ASTM D Standard Test Method for Dissipation Factor (or Power Factor) and Relative Permittivity (Dielectric Constant) of Electrical Insulating Liquids. Find the most up-to-date version of ASTM D at Engineering We perform testing by ASTM D on electrical insulating liquids used in cables, transformers, oil circuit breakers, and other electrical apparatus.
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D — 08 Standard Test Method for Dissipation Factor or Power Factor and Relative Permittivity Dielectric Constant of Electrical Insulating Liquids1 This standard is issued asttm the xed designation D ; the number immediately following the designation indicates the year of original adoption or, in the case of revision, the year of last revision.
A number in parentheses indicates the year of last reapproval. A superscript 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. It is the responsibility of the user of this standard to establish appropriate safety and health practices and to determine the applicability of regulatory limitations prior to use.
Specic warnings are given in Mercury, or its vapor, may be hazardous to health and corrosive to materials. Caution should be taken when handling mercury and mercury containing products.
Current edition approved Nov. Originally approved in as D — 47 T. Last previous edition approved in as D — Also refer to Test Methods D for detailed discussion of terms.
Signicance and Use 4. A low dissipation factor or power factor indicates low ac dielectric losses. Dissipation factor or power factor may be useful as a means of quality control, and as an indication of changes in quality resulting from contamination and deterioration in service or as a result of handling.
For decimal values up to 0. In general, since the dissipation factor or power factor of insulating oils in good condition have decimal values below 0. No further reproductions authorized.
For the rst use, a low value of relative permittivity is often desirable in order to have the capacitance be as s924 as possible, consistent with acceptable chemical and heat transfer properties. However, an intermediate value of relative permittivity may sometimes be advantageous in achieving a better voltage distribution of a-c electric elds between the liquid and solid insulating materials with which the liquid may be in series.
When used as the dielectric in a capacitor, it is desirable to have a higher value of relative permittivity so the physical size of the capacitor may be as small as possible.
Samples to be subjected to this test should preferably be obtained through a closed system. If it is not feasible, the length of time the sample is exposed to atmospheric conditions must be kept ast a minimum. Consult such procedures before samples are taken. The oven must be capable of meeting the temperature requirements set out in Section For tests at room temperature the unheated oven can be conveniently used as the test chamber.
Use a perforated ceramic plate or disk to insulate the test cell from the metal ooring of the oven if the ooring is not insulated from the oven.
Provide a safety interlock on the astj of the oven so that the electrical circuit supplying voltage to the test cell will be broken when the oven door is opened.
Measurements are made at many different temperatures. In some research investigations, tests may be made at considerably higher temperatures while in other cases, particularly for tests on cable oils in service, tests may be made over a range of temperatures. Tests at higher stresses are desirable but shall not reach such values that electrical discharges across the cell insulating surfaces occur or that x924 ionization of the specimen may be expected.
D — 08 FIG. Cleaning Test Cell For this reason, clean and dry the cell immediately prior to making the test, and strictly observe the procedures and precautions outlined in Wash the component parts with a mild abrasive soap or detergent.
Take care not to lay the electrodes on any surface. Rinse all parts thoroughly with hot tap water, then with cold tap water, followed by several rinses with distilled water. Take extreme care during the washing and rinsing of asgm test cells to prevent any moisture from entering the thermometer well in the inner electrode. As a precaution against this eventuality, use a suitable stopper to awtm this opening prior to starting the axtm operation. Do not dry test cells made of Monel 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.
Preparation of Specimen and Asym Test Cell Some axtm, such as oils of petroleum origin, undergo changes when exposed to sunlight. Allow the sealed container to stand undisturbed in the room in which the test is to be made for a sufficient period of time to permit the sample to attain room temperature before it is opened.
It is therefore desirable that the elapsed time necessary for the test specimen to attain temperature equilibrium with the test cell be held to a minimum. For optimum procedure do not exceed 20 min for this time.
ASTM D924 Large-Screen Auto Washing Insulating Oil Dielectric Loss Tester
It is essential, therefore, that the procedures outlined below be atsm followed. Stir the uid frequently during heating. Replace the beaker with the remainder of the heated sample on the c924 plate. Insert the inner electrode and rinse the electrodes by twice raising and lowering the inner electrode. Remove the inner electrode and hold it suspended in air; then decant the rinsing liquid and immediately ll the cell from the remainder of the heated specimen.
Replace the inner electrode. Immediately return the lled cell to the test chamber adjusted to a temperature above the desired test temperature and make the necessary electrical connections to the cell.
Decant the rinsing liquid and immediately ll the cell with a new aliquot of sample. On some instruments the cell must be in place before lling with specimen. Record data as soon as the test temperature is reached. If the difference in the measurements of the two test specimens is equal to or less than 0.
If the difference d942 the measurements of the two test specimens is greater than 0. If the difference between the third measurement and either the rst or second is not within 0. Both measurements should be made at the same temperature.
Use these measurements in calculating the relative permittivity from the following equation: Precision and Bias For routine tests, however, the requirement for a guard electrode may be waived, provided that the two-electrode cell used is of adequate capacitance and with sufficient ratio of surface area to sample thickness, in order to provide proper operation of the measuring equipment. A less satisfactory method is use of a hot plate, but variations in temperature throughout the cell may lead to questionable results.
In general, the use of a forced-draft air test d9244 or automatic thermo-regulator cell is preferable.
However, the precaution on high electrical stresses given in Section 9 shall be observed. NOTE 1—The dissipation factor of an electrical insulating liquid usually decreases with increasing frequency in the frequency range covered by The manner in which dissipation factor varies with frequency is determined by the nature of the dielectric losses, that is, whether they are predominantly polar or ionic, or are a combination of both types.
Accordingly, there is no simple conversion factor for deter- mining the dissipation factor at 60 Hz, for example, if the measurements are made at either a higher or lower frequency. Where this applies, it is imperative that each laboratory evolves a good cleaning procedure for the cell used so that repeatable results can be obtained. Solvents mentioned in If the measured value of the last sample tested was greater than the specied value, the test cell shall be cleaned before being used for further tests.
Due regard should be given to the precautions outlined in Section Number of Tests The alignment of the electrodes shall not be inuenced by this temperature nor by the operation of lling the cell with the test liquid. Metals that have been found satisfactory from this standpoint are gold, nickel, Monel, platinum, and stainless steel. In general, plated surfaces have been found less satisfactory than solid metal electrodes when testing liquids having low loss.
Plated surfaces that may be satisfactory for testing liquids having low acidity and for short periods of time are gold, platinum, nickel, chromium over nickel, or rhodium. Use a shielded wire or coaxial cable for connecting the guard and measuring electrodes to the bridge. The dissipation factor of astj insulating materials must necessarily be low, particularly that between the guard and measuring electrodes; otherwise difficulty may be experienced in balancing the guard circuits at elevated temperatures.
Insulating materials that have proven satisfactory are boron nitride, borosilicate glass, quartz, steatite, and TFEuorocarbon. Insulating materials of the molded mica-dust type, have been found to absorb solvents and therefore are not considered as satisfactory in the measurement wstm low loss liquids. Leakage across these paths has been found to produce an unsteady bridge balance on some bridges.
No minimum capacitance is therefore suggested. It is required, however, that the precision of the measurements meets the intended accuracy of this test method. The concentric cylinders are of nickel-plated brass which are mounted on a TFE-uorocarbon base and contained in an mL borosilicate glass beaker. The volume of oil required when using this cell is mL.
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