1、Designation: D 1169 09Standard Test Method forSpecific Resistance (Resistivity) of Electrical InsulatingLiquids1This standard is issued under the fixed designation D 1169; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of
2、 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.1. Scope1.1 This test method covers the determin
3、ation of specificresistance (resistivity) applied to new electrical insulatingliquids, as well as to liquids in service, or subsequent toservice, in cables, transformers, circuit breakers, and otherelectrical apparatus.1.2 This test method covers a procedure for making refereetests with dc potential
4、.1.3 When it is desired to make routine determinationsrequiring less accuracy, certain modifications to this testmethod are permitted as described in Sections 19-26.1.4 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.5 This st
5、andard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use. See 17.6 for aspecific wa
6、rning statement.2. Referenced Documents2.1 ASTM Standards:2D 150 Test Methods for AC Loss Characteristics and Per-mittivity (Dielectric Constant) of Solid Electrical Insula-tionD 257 Test Methods for DC Resistance or Conductance ofInsulating MaterialsD 923 Practices for Sampling Electrical Insulatin
7、g LiquidsD 924 Test Method for Dissipation Factor (or Power Factor)and Relative Permittivity (Dielectric Constant) of Electri-cal Insulating Liquids2.2 ASTM Adjunct:3Test cells3. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 specific resistance (resistivity), nthe ratio of the
8、dcpotential gradient in volts per centimetre paralleling the currentflow within the specimen, to the current density in amperes persquare centimetre at a given instant of time and underprescribed conditions. This is numerically equal to the resis-tance between opposite faces of a centimetre cube of
9、the liquid.The units are ohm-centimetres.4. Significance and Use4.1 The resistivity of a liquid is a measure of its electricalinsulating properties under conditions comparable to those ofthe test. High resistivity reflects low content of free ions andion-forming particles, and normally indicates a l
10、ow concentra-tion of conductive contaminants.5. General Considerations5.1 Theory and measuring equipment pertaining to thismethod shall be in accordance with Test Methods D 257.5.2 Where both ac loss characteristic (dissipation factor orpower factor) and resistivity measurements are to be madeconsec
11、utively on the same specimen, make the ac measurementbefore applying the dc potential to the specimen, and shortcircuit the cell electrodes for 1 min immediately prior tomaking the resistivity measurements.5.3 Make referee tests for resistivity in an atmosphere ofless than 50 % relative humidity. Fo
12、r repeatable results makethese tests under carefully controlled atmospheric conditions.5.4 Aside from the adverse influence of contamination onresults of the resistivity test, there are other factors that cancontribute to variations in the test results as follows:5.4.1 The use of an instrument not h
13、aving an adequate rangefor accurately measuring the current flowing in the circuit. (SeeSection 6 for two types of recommended instruments.)1This test method is under the jurisdiction of ASTM Committee D27 onElectrical Insulating Liquids and Gases and is the direct responsibility of Subcom-mittee D2
14、7.05 on Electrical Test.Current edition approved May 1, 2009. Published June 2009. Originallyapproved in 1951 as as D 1169 51 T. Last previous edition approved in 2002 asD1169021.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org.
15、 For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Information as to where these cells can be purchased and working drawings ofthem may be obtained from ASTM International Headquarters. Order Adjunct No.ADJD116901.1Copyright ASTM In
16、ternational, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.5.4.2 When the time of electrification is not exactly thesame for every test. Upon the application of voltage, thecurrent flow through the specimen decreases asymptoticallytoward a limiting value. Variat
17、ion in the time of electrificationcan result in appreciable variation in the test results.5.4.3 Undue length of time required for the test specimen inthe cell to attain the desired test temperature. This is one of themain sources of erroneous results. For optimum results, attainthe test temperature
18、within 20 min.5.4.4 Fluctuations in the test voltage (see 6.1.4).6. Instrumentation6.1 Instrumentation listed in Test Methods D 257 is suitable,with the exception of the Voltage Rate-of-Change Method.However, in order to obtain the greatest precision when makingthis test, use the voltage-current met
19、hod with the followinginstruments:6.1.1 Voltmeter, having an accuracy of 2 % or better, oper-ated in the upper one third of its scale range for measuring thevoltage supply.6.1.2 Current-Measuring DeviceAny type of instrumenthaving adequate sensitivity and precision and with a suitablerange for measu
20、rement of the wide spread of currents encoun-tered when making this test on new or used liquids will besatisfactory. For currents greater than 109A an Ayrton shuntand galvanometer, an appropriate electrometer or picoammeterhaving a sensitivity of 50 pA (50 3 1012A) per division hasbeen found conveni
21、ent and satisfactory. The galvanometerdeflection shall be not less than 20 divisions for the applicableAyrton shunt ratio. For currents less than 109A an electronicpicoammeter has been found suitable. In using this instrumentthe multiplier selected shall be such as to give at least one-halffull-scal
22、e deflection on the indicating instrument.6.1.3 Time-Measuring Device, accurate to 0.5 s, for measur-ing the time of electrification.6.1.4 Batteries or other stable direct-voltage supplies arerecommended for the steady voltage source.NOTE 1Rectified high-frequency power supplies cannot be usedbecaus
23、e the high frequency ripple in these supplies can cause the accomponent of current to equal or exceed the dc current being measured.The ac component of current is equal to 2 p times the product of the ripplevoltage, the ripple frequency, and the capacitance of the test cell in farads(where p = 3.14)
24、. If the capacitance of the test cell is 100 pF (1010F), theripple frequency is 100 kHz, and the ripple voltage is 5 mV (0.001 % ofa 500 V test voltage), the alternating component of current is 3.14 3 107amperes. The meter would be unreadable under these conditions.7. Test Circuit7.1 A schematic dia
25、gram of the test circuit is shown in Fig.1.7.2 Construct the circuitry so that leakage is minimal. Tothis end, mount the transfer switches on polystyrene orTFE-fluorocarbon insulation of sufficient thickness to mini-mize possible leakage. Make all soldered connections withlow-thermal-emf solder usin
26、g a soldering flux of resin andalcohol.NOTE 2The use of ordinary solder and flux can result in spuriousthermal emfs that will cause erroneous indications.7.3 Completely shield the test circuit. Make connections tothe current-measuring instrument with shielded leads. TFE-fluorocarbon-insulated shield
27、ed leads are recommended forconnecting the high-voltage electrode and measuring electrodeof the test cell to the test circuit.8. Sampling8.1 Sample liquids for use in this test in accordance withPractices D 923. When possible, obtain samples for testingthrough a closed system. If exposed to atmosphe
28、ric conditions,take the sample when the relative humidity is 50 % or less.Some liquids, in certain applications, require special handlingNOTE 1For measurements of current less than 109A replace galvanometer and shunt with picoammeter.NOTE 2With the S.P.D.T. switch on C terminal the galvanometer may
29、be calibrated while the electrodes of the test cell are short-circuited.FIG. 1 Circuit Diagram and Connections with Complete Shielding for Measuring Specific Resistance (Resistivity) of ElectricalInsulating LiquidsD1169092and processes in the sampling, and these will be found in thegoverning procedu
30、res. Consult such procedures before samplesare taken.8.2 Take a sufficient quantity of sample for this test for atleast three separate resistivity determinations.9. Galvanometer Calibration and Sensitivity9.1 When a dc galvanometer is used to measure the current,it shall first be calibrated to ensur
31、e that it is properly balanced,that is, that the deflections on either side of zero are equal whenthe galvanometer is energized with “direct” and “reverse”polarities of the test potential.NOTE 3Throughout this test method the terms “direct polarity” and“reverse polarity” are used to indicate when th
32、e positive and negativepotential leads, respectively, are connected to the outer electrode of thetest cell.9.2 The galvanometer sensitivity, Gs, in amperes per divi-sion, is used in computing the resistivity and is derived fromthe following equation:Gs5 E/R! 3 S/D!where:E = test voltage, V,R = calib
33、rating resistor,V ,S = shunt multiplying factor (ratio of galvanometer currentto total current), andD = galvanometer deflection, in divisions.10. Test Cells310.1 The design of test cells that conform to the generalrequirements given in theAnnex are considered suitable for usein making these tests.10
34、.2 Atwo-electrode cell suitable for making routine tests isshown in Fig. A1.1. A brief description of this cell is given inthe Annex.10.3 Because the configuration of the electrodes of thesetest cells is such that their effective area and the distancebetween them are difficult to measure, each test
35、cell constant,K, can be derived from the following equation:K 5 3.6p C 5 11.3Cwhere:K = test cell constant, cm, andC = capacitance, pF, of the electrode system with air as thedielectric. (For methods of measuring C, see TestMethods D 150).11. Test Chamber11.1 When the tests are to be made above room
36、 temperaturebut below 300C, use a forced-draft, thermostatically con-trolled oven that conforms to the requirements of Section 17 asthe test chamber. For tests at room temperature the unenergizedoven can be conveniently used as the test chamber.11.2 Provide the test chamber with an opening in the wa
37、llthrough which two lengths of TFE-fluorocarbon-insulatedshielded cable will pass to make electrical connection from themeasuring equipment and voltage source, respectively, to thetest cell. Use a perforated ceramic plate or disk to insulate thetest cell from the metal flooring of the oven if the fl
38、ooring is notinsulated from the oven.11.3 Provide a safety interlock on the door of the testchamber so that the electrical circuit supplying voltage to thetest cell will be broken when the door is opened.11.4 A cross-sectional view of the test chamber with athree-electrode test cell in place and wit
39、h test cables connectedis shown in Fig. 1.12. Test Temperature12.1 The temperature at which a referee test is made shall bemutually agreed upon between the purchaser and the seller.Resistivity measurements are made at many different tempera-tures. For acceptance tests, it is generally made at a temp
40、era-ture of 100C, while for routine testing, it is usually made atroom temperature, 85, or 100C. In some research investiga-tions, tests may be made at considerably higher temperatures,while in other cases, particularly for tests on cable oils inservice, tests may be made over a range of temperature
41、s.13. Test Voltage13.1 The average electrical stress to which the specimen issubjected shall be not less than 200 V/mm (5 V/mil) nor morethan 1200 V/mm (30 V/mil). The upper limit has been set withthe purpose of avoiding possible ionization if higher stresseswere permitted. For acceptance testing, t
42、he stress and time ofelectrification should be mutually agreed upon by the purchaserand the seller. The time of electrification in general usage is 1min.NOTE 4The dc volume resistivity of new oil, particularly at roomtemperature, has been shown to be a function of both electrical stress andelectrode
43、 spacing. The resistivity has been found to have a maximumvalue when the applied electrical stress is about 50 V/mil; electricalstresses either below or above this critical value yield lower values ofvolume resistivity.4 ,514. Conditioning14.1 Store the sample in its original sealed container andshi
44、eld it from light. Some liquids, such as oils of 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.1
45、5. Storing Test Cell15.1 Clean and dry the test cell, when not in use, inaccordance with Section 16. Store it in a dust-free cabinet untilit is to be used again, at which time clean and dry as directedby Section 16.16. Cleaning Test Cell16.1 The cleanliness of the test cell is of paramount impor-tan
46、ce when making resistivity measurements because of the4Gnger, B., and Maier, G., “The Resistivity of Insulating Oil in a Direct VoltageField,” Brown-Boveri Review, Vol 56, October 1969, pp. 525533.5Harrison, N. L., “Resistivity of Transformer Oil at Low and Medium FieldStrengths,” Proceedings IEEE,
47、IEEEA, Vol 115, May 1968, pp. 736741.D1169093inherent susceptibility of most insulating liquids to contami-nating influences of the most minute nature. For this reasonclean and dry the cell immediately prior to making the test. Itis essential that the procedures and precautions outlined in16.2-16.5
48、be strictly observed.16.2 Dismantle the cell completely and wash all the com-ponent parts thoroughly with a technical grade of a suitablesolvent (such as acetone or pentane). Wash the componentparts with a mild abrasive soap or detergent. Take care not tolay the electrodes on any surface. Rinse all
49、parts thoroughlywith hot tap water, then with cold tap water, followed byseveral rinsings with distilled water. Take extreme care duringthe washing and rinsing of the test cell shown in Fig. 2 toprevent any moisture from entering the thermometer well in theinner electrode. As a precaution against this eventuality, use asuitable stopper to plug this opening prior to starting thecleaning operation.16.3 After the surfaces of the electrodes and guard havebeen washed, take care not to touch these surfaces during therinsing or any subsequent operation.16.4 Place t
