IEEE 442-1981 en Guide for Soil Thermal Resistivity Measurements《土壤耐热性测量指南》.pdf

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1、 IEEE Std 442-1981(reaffirmed 2003)IEEE Guide for Soil Thermal Resistivity MeasurementsSponsorInsulated Conductors Committeeof theIEEE Power Engineering SocietyReaffirmed 2003IEEE Standards BoardCopyright 1981 byThe Institute of Electrical and Electronics Engineers, Inc 345 East 47th Street, New Yor

2、k, NYNo part of this publication may be reproduced in any form, in an electronic retrieval system or otherwise, without theprior written permission of the publisher.IEEE Standards documents are developed within the Technical Committees of the IEEE Societies and the StandardsCoordinating Committees o

3、f the IEEE Standards Board. Members of the committees serve voluntarily and withoutcompensation. They are not necessarily members of the Institute. The standards developed within IEEE represent aconsensus of the broad expertise on the subject within the Institute as well as those activities outside

4、of IEEE whichhave 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 otherways to produce, test, measure, purchase, market, or provide other goods and services relat

5、ed to the scope of the IEEEStandard. Furthermore, the viewpoint expressed at the time a standard is approved and issued is subject to changebrought about through developments in the state of the art and comments received from users of the standard. EveryIEEE Standard is subjected to review at least

6、once every five years for revision or reaffirmation. When a document ismore than five years old, and has not been reaffirmed, it is reasonable to conclude that its contents, although still ofsome value, do not wholly reflect the present state of the art. Users are cautioned to check to determine tha

7、t they havethe latest edition of any IEEE Standard.Comments for revision of IEEE Standards are welcome from any interested party, regardless of membership affiliationwith IEEE. Suggestions for changes in documents should be in the form of a proposed change of text, together withappropriate supportin

8、g comments.Interpretations: Occasionally questions may arise regarding the meaning of portions of standards as they relate tospecific applications. When the need for interpretations is brought to the attention of IEEE, the Institute will initiateaction to prepare appropriate responses. Since IEEE St

9、andards represent a consensus of all concerned interests, it isimportant to ensure that any interpretation has also received the concurrence of a balance of interests. For this reasonIEEE and the members of its technical committees are not able to provide an instant response to interpretation reques

10、tsexcept 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 Board345 East 47th StreetNew York, NY 10017USAiiiForeword(This Foreword is not a part of IEEE Std 442-1981, IE

11、EE Guide for Soil Thermal Resistivity Measurements.)Throughout the years, many utilities, consultants, and testing firms have measured soil thermal resistivity both in situand in the laboratory on selected soil samples. Such measurements have utilized various types of equipment andmeasurement techni

12、ques. In many cases, these testing methods have yielded inaccurate or inconsistent measurementsof soil thermal resistivity. This has been attributed to the unavailability of commercial testing equipment and the lackof standardization associated with the measurements.The Insulated Conductors Committe

13、e, recognizing the need for industry guidelines for the measurement of soilthermal resistivity, organized a working group of Subcommittee 12, Tests and Measurements, to write this neededguide. During the preparation of this guide, members of the working group made many round-robin tests andmeasureme

14、nts on selected soil samples. The expertise developed during these tests is reflected in many parts of thisguide.The IEEE will maintain this guide current with changes in the state of technology. However, comments or suggestionsfor additions are invited on this guide. These should be addressed to:Se

15、cretaryIEEE Standards CommitteeInstitute of Electrical and Electronics Engineers, Inc345 East 47th StreetNew York, NY 10017USAThe membership and individuals contributing to the writing of this guide and the performance of the round-robin testsconsisted of the following:M. A. Martin, Jr, Chair Mr. A.

16、 F. BaljetMr. R. A. BushMr. D. ClarkeMr. J. R. EasterlingMr. M. L. FengerMr. S. W. MargolinMr. J. J. RueckertMr. J. StolpeDr. W. W. WelnaAt the tune this guide was approved the members of the Test and Measurements Subcommittee were:T. A. Balaska, Chair C. F. AckermanE. M. AllamA.M. AubreyA. T. Baker

17、 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. Duffy G. S. Eager N. W. Edgerton R. M. Eichorn A. Fitspatrick E. O. Forster R.W. Foste

18、r 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. Howard H. I. Jehan C. V. Johnson R. J. Kasper ivL. J. Kelly W. B. KenyonF. KimseyM. Kopch

19、ik, JrJ. R. KushnerF. E. LaFetraA. F. LaScalaJ. S. LaskyR. H. LeeR. E. LeuchT. H. LingR. LukacG. E. LuskR. LutherE. A. MacKenzieM. A. Martin, JrI. J. MarwickE. J. McGowanA. L. McKeanM. I. F. MonzonC. E. MuhlemanJ. H. NicholasM. G. NobleH. OrtonJ. J. Pachot A. S. Paniri W. M. Pate J. R. Perkins K. A.

20、 Petty C. A. Pieroni J. S. Pirrong J. O. Punderson J. G. Quin P. H. Reynolds N. M. Sacks C. Saldivar D. Sandwick yE. L. Sankey A. Sansores G.W. Seman J. J. Shortall N. Singh H. B. Slade D. E. Soffrin N. Srinivas W. T. Starr J. L. Steiner R. Thayer K. TomoriR. T. TrautP. D. TuttleJ. R. TuzinskiC. F.

21、von HermannJ. F. WagnerE. M. WaltonR. H. W. WatkinsW. D. WilkensO. L. WillisP. J. WilsonR.T. ZukowskiWhen the IEEE Standards Board approved this standard on March 5, 1981, it had the following membership:I. N. Howell, Jr, Chair Irving Kolodny, Vice Chair Sava I. Sherr, Secretary G. Y. R. Allen J. H.

22、 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. Michael *F. RosaR.W. SeelbachJ.S. StewartW.E. VannahVirginius N. Vaughan, JrArt WallRobert E. Weiler* Member emeritusvCLAUSE PAGE1. Sc

23、ope.12. Purpose13. References.14. Factors Influencing Soil Thermal Resistivity .24.1 Factors Influencing Measurements 24.2 Factors Influencing Application of Measured Soil Thermal Resistivity . 35. Test Equipment .35.1 Equipment Required for Field Measurements . 45.2 Equipment Required for Laborator

24、y Measurements 56. Test Methods.56.1 Methods for Field Measurements 56.2 Methods for Laboratory Measurements. 67. Analysis of Test Results77.1 Sample Calculation 77.2 Interpretation of Results. 8Annex A Field Needle (Informative) 10Annex B Laboratory Needle (Informative).11Annex C Slide Hammer Assem

25、bly (Informative).12Annex D Miniature Needle Data Sheet (Informative) 13Copyright 1998 IEEE All Rights Reserved1IEEE Guide for Soil Thermal Resistivity Measurements1. ScopeThis guide covers the measurement of soil thermal resistivity. A thorough knowledge of the thermal properties of a soilwill enab

26、le the user to properly install and load underground cables. The method used is based on the theory that therate of temperature rise of a line heat source is dependent upon the thermal constants of the medium in which it isplaced. The designs for both laboratory and field thermal needles are also de

27、scribed in this guide.2. PurposeThe purpose of this guide is to provide sufficient information to enable the user to select useful commercial testequipment, or to manufacture equipment which is not readily available on the market, and to make meaningfulresistivity measurements with this equipment. M

28、easurements may be made in the field or in the laboratory on soilsamples or both.If the native soil is to be tamped back into the trench at the same density at which it was removed, it may be desirableto make in-situ resistivity measurements along the route of the cable.If the native soil is to be p

29、laced in the trench at a density different than undisturbed soil in the same vicinity, laboratorymeasurements are required on soil samples recompacted to the desired density.In order to draw meaningful comparisons on selected foreign backfill materials, thermal resistivity measurementsshould be made

30、 in the laboratory on soils which are compacted so as to provide maximum dry densities.3. References1 ANSI/ASTM D 698-78, Standard Test Methods for Moisture-Density Relations of Soils and Soil-AggregateMixtures Using 5.5 lb (2.49 kg) Rammer and 12 in (305 mm) Drop12 ANSI/ASTM D 1557-78, Standard Tes

31、t Methods for Moisture-Density Relations of Soils and Soil-AggregateMixtures Using 10 lb (4.54 kg) Rammer and 18 in (457 mm) Drop1ANSI documents are available from The American National Standards Institute, 1430 Broadway, New York, NY 10018.2Copyright 1998 IEEE All Rights ReservedIEEE Std 442-1981 I

32、EEE GUIDE FOR SOIL THERMAL3 ANSI/ASTM D 2049-69, Standard Test Method for Relative Density of Cohesionless Soils4 MANTEL, C. L. Engineering Materials Handbook, First ed. McGraw-Hill, 19584. Factors Influencing Soil Thermal ResistivityThe thermal resistivity of soft depends on the type of soil encoun

33、tered as well as the physical conditions of the soft.The conditions which most influence the resistivity of a specific soil are the moisture content and dry density. As themoisture content or dry density or both of a soil increases, the resistivity decreases. The structural composition of thesoil al

34、so affects the resistivity. The shape of the soil particles determines the surface contact area between particleswhich 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 w

35、ith the lowest thermal resistivity has a maximum amountof soil grains and water. It also has a minimum amount of air.4.1 Factors Influencing MeasurementsDuring the measurement of soil thermal resistivity, the following factors may adversely affect the accuracy of the testmeasurement.Migration of the

36、 soil moisture away from the needle during the test can result in higher or lower resistivitymeasurements. This migration may be significant, and normally takes place when the input power per unit area of theneedle is too high. Moisture migration associated with preliminary mass transfer may lower r

37、esistivity measurementswhen initial soil moisture content is less than 5% in some soils, particularly sands. Moisture migration can take placetoward the end of the test resulting in increasing the apparent soil thermal resistivity.Laboratory measurements of soil thermal resistivity may be affected b

38、y the redistribution of moisture due to gravity.If gravity induced moisture redistribution takes place during the measurement, the resistivity measurement normallygoes up. The error can be significant if the resistivity is sensitive to the change in moisture content at the dry soildensity selected f

39、or the test.Soil Material ()(Ccm/W)Quartz Grains 11Granite Grains 26Limestone Grains 45Sandstone Grains 58Mica Grains 170Water 165Organic 400 Wet 700 DryAir 4000Copyright 1998 IEEE All Rights Reserved3RESISTIVITY MEASUREMENTS IEEE Std 442-1981Power supply stability must be maintained throughout the

40、test. The power dissipated in the needle must be controlledso that variation in the magnitude of heat flux is kept within 1%.Under certain circumstances the in-situ resistivity measured using the field needle may vary from one soil depth to thenext. If the surface contact area between the needle and

41、 the soil is decreased due to improper installation of the needle,the measured resistivity would be high. When a local nonhomogeneous material, such as a large rock, is present in thevicinity of any of the thermocouples located in the field needle, a misleading resistivity will be measured. Also, if

42、 soillayers are present which have different soil thermal resistivities, the field needle should be inserted so that thethermocouples 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 determi

43、ned by taking core samples at various depths.4.2 Factors Influencing Application of Measured Soil Thermal ResistivityThe temperature rise of buried cables is directly dependent on the resistivity of the adjacent soil. The soil resistivityvalue that is used for temperature rise calculations is normal

44、ly derived from soil thermal resistivity measurements. Thein-situ resistivity of a soil changes from season to season, due to changes in the moisture content of the soil or due tothe relocation of the water table. It is important to consider these factors when determining a resistivity value forampa

45、city calculations.Another major factor that must be considered while utilizing measured resistivity values is the phenomenon ofmoisture migration and possible soil thermal runaway, therefore, soil thermal stability must be considered.The moisture migration process begins when a temperature gradient

46、is imposed across the soil. This temperaturegradient will cause a water vapor pressure gradient to develop, resulting in moisture migration away from the heatsource. If the soil is stable, equilibrium is maintained by moisture moving back toward the cable due to capillaryaction. If unstable conditio

47、ns exist, the moisture movement due to the vapor pressure gradient predominates, causinglocal drying of the soil near the cable. As the soil dries, the thermal resistivity of the soil increases resulting in anincreased temperature gradient across the soil. This condition causes the vapor pressure gr

48、adient to increase resultingin more moisture migration away from the cable. This leads to thermal runaway conditions which may result in thedestruction of the cable due to excessively high temperatures.In the past, cables have been rated based on maximum cable-earth interface temperature limits to m

49、inimize the risk ofexcessive soil moisture migration. Research work recently reported in the literature indicates that maximum interfacetemperature should not be employed in rating buried cables, as heat generated is the controlling factor associated withinducing soil moisture migration.5. Test EquipmentFigure 1 is a schematic of the system required to measure thermal resistivity in the laboratory or in the field. Theequipment for the two techniques differs primarily in the size of the needle and the portability requirements of thedevices used in the field as shown