1、NEMA Standards PublicationNational Electrical Manufacturers AssociationNEMA ABP 10-2015Arc Flash AnalysisUtility System Parameters Critical for Accurate PPEA NEMA Low Voltage Distribution Equipment Section White Paper ABP 10-2015 Arc Flash Analysis Utility System Parameters Critical for Accurate PPE
2、 Published by National Electrical Manufacturers Association 1300 North 17th Street, Suite 900 Rosslyn, Virginia 22209 www.nema.org 2015 National Electrical Manufacturers Association. All rights, including translation into other languages, reserved under the Universal Copyright Convention, the Berne
3、Convention for the Protection of Literary and Artistic Works, and the International and Pan American copyright conventions. 2015 National Electrical Manufacturers Association NOTICE AND DISCLAIMER The information in this publication was considered technically sound by the consensus of persons engage
4、d in the development and approval of the document at the time it was developed. Consensus does not necessarily mean that there is unanimous agreement among every person participating in the development of this document. NEMA standards and guideline publications, of which the document contained herei
5、n is one, are developed through a voluntary consensus standards development process. This process brings together volunteers and/or seeks out the views of persons who have an interest in the topic covered by this publication. While NEMA administers the process and establishes rules to promote fairne
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10、nyone using this document should rely on his or her own independent judgment or, as appropriate, seek the advice of a competent professional in determining the exercise of reasonable care in any given circumstances. Information and other standards on the topic covered by this publication may be avai
11、lable from other sources, which the user may wish to consult for additional views or information not covered by this publication. NEMA has no power, nor does it undertake to police or enforce compliance with the contents of this document. NEMA does not certify, test, or inspect products, designs, or
12、 installations for safety or health purposes. Any certification or other statement of compliance with any health- or safety-related information in this document shall not be attributable to NEMA and is solely the responsibility of the certifier or maker of the statement. NEMA ABP 10-2015 2015 Nation
13、al Electrical Manufacturers Association Foreword This is an update to a NEMA white paper originally published in 2002. To ensure that a meaningful publication was being developed, draft copies were sent to a number of groups within NEMA having an interest in this topic. Their resulting comments and
14、suggestions provided vital input prior to final NEMA approval and resulted in a number of substantive changes in this publication. This white paper will be periodically reviewed by the Molded Case Circuit Breaker Product Group of NEMAs Low Voltage Distribution Equipment Section for any revisions nec
15、essary to keep it up to date with evolving technology. Proposed or recommended revisions should be submitted to: Vice President, Technical Services National Electrical Manufacturers Association 1300 North 17th Street, Suite 900 Rosslyn, Virginia 22209 This white paper was developed by the Molded Cas
16、e Circuit Breaker Product Group of NEMAs Low Voltage Distribution Equipment Section. Approval does not necessarily imply that all members of the Product Group voted for its approval or participated in its development. At the time this document was approved, the Molded Case Circuit Breaker Product Gr
17、oup had the following members: ABB, Inc.Wichita Falls, TX Eaton CorporationPittsburgh, PA General ElectricPlainville, CT Siemens Industry, Inc.Norcross, GA Schneider Electric USAAndover, MA NEMA ABP 10-2015 2015 National Electrical Manufacturers Association 1 Introduction NEMA has long recognized th
18、at equipment short circuit current ratings and interrupting ratings are determined by the engineer or contractor after understanding the available fault currents to which they will be subjected. Utilities have longstanding practices to provide a conservatively high maximum level of available fault c
19、urrent based on their current and future power generation equipment, transmission, and distribution systems required to support their customers electrical power demands. Once again, NEMA recognizes that this has been an accepted industry practice that ensures equipment is appropriately rated to cont
20、rol electrical energy safely. However, the introduction of arc flash protection in NFPA 70E, Electrical Standard for Safety in the Workplace, is changing industry needs to ensure a safe maintenance environment beyond safe operation of the equipment. 2 Arc Flash NEMA member companies support the safe
21、 maintenance of electrical equipment and systems. NEMA strongly encourages de-energizing electrical systems before maintenance is performed. For service equipment, this typically involves contacting the utility. In order to support an electrical safety program in the workplace, it might be necessary
22、 to perform an arc flash study. Although NFPA 70E provides tables for determining the level of personal protective equipment (PPE) required, recognize that these tables were developed for use only within specific system parameters, and that an arc flash study would provide more accurate guidance for
23、 PPE selection. The arc flash study provides information necessary to establish the level of PPE needed for each specific location of the electrical system. 3 The NEC and NFPA 70E The 2002 National Electrical Code (NEC) introduced a new requirement in Article 110.16, which establishes a field-markin
24、g requirement to warn qualified persons of potential electric arc flash hazards. This requirement is driving awareness of the need to perform an arc flash analysis as a component of an electrical safety program, as outlined in NFPA 70E. This requirement has not changed significantly since that time.
25、 The awareness of potential arc flash hazards has advanced electrical safety by causing the industry to review electrical safety programs and electrical safety training. Driven by NFPA 70E and the review of company safety programs, many companies are now performing fault current studies, which are n
26、ecessary even to properly use the tables in NFPA 70E within their specific system parameters. The next logical step is to collect overcurrent device information and determine the potential arc flash hazard and PPE requirement by calculating the incident energy. 4 The Utilitys Role The increased numb
27、er of arc flash studies being performed by industry and consultants is driving the need for information that has historically been beyond responses provided by the utility. The foundation for a proper arc flash study includes having access to the following accurate information from the utility: The
28、actual available short circuit current for the existing installation. The parameters or settings for the final utility overcurrent protective device. Note that a fault current value (which historically has been provided by utilities) may not provide the “worst case” arc flash condition. In many case
29、s, calculations of arc flash hazard based on conservatively high available fault current values can underestimate the actual flash hazard at circuit locations. This is because overcurrent protective devices might not operate as fast at the actual fault current level as at the conservatively high fau
30、lt current level. Therefore, having the actual available fault current is necessary in order to properly estimate the potential arc flash incident energy and thus determine the appropriate PPE. NEMA ABP 10-2015 2015 National Electrical Manufacturers Association Accurate overcurrent protective device
31、 parameters are also necessary to establish accurate arc flash calculations to ensure appropriate PPE. Keep in mind that appropriate PPE is typically required even for the process of placing the electrical equipment in an electrically safe working condition. NEMA expects that utilities will recogniz
32、e the need to have a system in place to provide, upon request, the necessary information for an arc flash analysis and that protective device plays a significant role in the potential arc flash hazard at the service. The utility distribution system periodically changes due to transformer replacement
33、, temporary or permanent feeder reconfiguration, voltage conversion, or substation changes. These changes can impact the protective devices, available short circuit current, and the resulting potential arc flash hazard. NEMA also expects that utilities will understand their customers needs and will
34、thus ensure that customer service policies and procedures are in place to support customer requests for the utility information necessary to perform a proper arc flash analysis. This will support accurate PPE requirements to protect qualified workers from potential arc flash hazards. We suggest that
35、 utility procedures will also need to consider a “notification system” to alert customers in the event that a utility system change impacts locations that are known to have requested information on the magnitude of the available short-circuit current. Finally, NEMA encourages that electrical equipme
36、nt be de-energized and subsequent maintenance be performed in accordance with NFPA 70E. Work on service equipment might require the utility to de-energize service conductors feeding the service. NEMA recommends that users contact their local utility to arrange a power outage before working service equipment. NATIONAL ELECTRICAL MANUFACTURERS ASSOCIATION 1300 NORTH 17TH STREET, SUITE 900 ROSSLYN. VA 22209www.NEMA.orgTO ORDER ADDITIONAL NEMA STANDARDS VISITwww.gLObAL.IhS.cOM OR cALL 1-800-854-7179/1-303-397-79565612_0514TB
