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1、 NEMA PB 2.2 NEMA PB 2.2 APPLICATION GUIDE FOR GROUND FAULT PROTECTIVE DEVICES FOR EQUIPMENT Copyright National Electrical Manufacturers Association Provided by IHS under license with NEMALicensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/19/2007 08:40:12 MDTNo reproduction or network
2、ing permitted without license from IHS -,-,- Copyright National Electrical Manufacturers Association Provided by IHS under license with NEMALicensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/19/2007 08:40:12 MDTNo reproduction or networking permitted without license from IHS -,-,- NEM
3、A Standards Publication PB 2.2-2004 Application Guide for Ground Fault Protective Devices for Equipment Published by: National Electrical Manufacturers Association 1300 North 17th Street, Suite 1847 Rosslyn, Virginia 22209 www.nema.org Copyright 2004 by the National Electrical Manufacturers Associat
4、ion. 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 International and Pan American Copyright Conventions. Copyright National Electrical Manufacturers Association
5、 Provided by IHS under license with NEMALicensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/19/2007 08:40:12 MDTNo reproduction or networking permitted without license from IHS -,-,- Copyright 2004 by the National Electrical Manufacturers Association. NOTICE AND DISCLAIMER The informat
6、ion 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 of this
7、 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 seeks out the views of pe
8、rsons 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 an
9、y 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 or indirectly resulting fr
10、om 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 this document will fulfil
11、l 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 render professional or oth
12、er 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 professional in determining
13、 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. NEMA has no power, nor do
14、es 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 safety related information in this docu
15、ment shall not be attributable to NEMA and is solely the responsibility of the certifier or maker of the statement. Copyright National Electrical Manufacturers Association Provided by IHS under license with NEMALicensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/19/2007 08:40:12 MDTNo
16、reproduction or networking permitted without license from IHS -,-,- PB 2.2-2004 Page i Copyright 2004 by the National Electrical Manufacturers Association. CONTENTS Page Foreword . iii Section 1 GENERAL 1.1 Scope1 1.2 Referenced Standards .1 1.2.1 Other References.2 Section 2 INTRODUCTION 2.1 Arcing
17、 Ground Faults4 2.2 Need for Ground Fault Protection 4 2.3 Standards .4 2.4 Application, General.5 2.5 Relay Setting Selections, General5 2.6 Methods of GFP Device Selectivity5 2.7 Damage Levels.5 Section 3 POWER CIRCUIT 3.1 Voltage .6 3.2 Frequency.6 3.3 Current Rating6 3.4 Location of Ground Fault
18、 Sensing Devices6 3.4.1 Ground Return Method 6 3.4.2 Outgoing 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 Systems7 3.8 Neutrals and Grounding .7 3.9 Need for Complete System Information.7 3.10
19、Systems Containing Transformers.8 3.11 System Design .8 Section 4 CONTROL CIRCUIT 4.1 Control Power.9 4.2 AC Control Power.9 4.3 DC Control Power.9 4.4 Control Circuit Protection .9 4.5 Control Wiring.9 4.6 Indication and Test Circuits9 4.7 Compatibility of GFP Devices.9 Section 5 TYPICAL APPLICATIO
20、N DIAGRAMS 5.1 General .10 5.1.1 Abbreviations10 5.2 Ground Fault Protection on Main Disconnect Only, Ground Return Type.10 5.3 Ground Fault Protection on Main Disconnect Only, Outgoing Circuit Type.11 5.4 Ground Fault Protection on Main and Feeder Disconnects, Ground Return Type on Main12 5.5 Groun
21、d Fault Protection on Main and Feeder Disconnects, Outgoing Circuit Type on Main.13 5.6 Ground Fault Protection on Main and Feeder Disconnects with Zone Selective Interlocking, Ground Return Type on Main 14 5.7 Ground Fault Protection on Main, Feeders, and Selected Branch Disconnects with Zone Selec
22、tive Interlocking, Outgoing Circuit Type on Main.15 5.8 Double-Ended System with Ground Fault Protection on Mains, Tie, and Feeder Disconnects, Ground Return Type on Mains.16 Copyright National Electrical Manufacturers Association Provided by IHS under license with NEMALicensee=NASA Technical Standa
23、rds 1/9972545001 Not for Resale, 04/19/2007 08:40:12 MDTNo reproduction or networking permitted without license from IHS -,-,- PB 2.2-2004 Page ii Copyright 2004 by the National Electrical Manufacturers Association. Section 6 TIME AND CURRENT SETTINGS 6.1 Application of Ground Fault Protective Syste
24、ms for Coordinated Ground Fault Tripping .18 6.2 Types of Coordinated Ground Fault Tripping Systems18 6.3 Time-Current Band Selective System18 6.4 Zone Selective System.18 6.5 Coordination of Low-Voltage Disconnects with the High-Voltage Side of a System .19 6.6 Coordination with Downstream Overcurr
25、ent Devices Not Equipped with Ground Fault Protection19 6.7 Typical Settings 20 6.7.1 Single Zone-Ground Fault Protection on Main Disconnect Only.20 6.7.2 Multiple Zone Time Current Band Selective SystemGround Fault Protection on Mains, Feeders, and Branch Circuits.21 6.7.3 Zone Selective System, Gr
26、ound Fault Protection on Mains and Feeders.23 Section 7 TYPICAL COORDINATED SYSTEMS 7.1 Coordinated Protection.25 7.2 Examples25 7.2.1 GFP on Main Disconnect Only.25 7.2.2 GFP on Main Disconnect and Feeders26 7.2.3 Fully Coordinated Multiple Zone Ground Fault Protection Systems26 Section 8 TESTING O
27、F GROUND FAULT SENSING AND RELAYING EQUIPMENT 8.1 Design Tests.27 8.2 Production Tests.27 8.3 Tests on Assembled Equipment.27 8.4 Preparation for Field Testing27 8.5 Field Testing.28 Annex A ARCING FAULT DAMAGE LEVELS A.1 Approximate Arcing Fault Damage Levels for 480y/277 V Systems .29 A.2 Arcing F
28、ault Current .29 A.3 Assumed Tolerable Damage Levels 29 A.4 Probable Amount of Damage.30 Annex B SYSTEM DESIGN CONSIDERATIONS B.1 General .33 B.2 Power System 33 B.3 Ground Fault Current Paths .33 B.4 Ground Fault Protective Devices and Settings 33 B.5 Control Power.34 Copyright National Electrical
29、Manufacturers Association Provided by IHS under license with NEMALicensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/19/2007 08:40:12 MDTNo reproduction or networking permitted without license from IHS -,-,- PB 2.2-2004 Page iii Copyright 2004 by the National Electrical Manufacturers A
30、ssociation. Foreword This Standards Publication is intended to provide a basis of common understanding within 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
31、Services National Electrical Manufacturers Association 1300 North 17th Street, Suite 1847 Rosslyn, VA 22209 This Standards 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 ap
32、proval or participated in its development. At the time it was approved, the Section was composed of the following members: Eaton CorporationPittsburgh, PA General ElectricPlainville, CT Hubbell IncorporatedBridgeport, CT Industrial Electric Manufacturing, Inc.Fremont, CA Milbank Manufacturing Compan
33、yKansas City, MO Penn Panel and they may persist for many sec, several min, or longer. The circuit conductors can generally tolerate these low-level currents for the time required to operate conventional overcurrent devices, but the same current flowing through the arc and high impedance ground path
34、 (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 referring to the time-current curves of the properly applied overcurrent protective devices in a distribution system, w
35、hether 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 initiate opening action accordingly. The nature of low level arcing ground faults makes their detection impractic
36、al 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 requirements for Class I GFP devices are covered in Underwriters Laboratories, Inc. standard for Ground Fault Sensing and R
37、elaying 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 use with: (1) circuit breakers, (2) fused circuit breakers, (3) fused switches having an interrupting rating not l
38、ess than 12 times their amp rating, or (4) fused switches having integral means to prevent disconnection at levels or fault current exceeding the contact interrupting rating of the switch. The Class II GFP devices defined in Underwriters Laboratories, Inc. standard for Ground Fault Sensing and Relay
39、ing 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 fault current. This application guide is directed to Class I GFP devices. Additional requirements for GFP devices, i
40、ncluding shunt trip devices, are covered in other standards including: ANSI C37.16, ANSI C37.17, NEMA AB 1, UL 489, and UL 977. Copyright National Electrical Manufacturers Association Provided by IHS under license with NEMALicensee=NASA Technical Standards 1/9972545001 Not for Resale, 04/19/2007 08:
41、40:12 MDTNo reproduction or networking permitted without license from IHS -,-,- PB 2.2-2004 Page 5 Copyright 2004 by the National Electrical Manufacturers Association. 2.4 APPLICATION, GENERAL GFP devices, when properly applied, will satisfy the requirements for the ground fault protection of servic
42、e entrance equipment as outlined in Articles 230 and 517 of the National Electrical Code. When the above GFP devices are 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
43、 can be achieved. Therefore, for maximum continuity of service, GFP devices are recommended for downstream feeder and branch circuits as well as the main service disconnects. The additional installation of this equipment on downstream disconnecting devices provides for maximum continuity of electric
44、al service as suggested in Article 230 and as required in Article 517 of the National Electrical Code. Equally effective 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
45、 means is capable of interrupting any fault current expected. Some switches are not designed to interrupt 12 times their amp 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 S
46、ETTING SELECTIONS, GENERAL The entire distribution system should be properly analyzed before GFP devices are selected and their settings determined. Consideration must be given to the selection of GFP devices to achieve the best possible coordination of overcurrent and ground fault tripping. GFP dev
47、ice settings determine only the nominal current 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 ma
48、gnitude; they can only limit the length of 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 consider 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 acciden