1、IEEE Std 1617-2007IEEE Guide for Detection, Mitigation,and Control of Concentric NeutralCorrosion in Medium-VoltageUnderground CablesIEEE3ParkAvenueNew York, NY 10016-5997, USA18 February 2008IEEE Power Engineering SocietySponsored by theInsulated Conductors Committee1617TMIEEE Std 1617TM-2007 IEEE
2、Guide for Detection, Mitigation, and Control of Concentric Neutral Corrosion in Medium-Voltage Underground Cables Sponsor Insulated Conductors Committee of the IEEE Power Engineering Society Approved 27 September 2007 IEEE-SA Standards Board Abstract: This guide provides a summary of the methods for
3、 detection, mitigation, and control of concentric neutral corrosion in medium-voltage, unjacketed, underground distribution cable installed direct buried or in conduit. The causes of corrosion in cable concentric neutral wires and straps and the methods available to detect this corrosion are describ
4、ed. The purpose of the concentric neutral and the consequences of significant loss of the concentric neutral are discussed. Recommendations are made for the mitigation and control of the cable concentric neutral corrosion. Keywords: cable, cable systems, concentric neutral, corrosion, insulated cond
5、uctor, power cable The Institute of Electrical and Electronics Engineers, Inc. 3 Park Avenue, New York, NY 10016-5997, USA Copyright 2008 by the Institute of Electrical and Electronics Engineers, Inc. All rights reserved. Published 18 February 2008. Printed in the United States of America. IEEE is a
6、 registered trademark in the U.S. Patent +1 978 750 8400. Permission to photocopy portions of any individual standard for educational classroom use can also be obtained through the Copyright Clearance Center. iv Copyright 2008 IEEE. All rights reserved. Introduction This introduction is not part of
7、IEEE Std 1617-2007, IEEE Guide for Detection, Mitigation, and Control of Concentric Neutral Corrosion in Medium-Voltage Underground Cables. IEEE Std 1617-2007 is a new guide written over a seven-year period by a dedicated group of volunteer experts. The work was done through the Insulated Conductors
8、 Committee Working Group C7, Neutral Corrosion, which met formally twice a year from 2001 through 2004 to develop initial drafts. A total of seven drafts were produced and edited in the formal meetings and follow-up discussions and e-mail communications. Notice to users Errata Errata, if any, for th
9、is and all other standards can be accessed at the following URL: http:/ standards.ieee.org/reading/ieee/updates/errata/index.html. Users are encouraged to check this URL for errata periodically. Interpretations Current interpretations can be accessed at the following URL: http:/standards.ieee.org/re
10、ading/ieee/interp/ index.html. Patents Attention is called to the possibility that implementation of this standard may require use of subject matter covered by patent rights. By publication of this standard, no position is taken with respect to the existence or validity of any patent rights in conne
11、ction therewith. The IEEE is not responsible for identifying Essential Patent Claims for which a license may be required, for conducting inquiries into the legal validity or scope of Patents Claims or determining whether any licensing terms or conditions are reasonable or non-discriminatory. Further
12、 information may be obtained from the IEEE Standards Association. v Copyright 2008 IEEE. All rights reserved. Participants At the time this guide was submitted to the IEEE-SA Standards Board for approval, the Working Group C7 on Neutral Corrosion of the Cable Systems Subcommittee C had the following
13、 membership: Vern L. Buchholz, Chair Glen J. Bertini Lawrence W. Bobb Kenneth E. Bow Jack E. Cherry Frank DiGuglielmo John M. Hans John L. Hinkle Fred B. Koch Carl C. Landinger William M. McDermid Henning Oetjn Ralph E. Patterson Timothy M. Robeson Kenneth Romano Gail A. Shaw Michael J. Smalley Will
14、iam Stagi William Thue Jorge G. Valdes Juli Wagner Joseph T. Zimnoch The following members of the individual balloting committee voted on this guide. Balloters may have voted for approval, disapproval, or abstention. Michael P. Baldwin Thomas M. Barnes Martin Baur Michael G. Bayer Wallace B. Binder
15、Steven A. Boggs Kenneth E. Bow Harvey L. Bowles Chris Brooks Vern L. Buchholz William A. Byrd Thomas P. Callsen Michael D. Clodfelder John H. Cooper Tommy P. Cooper F. A. Denbrock John R. Densley J. F. Doering Randall L. Dotson Gary R. Engmann Rabiz N. Foda Marcel Fortin David L. Gilmer Randall C. G
16、roves Ajit K. Gwal John M. Hans Jeffrey L. Hartenberger Gary A. Heuston Lauri J. Hiivala David A. Horvath Dennis Horwitz A. S. Jones Joseph L. Koepfinger Jim Kulchisky Solomon Lee William E. Lockley G. L. Luri Glenn J. Luzzi Eric P. Marsden William M. McDermid Mark F. McGranaghan John E. Merando Jr.
17、 Gary L. Michel Kyaw Myint Shantanu Nandi Michael S. Newman Neal K. Parker Ralph E. Patterson Serge Pelissou Percy E. Pool Dennis B. Schlender Robert Schlesinger Gail A. Shaw David Singleton Michael J. Smalley Nagu N. Srinivas Martin J. Von Herrmann Waldemar G. Von Miller Mark D. Walton James W. Wil
18、son Donald W. Zipse Ahmed F. Zobaa vi Copyright 2008 IEEE. All rights reserved. When the IEEE-SA Standards Board approved this guide on 27 September 2007, it had the following membership: Steve M. Mills, Chair Robert M. Grow, Vice Chair Don Wright, Past Chair Judith Gorman, Secretary Richard DeBlasi
19、o Alex Gelman William R. Goldbach Arnold M. Greenspan Joanna N. Guenin Kenneth S. Hanus William B. Hopf Richard H. Hulett Hermann Koch Joseph L. Koepfinger* John Kulick David J. Law Glenn Parsons Ronald C. Petersen Tom A. Prevost Narayanan Ramachandran Greg Ratta Robby Robson Anne-Marie Sahazizian V
20、irginia C. Sulzberger Malcolm V. Thaden Richard L. Townsend Howard L. Wolfman *Member Emeritus Also included are the following nonvoting IEEE-SA Standards Board liaisons: Satish K. Aggarwal, NRC Representative Michael H. Kelley, NIST Representative Michelle D. Turner IEEE Standards Program Manager,
21、Document Development Matthew J. Ceglia IEEE Standards Program Manager, Technical Program Development vii Copyright 2008 IEEE. All rights reserved. Contents 1. Overview 1 1.1 Scope . 1 1.2 Purpose 1 2. Normative references 2 3. Definitions 2 4. Purpose of the concentric neutral wires 2 4.1 Path for f
22、low of charging currents . 2 4.2 Path for flow of fault currents 3 4.3 Reduce step and touch potential 3 4.4 Provide a system neutral 3 4.5 Types of concentric wires 3 5. Consequences of significant neutral corrosion . 3 5.1 Cable failures caused by loss of metallic shield component 3 5.2 Improper o
23、peration of protective devices 4 5.3 Stray currents and interference 4 5.4 Effects on power quality 4 5.5 National Codes 4 6. Causes of neutral corrosion 4 6.1 Galvanic corrosion cell 5 6.2 Corrosion cell set up on a single metal 5 6.3 Soil corrosion. 6 6.4 Differential aeration. 6 6.5 Unintended or
24、 stray electrical currents 6 6.6 The coating of concentric neutral wires. 6 7. Detection and evaluation 7 7.1 Visual inspection . 7 7.2 Test concentric neutral using a time domain reflectometer (TDR) 7 7.3 Concentric neutral resistance measurement method9 7.4 Surface voltage measurement technique 11
25、 viii Copyright 2008 IEEE. All rights reserved. 8. Control and mitigation 12 8.1 Cathodic protection using anodes and rectifiers 12 8.2 Cable replacement . 13 8.3 Use of jacketed cable. 13 8.4 Economic considerations with existing and new cable 14 Annex A (informative) Bibliography . 17 IEEE Guide f
26、or Detection, Mitigation, and Control of Concentric Neutral Corrosion in Medium-Voltage Underground Cables 1 1. 1.11.2Overview Since 1960, large quantities of unjacketed underground distribution cable have been installed direct buried and in conduit. Uncoated and coated copper concentric neutral wir
27、es and straps (called only neutral wires in this guide) have been used for the metallic shield of these cables. The integrity of the neutral wires is important because, connected to the grounding system, these wires provide a path for the flow of charging, load and fault currents, and limit touch po
28、tential. The concentric neutral wires, in direct contact with the environment, are susceptible to corrosion. Scope The primary focus of this guide is unjacketed, underground distribution cable installed direct buried or in conduit. The causes of corrosion in cable concentric neutral wires and straps
29、 and the methods available to detect this corrosion are described. The purpose of the concentric neutral and consequences of significant loss of the concentric neutral are discussed. Recommendations are made for the mitigation and control of the cable concentric neutral corrosion. Purpose The purpos
30、e of this document is to provide guidance for the detection, mitigation, and control of corrosion in medium-voltage cable concentric neutral wires and straps. Copyright 2008 IEEE. All rights reserved. IEEE Std 1617-2007 IEEE Guide for Detection, Mitigation, and Control of Concentric Neutral Corrosio
31、n in Medium-Voltage Underground Cables 2 Copyright 2008 IEEE. All rights reserved. 2. Normative references The following referenced documents are indispensable for the application of this document (i.e., they must be understood and used, so each referenced document is cited in text and its relations
32、hip to this document is explained). For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments or corrigenda) applies. Accredited Standards Committee C-2, National Electrical Safety Code(NESC).1,2ICEA S-94-649
33、, Standard for Concentric Neutral Cables Rated 5 Through 46 kV.3IEEE Std 532TM, IEEE Guide for Selecting and Testing Jackets for Underground Cables.4NACE Standard RP0285-2002, Recommended Practice: Corrosion Control of Underground Storage Tank Systems by Cathodic Protection.53. Definitions For purpo
34、ses of this document, the following terms and definitions apply. The Authoritative Dictionary of IEEE Standards Terms B156should be referenced for terms not defined in this clause. 3.1 cable in conduit (CIC): Cable preinstalled in a continuous conduit, buried as a unit in a single operation. 4. Purp
35、ose of the concentric neutral wires 4.1 Path for flow of charging currents The conductor polymeric stress relief layer (semiconducting or high relative permittivity; see ICEA S-94-6497) and insulation polymeric stress relief layer separated by a layer of insulation comprising a medium-voltage or hig
36、h-voltage cable defines a capacitor. When alternating voltage is placed on the central conductor, charging current is induced in the insulation stress relief layer by capacitive action. To provide a defined path for the flow of these charging currents, a metallic shield component is applied over the
37、 insulation stress relief layer, and it is grounded at one or several points. The charging currents are relatively small, and a small conductor would serve this purpose. 1The NESC is available from the Institute of Electrical and Electronics Engineers, 445 Hoes Lane, Piscataway, NJ 08854, USA (http:
38、/standards/ieee.org/). 2National Electrical Safety Code and NESC are registered trademarks in the U.S. Patent hence, potential differences will exist on the surface. When placed in a corrosive environment, these potential differences will provide the driving force for the steel to begin to oxidize.
39、Locations with a higher driving potential where corrosion then occurs are termed anodes. Surrounding noncorroding areas are termed cathodes. As in the two-metal galvanic corrosion cell, the corrosion mechanism, therefore, requires four elements to occur: Anode area on the metal Cathode area on the m
40、etal Metallic connection between the anode and the cathode areas for electron current Environment connecting the anode and the cathode areas for ionic current The removal of any one of the above four elements would prevent corrosion from occurring. Copyright 2008 IEEE. All rights reserved. IEEE Std
41、1617-2007 IEEE Guide for Detection, Mitigation, and Control of Concentric Neutral Corrosion in Medium-Voltage Underground Cables 6 6.36.46.56.6Soil corrosion Soils of different composition will cause different rates of corrosion to occur on copper neutral wires. In addition to certain soil types bei
42、ng more corrosive than others, corrosion can also be promoted by the potential differences that exist when the cable passes through two different soil types. Copper is more susceptible to corrosion in acidic soils, such as those containing cinders. Resistivity measurements provide a measure of the r
43、elative corrosivity of different soil types. Differential aeration Similar to different soil types causing corrosion, differences in the soil oxygen content contacting the surface of the copper neutral wires can result in potential differences. For example, a bare cable passing from a clay soil of p
44、oor aeration into a gravel soil of greater aeration will form a differential aeration corrosion cell, with the soil of low oxygen content becoming anodic. Similarly, water that migrates through jacket defects will also tend to form differential aeration cells in contact with the copper neutral wires
45、, since there will be less oxygen present in the occluded area under the jacket compared with the surrounding soil outside of the cable jacket. Another common situation that causes differential aeration is where a cable goes into a conduit for a short run (such as under a street) and where the cable
46、 runs through a puddle of water caused by a low spot in the conduit. Differential aeration is also the root cause of the mechanism known as crevice corrosion. Unintended or stray electrical currents Stray electrical currents, which are typically from proximate dc sources such as welding generators,
47、impressed current cathodic protection systems operating on adjacent foreign structures, transit systems, and so on, can be picked up on the copper neutral wires. The location where the dc currents discharge from the cable will be anodic. Compared with dc, the discharge of stray or circulating ac cur
48、rents from the neutral wires has typically not been considered. However, ac corrosion can be a very serious concern for buried cables where high current densities may be present in the neutral wires, such as feeder cables or heavily loaded URD circuits. Current densities above 1.5 mA/cm2can result i
49、n rapid deterioration of metallic neutral wires since the passage of ac current between the earth and the metallic neutral wires shifts the potential to earth of these wires. Where the ac current density varies along the cable route, the related shifts in potential produce a long-line corrosion cell. Those areas where the potential is shifted more negatively are anodic to those areas where the potential is shifted less negatively. Rapid deterioration of the neutral wires may result. The coating of concentric neutral wires Under normal conditions, tin is anodic to cop
