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1、 IEEE Std 442-1981 (reaffirmed 2003) IEEE Guide for Soil Thermal Resistivity Measurements Sponsor Insulated Conductors Committee of the IEEE Power Engineering Society Reaffirmed 2003 IEEE Standards Board Copyright 1981 by The Institute of Electrical and Electronics Engineers, Inc 345 East 47th Stree
2、t, New York, NY No part of this publication may be reproduced in any form, in an electronic retrieval system or otherwise, without the prior written permission of the publisher. IEEE Standards documents are developed within the Technical Committees of the IEEE Societies and the Standards Coordinatin
3、g Committees of the IEEE Standards Board. Members of the committees serve voluntarily and without compensation. They are not necessarily members of the Institute. The standards developed within IEEE represent a consensus of the broad expertise on the subject within the Institute as well as those act
4、ivities outside of IEEE which have expressed an interest in participating in the development of the standard. Use of an IEEE Standard is wholly voluntary. The existence of an IEEE Standard does not imply that there are no other ways to produce, test, measure, purchase, market, or provide other goods
5、 and services related to the scope of the IEEE Standard. Furthermore, the viewpoint expressed at the time a standard is approved and issued is subject to change brought about through developments in the state of the art and comments received from users of the standard. Every IEEE Standard is subject
6、ed to review at least once every fi ve years for revision or reaffi rmation. When a document is more than fi ve years old, and has not been reaffi rmed, it is reasonable to conclude that its contents, although still of some value, do not wholly refl ect the present state of the art. Users are cautio
7、ned to check to determine that they have the latest edition of any IEEE Standard. Comments for revision of IEEE Standards are welcome from any interested party, regardless of membership affi liation with IEEE. Suggestions for changes in documents should be in the form of a proposed change of text, t
8、ogether with appropriate supporting comments. Interpretations: Occasionally questions may arise regarding the meaning of portions of standards as they relate to specifi c applications. When the need for interpretations is brought to the attention of IEEE, the Institute will initiate action to prepar
9、e appropriate responses. Since IEEE Standards represent a consensus of all concerned interests, it is important to ensure that any interpretation has also received the concurrence of a balance of interests. For this reason IEEE and the members of its technical committees are not able to provide an i
10、nstant response to interpretation requests except in those cases where the matter has previously received formal consideration. Comments on standards and requests for interpretations should be addressed to: Secretary, IEEE Standards Board 345 East 47th Street New York, NY 10017 USA iii Foreword (Thi
11、s Foreword is not a part of IEEE Std 442-1981, IEEE Guide for Soil Thermal Resistivity Measurements.) Throughout the years, many utilities, consultants, and testing fi rms have measured soil thermal resistivity both in situ and in the laboratory on selected soil samples. Such measurements have utili
12、zed various types of equipment and measurement techniques. In many cases, these testing methods have yielded inaccurate or inconsistent measurements of soil thermal resistivity. This has been attributed to the unavailability of commercial testing equipment and the lack of standardization associated
13、with the measurements. The Insulated Conductors Committee, recognizing the need for industry guidelines for the measurement of soil thermal resistivity, organized a working group of Subcommittee 12, Tests and Measurements, to write this needed guide. During the preparation of this guide, members of
14、the working group made many round-robin tests and measurements on selected soil samples. The expertise developed during these tests is refl ected in many parts of this guide. The IEEE will maintain this guide current with changes in the state of technology. However, comments or suggestions for addit
15、ions are invited on this guide. These should be addressed to: Secretary IEEE Standards Committee Institute of Electrical and Electronics Engineers, Inc 345 East 47th Street New York, NY 10017 USA The membership and individuals contributing to the writing of this guide and the performance of the roun
16、d-robin tests consisted of the following: M. A. Martin, Jr , Chair Mr. A. F. Baljet Mr. R. A. Bush Mr. D. Clarke Mr. J. R. Easterling Mr. M. L. Fenger Mr. S. W. Margolin Mr. J. J. Rueckert Mr. J. Stolpe Dr. W. W. Welna At the tune this guide was approved the members of the Test and Measurements Subc
17、ommittee were: T. A. Balaska , Chair C. F. Ackerman E. M. Allam A.M. Aubrey A. T. Baker A. F. Baljet R. Bartnikas E. W. Bennett C. W. Baldes L. A. Bondon J. A. Bradley R. A. Burkhardt M. D. Calcumuggio P. Chowdhuri W. Cole J. E. Conley W. F. Constantine J. N. Cooper F. V. Cunningham J. Densley E. K.
18、 Duffy G. S. Eager N. W. Edgerton R. M. Eichorn A. Fitspatrick E. O. Forster R.W. Foster R. D. Fulcomer J. B. Gardner J. Garland A. Garschick D. W. Gasda S. Gerhard W.R. Goldbach O.K. Gratzol R. A. Guba L. F. Hamilton C. A. Hatstat J. G. C. Henderson W. J. Herbert V. Herter H. C. Hervig, Jr R. R. Ho
19、ward H. I. Jehan C. V. Johnson R. J. Kasper iv L. J. Kelly W. B. Kenyon F. Kimsey M. Kopchik, Jr J. R. Kushner F. E. LaFetra A. F. LaScala J. S. Lasky R. H. Lee R. E. Leuch T. H. Ling R. Lukac G. E. Lusk R. Luther E. A. MacKenzie M. A. Martin, Jr I. J. Marwick E. J. McGowan A. L. McKean M. I. F. Mon
20、zon C. E. Muhleman J. H. Nicholas M. G. Noble H. Orton J. J. Pachot A. S. Paniri W. M. Pate J. R. Perkins K. A. Petty C. A. Pieroni J. S. Pirrong J. O. Punderson J. G. Quin P. H. Reynolds N. M. Sacks C. Saldivar D. Sandwick y E. L. Sankey A. Sansores G.W. Seman J. J. Shortall N. Singh H. B. Slade D.
21、 E. Soffrin N. Srinivas W. T. Starr J. L. Steiner R. Thayer K. Tomori R. T. Traut P. D. Tuttle J. R. Tuzinski C. F. von Hermann J. F. Wagner E. M. Walton R. H. W. Watkins W. D. Wilkens O. L. Willis P. J. Wilson R.T. Zukowski When the IEEE Standards Board approved this standard on March 5, 1981, it h
22、ad the following membership: I. N. Howell, Jr , Chair Irving Kolodny , Vice Chair Sava I. Sherr , Secretary G. Y. R. Allen J. H. Beall J. T. Boettger Edward Chelotti Edward J. Cohen Warren H. Cook Len S. Corey Jay Forster Kurt Greene Loering M. Johnson Joseph L. Koepfinger J. E. May Donald T. Michae
23、l * F. Rosa R.W. Seelbach J.S. Stewart W.E. Vannah Virginius N. Vaughan, Jr Art Wall Robert E. Weiler * Member emeritus -,-,- v CLAUSEPAGE 1. Scope.1 2. Purpose1 3. References.1 4. Factors Influencing Soil Thermal Resistivity .2 4.1 Factors Influencing Measurements 2 4.2 Factors Influencing Applicat
24、ion of Measured Soil Thermal Resistivity . 3 5. Test Equipment.3 5.1 Equipment Required for Field Measurements. 4 5.2 Equipment Required for Laboratory Measurements 5 6. Test Methods.5 6.1 Methods for Field Measurements 5 6.2 Methods for Laboratory Measurements. 6 7. Analysis of Test Results7 7.1 Sa
25、mple Calculation 7 7.2 Interpretation of Results. 8 Annex A Field Needle (Informative)10 Annex B Laboratory Needle (Informative).11 Annex C Slide Hammer Assembly (Informative).12 Annex D Miniature Needle Data Sheet (Informative)13 -,-,- Copyright 1998 IEEE All Rights Reserved 1 IEEE Guide for Soil T
26、hermal Resistivity Measurements 1. Scope This guide covers the measurement of soil thermal resistivity. A thorough knowledge of the thermal properties of a soil will enable the user to properly install and load underground cables. The method used is based on the theory that the rate of temperature r
27、ise of a line heat source is dependent upon the thermal constants of the medium in which it is placed. The designs for both laboratory and fi eld thermal needles are also described in this guide. 2. Purpose The purpose of this guide is to provide suffi cient information to enable the user to select
28、useful commercial test equipment, or to manufacture equipment which is not readily available on the market, and to make meaningful resistivity measurements with this equipment. Measurements may be made in the fi eld or in the laboratory on soil samples or both. If the native soil is to be tamped bac
29、k into the trench at the same density at which it was removed, it may be desirable to make in-situ resistivity measurements along the route of the cable. If the native soil is to be placed in the trench at a density different than undisturbed soil in the same vicinity, laboratory measurements are re
30、quired on soil samples recompacted to the desired density. In order to draw meaningful comparisons on selected foreign backfi ll materials, thermal resistivity measurements should be made in the laboratory on soils which are compacted so as to provide maximum dry densities. 3. References 1 ANSI/ASTM
31、 D 698-78, Standard Test Methods for Moisture-Density Relations of Soils and Soil-Aggregate Mixtures Using 5.5 lb (2.49 kg) Rammer and 12 in (305 mm) Drop 1 2 ANSI/ASTM D 1557-78, Standard Test Methods for Moisture-Density Relations of Soils and Soil-Aggregate Mixtures Using 10 lb (4.54 kg) Rammer a
32、nd 18 in (457 mm) Drop 1 ANSI documents are available from The American National Standards Institute, 1430 Broadway, New York, NY 10018. -,-,- 2 Copyright 1998 IEEE All Rights Reserved IEEE Std 442-1981IEEE GUIDE FOR SOIL THERMAL 3 ANSI/ASTM D 2049-69, Standard Test Method for Relative Density of Co
33、hesionless Soils 4 MANTEL, C. L. Engineering Materials Handbook, First ed. McGraw-Hill, 1958 4. Factors Influencing Soil Thermal Resistivity The thermal resistivity of soft depends on the type of soil encountered as well as the physical conditions of the soft. The conditions which most infl uence th
34、e resistivity of a specifi c soil are the moisture content and dry density. As the moisture content or dry density or both of a soil increases, the resistivity decreases. The structural composition of the soil also affects the resistivity. The shape of the soil particles determines the surface conta
35、ct area between particles which affects the ability of the soil to conduct heat. The thermal resistivity ( ) of various soil materials are listed below: From the above list, one can generally conclude that the soil with the lowest thermal resistivity has a maximum amount of soil grains and water. It
36、 also has a minimum amount of air. 4.1 Factors Influencing Measurements During the measurement of soil thermal resistivity, the following factors may adversely affect the accuracy of the test measurement. Migration of the soil moisture away from the needle during the test can result in higher or low
37、er resistivity measurements. This migration may be signifi cant, and normally takes place when the input power per unit area of the needle is too high. Moisture migration associated with preliminary mass transfer may lower resistivity measurements when initial soil moisture content is less than 5% i
38、n some soils, particularly sands. Moisture migration can take place toward the end of the test resulting in increasing the apparent soil thermal resistivity. Laboratory measurements of soil thermal resistivity may be affected by the redistribution of moisture due to gravity. If gravity induced moist
39、ure redistribution takes place during the measurement, the resistivity measurement normally goes up. The error can be signifi cant if the resistivity is sensitive to the change in moisture content at the dry soil density selected for the test. Soil Material( )( Ccm/W) Quartz Grains11 Granite Grains2
40、6 Limestone Grains45 Sandstone Grains58 Mica Grains170 Water165 Organic400 Wet 700 Dry Air4000 Copyright 1998 IEEE All Rights Reserved 3 RESISTIVITY MEASUREMENTSIEEE Std 442-1981 Power supply stability must be maintained throughout the test. The power dissipated in the needle must be controlled so t
41、hat variation in the magnitude of heat fl ux is kept within 1%. Under certain circumstances the in-situ resistivity measured using the fi eld needle may vary from one soil depth to the next. If the surface contact area between the needle and the soil is decreased due to improper installation of the
42、needle, the measured resistivity would be high. When a local nonhomogeneous material, such as a large rock, is present in the vicinity of any of the thermocouples located in the fi eld needle, a misleading resistivity will be measured. Also, if soil layers are present which have different soil therm
43、al resistivities, the fi eld needle should be inserted so that the thermocouples are located at a distance 25 times the diameter of the needle away from the boundary layer of the soil. The location of different soil layers can be physically determined by taking core samples at various depths. 4.2 Fa
44、ctors Influencing Application of Measured Soil Thermal Resistivity The temperature rise of buried cables is directly dependent on the resistivity of the adjacent soil. The soil resistivity value that is used for temperature rise calculations is normally derived from soil thermal resistivity measurem
45、ents. The in-situ resistivity of a soil changes from season to season, due to changes in the moisture content of the soil or due to the relocation of the water table. It is important to consider these factors when determining a resistivity value for ampacity calculations. Another major factor that m
46、ust be considered while utilizing measured resistivity values is the phenomenon of moisture migration and possible soil thermal runaway, therefore, soil thermal stability must be considered. The moisture migration process begins when a temperature gradient is imposed across the soil. This temperatur
47、e gradient will cause a water vapor pressure gradient to develop, resulting in moisture migration away from the heat source. If the soil is stable, equilibrium is maintained by moisture moving back toward the cable due to capillary action. If unstable conditions exist, the moisture movement due to t
48、he vapor pressure gradient predominates, causing local drying of the soil near the cable. As the soil dries, the thermal resistivity of the soil increases resulting in an increased temperature gradient across the soil. This condition causes the vapor pressure gradient to increase resulting in more m
49、oisture migration away from the cable. This leads to thermal runaway conditions which may result in the destruction of the cable due to excessively high temperatures. In the past, cables have been rated based on maximum cable-earth interface temperature limits to minimize the risk of excessive soil moisture migration. Research work recently reported in the literature indicates that maximum interface temperature should not be employed in