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14、Association. Copyright 2012 IEEE. All rights reserved. viParticipants At the time this IEEE recommended practice was completed, the P3007.3 Working Group had the following membership: Dennis K. Neitzel, Chair Ron Widup, Vice Chair Terry Becker Alireza Daneshpooy H. Landis Floyd Charles Hemrick Mike
15、Moore Kelly ODonnell David Pace James White Steve Wilson The following members of the individual balloting committee voted on this recommended practice. Balloters may have voted for approval, disapproval, or abstention. William J. Ackerman Ali Al Awazi John Barker Paul Barnhart Michael Bayer James B
16、eall W. J. (Bill) Bergman Wallace Binder Michael Bio Thomas Bishop William Bloethe Frederick Brockhurst Chris Brooks William Brumsickle Gustavo Brunello William Byrd Keith Chow Kurt Clemente Donald Colaberardino Stephen Conrad Terry Conrad Carey Cook Alireza Daneshpooy Charles DeNardo Gary Donner Do
17、uglas Dorr Randall Dotson Neal Dowling Donald Dunn Gary Engmann Dan Evans Keith Flowers H. Landis Floyd Carl Fredericks George Gela Kenneth Gettman Manjinder Gill Randall C. Groves Paul Hamer Adrienne Hendrickson Steven Hensley Lee Herron Scott Hietpas Werner Hoelzl John Houdek Gael Kennedy John Ken
18、nedy Edwin Kramer Jim Kulchisky Saumen Kundu Ed Larsen Wei-Jen Lee Duane Leschert Albert Livshitz William McBride Kenneth McClenahan L. McClung John Merando James Mitchem Daleep Mohla Kimberly Mosley Jerry Murphy Paul Myers Daniel Neeser Dennis K. Neitzel Arthur Neubauer Michael S. Newman Joe Nims T
19、ed Olsen Giuseppe Parise Donald Parker David Parman Christopher Petrola Percy Pool Louie Powell Iulian Profir Michael Roberts Charles Rogers Steven Sano Vincent Saporita Bartien Sayogo Robert Schuerger Gil Shultz Hyeong Sim Michael Simon James Smith Jeremy Smith Jerry Smith Peter Sutherland Michael
20、Swearingen David Tepen Demetrios Tziouvaras Kenneth White Ron Widup Larry Yonce Larry Young David Zaprazny When the IEEE-SA Standards Board approved this recommended practice on 6 February 2012, it had the following membership: Richard H. Hulett, Chair John Kulick, Vice Chair Robert M. Grow, Past Ch
21、air Judith Gorman, Secretary Masayuki Ariyoshi William Bartley Ted Burse Clint Chaplin Wael Diab Jean-Philippe Faure Alexander Gelman Paul Houz Jim Hughes Joseph L. Koepfinger* David J. Law Thomas Lee Hung Ling Oleg Logvinov Ted Olsen Gary Robinson Jon Walter Rosdahl Sam Sciacca Mike Seavey Curtis S
22、iller Phil Winston Howard L. Wolfman Don Wright *Member Emeritus Also included are the following nonvoting IEEE-SA Standards Board liaisons: Richard DeBlasio, DOE Representative Michael Janezic, NIST Representative Satish K. Aggarwal, NRC Representative Julie Alessi IEEE Standards Program Manager, D
23、ocument Development Patricia A. Gerdon IEEE Standards Program Manager, Technical Program Development Copyright 2012 IEEE. All rights reserved. viiIntroduction This introduction is not part of IEEE Std 3007.3-2012, IEEE Recommended Practice for Electrical Safety in Industrial and Commercial Power Sys
24、tems. IEEE Std 902-1998 B27, also known as the IEEE Yellow Book, has been an excellent resource for engineering, management, safety professionals, and maintenance personnel since it was published.aThe entire IEEE Color Booksseries is in the process of being revised and reorganized into numerous “dot
25、” standards, under the 3000 series of standards, with the IEEE Yellow Book being divided into three such “dot” standards. The new “dot” standards for operations and management, maintenance, and safety are as follows: IEEE Std 3007.1-2010 B29 IEEE Std 3007.2-2010 B30 IEEE Std 3007.3-2012 (this standa
26、rd) IEEE Color Book reorganization The thirteen recommended practices, known as the IEEE Color Books, have been industry-proven tools specifically developed for engineers, involved in all facets of industrial and commercial power systems, for many years. This set of recommended practices covers the
27、many varied subjects dealing with all aspects of industrial and commercial power systems, including: analyzing, planning, calculating, coordinating, protecting, and assuring the safety of the power systems elements, equipment, and systems. In 2002, the Industrial and Commercial Power Systems (I thos
28、e between 90 mA and 4 A can be fatal due to heart disruption. Those above 5 A may be fatal from severe internal or external burns. It is a fact, however, that shocks in this last current range are statistically less likely to be fatal than those in the 90 mA to 4 A range. In view of the diversity of
29、 injuries resulting from contact with electrical energy, it is only logical that, to minimize electrical shock or electrocution, exposure to energized conductors and circuit parts should be eliminated where possible, or at the very least minimized as much as possible. Table 1 Current range and effec
30、t on a 68 kg (150 lb) human Current (60 Hz) Physiological phenomena Feeling or lethal incidents 20 000 000 Dry concrete above grade 1 000 000 to 5 000 000 Dry concrete on grade 200 000 to 1 000 000 Leather sole, dry, including foot 100 000 to 500 000 Leather sole, damp, including foot 5 000 to 20 00
31、0 Wet concrete on grade 1 000 to 5 000 Reprinted with permission from: Lee B32. In fibrillation, the victim may not recover consciousness. On the other hand, the victim may be conscious, deny needing help, walk a few feet, and then collapse. Death may occur within a few minutes, or may take hours wi
32、th vulnerability possible up to a week later. Detection of the fibrillation condition requires medical skill and training. Portable heart defibrillators are often available at the work place or in public buildings, which can be used to stabilize the heartbeat of a victim who has gone into fibrillati
33、on. Many of these units provide vocalized step-by-step directions on their use and are suitable for use by non-professionals. In Figure 1, note the fibrillation line for an exposure time of 5.0 s or more is shown at 75 mA. For shorter times, the threshold current is higher. It should be noted that,
34、if the duration of shock is only 0.004 s, or one-quarter cycle of 60 Hz, the fibrillation threshold current is determined by the energy in the impulse, i.e., Energy = VI(t). Dalziel has determined that the safe limit for impulse shock is 50 Joules (J). For an impulse shock of 4 A at 4 msec from a 12
35、0 V source, the impulse shock energy is only 2 J and is unlikely to be harmful to a human. When the impulse shock is 4 A at 4 ms from a 4000 V source, the impulse shock energy is 64 J, so then it is more likely that a harmful injury will occur. Figure 1 Resistancevoltagecurrent effect appraisal char
36、t Copyright 2012 IEEE. All rights reserved. 8IEEE Std 3007.3-2012 IEEE Recommended Practice for Electrical Safety in Industrial and Commercial Power Systems This sensitivity, increasing with time, explains why a victim who is “frozen” to a current source is much more likely to be electrocuted than o
37、ne whose contact does not involve hand grasp. A full hand grasp can immobilize the victim such that he cannot let go; hence, the exposure time may extend to many seconds, placing it in range of the 90 mA threshold. In comparison, a casual contact (such as with a fingertip) causes a reflexive retract
38、ion of the arm, thereby interrupting the shock current path. In this case, the victim is exposed for only a few thousandths of a second and is much less likely to sustain an injury. In addition, data has been compiled that shows the corresponding voltage required to force certain current values thro
39、ugh a person who has a circuit resistance of 500 . Although this value appears to be rather low for human body resistance, it can be approached by someone who has sweat-soaked cloth gloves on both hands and a full hand grasp of a large energized conductor and a grounded pipe or conduit. Moreover, cu
40、ts, abrasions, or blisters on hands can negate the skin resistance, leaving only internal body resistance to oppose current flow. A circuit value as low as 18 V could be dangerous in this instance. For a person with a resistance of 1000 , 90 V could be dangerous; 120 V would be dangerous for a human
41、 body with a resistance of 1333 or less. Defibrillation involves placing electrodes and conductive jelly on the chest. A pulse of over 1000 V dc is applied; this results in current flow up to a few tens of amperes, but only for several milliseconds. These numbers vary with the type of instrument, se
42、ttings, and other factors. This pulse of dc causes a violent muscle contraction in the chest. Such defibrillation places the heart in asystole: a complete stoppage of electrical activity of the heart. Within a few seconds, the heart will usually resume a normal pattern of beating. Once the heart goe
43、s into ventricular fibrillation it usually does not spontaneously revert to a normal heart rhythm, though it may do so. 4.2.2 Burns from contact, arcs, or flashes Electrical shock can be a hazard to life. Many people, however, have experienced minor shocks with no dire consequencesnot even skin burn
44、s. This tends to make people somewhat complacent around electricity. What most people do not know is that approximately half of the serious electrical injuries involve burns. Electrical burns include not only burns from contact, but also radiation burns from the extreme temperatures of electric arcs
45、 that result from short circuits due to poor electrical contact or insulation failure. The electric arc between metals is, next to the laser, the hottest thing on earth. It is about four times as hot as the suns surface, or 20 000 K (35 000 F). Where high arc currents are involved, burns from such a
46、rcs can be fatal, even when the victim is some distance from the arc. Serious or fatal burns can occur at distances of more than 304 cm (10 ft) from the source of a flash. In addition to burns from the flash itself, clothing is often ignited. Fatal burns can result because the clothing cannot be rem
47、oved or extinguished quickly enough to prevent serious burns over much of the body. Wearing clothing made of meltable fibers will also add to the problem. Because of this Occupational Safety and Health Administration (OSHA) 29CFR1910.269(l)(6)(iii) requires the employer to have employees who are exp
48、osed to flames or electric arcs wear only clothing that will not increase the extent of injury. Clothing that is made of acetate, nylon, polyester, or rayon is prohibited unless the employer can demonstrate that the fabric has been treated to withstand the conditions that may be encountered. Visible
49、 skin burns from direct contact electrical shock are caused by the I2R heating of body tissue and vary according to many factors such as voltage, contact resistance, skin conditions, contact duration, and bodily current path. It has been estimated by various researchers that the minimum current necessary to produce first-degree skin burns is an exposure of approximately 100 mA for 1.0 s to 9.0 s for a skin area of 1.0 cm2. Even at what a person may believe to be a large and safe distance, serious or fatal injuries can occur to a persons bare ski
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