NEMA PB 2.2-1999(R2004, R2009) Application Guide for Ground Fault Protective (GFP) Devices for Equipment1.pdf

《NEMA PB 2.2-1999(R2004, R2009) Application Guide for Ground Fault Protective (GFP) Devices for Equipment1.pdf》由会员分享，可在线阅读，更多相关《NEMA PB 2.2-1999(R2004, R2009) Application Guide for Ground Fault Protective (GFP) Devices for Equipment1.pdf（41页珍藏版）》请在三一文库上搜索。

1、 N NE EMMA A PB B 2. .2 2 APPLICATION GUIDE FOR GROUND FAULT PROTECTIVE DEVICES FOR EQUIPMENT NEMA Standards Publication PB 2.2-1999 (R2004, R2009) Application Guide for Ground Fault Protective Devices for Equipment Published by National Electrical Manufacturers Association 1300 N 17th Street, Suite

2、 1752 Rosslyn, VA 22209 www.nema.org ! Copyright 2009 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 Literacy and Artistic Works, and the Intern

3、ational and Pan American Copyright Conventions. ? 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 developed. Consensus does not necessarily mean that ther

4、e 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 developed through a voluntary consensus standards developme

5、nt 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 of consensus, it does not write the document and it

6、 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, or other damages of any nature whatsoever, whether sp

7、ecial, 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, expressed or implied, as to the accuracy or completeness of any information published herein, a

8、nd 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 sellers products or services by virtue of this standard or guide. In publishing and m

9、aking 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 document should rely on his or her own independent jud

10、gment 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 sources, which the user may wish to consult for additi

11、onal 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 safety or health purposes. Any certification or othe

12、r 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. ? PB 2.2-1999 (R2004, R2009) Page i TABLE OF CONTENTS Section 1 GENERAL .1 1.1 Scope1 1.2 Referenced

13、 Standards1 1.2.1Other references .2 Section 2 INTRODUCTION.4 2.1 Arcing Ground Faults4 2.2 Need for Ground Fault Protection.4 2.3 Standards4 2.4 ApplicationGeneral4 2.5 Relay Setting SelectionsGeneral 5 2.6 Methods of GFP Device Selectivity.5 2.7 Damage Levels.5 Section 3 POWER CIRCUIT.6 3.1 Voltag

14、e6 3.2 Frequency.6 3.3 Current Rating.6 3.4 Location of Ground Fault Sensing Devices 6 3.4.1Ground Return Method .6 3.4.2Outgoing Circuit Method (Residual or Zero-Sequence)6 3.5 Ground Connections.6 3.6 Mounting and Connection Of Ground Fault Sensing Devices7 3.7 Delta Connected Systems 7 3.8 Neutra

15、ls and Grounding7 3.9 Need for Complete System Information7 3.10Systems Containing Transformers.8 3.11System Design .8 Section 4 CONTROL CIRCUIT.9 4.1 Control Power .9 4.2 AC Control Power .9 4.3 DC Control Power.9 4.4 Control Circuit Protection9 4.5 Control Wiring .9 4.6 Indication And Test Circuit

16、s9 4.7 Compatibility of GFP Devices.9 Section 5 TYPICAL APPLICATION DIAGRAMS10 5.1 General .10 5.1.1Abbreviations.10 5.2 Ground Fault Protection on Main Disconnect OnlyGround Return Type10 5.3 Ground Fault Protection on Main Disconnect OnlyOutgoing Circuit Type11 5.4 Ground Fault Protection on Main

17、And Feeder DisconnectsGround Return Type On Main 12 5.5 Ground Fault Protection on Main and Feeder DisconnectsOutgoing Circuit Type on Main 13 5.6 Ground Fault Protection On Main And Feeder Disconnects With Zone Selective InterlockingGround Return Type On Main.14 5.7 Ground Fault Protection On Main,

18、 Feeders, And Selected Branch Disconnects With Zone Selective InterlockingOutgoing Circuit Type On Main.15 5.8 Double-Ended System With Ground Fault Protection On Mains, Tie, And Feeder DisconnectsGround Return Type On Mains16 Section 6 TIME AND CURRENT SETTINGS .18 Copyright 2009 by the National El

19、ectrical Manufacturers Association. ? PB 2.2-1999 (R2004, R2009) Page ii 6.1 Application Of Ground Fault Protective Systems For Coordinated Ground Fault Tripping18 6.2 Types Of Coordinated Ground Fault Tripping Systems18 6.3 Time-Current Band Selective System.18 6.4 Zone Selective System .18 6.5 Coo

20、rdination of Low-Voltage Disconnects With The High-Voltage Side Of A System.19 6.6 Coordination with Downstream Overcurrent Devices Not Equipped With Ground Fault Protection.19 6.7 Typical Settings.19 6.7.1Single Zone-Ground Fault Protection on Main Disconnect Only20 6.7.2Multiple Zone Time Current

21、Band Selective System -Ground Fault Protection on Mains, Feeders, and Branch Circuits.22 6.7.3Zone Selective SystemGround Fault Protection on Mains and Feeders23 Section 7 TYPICAL COORDINATED SYSTEMS .25 7.1 Coordinated Protection.25 7.2 Examples 25 7.2.1GFP on Main Disconnect Only25 7.2.2GFP on Mai

22、n Disconnect and Feeders.26 7.2.3Fully Coordinated Multiple Zone Ground Fault Protection Systems.26 Section 8 TESTING OF GROUND FAULT SENSING AND RELAYING EQUIPMENT 27 8.1 Design Tests.27 8.2 Production Tests.27 8.3 Tests on Assembled Equipment.27 8.4 Preparation for Field Testing.27 8.5 Field Testi

23、ng28 Annex A ARCING FAULT DAMAGE LEVELS.29 A.1 APPROXIMATE ARCING FAULT DAMAGE LEVELS FOR 480Y/277 VOLT SYSTEMS29 A.2 ARCING FAULT CURRENT.29 A.3 ASSUMED TOLERABLE DAMAGE LEVELS.29 A.4 PROBABLE AMOUNT OF DAMAGE .30 Annex B SYSTEM DESIGN CONSIDERATIONS 33 B.1 GENERAL.33 B.2 POWER SYSTEM.33 B.3 GROUND

24、 FAULT CURRENT PATHS33 B.4 GROUND FAULT PROTECTIVE DEVICES AND SETTINGS.33 B.5 CONTROL POWER33 Copyright 2009 by the National Electrical Manufacturers Association. ? PB 2.2-1999 (R2004, R2009) Page iii Foreword This Standards Publication is intended to provide a basis of common understanding within

25、the electrical community. User needs have 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 N 17th Street, Suite 1752 Rosslyn, VA 22209 This S

26、tandards Publication was developed by the Panelboard and Distribution Board Section. Section approval of the standard does not necessarily imply that all section members voted for its approval or participated in its development. At the time it was approved, the Section was composed of the following

27、members: Cooper BussmannEllisville, MO Eaton Electrical Inc.Pittsburgh, PA GEPlainville, CT Hubbell, Inc.Bridgeport, CT Penn Panel and they may persist for many seconds, several minutes, or longer. The circuit conductors can generally tolerate these low-level currents for the time required to operat

28、e conventional overcurrent devices, but the same current flowing through the arc and high impedance ground path (conduit or enclosure) can produce extensive damage in the arcing area. 2.2 Need for Ground Fault Protection The basic need for ground fault protection can be better understood by referrin

29、g to the time-current cur- ves of the properly applied overcurrent protective devices in a distribution system, whether fuses or circuit breakers are used. Properly applied conventional over current protective devices are designed to recognize currents in the overload and short circuit range and to

30、initiate opening action accordingly. The nature of low level arcing ground faults makes their detection impractical by conventional phase overcurrent devices. Unless ground fault protection is included, the system has no protection against low-level arcing ground faults. 2.3 Standards The requiremen

31、ts for Class I GFP devices are covered in Underwriters Laboratories, Inc. standard for Ground Fault Sensing and Relaying Equipment, UL 1053. A Class I GFP device is one that does not incorporate means to prevent opening of the disconnecting means at high levels of fault current. It is intended for u

32、se with: (1) circuit breakers, (2) fused circuit breakers, (3) fused switches having an interrupting rating not less than 12 times their ampere rating, or (4) fused switches having integral means to prevent disconnection at levels or fault current exceeding the contact interrupting rating of the swi

33、tch. The Class II GFP devices defined in Underwriters Laboratories, Inc. standard for Ground Fault Sensing and Relaying Equipment, UL 1053, are intended for use with disconnects of limited interrupting rating and incorporate means to prevent opening of the disconnecting means at excessive levels of

34、fault current. This application guide is directed to Class I GFP devices. Additional requirements for GFP devices, including shunt trip devices, are covered in other standards including: ANSI-C37.16, ANSI-C37.17, NEMA AB 1, UL 489, and UL 977. 2.4 ApplicationGeneral GFP devices, when properly applie

35、d, will satisfy the requirements for the ground fault protection of service entrance equipment as outlined in Articles 230 and 517 of the National Electrical Code. When the Copyright 2009 by the National Electrical Manufacturers Association. ? PB 2.2-1999 (R2004, R2009) Page 5 above GFP devices are

36、extended to include downstream feeder and branch circuits as well as the main disconnecting devices, additional protection will be provided and selective tripping on ground faults can be achieved. Therefore, for maximum continuity of service, GFP devices are recommended for downstream feeder and bra

37、nch circuits as well as the main service disconnects. The additional installation of this equipment on downstream disconnecting devices provides for maximum continuity of electrical service as suggested in Article 230 and as required in Article 517 of the National Electrical Code. Equally effective

38、results can be expected in separately derived systems when GFP devices are properly applied. (See 3.10.) Special precautions should be taken to ensure that the selected disconnect means is capable of interrupting any fault current expected. Some switches are not designed to interrupt 12 times their

39、ampere rating. Likewise, magnetic contactors are not required to have high fault current interrupting ratings and their use with GFP devices should be carefully reviewed. 2.5 Relay Setting SelectionsGeneral The entire distribution system should be properly analyzed before GFP devices are selected an

40、d their selection of GFC devices to achieve the best possible coordination of overcurrent and ground fault tripping. Improper coordination may result in nuisance tripping of the upstream device when a downstream device should have cleared the fault. GFP device settings determine only the nominal cur

41、rent and time delay values at which an opening action is initiated. The actual amount of let-through energy is determined by the arcing fault current magnitude and the time that the fault is allowed to persist. GFP devices cannot limit the arcing current magnitude; they can only limit the length of

42、time that a ground fault above the selected pickup current setting is allowed to exist. Relay setting tolerances and operating times for the disconnects or protective devices to open and clear the fault must be included in any analysis of coordination or clearing speeds. It may be advisable to consi

43、der different settings for the construction and operational phases of a project. Minimum settings should be selected during the construction phase while equipment is being installed and the probability of construction accidents is high. For the operational phase, in addition to protection, settings

44、should allow for proper system coordination and provide optimum service continuity to avoid possible safety problems resulting from loss of lights, and operating power required for elevators, exhaust fans, and other safety oriented electrical loads. Loss of power resulting from too sensitive GFP dev

45、ice settings could cause more serious consequences than the equipment damage incurred as a result of a minor ground fault. 2.6 Methods of GFP Device Selectivity There are two basic methods of achieving selectivity between GFP devices in a coordinated distribution system: (1) time-current band, and (

46、2) zone selective. Each of these methods is described in Section 6. 2.7 Damage Levels Tolerable damage levels should be established for each system as a basis for selecting equipment and determining time and current settings of all devices. Appendix A illustrates the methods for calculating tolerabl

47、e damage levels used in this guide. Copyright 2009 by the National Electrical Manufacturers Association. ? PB 2.2-1999 (R2004, R2009) Page 6 Section 3POWER CIRCUIT 3.1 Voltage GFP devices are designed for use on power systems of 1000 volts or less. They may be used on higher voltage power circuits i

48、f sufficient insulation and spacing is provided. 3.2 Frequency GFP devices should be used only on power circuits of the frequency for which they are marked, or as recommended by the manufacturer. 3.3 Current Rating GFP devices are designed to withstand continuously a fault current at least equal to

49、the maximum pick-up setting available on the relay. They should not be applied to a power circuit in such a way that a continuous unbalanced current in excess of the maximum continuous current rating can flow through the sensing device without being interrupted. When GFP devices are applied to a system, their maximum permissible fault current withstand rating must not be exceeded. This involves the calculation of the maximum ground fault current to which the devices may be subjected.