NEMA AB 4-2017 Guidelines for Inspection and Preventive Maintenance of Molded Case Circuit Breakers Used in Commercial and Industrial Applications.pdf

1、NEMA Standards PublicationNational Electrical Manufacturers AssociationNEMA AB 4-2017Guidelines for Inspection and Preventive Maintenanceof Molded Case Circuit Breakers Used inCommercial and Industrial ApplicationsNEMA AB 4-2017 Guidelines for Inspection and Preventive Maintenance of Molded Case Cir

2、cuit Breakers Used in Commercial and Industrial Applications Published by: National Electrical Manufacturers Association 1300 North 17th Street, Suite 900 Rosslyn, Virginia 22209 www.nema.org 2017 National Electrical Manufacturers Association. All rights including translation into other languages, r

3、eserved under the Universal Copyright Convention, the Berne Convention for the Protection of Literary and Artistic Works, and the International and Pan American Copyright Conventions. 2017 National Electrical Manufacturers Association NOTICE AND DISCLAIMER The information in this publication was con

4、sidered 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 in the development of this document. The National Electri

5、cal 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 seeks out the views of persons who have an interest in t

6、he 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 accuracy or completeness of any information or the soundness

7、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 or indirectly resulting from the publication, use of, app

8、lication, 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 this document will fulfill any of your particular purpos

9、es 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 render professional or other services for or on behalf of

10、 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 professional in determining the exercise of reasonable car

11、e 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. NEMA has no power, nor does it undertake to police or en

12、force 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 information in this document shall not be attributable t

13、o NEMA and is solely the responsibility of the certifier or maker of the statement. NEMA AB 4-2017 Page i 2017 National Electrical Manufacturers Association CONTENTS 1. General 1 1.1 Scope 1 1.2 Referenced Standards 1 Underwriters Laboratories, Inc. . 2 2. Safety Procedures . 3 2.1 Warning 3 2.2 Saf

14、ety Procedure 3 2.3 Reinstallation Safety Procedure . 3 3. Guidelines . 4 3.1 The National Electrical Code 4 3.2 A Molded Case Circuit Breaker 4 3.4 To Avoid Damaged or Otherwise Inoperable Circuit Breakers Being Inadvertently Returned to Service 4 3.5 Guidance Regarding Inspection And Preventive Ma

15、intenance Procedures 4 3.6 For Information Regarding Molded Case Circuit Breaker Performance and Application . 4 3.7 Water Damaged Molded Case Circuit Breakers 4 3.8 Heat Demaged Molded Case Circuit Breakers 4 4. Inspection Procedures 5 4.1 General . 5 4.2 Exposed Face Temperature Check 5 4.3 Inspec

16、tion Of Enclosure Interior . 5 4.4 Electronic Trip Unit Check 9 5. Preventive Maintenance 10 5.1 General . 10 5.2 Environmental Evaluation . 10 5.3 Interchangeable Trip Units . 11 5.4 Wire Connectors . 11 5.5 Reinstallation Procedure 12 6. Test Procedures . 12 6.1 General . 12 6.2 Mechanical Operati

17、on Tests . 12 6.3 Insulation Resistance Test . 13 6.4 Individual Pole Resistance Test (Millivolt Drop) . 14 6.5 Inverse-Time Over Current Trip Test 17 6.6 Instantaneous Over Current Trip Test 21 6.7 Rated Hold-In Test 23 7. Accessory Device Test Procedures . 25 7.1 General . 25 7.2 Shunt Trip Releas

18、e Tests . 25 7.3 Under-Voltage Trip Release Tests . 26 7.4 Electrical Operator Tests 28 7.5 Auxiliary Switch Tests . 29 7.6 Alarm Switch Tests . 30 NEMA AB 4-2017 Page ii 2017 National Electrical Manufacturers Association 8. ICCB Inspection And Test Procedures 31 8.1 General . 31 8.2 Primary Connect

19、or Check 31 8.3 Cradle Check 32 8.4 Arc Chute Check . 32 8.5 Main Contact Check . 32 8.6 Mechanism Check 32 9. Electronic Trip Unit Secondary Injection Test Procedures . 33 9.1 General . 33 9.2 Sensor Check . 33 9.3 Tripping Check 33 FIGURES Figure 1 Improperly Sealed Enclosure 6 Figure 2 Front View

20、 of Circuit Breaker with Cracked Molded Case 6 NEMA AB 4-2017 Page iii 2017 National Electrical Manufacturers Association Foreword This NEMA standards publication supersedes and fully replaces NEMA AB 4-2003. To ensure that a meaningful publication was being developed, draft copies were sent to a nu

21、mber of individuals 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

22、approval and resulted 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

23、 should be submitted to: Senior Technical Director, Operations National Electrical Manufacturers Association 1300 North 17th Street, Suite 900 Rosslyn, Virginia 22209 This standards publication was developed by the Molded Case Circuit Breaker Voting Classification of the National Electrical Manufact

24、urers Association. Approval of this 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: Eaton CorporationPit

25、tsburgh, PA General ElectricPlainville, CT Siemens Industry, Inc.Norcross, GA Schneider Electric USA Andover, MA ABB Inc.Memphis, TN NEMA AB 4-2017 Page iv 2017 National Electrical Manufacturers Association Introduction ANSI/NEMA AB 4 deals with “Guidelines for Inspection and Preventive Maintenance

26、of Molded Case Circuit Breakers used in Commercial and Industrial Applications.” These guidelines are to be used to identify circuit breakers requiring maintenance or replacement. Good practice includes periodic circuit breaker maintenance during plant shutdown or during a regular maintenance period

27、 as specified, for example, in NFPA 70B. When a circuit breaker operates automatically, good practice dictates that the source of the overcurrent should be located, and if it is suspected that the operation was at or near the interrupting rating, the circuit breakers condition should be checked prio

28、r to circuit re-energization. When appropriately maintained, molded case circuit breakers provide reliable protection for many years. It would be impractical for any manufacturer to test their products lifecycle in each and every application. The exact lifetime of the breaker, however, is determined

29、 by the circuit breakers operational duty and by its environment. With respect to operational duty, for some circuits there will be occasional overload conditions or low-current fault conditions. Here, the operating life will be tens of years. In other circuits, there may be high short-circuit-curre

30、nt faults but it should be noted that bolted faults at the interrupting rating of the breaker are rarely encountered. These will reduce the circuit breakers operating life and may necessitate circuit breaker replacement. Molded case circuit breakers are evaluated to the UL 489 (NEMA AB 1) standard M

31、olded-Case Circuit Breakers, Molded-Case Switches and Circuit-Breaker Enclosures. They are subjected to thousands of endurance test operations (UL 489 Table 7.1.5.1); 50 overload test operations for circuit breakers rated up to 1600A and 25 operations for circuit breakers rated 2000A and higher (UL

32、489 Table 7.1.3.1); 3 to 7 interrupting tests, depending on breaker 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 breaker

33、s that experience multiple high short-circuit-current faults should 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 host

34、ile to long term performance. For example, industries may have corrosive 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 p

35、eriodic maintenance or during specific inspection following a high 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 follow

36、s: Clause 1 presents the Scope and reference standards. Clause 2 details 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. Ov

37、erheating of the circuit breaker would necessitate further investigation, 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 object

38、ives are that the circuit breaker operates in a clean environment and 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

39、 procedures that can be used to verify specific operating characteristics 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 test NEMA AB 4-2017 Page v

40、 2017 National Electrical Manufacturers Association (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

41、would lead to replacement of that accessory or circuit breaker replacement if accessories are not removable. Clause 8 deals with inspection and test procedures for insulated case circuit breakers, including checking and servicing the primary connectors and cradle (chassis) if so equipped, and checki

42、ng a servicing the arc chutes, contacts and mechanism (if accessible). Clause 9 deals with testing electronic trip units using secondary injection. In summary, following an automatic overcurrent interruption at or near its interrupting rating, the condition of any protective device should be checked

43、 prior to circuit re-energization. For molded case circuit breakers, the condition of the circuit 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 fault

44、s, should receive a thorough inspection per the guidelines of NEMA AB 4. This document should also be used for recommended, periodic, preventive maintenance. NEMA AB 4-2017 Page vi 2017 National Electrical Manufacturers Association NEMA AB 4-2017 Page 1 2017 National Electrical Manufacturers Associa

45、tion 1. General 1.1 Scope NEMA AB 4 sets forth, for use by qualified personnel,1a number of basic procedures that may be used for 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 A

46、C/DC. Noteconsult the manufacturer for DC-only or 400 Hz circuit breakers. The methods outlined may be used to verify specific characteristics 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

47、methods are intended for field application and are, therefore, non-destructive in nature. Accordingly, these methods cannot be used to verify all performance capabilities of a molded case circuit breaker since verification of some capabilities requires tests of a destructive nature. Many tests, incl

48、uding those of a destructive nature, as defined in AB 1 (UL 489), are performed on representative samples of circuit breakers by 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 perfo

49、rmance of a molded case circuit breaker that has been disassembled (broken factory seal or removal of rivets), modified, rebuilt, refurbished, or handled in any manner not 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 Protection Association Batterymarch Park Quincy, MA 02269 NFPA 70 National Electrical Code NFPA 70B R