Mark Lyvers LLC / Cooper Bussmann Arc Flash Script Script to accompany PowerPoint on New 2002 NEC Arc Flash Hazard Marking Requirement

Transcription

1 Mark Lyvers LLC / Cooper Bussmann Arc Flash Script Script to accompany PowerPoint on New 2002 NEC Arc Flash Hazard Marking Requirement Slide 1 Suggestion on How to Use Download both the Mark Lyvers LLC / Cooper Bussmann Arc Flash PowerPoint file (.ppt) and script file (.pdf). Print the script file (.pdf) and read the script as you view the PowerPoint (.ppt) presentation in the "Slide Show" view. In this way you see the slides in large format and have animation (if there is any). Must have PowerPoint and Adobe reader application software on your system. Slide 2 to 9 Photos of arcing fault incident. There is a new requirement in the 2002 National Electrical Code for arc flash hazard labeling. Slide is this new requirement. Slide 11 Let's take a closer look at what it says Flash Protection. Switchboards, panelboards, industrial control panels, and motor control centers in other than dwelling occupancies, that are likely to require examination, adjustment, servicing, or maintenance while energized, shall be field marked to warn qualified persons of potential electric arc flash hazards. The marking shall be located so as to be clearly visible to qualified persons before examination, adjustment, servicing, or maintenance of the equipment. " Slide 12 This requirement excludes electrical equipment in dwelling units. But for all other electrical equipment where a worker might perform tasks that could place him or her at risk, it requires that a label be affixed warning of the potential for an arc flash hazard. This encompasses most industrial and commercial electrical equipment since equipment that is being checked for voltage during the lockout/tagout procedure for putting equipment into a "safe working condition" is considered "live". This new requirement is intended to reduce the occurrence of serious injury or death due to arcing faults for workers who work on or near energized electrical equipment. The warning label should remind a qualified worker who intends to open the equipment for analysis or work that a serious hazard exists and that the worker should follow work practices and wear personal protection equipment (PPE) for the specific hazard (a non qualified worker must not be opening the equipment). Slide 13 This is a close-up of an example warning label this label warns of both arc flash and shock hazards plus reminds workers to use proper PPE. PPE stands for Personal Protection Equipment only requires the label to warn of arc flash hazard. Slide 14 The type of equipment specified in that is likely to be worked on as described is required to have a field affixed are flash warning label. This will serve as a reminder to qualified workers that a serious hazard exists, that they or their management must assess the risk prior to approaching the hazard. Also it should remind them that they must follow the work practices for the level of hazard they may be working on or near only requires that this label state the existence of an arc flash hazard. It is suggested that the party responsible for the label include more information on the specific parameters of the hazard. In this way the qualified worker and his/her management can more readily assess the risk and better ensure proper work practices, PPE and tools. The specific additional information that should be added to the label includes: Mark Lyvers LLC / Cooper Bussmann Arc Flash Script - Page 1 of 6

2 Slide 15 ( denotes certain points where it is suggested to left mouse "click" or "enter" or "page down" to synchronize with the slide animation.) Flash Protection Boundary Incident energy at 18 inches expressed in cal/cm2 PPE required Voltage shock hazard Limited shock approach boundary Restricted shock approach boundary Prohibited shock approach boundary This example label shown includes more of the vital information that fosters safer work practices. You can see that the detailed information is a greater aid to workers. Warning labels with this detail provide vital information specific to the particular equipment installation. The information quantifies the electrical shock and arch flash hazards for the specific equipment noted. Informative labels communicate to a qualified worker and his management vital parameters that are needed to fulfill safe work practices. If you are unfamiliar with some of the terminology on this label it is suggested you get NFPA 70E or The 70E Handbook. Some of these terms will be discussed later in this presentation. Slide 16 The fine print note for references NFPA 70E. This standard provides information to assess electrical hazards. Slide 17 What is NFPA70E? NFPA70E is the standard for electrical safety requirements for employee workplaces. In the 1970's, OSHA requested that the National Fire Protection Association develop a standard for electrical safety for workers. NFPA 70E is this standard that has been through several revision cycles. NFPA 70E has evolved through these revisions to be a standard and reference for electrical safety. This document provides requirements for: electrical safe work practices electrical shock and arc flash boundaries and proper personal protective equipment This standard addresses safe work practices for both qualified and unqualified workers. If you are not familiar with this standard, it is suggested you obtain a copy from NFPA, study it and implement the requirements. Slide 18 So why have this arc flash warning label requirement specified in ? Each year many workers are injured or die due to electrical incidents. Most people recognize the electrical shock hazard. Still, each year, many are injured or die from shock or electrocution. Many workers do not yet recognize the hazards associated with arc flash. An arc flash is the result of an arcing fault. As a side note: This slide is a photo of a test cell with mannequins in which arc fault testing was performed. The mannequins are not wearing appropriate personal protection equipment for equipment that is not in a "safe work condition". Mark Lyvers LLC / Cooper Bussmann Arc Flash Script - Page 2 of 6

3 Slide 19 First let's contrast a bolted short circuit current incident from an arcing fault incident. Depicted in each drawing are two bare conductors such as phase A conductor and phase B conductor. When a bolted short circuit occurs, essentially the circuit path by-passes the load and shorts the circuit. The current that flows can be hundreds or thousands of times the normal load current. In this case the power of the fault current is dissipated throughout the circuit from the generation source to the bolted short. Typically there is not a great deal of energy dissipated at the point of the bolted conductors. There are serious hazards associated with bolted short circuit currents such as protecting components from rupturing and ensuring overcurrent protective devices have adequate interrupting ratings. In contrast, an arcing fault is the flow of current through the air between phase conductors or between phase conductors and neutral or ground. In this case the load is also by-passed which results in currents higher then the load current. Arcing fault currents can be extremely high in current magnitude approaching the bolted short- circuit current. However, arcing faults are typically less than the bolted short circuit. The magnitude of an arcing fault is subject to many variables and therefore is unpredictable. Arcing faults in 480 volt equipment may vary from approximately a minimum of 38% for L-G faults to 89% for three phase faults. The point to make in this discussion is that an arcing fault can release tremendous amounts of energy at the point of the arcing in a small fraction of a second. Slide 20 When an arcing fault occurs, the result can be extremely high temperatures, a tremendous pressure blast and shrapnel (equipment parts) hurling at high velocity (in excess of 700 miles per hour). An accidental slip of a tool or a lose part tumbling across live parts can initiate an arcing fault in the equipment. If a person is in the proximity of an arcing fault, the flash can cause serious injury or death. The point of the warning label is to remind qualified workers of the arc flash hazard when working on electrical equipment. This slide models some of the effects of an arcing fault. At the tips of the arc the temperature can reach 35,000 degrees Fahrenheit. This intense thermal event can create these phenomenon: Pressure waves (Result of super heating of air & resulting metal vapors) High decibel sound waves Molten Metal Copper vapor Intense Light Shrapnel A phase to ground or phase to phase arcing fault can quickly escalate into a three phase arcing fault due to the expansive cloud of conductive copper vapor which can engulf all phase conductors. The chain of events during an arcing fault can be extremely rapid. The incident can be so rapid that the human system (eyes, optic nerves, brain, etc.) is incapable of observing and recalling the event in detail. The event occurs too fast. Slide 21 We have a series of photos to show you to illustrate the tremendous energy that can be released by an arcing fault. This is a photo of the test cell prior to initiating the fault. These sequential photos show one of many staged tests that help to understand and quantify the effects of arcing faults on workers. In this test, mannequins with temperature and pressure sensors were placed in the test cell. This was a 480 volt, three phase system with an available three phase short-circuit current of 22,600 symmetrical rms amperes. A non current-limiting overcurrent protective device was the nearest upstream protective device. An arcing fault was initiated in a combination motor controller enclosure. The arcing fault quickly escalated into a three phase arcing fault in the enclosure. The current flowed for 6 cycles (1/10 second). Mark Lyvers LLC / Cooper Bussmann Arc Flash Script - Page 3 of 6

4 Slide 22 to 28 (This is a series of still photos taken from the test video footage. It is suggested to quickly click through these stills so you can get the feel for the sequence of events.) Slide 29 The temperature recorders (with maximum temperature limit of 437 º F) on the neck and hand closest to the arcing fault were pegged (beyond 437 º F limit); the threshold for incurable burn is for skin to reach 205 º F for 1/10 second. The pressure sensor on this mannequin's chest pegged the recorder at over 2160 lbs/ft 2 ; the threshold for severe lung damage is 2160 lbs/ft 2. The temperature sensor on the chest under the cotton shirt recorded 122 degrees F, which is below the threshold for incurable burn. This illustrates that personal protection equipment such as cotton garments can help. The sound level recorded was greater than a shot gun blast. Slide 30 Following will be another series of photos from the same test set-up but with a current-limiting overcurrent protective device clearing the arcing fault in less than 1/2 of a cycle. In this test a Bussmann Low Peak KRP-C 601 ampere fuse protects this circuit. Slide 31 to 35 (This is a series of still photos taken from the test video footage. It is suggested to quickly click through these stills so you can get the feel for the sequence of events.) Slide 36 Again, this was a 480 volt, three phase system with an available three phase short-circuit current of 22,600 symmetrical rms amperes. The difference: the first series of photos depict the tests with non current-limiting overcurrent protective device, this series of photos depict the tests protected by Bussmann Low Peak KPR-C 601 ampere fuses. An arcing fault was initiated in a combination motor controller enclosure. In the first series of photos the overcurrent protective device took 6 cycles to open. In this series of photos the fuses cleared in less than a 1/2 cycle thereby reducing the arc flash hazard and energy let-thru. Slide 37 This illustration shows that the 601 ampere current-limiting fuse did indeed reduce the arc fault energy. The temperature recorder on the hand closest to the arcing fault was pegged (beyond 347 º F ); the threshold for incurable burn is when the skin subjected to 205 º F for 1/10 second. However, the temperature sensor on the neck recorded a temperature considerably lower than the prior test: degrees F. This is below the threshold for incurable burn. Also the temperature under the shirt did not even record any change from ambient another indication of less energy being released. The pressure sensor on this mannequin's chest recorded 504 lbs/ft 2 ; much less than the prior test where it pegged the meter at 2160 lbs/ft 2. The temperature sensor on the chest under the cotton shirt recorded 122 degrees F, which is below the threshold for incurable burn. This illustrates that personal protection equipment such as cotton garments can help. The sound level recorded was 10 db lower than the previous test shown. Both of these tests and others are detailed in an IEEE paper "Staged Tests Increase Awareness of Arc-Fault Hazards in Electrical Equipment", IEEE Petroleum and Chemical Industry Conference Record, September, 1997, pp This paper is available on request from Mark Lyvers LLC. One finding of this IEEE paper is that current-limiting overcurrent protective devices reduce damage and arc-fault energy (provided the fault current is within the current-limiting range). Mark Lyvers LLC / Cooper Bussmann Arc Flash Script - Page 4 of 6

5 Slide 38 The arc flash labeling requirement is intended to help reduce injuries and deaths. While not a requirement in the National Electrical Code, we feel it is important to cover some important regulations in OSHA and requirements in NFPA 70E related to working on "live" equipment. Slide 39 OSHA regulations state in (a) that workers should not work on live equipment (greater than 50 volts) except for one of two reasons: #1 De-energizing introduces additional or increased hazards (such as cutting ventilation to a hazardous location) or #2 Infeasible due to equipment design or operational limitations (such as when voltage testing is required for diagnostics). Note: NFPA 70E Electrical Safety Requirements for Employee Workplaces 2000 in Part states essentially the same requirement. However, when it is necessary to work on equipment "live", it is necessary to follow safe work practices, which include assessing the risks, wearing adequate personal protection equipment and using the proper tools. The warning label of helps facilitate this practice. Slide 40 Until equipment is put into a "safe work condition" the equipment is considered to be "live". NFPA 70 E Part provides the procedural steps for placing equipment in a "safe work condition". One of the latter steps in this procedure is a voltage test of each phase conductor to verify they are de-energized. The worker performing this voltage testing must assume the equipment is live and therefore must wear appropriate personal protection equipment for the hazard assessed. Slide 41 The arc flash hazard can be assessed prior to working on equipment. NFPA 70E stipulates three shock boundaries and a flash protection boundary that must be known and observed. The shock boundaries, dependent on the system voltage, can be found in a NFPA 70E table. NFPA 70E also provides means to determine the flash protection boundary. It is possible to calculate the Flash Protection Boundary (FPB) and Incident Energy Exposure level, when the available bolted short circuit current, the minimum sustainable arcing fault current, and the time duration for the equipment supply overcurrent protective device to open are known. NFPA 70E provides the formulas for this critical information as well as other important information on safe work practices, personal protection equipment and tools to use. A qualified worker should not enter the flash protection boundary to work on live parts unless he/she is wearing the PPE for the level of hazard that could occur. Slide 42 Now you know the arc flash warning label requirement and related information. We have only given you an overview of many issues. But we wanted to mention there are some additional things you may want to know. First, there are other means to reduce the risks of shock and flash hazards. Slide 43 Finger safe products reduce the chance that a shock or arcing fault can occur. If all the electrical components are finger safe, a worker has a much lower chance of coming in contact with a live conductor. Cooper Bussmann manufactures the CubeFuse that is IP20 finger safe. In addition, they are a very current-limiting protective device, and also, Sami covers for fuses, Safety J holders for LPJ fuses, and CH holders available for a variety of Buss fuses. All these devices reduce the chance that a worker or tool with come in contact with a live conductor. Fuse and terminal shrouds for disconnect switches are also pictured. All of these products make for a safer electrical environment by reducing the chance that a shock or fault can occur. Mark Lyvers LLC / Cooper Bussmann Arc Flash Script - Page 5 of 6

6 You can make a difference too. Consider specifying finger safe products. Require finger safe products whenever designing or installing new panels or machinery,. Slide 44 Another way to reduce the risk of arc faults is to use current-limiting fuses or current-limiting circuit breakers. Current-limiting fuses or current-limiting circuit breakers can reduce the risks associated with arc flash hazards by limiting the magnitude of the fault currents (provided the fault current is within the current-limiting range) and reducing the time duration of the fault. Bussmann offers many types of current-limiting fuses for electrical power distribution systems and electrical panels and machinery. Comments: Contact Mark Lyvers LLC to learn more or obtain more information about electrical hazards and safety requirements. We only gave an overview on electrical safety and arc flash hazards. There are other sources that are more in-depth. NFPA publishes Code 70E, as well as a code handbook, Electrical Safety Program Book, and other applications brochures. The Color Book Series by the Institute of Electrical and Electronic Engineers (IEEE) provides recommended practices and guidelines that go beyond the minimum requirements of the NEC, NEMA, and UL standards. An overview of electrical safety requirements can be found in OSHA 29 CFR , Safety Related Work Practices. These requirements contain information on qualified vs. unqualified persons, training requirements, work practice selection, use of electrical equipment, and safeguards for personnel protection. An IEEE paper "Staged Tests Increase Awareness of Arc-Fault Hazards in Electrical Equipment", IEEE Petroleum and Chemical Industry Conference Record, September, 1997, pp This paper is available on request from Mark Lyvers LLC. Mark Lyvers LLC can assist to provide the electrical data required to comply with the recommended practices and guidelines of NFPA 70E. This requires a one line diagram of the non-residential electrical distribution system(s) and a point by point short circuit and arc fault analysis. Please contact us to discuss your needs: Phone Tech1@engntech.com Mark Lyvers LLC / Cooper Bussmann Arc Flash Script - Page 6 of 6