 to specify that the labeling requirement does not apply to all electrical equipment, only equipment that requires inspection, maintenance, adjustment, or servicing while energized. The label requirements have also changed. Each label must have at least one of the following: 1. Available incident energy and the corresponding working distance 2. Minimum arc rating of clothing 3. Required level of PPE 4. Hazard/Risk Category (HRC) for the equipment
FIGURE 7: A n Energized Electrical Work Permit is Required when Working Within the Arc-Flash Boundary of Exposed Parts
Second, the label must also include the nominal system voltage, and third, the label must contain the arc-flash boundary information.
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Arc-Flash Handbook Also, an additional new requirement states that the method used to calculate the values and the supported data must be documented. It does not necessarily have to be on the label, but it must be available for inspection, if needed. An exception was included that allows the use of labels placed onto equipment prior to September 30, 2011, if it has the available incident energy or the required level of PPE.
ARTICLE 130.7 PERSONAL AND OTHER PROTECTIVE EQUIPMENT Within Article 130.7(A), Personal and Other Protective Equipment, an IN was added that states the normal operation of an enclosed switch, disconnect, or circuit breaker that has been properly maintained probably does not expose the worker to an electrical hazard. The exact wording of IN No. 2 is:
circuit current and operating time of the overcurrent protective device (OCPD) in the headers, but also the arc-flash boundary at the maximum short-circuit current and operating time and the working distance. Voltage protection limits, the arcflash boundary and working distances for medium-voltage equipment were also provided, something that has not been provided previously. Also in Table 130.7(C)(15) (a), the device Switchboards in the category Panelboards or Switchboards Rated >240 V and up to 600 V was moved to category 600 V Class Switchgear (with power circuit breakers or fused switches). In Table 130.7(C)(15)(a), the equipment category 600 V Class Motor Control Centers (MCC), was split into two parts to reflect the difference in hazard level from working inside the bucket and working on the main bus. The first nine tasks are in one section that has limits of 65 kA shortcircuit available current and 0.03 second operating time.
It is the collective experience of the Technical Committee on Electrical Safety in the Workplace that normal operation of enclosed electrical equipment, operating at 600 volts or less, that has been properly installed and maintained by qualified persons is not likely to expose the employee to an electrical hazard.
The second section has three tasks and has limits of 42 kA short circuit available current and 0.33 second operating time.
Article 130.7(C)(5) requires that whenever you are working within the arc-flash boundary you shall wear hearing protection. An arc-flash event can be a very large and loud acoustic event. It is a good idea to protect your hearing from damage.
In Table 130.7(C)(16), formerly Table 130.7(C)(10), Hazard/Risk Category (HRC) 2* has been eliminated. All HRC 2 tasks now require the use of either an arc-rated balaclava and arc-rated face shield or an arc-rated hood. The format is unchanged from the 2009 NFPA 70E.
Table 130.7(C)(15)(b) is new for the 2012 edition of NFPA 70E. This has the same general format as the table for ac electrical power systems but is used for dc electrical systems.
There has been a long-standing argument about whether or not electrical equipment doors provide a quantifiable degree of protection form an arc-flash event. Article 130.7(C)(15) IN No. 2 and No.3 help to clarify the issue that cabinet doors do not provide enough protection to eliminate the use of PPE. The exact wording is: Informational Note No. 2:The collective experience of the task group is that, in most cases, closed doors do not provide enough protection to eliminate the need for PPE for instances where the state of the equipment is known to readily change ( for example, doors open or closed, rack in or rack out). Informational Note No. 3: The premise used by the task group in developing the criteria discussed in Informational Note No. 1 and Informational Note No. 2 is considered to be reasonable, based on the consensus judgment of the full NFPA 70E Technical Committee.
THE TABLES HAVE TURNED The tables in Article 130 are one of the most-used sections of the 70E, and extensive work was done on and with the tables for the 2012 edition, all of which was to help make the tables easier to understand and use. The table that outlined tasks and corresponding hazard risk categories and selection of PPE is now Table 130.7(C)(15)(a) which was formerly Table 130.7(C)(9). Notes 1, 2, 3, and 4 that provided the limits for this table were moved from the notes section and put in the headers for each type of equipment. Not only are the short-
FIGURE 9: T he Tables in 130.7 Provide Guidance on PPE Use and Hazard Risk Categories.
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28 AND FINALLY – LET’S TALK A LITTLE MAINTENANCE! IF you have a single-line diagram, take note. Article 205.2 Single Line Diagram states that single-line diagrams must be kept in a legible condition and must be kept current. Since not all facilities have single-line diagrams, this would not require one to be produced. A single line diagram, where provided for the electrical system, shall be maintained in a legible condition and kept current. If you read Article 205.3 General Maintenance Requirements, electrical equipment is required to be maintained in accordance with the manufacturer’s recommendations or, if they are not available, with industry consensus standards. There are only two industry consensus standards; NFPA 70B, Recommended Practice for Electrical Equipment Maintenance and ANSI/NETA MTS-2011, Standard for Maintenance Testing Specifications for Electrical Power Equipment and Systems. As was stated earlier, there are many other changes to the 2012 edition of the 70E. For you to be the very best you can be, and more importantly, for you to work safely while on or near electrical equipment, you really need to understand this very important safety standard. Ron Widup and Jim White are NETA’S representatives to NFPA Technical Committee 70E (Electrical Safety Requirements for Employee Workplaces). James R. 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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SWITCHING 2 MAINTENANCE NETA World, Winter 2011-2012 Issue by Kerry Heid, Magna Electric Corp.
One thing is for sure – if personnel are to establish an electrically safe work condition, electrical power systems apparatus must be switched. (I’m talking operating, opening, racking, removing, resetting, etc.) Any time there is interaction with the power distribution equipment, the risk of some type of failure increases. Switching an electrical device can be a dangerous act when regular maintenance on the equipment is not performed. So where does maintenance rank when doing a hazard analysis and a risk assessment during planned switching operations? Here are a few items to consider especially if your system is not properly maintained.
1. INSULATION FAILURE Switching the distribution equipment can initiate surges in the power system. Insulation systems that are not maintained can become weak over time. Partial discharge activity may cause the insulation to slowly decrease its resistance value phase-to-phase and phaseto- ground. Transient voltage spikes during switching can sometimes exceed the insulation dielectric values. This is of particular concern during the switching processes as workers are interacting with the equipment during the switching procedures. Regular maintenance involving cleaning, inspecting, insulation resistance testing, and partial discharge testing will help eliminate these issues.
Figure 1: Main contacts open with arcing contacts closed on a medium voltage disconnect switch
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30 2. SWITCHING DEVICES DO NOT OPERATE PROPERLY One of the key facets of performing regular maintenance is to ensure that the switching devices will operate when called upon either during routine switching activities or during a fault condition. During regular maintenance, equipment is operated numerous times to ensure that it operates as originally designed. From a 2011 NETA survey, we know that most of the issues with these devices are related to mechanical problems. The fact that the device has not operated in years is not a good thing. Often these dormant devices will not open when called upon in a critical fault condition or when trying to perform normal switching operations. Routine testing requires the devices to be operated numerous times to perform the various tests and assures that the equipment will operate when called upon. Some of the serious issues that have been experienced are:
Circuit breaker closed when racking This is a legitimate concern as it can cause a serious arc flash if the device is racked in or out in this state. If the mechanism operated and the mechanical indicator says open, are you sure that all three power contacts actually opened? NETA maintenance testing is designed to ensure that these devices operate correctly between service intervals.
Only two of three vacuum bottle contacts open Not only does this pose the same arc-flash issues as above, it can cause the misconception that the circuit is de-energized fully, particularly in contactors that do not rack out. In one instance an electrical worker at a mine opened the bolt in contactor on a 4160 volt mine circuit. The electrical worker received an electrical shock at phase-to-ground voltage in the motor connection box as one of the motor leads was still energized.
Disconnect switch arc blade stays in (See figure 1) This is a serious concern when switching. It is very important to check the arc blade through the viewing window on mediumvoltage switches or visually on outdoor switches. The main blades of the disconnect switches may open, but the arcing blades may not as the arcing blades release after the main blades. This can cause a misconception that the circuit is fully isolated.
equipment damage as the fault clearing time extends. Here are some things to ensure when maintaining the relaying protection systems:
Setpoints Always ensure the settings are current with a recent arc-flash hazard analysis and coordination study. With newer vintage relays, review the entire set point file and compare it to the original engineered design.
Relay function and trip testing Make sure the relay itself works according to the manufacturer’s functional design. Ensure the inputs are being received from the power system and the associated switching devices operate when called upon. Utilize the up-to-date and accurate drawings to prove this vital interaction of the protection scheme.
Clean and calibrate Particularly on vintage electromechanical relays, additional steps are required to clean and calibrate the devices. Other survey results indicated that equipment reliability is the worst once the equipment is over 25 years old. There were some significant performance issues found during the acceptance testing phase of the equipment life cycle. The most common reasons facilities do not perform maintenance are challenges surrounding scheduling, financial or technical constraints, or having a run-to-failure philosophy. The highest failure mode was mechanical problems edging out protection relaying (including settings) and well ahead of electrical diagnostic issues such as insulation resistance and contact resistance.
NETA 2011 Survey At the recent PCIC in Toronto, Ontario, the results of our latest NETA survey were released. After asking a number of questions regarding the reliability of electrical power systems, the following results were obtained. To learn more about this survey you can access PowerTest 2012 pressentations at netaworld.org and listen to the entire presentation. • Highest reliability by equipment type: Fuses • Lowest Reliability: Molded-Case C ircuit Breakers
3. PROTECTION FAILS
• Highest failure rate by Industry: Mining
It is not difficult to notice electrical systems that are poorly maintained, dirty, or appear to be in terrible condition. Precautions can be taken when switching to avoid putting workers in dangerous switching scenarios. This is not always the case with the relaying protection scheme. Older solid-state relaying protection can fail without notice and what is worse – if the protection does not operate at all or even operates milliseconds slower than designed, there will be a large impact on incident energy during an arc-flash event. This causes higher risk to workers and will result in major
• Lowest failure rate: Commercial facilities • Highest Failure Rate during acceptance testing: Molded Case Circuit Breakers • Lowest Failure Rate during acceptance testing: Fuses
Arc-Flash Handbook CONCLUSION: Maintenance testing assures that the equipment is ready and capable of being operated safely when establishing an electrically safe work condition. Partnering with a NETA Accredited Company using NETA Certified Technicians who follow the ANSI/NETA Standard for Maintenance Testing Specifications for electrical Power Equipment and Systems, 2011 edition, will give you everything you need to keep your electrical system safe and reliable. If you do not have a regular maintenance plan for your electrical power distribution equipment, it might be time for a switch. Kerry Heid is the President of Magna Electric Corporation, a Canadian based electrical projects group providing NETA certified testing and related products and solutions for electrical power distribution systems. Kerry is a past President of NETA and has been serving on its board of directors since 2002. Kerry is chair of NETA’s training committee and its marketing committee. Kerry was awarded NETA’s 2010 Outstanding Achievement Award for his contributions to the association and is a NETA senior certified test technician level IV. Kerry is the chair of CSA Z463 Technical committee on Maintenance of Electrical Systems. He is also a member of the executive on the CSA Z462 technical committee for Workplace Electrical Safety in Canada and is chair of working group 6 on safety related maintenance requirements as well as a member of the NFPA 70E – CSA Z462harmonization working group.
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SAFER LOCK-OUT TAG-OUT WITH PERMANENT ELECTRICAL SAFETY DEVICES–ELECTRICALLY SAFE WORK CONDITIONS BASED UPON NFPA 70E AND OSHA PowerTest 2012 by Philip B. Allen, Grace Engineered Products
Article 120.1 of the NFPA 70E establishes the procedure for creating an electrically safe work condition. Since this was written, the day-to-day practice of electrical safety has changed and goes beyond the precise language of Article 120.1(1-6). This is due to the increased usage of permanent electrical safety devices (PESDs) in Lock-out/Tag-out procedures (LOTO). The relatively new concept of permanent electrical safety devices actually improves the workers’ ability to safely isolate electrical energy beyond that which was originally conceived when Article 120 was written. PESDs go beyond the high standard, yet they still adhere to the core principles found in Article 120.1. With PESDs incorporated into safety procedures, installed correctly into electrical enclosures, and validated before and after each use, workers can transition the once-risky endeavor of verifying voltage into a less precarious undertaking that never exposes them to voltage. Combining a hazard risk analysis with PESDs on an electrical panel allows workers to open the panel without PPE. Since every electrical incident has one required ingredient – voltage - electrical safety is radically improved by eliminating exposure to voltage while still validating zero energy from outside the panel. Index Terms — voltage detectors, voltage portals, non-contact voltage detector, NCVD, power warning alerts, permanent electrical safety devices, voltage detector validation procedures, verification, voltmeters Key Points • Introduction: Applicable safety concepts • Definitions: Voltage Indicator, Voltage Portal • What happens with a voltage detector is ‘validated’? • Validating a voltage indicator and voltage portal • Multi-meter comparison • Written procedures and mechanical LOTO • Reduced arc flash risk and reduce PPE for workers accessing panels. • Other reference materials
INTRODUCTION To employees all safety – especially electrical safety – is personal. Little else matters to them unless electrically safe work
conditions can be created and maintained through their work environment. Article 120.1 of the NFPA 70E was, as its title suggests, penned with the important purpose of establishing the “gold standard” for creating an electrically safe work condition. Since then, however, innovation in the realm of electrical safety has surpassed the precise language of Article 120.1(1-6) because it fails to speak directly to the value permanent electrical safety devices have in achieving an electrically safe work environment. The relatively new concept of permanent electrical safety devices (PESDs) actually improves the workers’ ability to safely isolate electrical energy beyond that which was originally conceived when Article 120 was written. The forward-thinking concept of PESDs goes beyond the high standard of safety for which competent companies strive, yet it still adheres to the core principles found in Article 120.1. With PESDs incorporated into safety procedures, installed correctly into electrical enclosures, and validated before and after each use, workers can transition the once-risky endeavor of verifying voltage into a less precarious undertaking that never exposes them to voltage. Let’s face it; every electrical incident has one required ingredient – voltage. Electrical safety is radically improved by eliminating exposure to voltage while still validating zero energy from outside the panel.
TIME-TESTED PRACTICES: THE FOUNDATION FOR SAFETY IMPROVEMENTS The standard shoulder belt you (hopefully) use each time you are in a vehicle is an improvement on a simple lap belt found in many vehicles of the past. American car manufacturers offered seat belts only as options until Saab introduced them in 1958 as a standard safety element – an act that changed the landscape of passenger safety in vehicles. Later, driver- and passenger-side air bags offered breakthrough safety advances beyond the thensimplistic seatbelt only to later be enhanced by side-impact air bags. Each of these safety innovations relies upon each other for peak functionality and surpassed conventional safety protocols of 1958. Air bags provide little protection if drivers are not wearing seatbelts; shoulder belts without lap belts are ineffective, and side air bags alone are insufficient. These safety reformations, when used in conjunction with each other, raised the expectations of
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Arc-Flash Handbook safety for all users and ultimately manufacturers began offering them as standard equipment. Similarly, PESDs are revolutionizing electrical safety and should be used in conjunction with existing safety practices.
DEFINITIONS AND RESOURCES1 Non-Contact Voltage Detector (NCVD) – A battery operated voltage detector that senses voltage without actually touching an energized conductor.
Voltage Portal – Extends a voltage source to the outside of an
electrical enclosure in an encapsulated non-conductive housing designed for a NCVD to sense voltage if placed into the voltage portal (Fig 1).
Voltage Indicator – A hardwired LED indicator permanently
wired to the phase(s) and ground that illuminates when a 40VAC/30VDC or greater voltage deferential exists between two lone inputs. Typical 3-phase/4-wire voltage indicator requirements include (Fig 2): • Powered from the line voltage (no batteries) • Applies to any power system by operating on a wide voltage range (40-750VAC/30-1000VDC) • Cat IV rated for high surge immunity • UL Certified to UL 61010-1 as per NFPA 70E 120.1(5) FPN
Written Procedures and Training: Using PESDs in an electrical safety program requires written Lock-out/Tag-out (LOTO) procedures. Employees need to be trained and have access to these procedures.2 VALIDATING A VOLTAGE DETECTOR Creating an electrically safe work condition depends upon a process that ensures 100% accuracy from voltage detectors. To help ensure this, the NFPA 70E says, “Before and after each test, determine that the voltage detector is operating satisfactorily,” (NFPA 70E 120.1(5). Validation means that electricians first check their voltage detector to an independent voltage source (i.e. a nearby 120VAC outlet). Next, they check for zero voltage on the primary source. Work begins only after the voltage detector is rechecked to the independent live voltage source. This straightforward validation procedure works for a portable voltage detector because it can be physically moved between two voltage sources. Because of this, perhaps the authors of NFPA 70E only considered portable voltage detectors (i.e. voltmeters), not PESDs, when writing Article 120.1? Over the past several years, PESDs have become a way for Fortune 500 companies to increase safety and productivity simultaneously. Weyerhaeuser started using voltage indicators (a PESD) in 2004 and that quickly spread to other facilities. Warren Hopper, Manufacturing Services Manager Weyerhaeuser stated, “Use of the fixed voltage indicators would allow us to avoid opening starter or disconnect compartment doors for approximately three quarters of all lockouts.”3 The same
principles absolutely apply to PESDs. However, because a PESD cannot be moved between two voltage sources, the technique for validation needs a slightly different approach. So what actually needs to happen to validate a voltage detector? Testing for voltage simply requires a small amount of current to flow between the two voltage potentials. The voltage detector circuit determines a voltage potential by relating this current flow to actual voltage and providing the worker an appropriate indication (audible, visual or digital display).
VALIDATING A VOLTAGE PORTAL & NCVD COMBINATION A NCVD determines whether or not voltage exists in a conductor by creating a low current capacitive circuit between the conductor, the NCVD, the worker, and ground (Fig 3). Therefore, when the NCVD is positioned close to a live conductor this completed circuit causes the NCVD to beep or flash telling the worker that voltage exists in the conductor. Because voltage portals mount permanently to the outside of enclosures, the worker has to stand in the same place when using his NCVD. This makes this capacitive circuit more reliable and more repeatable than it would be when workers use a NCVD in all other applications.4 Since NCVDs are portable, they can also be checked to an independent voltage source as per NFPA 70E 120.1(5).
MINIMUM REQUIREMENT FOR A VOLTAGE INDICATOR A voltage indicator is hardwired to the 3-phase disconnect and earth ground (Fig 2). The circuit illuminates LEDs when AC/ DC voltage exists between any two phase(s) and(or) ground. Since voltages above 50 volts are deemed unsafe by NFPA 70E,5 it is imperative that the LEDs on a voltage indicator illuminate for all voltages above 50 volts. Perhaps, the most compelling characteristic of a voltage indicator is the wide operating characteristics (40-750AC/30-1000VDC). This feature separates it from other devices, like a pilot light, for example, that would quickly fail if the voltage exceeded its normal operating range (i.e. 120VAC +/- 10%).
VALIDATING A VOLTAGE INDICATOR A hardwired voltage indicator brings up three interesting issues. First, it is impractical to verify the voltage indicator to another independent voltage source. Trying to accomplish this by adding a switch to toggle between the line voltage and the test voltage adds more components and complexity and leads to unreliability.6 Second, since the voltage indicator’s sole purpose is to indicate voltage, anything installed between the source voltage and the voltage indicator increases the chance of a false negative voltage reading - switches, relays and fuses included.7 Third, because of the three phase circuit design, a voltage indicator accommodates multiple current paths between phase(s) and ground, thereby reducing the number of possible failure modes.8 In one possible
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34 circuit design, before a single LED illuminates, the current must pass through at least four LED flashing circuits. “Voltage when illuminated” means if only one of the four LEDs illuminates, it still provides voltage indication to the worker.
MULTI-METERS COMPARED TO PESDS Creating electrically safe work conditions relied solely upon the portable multi-meter before PESDs came along. This tool is not only used in electrical safety, but has features making it invaluable for other purposes such as electrical troubleshooting and diagnostics. Additionally, a PESD leaves no question or confusion when a worker uses it in creating an electrical safe work condition because it was designed, built, and installed for a single purpose – voltage indication for electrical safety. Understanding these differences helps determine an acceptable validation procedure for PESDs. Voltage indicators and voltage portals have unique strengths and complementary characteristics, and when used together they meet the validation requirements of NFPA 70E 120.1. The traditional method of validating the voltage detector to an independent voltage source is met with the NCVD/voltage portal combination. On the other hand, it can be argued that a voltage indicator by itself cannot be validated by the traditional method. However, because permanently-mounted voltage detectors are designed to only detect voltage, the built-in advantages over a simple multimeter needs to also be considered in validating this device (Fig 5).
WRITTEN LOTO PROCEDURES & MECHANICAL LOTO A PESD only becomes a real safety device only after it is included as part of a written LOTO procedure. Without this, PESDs are nothing more than just another electrical component. The LOTO procedure must explain to the worker each step in the LOTO procedure that involves the PESD. At a minimum, workers will need to verify proper operation of the PESD before and after performing a LOTO procedure. Interestingly, the mechanical maintenance workers receive a huge benefit with PESDs when these devices are used in mechanical LOTO procedures. Workers performing mechanical LOTO (work involving no contact with conductors or circuit parts) procedures must still isolate electrical energy. PESDs provide a means of checking voltage inside an electrical panel without exposure to that same voltage. Without these devices, a mechanic performing mechanical LOTO would be required to work in tandem with an electrician using a voltmeter to physically verify zero voltage inside an electrical panel before work begins. In this case, the electrician is exposed to voltage. With PESDs, the mechanic can single-handedly check for zero electrical energy without any exposure to voltage, thereby making the LOTO procedure safer and more productive. This is exactly how a western Pennsylvania power plant increased both the safety and efficiency of their operators. Operators were able to perform more maintenance tasks during off-shift hours by
installing voltage portals into each motor control center bucket, rewriting their LOTO procedure, and training the operators to use NCVD detectors with voltage portals. In the past, even a simple maintenance task like replacing a broken fan belt was side-barred until the first-shift electrician arrived to lock-out the electrical energy feeding the fan motor. In the end, both electricians and operators became more productive and still complied with OSHA LOTO requirements.9
REDUCED ARC FLASH RISK AND PERSONAL PROTECTIVE EQUIPMENT An electrical safety program is safer when workers can determine a zero electrical energy state without any voltage exposure to themselves. Verifying the proper operation of a meter and testing for absence of voltage before working on electrical conductors (test- before-touch) must remain a habitual practice for workers. The goal of PESDs is to ensure when workers test-before- touch they test only dead conductors. Therefore, after completing a hazard risk analysis (NFPA70E Annex F) on the installation and PESDs written into this procedure, users may conclude this task may be done without special PPE. Without PESDs, a failure of an isolator may go undetected until the electrician discovers live voltage after opening the panel. This exact scenario is a common cause of arc flash. A direct short circuit may result from one misstep by the electrician while checking voltage. Even worse yet, the electrician would take a direct hit in the face from the resulting arc flash. Because PESDs meet NFPA 70E 120.1 and the lessened risk of voltage exposure, some will conclude that the need for personal protection equipment (PPE) is reduced once the panel is open. Whether or not you agree with this, voltage detectors are a low-cost, redundant voltage verification tool that reduces arc flash risk, increases safety, and adds productivity for an installed cost of $150.
CONCLUSION Safety is an evolution based on best work practices and innovation. High safety standards not only create safer workplaces, but also encourage safety innovations. Ultimately, safety standards must be rigid enough to garner the highest level of safety while still being flexible enough allowing for advances through innovation to be incorporated while still adhering to the principles of Article 120.1. Now, thinking outside the panel doesn’t leave you boxed in.
REFERENCES (1) For more reference information please see http://graceport. com/thru_door.cfm (2) O SHA 29 CFR 1910.147, 1910,333(b) NFPA 70E 120.2(B) (2), 120.2(C)(1) (3) One Mill’s Response to a Specific Type of Arc Flash Problem, Warren S. Hopper, PE, Senior Member, IEEE, Weyerhaeuser Company, Springfield, OR
Arc-Flash Handbook (4) For more info, see Voltage Portals Improve Non-Contact Voltage Detectors paper http://www.graceport.com/assets/files/ Application%20Notes/Application_VoltagePortals%20Improve%20NCVD.pdf (5) NFPA 70E 110.6(D)(1)(b), 110.7(E) (6) This is impractical because it requires a 600V fused three -pole double throw relay. The fusing, the relay wiring, and switching introduces 18 connections (failure points) between the voltage source and the voltage indicator. (7) False-Negative: When voltage exists in a conductor and the voltage detector does not sense it. (8) This design has four voltage detection circuits (L1, L2, L3, GRD) with two LED flashing circuits each. Therefore a current path between two phases passes through at least four LED flashing circuits. For more information, see: http://graceport. com/assets/files/Application%20Notes/How%20does%20 it%20work%204page.pdf (9) OSHA 1910.147
Phil Allen (
[email protected]) is the President and owner of Grace Engineered Products, the leading innovator of permanent electrical safety devices. He holds two US Patents, a power receptacle design and a voltage detector test circuit. His passion is finding new and more efficient ways of bringing electrical safety to the forefront. Phil did his undergraduate work at California State University, San Luis Obispo and is a 1984 graduate with a BSIE. Grace Engineered Products is best known for its GracePort® line of custom-made data port interfaces. In addition to the GracePort® line, the company provides a well-established line of products – ChekVolt® and VoltageVision® - that make pre-verifying electrical isolation through enclosure doors safe and easy. Their focus is on NFPA 70E guidelines and making companies electrically safe while also increasing their employee productivity.
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CHANGES AND ENHANCEMENTS TO THE 2012 NFPA 70E PowerTest 2012 by James R. White, Shermco Industries, Inc.
THE NFPA CONSENSUS PROCESS Briefly, the 70E committee is managed by the NFPA by a consensus process, which allows input from any member of the general public or from within the 70E committee. Proposals are solicited from the public and compiled by the NFPA staff. A report is generated listing each proposal and is posted on the NFPA website in an area that is accessible to anyone who may have an interest. The 70E Technical Committee reviews each of the proposals at a meeting, usually referred to as the ROP (Report on Proposals). The committee recommends action of each proposal and can accept it as written, reject it outright or accept it with changes. These actions are published on the NFPA website, again in an area that is accessible to the general public. Comments to the proposed actions are solicited from any interested party by the NFPA and are complied in a Report on Comments. The next step in the process is the Report on Comments (ROC) meeting, where all comments received by the NFPA are discussed and actions voted on. The NFPA consensus process requires a 2/3 majority on all votes. Comments can be accepted, rejected or accepted with changes. Once the ROC meeting is finished, the standard is finished, at least for the Technical Committee. The NFPA staff takes all the actions and correlates them with each other and produces a document for the committee and the Technical Correlating Committee (TCC) to review. The TCC will sometimes make motions to modify what the committee has done in what is referred to as a NITMAM (Notice of Intent to Make a Motion). This is voted on at the national meeting and is the completion of the process. Rarely, someone may file an appeal if they disagree with the action taken on a NITMAM. This was the case during the 2012 cycle. The chances of an appeal being successful are very small, as the issues would have been voted on twice by the committee and ruled on by the TCC. Once the NFPA blesses the document, it becomes the new 70E and is usually published in October of the year preceding its listed date (October, 2011 for the 2012 edition).
DISCLAIMER The opinions expressed in this paper are the author’s and in no way represent the official NFPA interpretation or even that of the Technical Committee.
CHANGES IN TABLES FOR ARC FLASH CLOTHING AND PPE There are now two tables for determining the Hazard/Risk Category (HRC) for the arc flash protective clothing. Table 130.7(C)(9) is now 130.7(C)(15)(1) for AC power systems and a 130.7(C)(15)(2) will be added for choosing PPE when working on DC power systems. Table 130.2(C) is now 130.4(C)(a) for shock approach boundaries for AC power systems and 130.4(C)(b) for shock approach boundaries for dc power systems. The new table for DC systems was necessary, as Table 130.7(C)(9) used phaseto-phase voltages, whereas DC systems are phase-to-ground (or positive-to-negative). The notes that used to appear at the bottom of Table 130.7(C)(9) have been moved into the header for each type of equipment to make them more noticeable. The Arc Flash Boundary and the working distance are also specified in the table headers at the maximum short circuit available current and operating times. In general, the committee believed that the notes, as they were positioned in Table 130.7(C)(9), were not being utilized by the average user of the standard and that those people could be seriously under-protected if they are not aware of the limits of the table. The equipment category “600V class motor control centers” has been split into two sections; one section for the hazards and risks involved in work inside the bucket and another for work involving the main bus that feeds the bucket. This change should make determining the proper arc flash protective PPE more straightforward. The equipment type “600V class switchboards” was removed from the equipment category “Panelborads and other equipment rated >240V and up to 600V” and inserted into the equipment category “600V class switchgear (with power circuit breakers or fused switches) and 600V class switchboards.” The 70E committee is still trying to sort out the best method of handling switchboards, as we believed they had more resemblance to switchgear than panelboards. This structure may change for the next edition of 70E. Medium-voltage equipment rated from 1kV through 38kV now has the same information in the header as the low-voltage equipment, including the Arc Flash Boundary and working distance. The Arc Flash Boundary is based on the short circuit available current and operating of the OCPD that would create approximately 40 cal/cm2 incident energy, if there were an arc
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Arc-Flash Handbook flash. No guidance for this type of equipment was provided in previous editions of NFPA 70E. Table 130.7(C)(11) was eliminated, as it was rendered redundant by changes made in the 2009 edition to Table 130.7(C)(10). Table 130.7(C)(16) [formerly 130.7(C)(10)] eliminate HRC 2*. All HRC 2 tasks will now require the use of a balaclava under an arc-rated face shield, or the use of an arc-rated hood. There was concern, based on substantiation provided with the original proposal, that the sharp edge of the face shield could create a vacuum as the heat flux flows past it, causing the heat to be pulled in towards the face. This could cause the unprotected face to suffer serious burn injuries, even though it is covered by the face shield. Annex H has been renamed “Guidance on Selection of Protective Clothing and Other Personal Protective Equipment” and contains new Table H.3(a), which is an easy method to locate references to PPE contained within NFPA 70E. New Table H.3(b) contains guidance on arc flash protective clothing and PPE when an Incident Energy Analysis is performed. Table H.3(b) shows the required arc flash protective clothing at three levels: • Less than or equal to 1.2 cal/cm2 • Greater than 1.2 cal/cm2 up to 12 cal/cm2 • Greater than 12 cal/cm2 Previously, the only guidance for arc-rated PPE was in Table 130.9(C)(10), and its use was discouraged by the 70E when an Incident Energy Analysis had been performed. There’s also new Table H.4, titled, “Two-Level Clothing Approach for Use with known Short Circuit Currents and Device Clearing Times.” There are actually two tables, H.4(a) for low-voltage systems and H.4(b) for high-voltage systems. These tables provide guidance for using 8cal/cm2 and 40cal/cm2 arc-rated clothing and PPE and should add clarity as to when the two-category method would be appropriate to use.
GLOBAL CHANGES TO ENTIRE DOCUMENT The phrase Fine Print Notes (FPN) will not be used in the 2012 edition. They will now be referred to as “Informational Notes” (IN) in order to conform to the NEC Manual of Style. Arc-rated will be used instead of FR. It was noted that all arcrated clothing is FR, while not all FR is arc-rated. This change ensures that arc flash protective clothing and PPE is designed and rated for electrical hazards. Calories/cm2 is now the preferred rating for arc-rated clothing and PPE. The use of Joules/cm2 is not used in the main body of the standard (one exception – 130.5(A) Arc Flash Boundary). The committee consensus was that all arc-rated clothing and PPE used cal/cm2 and any other term would only add confusion. Hazard/Risk Analysis has been changed to Hazard Identification and Risk Assessment. This was done to differentiate between the two steps required. Some people confused the hazard with the risk and were not completing both parts as required by the standard.
ARTICLE 100, “DEFINITIONS” Arc Rating – This definition was expanded upon with two new Informational Notes. One provides the ASTM F1959 definition of ATPV and the other is the ASTM definition of EBT or breakopen threshold. Boundary, Arc Flash – The word “Protection” was dropped, as it did not add clarity and did not appear in the shock boundaries. A new Informational Note was added that defined when a person could receive a second-degree burn on bare skin (1.2cal/cm2).
NEW ARTICLE 105, “APPLICATION OF SAFETYRELATED WORK PRACTICES” This new article relocated 110.1, “Scope” through 110.4, “Organization” and used them to make Article 105. The information contained in them is unchanged.
ARTICLE 110, “GENERAL REQUIREMENT FOR ELECTRICAL SAFETY RELATED WORK PRACTICES” This article now begins with “Relationships with Outside Contractors,” since the previous paragraphs were used to make new Article 105. 110.1 now requires that the meeting between a host employer and contractor be documented. This was required in the 2004 edition, was deleted in 2009 and is now back in the 2012 edition. Place your bets on the 2015 edition. 110.2(C) (formerly 110.6), “Emergency Procedures” has added the requirement for AED training annually. There was some concern about requiring training if the facility does not have AED’s, but the general feeling was that if no AED’s are present, no training is required. 110.2(D), “Employee Training” adds a new requirement that an annual inspection be performed verifying that each employee is complying with the safety-related work practices in NFPA 70E. The wording closely mimics wording in 1910.269. Also, in 110.2 retraining of employees is required every three years. The committee felt that safety training is needed to refresh worker’s awareness and that the three year maximum was not overly burdensome and coincided with the release of the new editions of NFPA 70E. If a company wanted to conduct the training annually there is nothing to restrict that, either. 110.2(E), “Training Documentation” now requires that the content of the training be documented. There was some discussion concerning whether the wording should be “content” or “description”. “Description” was considered to be too vague. 110.3(E), “Electrical Safety Program Procedures” now includes the wording, “An electrical safety program shall identify the procedures for working within the Limited Approach Boundary and for working within the arc flash boundary before work is started”. Since there are tasks that could create an arc flash hazard
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38 when there is no shock hazard (racking of breakers and similar tasks) this wording change made sense. 110.3(H), “Electrical Safety Auditing” includes a requirement that field safety audits be conducted to ensure procedures and principles of the electrical safety program are still compliant with the latest standards and regulations. This audit is required no more than every three years. NFPA 70E also requires a field safety audit to be performed to ensure workers are following those standards and regulations.
ARTICLE 120, “ESTABLISHING AN ELECTRICALLY SAFE WORK CONDITION” The provision for Individual Control was eliminated from this article. This allowed a worker to work within a MCC or other such equipment without locking it out. OSHA stated they would find that in violation of their regulations.
ARTICLE 130, “WORK INVOLVING ELECTRICAL HAZARDS” 130.5, “Arc Flash Hazard Analysis,” The erroneous wording of the exception for electrical systems fed by one transformer
