1、NEMA Standards PublicationNational Electrical Manufacturers AssociationANSI/NEMA KS 3-2010Guidelines for Inspection and Preventive Maintenance of Switches Used in Commercial and Industrial ApplicationsANSI/NEMA KS 3-2010 American National Standard Guidelines for Inspection and Preventive Maintenance
2、 of Switches Used in Commercial and Industrial Applications Secretariat: National Electrical Manufacturers Association Approved August 2, 2012 American National Standards Institute, Inc. KS 3-2010 Page ii Copyright 2012 by the National Electrical Manufacturers Association NOTICE AND DISCLAIMER The i
3、nformation 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 in the development
4、of this document. American National Standards Institute (ANSI) 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
5、 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 accuracy or completeness of any inf
6、ormation 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 or indirectly resulting from th
7、e 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 completeness of any information published herein, and disclaims and makes no warranty that the information in this document will fulfill any o
8、f 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 render professional or other serv
9、ices 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 professional in determining the ex
10、ercise 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. NEMA has no power, nor does it u
11、ndertake 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 information in this document sha
12、ll not be attributable to NEMA and is solely the responsibility of the certifier or maker of the statement.KS 3-2010 Page i Copyright 2010 by the National Electrical Manufacturers Association. CONTENTS Foreword ii Introduction iii SECTION 1 GENERAL . 1 1.1 Scope 1 1.2 Referenced Standards 1 SECTION
13、2 SAFETY PROCEDURES 3 2.1 Warning 3 2.2 Safety Procedure 3 2.3 Reinstallation Safety Procedure 3 SECTION 3 GUIDELINES 5 3.1 To Avoid Damaged or Otherwise Inoperable Switches Being Inadvertently Returned to Service 5 3.2 Guidance Regarding Inspection and Preventive Maintenance Procedures . 5 3.3 For
14、Information Regarding Switch Performance and Application . 5 3.4 Water-Damaged Switches 5 3.5 Switch Inspection Once Each Year. 5 SECTION 4 INSPECTION PROCEDURES 6 4.1 General . 6 4.2 Exposed Surfaces Temperature Check 6 4.3 Inspection of Enclosure Interior 6 SECTION 5 PREVENTIVE MAINTENANCE 9 5.1 G
15、eneral . 9 5.2 Environmental Evaluation . 9 5.3 Fuse Provisions 10 5.4 Wire Connectors . 10 5.5 Reinstallation Procedure . 10 SECTION 6 TEST PROCEDURES . 11 6.1 General . 11 6.2 Mechanical Operation Test . 11 6.3 Insulation Resistance Test 12 6.4 Individual Pole Resistance Test (Millivolt Drop) 13 S
16、ECTION 7 ACCESSORY DEVICE TEST PROCEDURES 17 7.1 General . 17 7.2 Shunt Trip Release Tests . 17 7.3 Electrical Operator Tests 18 7.4 Auxiliary Switch Tests . 20 Figure 1 Pitting . 7 Figure 2 Heat Damage 7 Figure 3 Typical Insulation Resistance Test Set-Up 12 Figure 4 Individual Pole Resistance Test
17、Set-Up 14 Figure 5 Fused Switch Individual Pole Resistance Test Set-Up 14 Figure 6 Non-Fused Switch Individual Pole Resistance Test Set-Up 15 Figure 7 Sample Shunt Trip Release 17 Figure 8 Sample Electrical Operator / Switch Assembly . 18 Figure 9 Sample Auxiliary Switch 20 KS 3-2010 Page ii Copyrig
18、ht 2010 by the National Electrical Manufacturers Association. Foreword This is the first edition of NEMA Standards Publication KS 3. To ensure that a meaningful publication was developed, draft copies were sent to a number of individuals and organizations in the public sector having an interest in o
19、r 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 resulted in a number of substantive changes to this publication. This
20、 publication will be periodically reviewed by the Switches Voting Classification of NEMA for any revisions necessary to keep it up to date with advancing technology. Proposed or recommended revisions should be submitted to: Vice President, Technical Services National Electrical Manufacturers Associa
21、tion 1300 North 17th Street Rosslyn, Virginia 22209 This Standards Publication was developed by the Switches Voting Classification of the National Electrical Manufacturers Association. Approval of this standard does not necessarily imply that all voting classification members voted for its approval
22、or participated in its development. At the time it was approved, the Switches Voting Classification had the following members: ABB Control, Inc.Wichita Falls, TX Boltswitch, Inc.Crystal Lake, IL Cooper BussmannSt. Louis, MO Eaton CorporationPittsburgh, PA GE Industrial SolutionsPlainville, CT Hubbel
23、l Inc.Bridgeport, CT Mersen USANewburyport, MA Siemens Industry, Inc.Alpharetta, GA Schneider ElectricPalatine, IL KS 3-2010 Page iii Copyright 2010 by the National Electrical Manufacturers Association. Introduction NEMA KS 3 deals with guidelines for inspection and preventive maintenance of switche
24、s used in commercial and industrial applications. These guidelines are to be used to identify switches requiring maintenance or replacement. Good practice includes periodic switch maintenance during plant shutdown or during a regular maintenance period as specified, for example, in NFPA 70B. When a
25、switch 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 switch condition should be checked prior to circuit re-energization. When appropriately maintained, switch
26、es provide reliable protection for many years. The exact lifetime of the switch, however, is determined by the switchs 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 o
27、perating life will be tens of years. In other circuits, there may be high short-circuit-current faults but it should be noted that bolted faults at the switch interrupting rating are rarely encountered. Short circuit events can significantly reduce the operating life of the switch and may necessitat
28、e replacement of the switch. Switches in this Guideline are evaluated to three different UL Standards: UL 98 Enclosed and Dead-Front Switches, UL 977 Fused Power-Circuit Devices, and UL 1429 Pullout Switches. They are subjected to thousands of endurance test operations; overload test operations; and
29、 two interrupting tests at maximum short-circuit-current rating. Thus switches have an extensive but finite interrupting capability, and switches that experience multiple high short-circuit-current faults should receive a thorough inspection and be replaced if necessary. With respect to environmenta
30、l effects, switches are sometimes exposed to high ambient temperatures, high humidity, and other ambient conditions that are hostile to long term performance. For example, industries may have corrosive environments or could be associated with dusty environments that could affect operating parts. It
31、is not intended that switches be disassembled for inspection. Rather, NEMA KS 3 should be referenced during periodic maintenance or during specific inspection following a high short-circuit-current fault. This document is intended to ensure that switches are well maintained, and provides guidelines
32、for switch replacement. This document is divided into separate sections as follows: Section 1 presents the scope and referenced standards. Section 2 details the safety procedures to be followed. Section 3 deals with general guidance. Section 4 deals with inspection procedures and describes thermal c
33、hecks (4.2) and visual checks (4.3) of the enclosure and switch condition. Overheating of the switch would necessitate further investigation, and cracks in the insulation systems would certainly necessitate switch replacement. Section 5 deals with preventive maintenance and ensures that the switchs
34、life is not compromised by external conditions. The objectives are that the switch operates in a clean environment and that the terminals are in good condition (5.2), that fuses (if required) are connected properly (5.3), and that wire connectors are in good condition and are correctly torqued (5.4)
35、. Section 6 deals with non-destructive test procedures that can be used to verify specific operating characteristics of switches. These include the Mechanical Operation Test (6.2), the Insulation Resistance Test (6.3), and the Individual Pole Resistance Test (millivolt drop test) (6.4). Non-complian
36、ce to one or more of these tests could necessitate switch replacement. KS 3-2010 Page iv Copyright 2010 by the National Electrical Manufacturers Association. Section 7 deals with the operation of accessory devices. Failure of an accessory would lead to replacement of that accessory, or switch replac
37、ement 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. Switches that have experienced multiple high short-circuit-current faults
38、, as evidenced by conditions at the source of the faults, should receive a thorough inspection per the guidelines of NEMA KS 3. This document should also be used for recommended, periodic, preventive maintenance. KS 3-2010 Page 1 Copyright 2010 by the National Electrical Manufacturers Association. S
39、ection 1 GENERAL 1.1 Scope NEMA Standards Publication KS 3 sets forth, for use by qualified personnel1, a number of basic procedures that may be used for the inspection and preventive maintenance of switches used in industrial and commercial applications rated up to and including 600 V 50/60 Hz ac o
40、r ac/dc. NOTEConsult the manufacturer for other manufacturer-specific ratings. The National Electrical Code defines several switch types: General Use Switch, Isolating Switch, Motor-Circuit Switch, and Double-Throw Switch. In most cases, a switch is capable of interrupting/disconnecting its rated cu
41、rrent at its rated voltage. An Isolating Switch does not have an interrupting rating and is actuated after the circuit has been opened by some other means. A Motor-Circuit Switch is rated in horsepower and is capable of interrupting the maximum overload current of a motor with the same horsepower ra
42、ting. The methods outlined may be used to verify specific characteristics of a switch that was originally built and tested in compliance with the requirements of NEMA Standards Publication KS 1. These methods are intended for field application and are, therefore, non-destructive in nature. According
43、ly, these methods cannot be used to verify all performance capabilities of a switch since verification of some capabilities requires tests of a destructive nature. Many tests, including those of a destructive nature, as defined in KS 1, are performed on representative samples of switches by the manu
44、facturer, as part of a routine program of factory inspection. The KS 3 Standards Publication is not intended, nor is it adequate, to verify proper electrical performance of a switch that has been disassembled, modified, rebuilt, refurbished, or handled in any manner not intended or authorized by the
45、 original manufacturer. Such switches 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 1 Batterymarch Park Quincy,
46、 MA 02169 NFPA 70 National Electrical Code NFPA 70B Recommended Practice for Electrical Equipment Maintenance NFPA 70E Standard for Electrical Safety in the Workplace 1 For purposes of these guidelines, a qualified person is one who has skills and knowledge related to the construction and operation
47、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 equipment in accordance with established safety practices. in the pro
48、per 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. KS 3-2010 Page 2 Copyright 2010 by the National Electrical Manufacturers Association. National Electr
49、ical Manufacturers Association 1300 North 17th Street Suite 1752 Rosslyn, Virginia 22209 Evaluating Water-Damaged Electrical Equipment NEMA KS 1 Enclosed and Miscellaneous Distribution Equipment Switches (600 Volts Maximum) NEMA KS 2 Distribution Equipment Switch Application and Maintenance Guide, A Users Reference NEMA 250 Enclosures for Electrical Equipment (1000 Volts Maximum) Underwriters Laboratories, Inc. 333 Pfingsten Road Northbrook, IL 60062 UL 98 Enclosed and Dead-Front Switches UL 977 Fused Power-Circuit Devices UL 1429 Pullout Switches KS 3-2010
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