1、NEMA Standards PublicationNational Electrical Manufacturers AssociationNEMA PB 2-2011Deadfront Distribution SwitchboardsNEMA Standards Publication PB 2-2011 Deadfront Distribution Switchboards Published by: National Electrical Manufacturers Association 1300 North 17th Street, Suite 1752 Rosslyn, Vir
2、ginia 22209 www.nema.org Copyright 2011 by the National Electrical Manufacturers Association. All rights including translation into other languages, reserved under the Universal Copyright Convention, the Berne Convention for the Protection of Literary and Artistic Works, and the International and Pa
3、n American Copyright Conventions. Copyright 2011 by the National Electrical Manufacturers Association NOTICE AND DISCLAIMER The information in this publication was considered technically sound by the consensus of persons engaged in the development and approval of the document at the time it was deve
4、loped. Consensus does not necessarily mean that there is unanimous agreement among every person participating in the development of this document. The National Electrical Manufacturers Association (NEMA) standards and guideline publications, of which the document contained herein is one, are develop
5、ed 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 fairness in the development
6、 of consensus, it does not write the document and it does not independently test, evaluate, or verify the accuracy or completeness of any information or the soundness of any judgments contained in its standards and guideline publications. NEMA disclaims liability for any personal injury, property, o
7、r other damages of any nature whatsoever, whether special, indirect, consequential, or compensatory, directly or indirectly resulting from the publication, use of, application, or reliance on this document. NEMA disclaims and makes no guaranty or warranty, express or implied, as to the accuracy or c
8、ompleteness of any information published herein, and disclaims and makes no warranty that the information in this document will fulfill any of your particular purposes or needs. NEMA does not undertake to guarantee the performance of any individual manufacturer or seller s products or services by vi
9、rtue of this standard or guide. In publishing and making this document available, NEMA is not undertaking to render professional or other services for or on behalf of any person or entity, nor is NEMA undertaking to perform any duty owed by any person or entity to someone else. Anyone using this doc
10、ument 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 available from other sou
11、rces, 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 installations for s
12、afety or health purposes. Any certification or other statement of compliance with any health or safetyrelated information in this document shall not be attributable to NEMA and is solely the responsibility of the certifier or maker of the statement. PB 2- 2011 Page i Copyright 2011 by the National E
13、lectrical Manufacturers Association CONTENTS Page Foreword iii Section 1 GENERAL 1.1 Scope . 1 1.2 Referenced Standards . 1 1.3 Definitions 3 Section 2 CLASSIFICATIONS, CHARACTERISTICS, AND RATINGS 2.1 General Standards . 11 2.1.1 Arrangement . 11 2.1.2 Equipment Specification . 11 2.1.3 Usual Servi
14、ce Conditions 12 2.1.4 Unusual Service Conditions 13 2.1.5 Temperature Limits . 13 2.2 Rating Standards . 13 2.2.1 General . 13 2.2.2 Voltage Rating 13 2.2.3 Frequency Rating 13 2.2.4 Continuous Current Rating . 13 2.2.5 Insulation Level Rating . 14 2.2.6 Basis of Short-Circuit Current Rating of Swi
15、tchboards . 14 2.2.7 Short-Circuit Current Ratings of Switchboard Devices . 14 Section 3 PRODUCT MARKING 3.1 Required Information . 16 3.2 Location of Markings 16 3.3 Nationally Recognized Standards or Applicable Laws or Regulations 16 Section 4 INSTALLATION, MAINTENANCE, AND STORAGE . 18 Section 5
16、CONSTRUCTION 5.1 General 19 5.2 Type of Enclosure 19 5.2.1 Type 1 . 19 5.2.2 Type 2 . 19 5.2.3 Type 3R 19 5.2.4 Type 5 . 19 5.3 Height of Indoor Enclosures 19 5.4 Phase or Polarity Arrangements 19 5.5 Grounding and Bonding . 20 5.6 Utility Transformer Compartment . 20 Section 6 TEST STANDARDS 6.1 Cl
17、assification of Tests 22 6.1.1 Design Tests (Type Test) . 22 6.1.2 Production Tests (Routine Test) . 23 PB 2-2011 Page ii Copyright 2011 by the National Electrical Manufacturers Association Section 7 APPLICATION STANDARDS 7.1 Selection of Apparatus . 25 7.2 Voltage Ratings 25 7.3 Continuous Current-
18、Carrying Ratings . 25 7.4 Determination of Section Bus and Through Bus Ampacity in a Multisection Switchboard . 25 7.4.1 Calculation of Section Bus Ampacity 25 7.4.2 Calculation of Through Bus Ampacity 27 7.5 Frequency Rating . 27 7.6 Short-Circuit Current Rating 27 7.6.1 Application on System 27 7.
19、6.2 Current-Limiting Devices 27 7.6.3 Calculation 27 7.6.4 Examples for ApplicationDetermination of Switchboard Short-Circuit Current Rating (See Figure 7-1) . 28 7.7 Location, Installation, Operation, and Maintenance 29 7.8 Ground-Fault Protection 30 7.9 Corner-Grounded (Grounded B Phase) Three-Pha
20、se Delta Applications 30 LIST OF FIGURES Figure 1-1 SERVICE EQUIPMENT-SYSTEM GROUND CONNECTED TO NEUTRAL TYPICAL DEADFRONT SWITCHBOARD LAYOUT 8 Figure 1-2 SERVICE EQUIPMENT-SYSTEM GROUND CONNECTED TO GROUND BUS TYPICAL DEADFRONT SWITCHBOARD LAYOUT . 9 Figure 1-3 NON-SERVICE TYPICAL DEADFRONT SWITCHB
21、OARD LAYOUT EQUIPMENT . 10 Figure 3-1 PRODUCT SAFETY LABEL 17 Figure 5-1 UTILITY CURRENT TRANSFORMER COMPARTMENTS 21 Figure 7-1 SWITCHBOARD DIAGRAM . 29 LIST OF TABLES Table 2-1 AMBIENT TEMPERATURE RANGES OF DEVICES COMMONLY MOUNTED IN SWITCHBOARDS . 12 Table 2-2 COMMON VOLTAGE RATINGS OF SWITCHBOAR
22、DS 15 Table 7-1 MINIMUM AMPACITY OF SECTION BUS 26 Table 7-2 MULTIPLYING FACTOR FOR BUS AMPACITIES . 26 PB 2- 2011 Page iii Copyright 2011 by the National Electrical Manufacturers Association Foreword This Standards Publication is intended to provide a basis of common understanding within the electr
23、ical community by aiding the user and specifier in selection and specification of deadfront distribution switchboards for specific applications by stating: a. The general standards for deadfront switchboards including the types, insulating requirements, unusual service conditions, service equipment
24、requirements, ampacity, and markings b. Standard switchboard ratings including short circuit current ratings c. Test procedures and tests for switchboard design and production d. Manufacturing standards for switchboards e. Switchboard application standards to provide proper selection of a switchboar
25、d and its components to ensure satisfactory service PB 2-2011 completely revises and supersedes PB 2- 2006. These standards are periodically reviewed by the Panelboard and Distribution Board Section of NEMA for any revisions necessary to keep them up-to-date with advancing technology. User needs hav
26、e been considered throughout the development of this publication. Proposed or recommended revisions should be submitted to: Vice President, Technical Services National Electrical Manufacturers Association 1300 North 17th Street Rosslyn, VA 22209 This Standards Publication was developed by the Panelb
27、oard and Distribution Board product group of the LVDE Section. At the time it was approved, the Panelboard and Distribution Board Section was composed of the following members: ABB, Inc.Houston, TX Cooper BussmannSt. Louis, MO Eaton CorporationPittsburgh, PA The Durham CompanyLebanon, MO GE Industri
28、al SolutionsPlainville, CT Hubbell, Inc.Bridgeport, CT Penn Panel solid neutral: An assembly consisting of an appropriate number of terminals to provide for the connection of the grounded (neutral) line and load conductors. When used as a component of service equipment, the neutral also includes: (1
29、) a means for making the required bonding connection between the neutral and the enclosure; and (2) a terminal for the service grounding conductor (unless that terminal is located as in Figure 1-2). neutral conductor: A conductor that is connected to the midpoint of a three-wire single-phase system,
30、 the center point of a wye-connected three-phase system, or the midpoint of one side of a delta-connected three-phase system. PB 2-2011 Page 7 Copyright 2011 by the National Electrical Manufacturers Association panel-mounted device: One of a closely grouped assembly of devices which is mounted on a
31、common base or mounting surface utilizing panelboard type construction. The total combination is then mounted in a switchboard combination or distribution section. peak let-through current: The maximum instantaneous current through an overcurrent device during the total clearing time. rating: A desi
32、gnated limit of operating characteristics based on definite conditions. service equipment: The necessary equipment, usually consisting of a circuit breaker or switch and fuses, and their accessories, located near the point of entrance of supply conductors to a building or other structure, or an othe
33、rwise defined area, and intended to constitute the main control and means of cutoff of the supply. short circuit current rating: The maximum RMS prospective (available) current to which a device can be connected. The rating is expressed in amperes and volts. stationary mounted device: A device which
34、 can be removed only by unbolting electrical connections and mounting supports. switch: A device, manually operated, unless otherwise designated, for opening and closing or for changing the connection of a circuit. switchboard: A large single panel, structural frame, or assembly of panels or structu
35、ral frames on which may be mounted, on the face or back or both: switches, overcurrent, and other protective devices, buses, and instruments. Switchboards may be accessible from the rear as well as from the front and are not intended to be installed in cabinets. switchboard section: A portion of a s
36、witchboard which is prevented by the structural framework from being physically separated into smaller units. symmetrical current: Symmetrical current is alternating current having no offset or transient component and, therefore, having a wave form essentially symmetrical about the zero axis. Symmet
37、rical current is expressed in terms of rms amperes. temperature rise: The difference in temperature between the temperature of the part under consideration and the ambient temperature. PB 2-2011 Page 8 Copyright 2011 by the National Electrical Manufacturers Association F R O M S O U RCEG R O U N D E
38、 D C O N D U C T O R ( N E U T R A L ) SUPPLY BUSLOADCONDUCTORSB R A N C H B U S OVERCU R R E N T DEVIC E ( S ) OVERCU R R E N T DEVIC E ( S ) OVERCU R R E N T DEVIC E ( S ) SPLI C E B U S THR O U G H B U S THROUGH BUSNEUTRALBUSSECTIO N S U P P L Y B U S NEUTRAL B U S O R NEUTRAL A S S E M B L Y GRO
39、UND BUS GRO U N D B U S BONDSEC T I O N B U S ENC L O S U R E SWITCHB O A R D DISTRIBUTIO N S E C T I O N G R O UNDING ELECTRODE CONDUCTOR( C O N NECTED TO NEUTRAL)SWITCHBOARDMAIN SECTIONG R O U N D I N G E L E C T R O D E C O N D U C T O R C O N N E C T O R ALTERNATELOCATIONSGFP SENSORS(RESIDUAL TY
40、PE)ALTERNATELOCATIONSGFP SENSORS(ZERO SEQUENCETYPE)GFP SENSOR(GROUND RETURNTYPE)UTILITYC/T COMP.N E U T R A L D I S C O N N E C T L I N K B O N D I N G J U M P E R B ONDMAIND I S C ONNECTD EVICEFigure 1-1 SERVICE EQUIPMENT-SYSTEM GROUND CONNECTED TO NEUTRAL TYPICAL DEADFRONT SWITCHBOARD LAYOUT PB 2-
41、2011 Page 9 Copyright 2011 by the National Electrical Manufacturers Association Figure 1-2 SERVICE EQUIPMENT-SYSTEM GROUND CONNECTED TO GROUND BUS TYPICAL DEADFRONT SWITCHBOARD LAYOUT F R O M S O U R C E G R O U N D E D C O N D U C T O R ( N E U T R A L ) SUPPLY BUSLOADCONDUCTORSB R A N C H B U S OV
42、ERCURRENT DEVICE(S)OVERCURRENT DEVICE(S)OVERCURRENT DEVICE(S)SPLICE BUS THROUGH B U S THROUGH BUSNEUTRALBUSSECTION SUP P L Y B U S NEUTRALBUSO R NEUTRAL ASSEM B L Y GROUND BUS GROUND B U S BONDSECTION B U S EN C L O S U R E G R O U N D I NG ELECTRODE CONDUCTOR CONNECTORALTERNATELOCATIONSGFP SENSORS(
43、RESIDUALTYPE)ALTERNATELOCATIONSGFP SENSORS(ZERO SEQUENCETYPE)GFP SENSOR(GROUND RETURNTYPE)UTILITYC/T COMP.N E U T R A L D I S C O N N E C T L I N K B O N D I N G J U M P E R B O N D G R O U N D I NG ELECTRODE CONDUCTOR( C O N N E C TED TO GROUND BUS)SWITCHBOARDDISTRIBUTIONSECTIONS W I T CHBOARDM A I
44、 N SECTIONM A I N D I S C O N N ECTD E V I C EPB 2-2011 Page 10 Copyright 2011 by the National Electrical Manufacturers Association Figure 1-3 NON-SERVICE TYPICAL DEADFRONT SWITCHBOARD LAYOUT EQUIPMENT F R O M S O U R C EG R O U N D E D C O N D U C T O R ( N E U T R A L ) SUPPLY BUSLOADCONDUCTORSB R
45、 A N C H B U S OVERCURREN T DEVICE(S)OVERCURREN T DEVICE(S)OVERCURREN T DEVICE(S)SPLICE B U S THROUG H B U S THROUGH BUSNEUTRALBUSSECTION SU P P L Y B U S NEUTRALBUS O R NEUTRAL ASS E M B L Y GROUND BUS GROUND B U S BONDSECTION B U S E N C L O S U R E E Q U I P M ENT GROUNDING CONDUCTOR CONNECTORALT
46、ERNATELOCATIONSGFP SENSORS(RESIDUAL TYPE)ALTERNATELOCATIONSGFP SENSORS(ZERO SEQUENCETYPE)N E U T R A L D I S C O N N E C T L I N K ( O P T I O N A L ) B O N DE Q U I P M ENT GROUNDING CONDUCTOR( T O S E R VICE ENTRANCE EQUIPMENT GROUND BUS)M A I ND I S C O N NECTD E V I CES W I TCHBOARDM A I N SECTI
47、ONSWITCHBOA R D DISTRIBUTION S E C T I O N PB 2-2011 Page 11 Copyright 2011 by the National Electrical Manufacturers Association Section 2 CLASSIFICATIONS, CHARACTERISTICS, AND RATINGS 2.1 General Standards 2.1.1 Arrangement A switchboard consists of one or more main, distribution, combination, and
48、auxiliary sections which are electrically and mechanically interconnected. Devices shall be applied in accordance with the manufacturers instructions. Main disconnect devices may be individually mounted or can be an integral part of a panel mounted assembly. 2.1.2 Equipment Specification In order to
49、 ensure that the proper switchboard is selected for a particular application, the user should provide the manufacturer with the following equipment specifications: a. Rating of supply 1. Voltage 2. Number of phases 3. Current in amperes 4. Available short circuit-current at the line terminals of the switchboard in rms symmetrical amperes 5. Frequency (if other than 60 Hz) b. Neutral ampacity as a p
