1、NEMA Standards PublicationNational Electrical Manufacturers AssociationANSI/NEMA AB 4-2009Guidelines for Inspection and Preventive Maintenance of Molded Case Circuit Breakers Used in Commercial and Industrial ApplicationsApproved as an American National Standard ANSI Approval Date: March 30, 2011 AN
2、SI/NEMA AB 4-2009 Guidelines for Inspection and Preventive Maintenance of Molded Case Circuit Breakers Used in Commercial and Industrial Applications Published by: National Electrical Manufacturers Association 1300 North 17th Street, Suite 1752 Rosslyn, Virginia 22209 www.nema.org Copyright 2009 by
3、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 Pan American Copyright Conventions. NOTICE AN
4、D 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 developed. Consensus does not necessarily mean that there is unanimous agreement among every person participating i
5、n the development of this document. The National Electrical Manufacturers Association (NEMA) standards and guideline publications, of which the document contained herein is one, are developed through a voluntary consensus standards development process. This process brings together volunteers and/or
6、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 of consensus, it does not write the document and it does not independently test, evaluate, or verify the accur
7、acy 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, or other damages of any nature whatsoever, whether special, indirect, consequential, or compensatory, directly o
8、r indirectly resulting from the publication, use of, application, or reliance on this document. NEMA disclaims and makes no guaranty or warranty, expressed or implied, as to the accuracy or completeness of any information published herein, and disclaims and makes no warranty that the information in
9、this document will fulfill any of your particular purposes or needs. NEMA does not undertake to guarantee the performance of any individual manufacturer or sellers products or services by virtue of this standard or guide. In publishing and making this document available, NEMA is not undertaking to r
10、ender 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 document should rely on his or her own independent judgment or, as appropriate, seek the advice of a competent pr
11、ofessional 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 sources, which the user may wish to consult for additional views or information not covered by this publication.
12、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 safety or health purposes. Any certification or other statement of compliance with any health or safetyrelated
13、information in this document shall not be attributable to NEMA and is solely the responsibility of the certifier or maker of the statement. AB 4-2009 Page i CONTENTS Page 1. GENERAL1 1.1 Scope1 1.2 Referenced Standards1 2. SAFETY PROCEDURES.3 2.1 Warning 3 2.2 Safety Procedure 3 2.3 Reinstallation S
14、afety Procedure3 3. GUIDELINES .4 3.1 The National Electrical Code 4 3.2 A Molded Case Circuit Breaker 4 3.3 To Avoid Damaged or Otherwise Inoperable Circuit Breakers Being Inadvertently Returned to Service4 3.4 Guidance Regarding Inspection and Preventive Maintenance Procedures .4 3.5 For Informati
15、on Regarding Molded Case Circuit Breaker Performance and Application .4 3.6 Water Damaged Molded Case Circuit Breakers 4 4. INSPECTION PROCEDURES.5 4.1 General .5 4.2 Exposed Face Temperature Check5 4.3 Inspection of Enclosure Interior 5 5. PREVENTIVE MAINTENANCE.9 5.1 General .9 5.2 Environmental E
16、valuation .9 5.3 Interchangeable Trip Units10 5.4 Wire Connectors.10 5.5 Reinstallation Procedure.10 6. TEST PROCEDURES .11 6.1 General .11 6.2 Mechanical Operation Tests .11 6.3 Insulation Resistance Test11 6.4 Individual Pole Resistance Test (Millivolt Drop)13 6.5 Inverse-Time Overcurrent Trip Tes
17、t .15 6.6 Instantaneous Overcurrent Trip Test20 6.7 Rated Hold-In Test22 7. ACCESSORY DEVICE TEST PROCEDURES .24 7.1 General .24 7.2 Shunt Trip Release Tests .24 7.3 Under-Voltage Trip Release Tests .25 7.4 Electrical Operator Tests 27 7.5 Auxiliary Switch Tests.28 7.6 Alarm Switch Tests .29 Copyrig
18、ht 2009 by the National Electrical Manufacturers Association. AB 4-2009 Page ii Foreword This NEMA Standards Publication supersedes and fully replaces NEMA Standards Publication AB 4-2003. To ensure that a meaningful publication was being developed, draft copies were sent to a number of individuals
19、and organizations in the public sector having an interest in or responsibility for the purchase, testing, application, use, and preventive maintenance of these products. Their resulting comments and suggestions provided a vital user and general interest input prior to final NEMA approval and resulte
20、d in a number of substantive changes in this publication. This publication will be periodically reviewed by the Molded Case Circuit Breaker Voting Classification of NEMA for any revisions necessary to keep it up to date with advancing technology. Proposed or recommended revisions should be submitted
21、 to: Vice President, Technical Services National Electrical Manufacturers Association 1300 North 17th Street Rosslyn, Virginia 22209 This Standards Publication was developed by the Molded Case Circuit Breaker Voting Classification of the National Electrical Manufacturers Association. Approval of thi
22、s standard does not necessarily imply that all voting classification members voted for its approval or participated in its development. At the time it was approved, the Molded Case Circuit Breaker Voting Classification had the following members: ABB Control, Inc.Wichita Falls, TX Eaton CorporationPi
23、ttsburgh, PA General ElectricPlainville, CT Moeller Electric CorporationFranklin, MA Siemens Energy 50 overload test operations for circuit breakers rated up to 1600A and 25 operations for circuit breakers rated 2000A and higher (UL 489 Table 7.1.3.1); 3 to 7 interrupting tests, depending on breaker
24、 type, at limited fault current (UL 489 Table 7.1.7.1, 7.1.7.2, and 7.1.7.3); and two interrupting tests at maximum short-circuit-current rating. Thus circuit breakers have an extensive but finite interrupting capability, and breakers that experience multiple high short-circuit-current faults should
25、 receive a thorough inspection with replacement if necessary. With respect to environmental effects, circuit breakers are sometimes exposed to high ambient temperatures, to high humidity, and to other ambient conditions that are hostile to long term performance. For example, industries may have corr
26、osive environments or could be associated with dusty environments that could affect operating parts. It is not intended that molded case circuit breakers be disassembled for inspection. Rather, NEMA AB 4 should be referenced during periodic maintenance or during specific inspection following a high
27、short-circuit-current fault. This document is intended to ensure that molded case circuit breakers are well maintained, and provides guidelines for circuit breaker replacement. This document is divided into separate clauses as follows: Clause 1 presents the Scope and reference standards. Clause 2 de
28、tails the safety procedures to be followed. Clause 3 deals with general guidance. Clause 4 deals with Inspection Procedures and describes thermal checks (4.2) and visual checks (4.3) of the enclosure and circuit breaker condition. Overheating of the circuit breaker would necessitate further investig
29、ation, and cracks in the molded case would certainly necessitate circuit breaker replacement. Clause 5 deals with Preventive Maintenance and ensures that the circuit breakers life is not compromised by external conditions. The objectives are that the circuit breaker operates in a clean environment a
30、nd that the terminals are in good condition (5.2), that interchangeable trip units are connected properly (5.3), and that wire connectors are in good condition and are correctly torqued (5.4). Clause 6 deals with non-destructive Test Procedures that can be used to verify specific operating character
31、istics of molded case circuit breakers. These include Mechanical Operation Test (6.2), Insulation Resistance Test (6.3), Individual Pole Resistance Test (millivolt drop test) (6.4), Inverse Time Overcurrent Copyright 2009 by the National Electrical Manufacturers Association. AB 4-2009 Page iv Test (
32、6.5), Instantaneous Overcurrent Trip Test (6.6), and Rated Hold-In Test (6.7). Non-compliance to one or more of these tests could lead to circuit breaker replacement. Clause 7 deals with the operation of accessory devices. Failure of an accessory would lead to replacement of that accessory, or circu
33、it breaker replacement if accessories are not removable. In summary, following an automatic overcurrent interruption at or near its interrupting rating, the condition of any protective device should be checked prior to circuit re-energization. For molded case circuit breakers, the condition of the c
34、ircuit breaker is assessed without opening or disassembling the breaker. Circuit breakers that have experienced multiple high short-circuit-current faults, as evidenced by conditions at the source of the faults, should receive a thorough inspection per the guidelines of NEMA AB 4. This document shou
35、ld also be used for recommended, periodic, preventive maintenance. Copyright 2009 by the National Electrical Manufacturers Association. AB 4-2009 Page 1 1. GENERAL 1.1 SCOPE NEMA Standards Publication AB 4 sets forth, for use by qualified personnel1, a number of basic procedures that may be used for
36、 the inspection and preventive maintenance of molded case circuit breakers used in industrial and commercial applications rated up to and including 1000 V 50/60 Hz AC or AC/DC. Noteconsult the manufacturer for DC-only or 400 Hz circuit breakers. The methods outlined may be used to verify specific ch
37、aracteristics of a molded case circuit breaker that was originally built and tested in compliance with the requirements of NEMA Standards Publication AB 1 (UL 489). These methods are intended for field application and are, therefore, non-destructive in nature. Accordingly, these methods cannot be us
38、ed to verify all performance capabilities of a molded case circuit breaker since verification of some capabilities requires tests of a destructive nature. Many tests, including those of a destructive nature, as defined in AB 1 (UL 489), are performed on representative samples of circuit breakers by
39、the manufacturer, as part of a routine program of factory inspection. The AB 4 Standards Publication is not intended, nor is it adequate, to verify proper electrical performance of a molded case circuit breaker that has been disassembled, modified, rebuilt, refurbished, or handled in any manner not
40、intended or authorized by the original circuit breaker manufacturer. Such breakers should be removed from service. 1.2 REFERENCED STANDARDS In this publication, reference is made to the latest edition of the standards listed below. Copies are available from the indicated sources: National Fire Prote
41、ction Association Batterymarch Park Quincy, MA 02269 NFPA 70 National Electrical Code NFPA 70B Recommended Practice for Electrical Equipment Maintenance NFPA 70E Standard for Electrical Safety Requirements for Employee Workplace 1For purposes of these guidelines, a qualified person is one who has sk
42、ills and knowledge related to the construction and operation of the electrical equipment and installation and has received training to recognize and avoid the hazards involved. In addition, the person is trained: and authorized to test, energize, clear, ground, tag, and lockout circuits and equipmen
43、t in accordance with established safety practices. in the proper care and use of protective equipment such as rubber gloves, hard hat, safety glasses or face shields, and flash resistant clothing, in accordance with established safety practices. in first aid. Copyright 2009 by the National Electrica
44、l Manufacturers Association. AB 4-2009 Page 2 National Electrical Manufacturers Association 1300 North 17th Street Rosslyn, Virginia 22209 AB 1 Molded Case Circuit Breakers, Molded Case Switches and Circuit Breaker Enclosures1AB 3 Molded Case Circuit Breakers and Their Application 250 Enclosures for
45、 Electrical Equipment (1000 Volts Maximum) Guidelines for Handling Water Damaged Electrical Equipment Underwriters Laboratories, Inc. 333 Pfingsten Road Northbrook, IL 60062 UL 489 Molded-Case Circuit Breakers, Molded-Case Switches and Circuit-Breaker Enclosures UL 1053 Ground Fault Sensing and Rela
46、ying Equipment 1NEMA AB 1 and UL 489 are the same. Copyright 2009 by the National Electrical Manufacturers Association. AB 4-2009 Page 3 2. SAFETY PROCEDURES The inspection and preventive maintenance of circuit breakers in service require the user to take all necessary precautions to avoid being inj
47、ured. 2.1 WARNING 2.1.1 Breaker Testing WARNINGHazardous voltages in electrical equipment can cause death or severe personal injury. Turn off and lock out the power supplying this equipment before performing any of the following operations. Unless otherwise specified in this publication, inspection,
48、 preventive maintenance, and testing must always be performed on equipment that is de-energized (note that certain tests require control power to conduct the test). Verify that there is no voltage present on incoming line terminals (and on control power terminals, if present) and between these termi
49、nals and ground to positively ascertain that the equipment is totally de-energized. The disconnecting or isolating means on the line side of the devices being checked and/or tested must be locked in the OFF position to ensure that the equipment will remain de-energized during these procedures. Safety related work practices described in NFPA 70E, Part II, must be followed at all times. 2.1.2 Test Equipment WARNINGHigh voltages involved with some test equipment can cause death or serious injury. Do not touch or permit anyone else to touch the breaker or the test
