1、Designation: D 924 08Standard Test Method forDissipation Factor (or Power Factor) and RelativePermittivity (Dielectric Constant) of Electrical InsulatingLiquids1This standard is issued under the fixed designation D 924; the number immediately following the designation indicates the year oforiginal a
2、doption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the Department of Defense.
3、1. Scope1.1 This test method describes testing of new electricalinsulating liquids as well as liquids in service or subsequent toservice in cables, transformers, oil circuit breakers, and otherelectrical apparatus.1.2 This test method provides a procedure for makingreferee tests at a commercial freq
4、uency of between 45 and 65Hz.1.3 Where it is desired to make routine determinationsrequiring less accuracy, certain modifications to this testmethod are permitted as described in Sections 16 to 24.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its us
5、e. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and to determine theapplicability of regulatory limitations prior to use. Specificwarnings are given in 11.3.3.1.5 Mercury has been designated by the EPA and many stateagencies as a hazardou
6、s material that can cause nervoussystem, kidney and liver damage. Mercury, or its vapor, may behazardous to health and corrosive to materials. Caution shouldbe taken when handling mercury and mercury containingproducts. See the applicable product Material Safety DataSheet (MSDS) for details and the
7、EPAs website: http:/www.epa.gov/mercury/faq.htm for additional information. Us-ers should be aware that selling mercury and/or mercurycontaining products into your state may be prohibited by statelaw.2. Referenced Documents2.1 ASTM Standards:2D 150 Test Methods for AC Loss Characteristics and Per-mi
8、ttivity (Dielectric Constant) of Solid Electrical Insulat-ing MaterialsD 923 Practices for Sampling Electrical Insulating LiquidsD 2864 Terminology Relating to Electrical Insulating Liq-uids and GasesD 2865 Practice for Calibration of Standards and Equip-ment for Electrical Insulating Materials Test
9、ingE 691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method2.2 IEEE Standard:Standard 4 IEEE Standard Techniques for High-VoltageTesting33. Terminology3.1 DefinitionsDefinitions of terms used in this testmethod are given in Terminology D 2864. Also refer to T
10、estMethods D 150 for detailed discussion of terms.4. Significance and Use4.1 Dissipation Factor (or Power Factor)This is a mea-sure of the dielectric losses in an electrical insulating liquidwhen used in an alternating electric field and of the energydissipated as heat. A low dissipation factor or p
11、ower factorindicates low ac dielectric losses. Dissipation factor or powerfactor may be useful as a means of quality control, and as anindication of changes in quality resulting from contaminationand deterioration in service or as a result of handling.4.1.1 The loss characteristic is commonly measur
12、ed interms of dissipation factor (tangent of the loss angle) or ofpower factor (sine of the loss angle) and may be expressed asa decimal value or as a percentage. For decimal values up to0.05, dissipation factor and power factor values are equal toeach other within about one part in one thousand. In
13、 general,since the dissipation factor or power factor of insulating oils ingood condition have decimal values below 0.005, the twomeasurements (terms) may be considered interchangeable.1This test method is under the jurisdiction of ASTM Committee D27 onElectrical Insulating Liquids and Gases and is
14、the direct responsibility of Subcom-mittee D27.05 on Electrical Test.Current edition approved Nov. 1, 2008. Published December 2008. Originallyapproved in 1947 as D 924 47 T. Last previous edition approved in 2004 asD 924 04.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcon
15、tact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Available from Institute of Electrical and Electronic Engineers, 445 Hoes Lane,Piscataway, NJ 08854.1Copyright ASTM International, 100
16、Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.4.1.2 The exact relationship between dissipation factor (D)and power factor (PF) is given by the following equations:PF 5D=1 1 D2D 5PF=12PF!2(1)The reported value of D or PF may be expressed as adecimal value or as a per
17、centage. For example:D or PF at 25C 5 0.002 or 0.2% (2)4.2 Relative Permittivity (Dielectric Constant)Insulatingliquids are used in general either to insulate components of anelectrical network from each other and from ground, alone orin combination with solid insulating materials, or to function as
18、the dielectric of a capacitor. For the first use, a low value ofrelative permittivity is often desirable in order to have thecapacitance be as small as possible, consistent with acceptablechemical and heat transfer properties. However, an intermedi-ate value of relative permittivity may sometimes be
19、 advanta-geous in achieving a better voltage distribution of a-c electricfields between the liquid and solid insulating materials withwhich the liquid may be in series. When used as the dielectricin a capacitor, it is desirable to have a higher value of relativepermittivity so the physical size of t
20、he capacitor may be assmall as possible.4.3 Theory relating to dielectric measurement techniquesand to sources of dielectric loss is given in Test MethodsD 150.5. Sampling5.1 Sample electrical insulating liquids in accordance withPractices D 923. Samples to be subjected to this test shouldpreferably
21、 be obtained through a closed system. If exposed toatmospheric conditions, it is preferable to take the samplewhen the relative humidity is 50 % or less. If it is not feasible,the length of time the sample is exposed to atmosphericconditions must be kept to a minimum.5.2 Some liquids, in certain app
22、lications, require specialhandling and processes in the sampling, and these will befound in the governing procedures. Consult such proceduresbefore samples are taken.5.3 The quantity of sample taken for this test shall besufficient for at least three separate determinations of losscharacteristics an
23、d relative permittivity.5.4 The loss characteristic measurement (dissipation factoror power factor) may be affected by contamination introducedduring sampling and subsequent handling.PROCEDURE FOR MAKING REFEREE TESTS6. Apparatus6.1 Measuring equipment used in these procedures shall bein accordance
24、with Test Methods D 150.6.2 Use only a three-terminal cell for these tests.6.3 The design of test cells that conform to the generalrequirements given in theAnnex are considered suitable for usein making these tests.6.4 Forced-Draft Oven:6.4.1 When the tests are to be made above room tempera-ture, a
25、suitable forced-draft, thermostatically controlled ovenshall be used as the test chamber. The oven must be capable ofmeeting the temperature requirements set out in Section 11. Fortests at room temperature the unheated oven can be conve-niently used as the test chamber.6.4.2 Provide the test chamber
26、 with an opening in the wallthrough which two lengths of TFE-fluorocarbon-insulated (orsimilar) shielded cable pass to make electrical connection fromthe measuring equipment and high-voltage transformer, respec-tively, to the test cell. Use a perforated ceramic plate or disk toinsulate the test cell
27、 from the metal flooring of the oven if theflooring is not insulated from the oven. Provide a safetyinterlock on the door of the oven so that the electrical circuitsupplying voltage to the test cell will be broken when the ovendoor is opened.6.4.3 A cross-sectional view of the test chamber with athr
28、ee-electrode test cell in place and with test cables connectedis shown in Fig. 1.6.5 Automatic Thermo-Regulator Cell:6.5.1 When tests are to be made above room temperaturebut below the flash point, an automatic thermo-regulator cellcan be used as long as it provides uniform heating of the testcell.6
29、.5.2 The automatic thermo-regulator cell must be able toprovide rapid, controlled rate of temperature rise, and be ableto maintain a liquid temperature constant to within 61C.7. Calibration7.1 Calibration of test instruments shall be traceable tonational standards.7.2 Verify the calibration at least
30、 annually using referencedevices that are traceable to national standards.7.3 Refer to Practice D 2865 and IEEE Standard 4 forguidelines on calibrating test equipment.8. Test Temperature8.1 The temperature at which a referee test is made shall bemutually agreed upon between the purchaser and the sel
31、ler.Measurements are made at many different temperatures. Foracceptance tests, it is generally made at a temperature of100C, while for routine testing it is usually made at 25, 85 or100C. In some research investigations, tests may be made atconsiderably higher temperatures while in other cases, part
32、icu-larly for tests on cable oils in service, tests may be made overa range of temperatures.9. Test Voltage9.1 The average stress to which the specimen is subjectedshall not be less than 200 V/mm (5 V/mil) (rms). Tests at higherstresses are desirable but shall not reach such values thatelectrical di
33、scharges across the cell insulating surfaces occur orthat internal ionization of the specimen may be expected.Stress ranges in normal usage for referee tests are 200 to 1200V/mm (5 to 30 V/mil) (rms).9.2 Because the ac loss characteristics can vary with voltagestress, for reference purposes it is de
34、sirable to make themeasurements at a specific value of voltage stress within thelimits in 9.1.9.3 Referee tests should be carried out in the frequencyrange 4565 Hz.D92408210. Cleaning Test Cell10.1 The cleanliness of the test cell is of paramount impor-tance when measuring loss characteristics becau
35、se of theinherent susceptibility of most insulating liquids to contami-nating influences of the most minute nature. For this reason,clean and dry the cell immediately prior to making the test, andstrictly observe the procedures and precautions outlined in 10.2to 10.5.10.2 Dismantle the cell complete
36、ly and wash all the com-ponent parts thoroughly with a technical grade of a suitablesolvent (such as acetone, pentane, petroleum ether, or heptane).Wash the component parts with a mild abrasive soap ordetergent. Take care not to lay the electrodes on any surface.Rinse all parts thoroughly with hot t
37、ap water, then with cold tapwater, followed by several rinses with distilled water. Takeextreme care during the washing and rinsing of some test cellsto prevent any moisture from entering the thermometer well inthe inner electrode.As a precaution against this eventuality, usea suitable stopper to pl
38、ug this opening prior to starting thecleaning operation.10.3 After the surfaces of the measuring, guard, and highvoltage electrodes have been washed, do not touch thesesurfaces during the rinsing or any subsequent operation.10.4 Place the component parts of the test cell in an ovenmaintained at 110C
39、 for a period of not less than 60 min. Donot dry test cells made of Monel at this elevated temperaturefor more than 90 min as oxidation will take place causingerroneous results. Take care that the surfaces on which thecomponent parts of the cell are placed in the oven are clean.10.5 At the expiratio
40、n of the drying period, assemble thecell using clean cotton gloves as protection for the hands andto prevent contamination from skin oils and salt.11. Preparation of Specimen and Filling Test Cell11.1 Store the sample in its original sealed container,shielded from light. Some liquids, such as oils o
41、f petroleumorigin, undergo changes when exposed to sunlight. Allow thesealed container to stand undisturbed in the room in which thetest is to be made for a sufficient period of time to permit thesample to attain room temperature before it is opened.11.2 When insulating liquids are heated to elevate
42、d tem-peratures, some of their characteristics undergo a change withtime and the change, even though of the minutest nature, maybe reflected in the loss measurement. It is therefore desirablethat the elapsed time necessary for the test specimen to attaintemperature equilibrium with the test cell be
43、held to a mini-mum. For optimum procedure do not exceed 20 min for thistime. It is essential, therefore, that the procedures outlinedbelow be closely followed.11.3 Forced-Draft Oven:11.3.1 In order that representative test specimens may beobtained, gently tilt or invert the sample container and swir
44、l theliquid several times. Immediately after mixing the sample, poura quantity of liquid sufficient for four fillings of the test cellinto a chemically clean dry beaker and heat on a hot plate to atemperature 2C below the desired test temperature. Stir thefluid frequently during heating.11.3.2 Remov
45、e the cell from the test chamber, lift out theinner electrode, but do not rest it on any surface, and fill the cellwith a portion of the heated specimen. Replace the beaker withthe remainder of the heated sample on the hot plate. Insert theinner electrode and rinse the electrodes by twice raising an
46、dlowering the inner electrode. Remove the inner electrode andhold it suspended in air; then decant the rinsing liquid andimmediately fill the cell from the remainder of the heatedspecimen. Replace the inner electrode.FIG. 1 Test Set-Up for Dissipation Factor Measurements at Elevated Temperatures Usi
47、ng Three-Electrode Test CellD92408311.3.3 Insert a mercury thermometer graduated in 0.25Cincrements, or other temperature measuring devices (for ex-ample, thermocouples) that provide equal accuracy, in thethermometer well provided in the inner electrode(WarningA spring-loaded thermocouple may be use
48、d formeasuring the temperature of the inner electrode, but extremecaution shall be exercised that these wires do not come incontact with the high-voltage lead and do not pick up strayemfs). Immediately return the filled cell to the test chamber(adjusted to a temperature above the desired test temper
49、ature)and make the necessary electrical connections to the cell.11.3.4 Perform the operations described in 11.3.2 and 11.3.3as rapidly as possible.11.4 Automatic Thermo-Regulator Cell:11.4.1 Gently swirl or invert the sample container to obtaina representative test specimen.11.4.2 Fill the test cell and flush to rinse thoroughly both theinner and outer electrodes with a portion of the sample. Decantthe rinsing liquid and immediately fill the cell with a newaliquot of sample.11.4.3 Replace inner electrode and make all necessaryelectrical connections to the cell. On s
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