1、Designation: D924 08D924 15Standard Test Method forDissipation Factor (or Power Factor) and RelativePermittivity (Dielectric Constant) of Electrical InsulatingLiquids1This standard is issued under the fixed designation D924; the number immediately following the designation indicates the year oforigi
2、nal adoption 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 U.S. Department o
3、f Defense.1. Scope1.1 This test method describes testing of new electrical insulating liquids as well as liquids in service or subsequent to servicein cables, transformers, oil circuit breakers, and other electrical apparatus.1.2 This test method provides a procedure for making referee tests at a co
4、mmercial frequency of between 45 and 65 Hz.1.3 Where it is desired to make routine determinations requiring less accuracy, certain modifications to this test method arepermitted as described in Sections 16 to 24.1.4 The values stated in SI units are to be regarded as standard. No other units of meas
5、urement are included in this standard.1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety and health practices and to determine the applicability of regulatoryl
6、imitations prior to use. Specific warnings are given in 11.3.3.1.6 Mercury has been designated by the EPA and many state agencies as a hazardous material that can cause nervous system,kidney and liver damage. Mercury, or its vapor, may be hazardous to health and corrosive to materials. Caution shoul
7、d be takenwhen handling mercury and mercury containing products. See the applicable product Material Safety Data Sheet (MSDS) fordetails and the EPAs website: http:/www.epa.gov/mercury/faq.htm for additional information. Users should be aware that sellingmercury and/or mercury containing products in
8、to your state may be prohibited by state law.2. Referenced Documents2.1 ASTM Standards:2D150 Test Methods for AC Loss Characteristics and Permittivity (Dielectric Constant) of Solid Electrical InsulationD923 Practices for Sampling Electrical Insulating LiquidsD2864 Terminology Relating to Electrical
9、 Insulating Liquids and GasesD2865 Practice for Calibration of Standards and Equipment for Electrical Insulating Materials TestingE691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method2.2 IEEE Standard:Standard 4 IEEE Standard Techniques for High-Voltage Te
10、sting33. Terminology3.1 DefinitionsDefinitions of terms used in this test method are given in Terminology D2864.Also refer to Test Methods D150for detailed discussion of terms.D1504. Significance and Use4.1 Dissipation Factor (or Power Factor)This is a measure of the dielectric losses in an electric
11、al insulating liquid when usedin an alternating electric field and of the energy dissipated as heat. A low dissipation factor or power factor indicates low ac1 This test method is under the jurisdiction of ASTM Committee D27 on Electrical Insulating Liquids and Gases and is the direct responsibility
12、 of Subcommittee D27.05on Electrical Test.Current edition approved Nov. 1, 2008Oct. 1, 2015. Published December 2008November 2015. Originally approved in 1947 as D924 47 T. Last previous editionapproved in 20042008 as D924 04.D924 08. DOI: 10.1520/D0924-08.10.1520/D0924-15.2 For referencedASTM stand
13、ards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. ForAnnual Book ofASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.3 Available from Institute of Electrical and Electronic Engineers, 445 Hoes Lane, Piscata
14、way, NJ 08854.08854, www.ieee.org.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recom
15、mends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1dielectric los
16、ses. Dissipation factor or power factor may be useful as a means of quality control, and as an indication of changesin quality resulting from contamination and deterioration in service or as a result of handling.4.1.1 The loss characteristic is commonly measured in terms of dissipation factor (tange
17、nt of the loss angle) or of power factor(sine of the loss angle) and may be expressed as a decimal value or as a percentage. For decimal values up to 0.05, dissipationfactor and power factor values are equal to each other within about one part in one thousand. In general, since the dissipation facto
18、ror power factor of insulating oils in good condition have decimal values below 0.005, the two measurements (terms) may beconsidered interchangeable.4.1.2 The exact relationship between dissipation factor (D) and power factor (PF ) is given by the following equations:PF5 D=11D 2D 5 PF=12PF! 2(1)The
19、reported value of D or PF may be expressed as a decimal value or as a percentage. For example:D or PF at 25C 50.002 or 0.2% (2)4.2 Relative Permittivity (Dielectric Constant)Insulating liquids are used in general either to insulate components of anelectrical network from each other and from ground,
20、alone or in combination with solid insulating materials, or to function as thedielectric of a capacitor. For the first use, a low value of relative permittivity is often desirable in order to have the capacitancebe as small as possible, consistent with acceptable chemical and heat transfer propertie
21、s. However, an intermediate value of relativepermittivity may sometimes be advantageous in achieving a better voltage distribution of a-cac electric fields between the liquidand solid insulating materials with which the liquid may be in series. When used as the dielectric in a capacitor, it is desir
22、able tohave a higher value of relative permittivity so the physical size of the capacitor may be as small as possible.4.3 Theory relating to dielectric measurement techniques and to sources of dielectric loss is given in Test Methods D150.5. Sampling5.1 Sample electrical insulating liquids in accord
23、ance with Practices D923. Samples to be subjected to this test should preferablybe obtained through a closed system. If exposed to atmospheric conditions, it is preferable to take the sample when the relativehumidity is 50 % or less. If it is not feasible, the length of time the sample is exposed to
24、 atmospheric conditions must be kept toa minimum.5.2 Some liquids, in certain applications, require special handling and processes in the sampling, and these will be found in thegoverning procedures. Consult such procedures before samples are taken.5.3 The quantity of sample taken for this test shal
25、l be sufficient for at least three separate determinations of loss characteristicsand relative permittivity.5.4 The loss characteristic measurement (dissipation factor or power factor) may be affected by contamination introduced duringsampling and subsequent handling.PROCEDURE FOR MAKING REFEREE TES
26、TS6. Apparatus6.1 Measuring equipment used in these procedures shall be in accordance with Test Methods D150.6.2 Use only a three-terminal cell for these tests.6.3 The design of test cells that conform to the general requirements given in the Annex are considered suitable for use inmaking these test
27、s.6.4 Forced-Draft Oven:6.4.1 When the tests are to be made above room temperature, a suitable forced-draft, thermostatically controlled oven shall beused as the test chamber. The oven must be capable of meeting the temperature requirements set out in Section 11. For tests atroom temperature the unh
28、eated oven can be conveniently used as the test chamber.6.4.2 Provide the test chamber with an opening in the wall through which two lengths of TFE-fluorocarbon-insulated (orsimilar) shielded cable pass to make electrical connection from the measuring equipment and high-voltage transformer,respectiv
29、ely, to the test cell. Use a perforated ceramic plate or disk to insulate the test cell from the metal flooring of the oven ifthe flooring is not insulated from the oven. Provide a safety interlock on the door of the oven so that the electrical circuit supplyingvoltage to the test cell will be broke
30、n when the oven door is opened.6.4.3 Across-sectional view of the test chamber with a three-electrode test cell in place and with test cables connected is shownin Fig. 1.6.5 Automatic Thermo-Regulator Cell:6.5.1 When tests are to be made above room temperature but below the flash point, an automatic
31、 thermo-regulator cell can beused as long as it provides uniform heating of the test cell.D924 1526.5.2 The automatic thermo-regulator cell must be able to provide rapid, controlled rate of temperature rise, and be able tomaintain a liquid temperature constant to within 61C.7. Calibration7.1 Calibra
32、tion of test instruments shall be traceable to national standards.7.2 Verify the calibration at least annually using reference devices that are traceable to national standards.7.3 Refer to Practice D2865 and IEEE Standard 4 for guidelines on calibrating test equipment.8. Test Temperature8.1 The temp
33、erature at which a referee test is made shall be mutually agreed upon between the purchaser and the seller.Measurements are made at many different temperatures. For acceptance tests, it is generally made at a temperature of 100C, whilefor routine testing it is usually made at 25, 8590 or 100C. In so
34、me research investigations, tests may be made at considerablyhigher temperatures while in other cases, particularly for tests on cable oils in service, tests may be made over a range oftemperatures.9. Test Voltage9.1 The average stress to which the specimen is subjected shall not be less than 200 V/
35、mm (5 V/mil) (rms). Tests at higherstresses are desirable but shall not reach such values that electrical discharges across the cell insulating surfaces occur or thatinternal ionization of the specimen may be expected. Stress ranges in normal usage for referee tests are 200 to 1200 V/mm (5 to30 V/mi
36、l) (rms).9.2 Because the ac loss characteristics can vary with voltage stress, for reference purposes it is desirable to make themeasurements at a specific value of voltage stress within the limits in 9.1.9.3 Referee tests should be carried out in the frequency range 4565 Hz.10. Cleaning Test Cell10
37、.1 The cleanliness of the test cell is of paramount importance when measuring loss characteristics because of the inherentsusceptibility of most insulating liquids to contaminating influences of the most minute nature. For this reason, clean and dry thecell immediately prior to making the test, and
38、strictly observe the procedures and precautions outlined in 10.2 to 10.5.10.2 Dismantle the cell completely and wash all the component parts thoroughly with a technical grade of a suitable solvent(such as acetone, pentane, petroleum ether, or heptane). Wash the component parts with a mild abrasive s
39、oap or detergent. Takecare not to lay the electrodes on any surface. Rinse all parts thoroughly with hot tap water, then with cold tap water, followed byseveral rinses with distilled water. Take extreme care during the washing and rinsing of some test cells to prevent any moistureFIG. 1 Test Set-Up
40、for Dissipation Factor Measurements at Elevated Temperatures Using Three-Electrode Test CellD924 153from entering the thermometer well in the inner electrode. As a precaution against this eventuality, use a suitable stopper to plugthis opening prior to starting the cleaning operation.10.3 After the
41、surfaces of the measuring, guard, and high voltage electrodes have been washed, do not touch these surfacesduring the rinsing or any subsequent operation.10.4 Place the component parts of the test cell in an oven maintained at 110C for a period of not less than 60 min. Do not drytest cells made of M
42、onel at this elevated temperature for more than 90 min as oxidation will take place causing erroneous results.Take care that the surfaces on which the component parts of the cell are placed in the oven are clean.10.5 At the expiration of the drying period, assemble the cell using clean cotton gloves
43、 as protection for the hands and to preventcontamination 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 of petroleum origin,undergo changes when exposed to sunlight. Allo
44、w the sealed container to stand undisturbed in the room in which the test is to bemade for a sufficient period of time to permit the sample to attain room temperature before it is opened.11.2 When insulating liquids are heated to elevated temperatures, some of their characteristics undergo a change
45、with time andthe change, even though of the minutest nature, may be reflected in the loss measurement. It is therefore desirable that the elapsedtime necessary for the test specimen to attain temperature equilibrium with the test cell be held to a minimum. For optimumprocedure do not exceed 20 min f
46、or this time. It is essential, therefore, that the procedures outlined below be closely followed.11.3 Forced-Draft Oven:11.3.1 In order that representative test specimens may be obtained, gently tilt or invert the sample container and swirl the liquidseveral times. Immediately after mixing the sampl
47、e, pour a quantity of liquid sufficient for four fillings of the test cell into achemically clean dry beaker and heat on a hot plate to a temperature 2C below the desired test temperature. Stir the fluidfrequently during heating.11.3.2 Remove the cell from the test chamber, lift out the inner electr
48、ode, but do not rest it on any surface, and fill the cell witha portion of the heated specimen. Replace the beaker with the remainder of the heated sample on the hot plate. Insert the innerelectrode and rinse the electrodes by twice raising and lowering the inner electrode. Remove the inner electrod
49、e and hold itsuspended in air; then decant the rinsing liquid and immediately fill the cell from the remainder of the heated specimen. Replacethe inner electrode.11.3.3 Insert a mercury thermometer graduated in 0.25C increments, or other temperature measuring devices (for example,thermocouples) that provide equal accuracy, in the thermometer well provided in the inner electrode (WarningA spring-loadedthermocouple may be used for measuring the temperature of the inner electrode, but extreme caution shall be exercised that thesewires do not come in contact with
