1、Designation: D 1169 02e1Standard 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
2、of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the Department of Defense.e1NOTEAdjunct references were corrected edito
3、rially in May 2006.1. Scope1.1 This test method covers the determination 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
4、method covers a procedure for making refereetests with dc potential.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 This standard does not purport to address all of thesafety conce
5、rns, 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 warning statement.2. Referenced Documents2.1 ASTM Standards
6、: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 Insulating LiquidsD 924 Test Method for Dissipation Factor (or Pow
7、er 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 dcpotential gradient in volts per centimetre paralleling
8、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 the liquid.The units are ohm-centimetres.4. Significance
9、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 low concentra-tion of conductive contaminants.5. General C
10、onsiderations5.1 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 madeconsecutively on the same specimen, make the ac measurementbefo
11、re 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. For repeatable results makethese tests under carefully cont
12、rolled atmospheric conditions.1This test method is under the jurisdiction of ASTM Committee D27 onElectrical Insulating Liquids and Gases and is the direct responsibility of Subcom-mittee D27.05 on Electrical Tests.Current edition approved Oct. 10, 2002. Published December 2002. Originallypublished
13、as D 1169 51 T. Last previous edition D 1169 95.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Information
14、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 International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.5.4 Aside from the adverse influen
15、ce 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 having an adequate rangefor accurately measuring the current flowing in the circuit. (SeeSection 6 for two types of recomm
16、ended instruments.)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. Variation in the time of electrificationcan result in appreciable variation in the t
17、est 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 within 20 min.5.4.4 Fluctuations in the test voltage (see 6.1.4).6. Instrument
18、ation6.1 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 method with the followinginstruments:6.1.1 Voltmeter, having an accuracy of 2 % o
19、r 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 measurement of the wide spread of currents encoun-tered when making this test on ne
20、w 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 convenient and satisfactory. The galvanometerdeflection shall be not less than 20 div
21、isions 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-scale deflection on the indicating instrument.6.1.3 Time-Measuring Device, accurat
22、e 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 usedbecause the high frequency ripple in these supplies can cause the accomponent of cur
23、rent 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). If the capacitance of the test cell is 100 pF (1010F), theripple frequency i
24、s 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 diagram of the test circuit is shown in Fig.1.7.2 Construct the circuitry so that
25、 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 using a soldering flux of resin andalcohol.NOTE 2The use of ordinary solder and fl
26、ux 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 shielded leads are recommended forNOTE 1For measurements of current less than 109A r
27、eplace galvanometer and shunt with picoammeter.NOTE 2With the S.P.D.T. switch on C terminal the galvanometer may 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 E
28、lectricalInsulating LiquidsD116902e12connecting 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
29、 atmospheric conditions,take the sample when the relative humidity is 50 % or less.Some liquids, in certain applications, require special handlingand processes in the sampling, and these will be found in thegoverning procedures. Consult such procedures before samplesare taken.8.2 Take a sufficient q
30、uantity 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 ensure that it is properly balanced,that is, that the deflections on either side
31、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 the positive and negativepotential leads, respectively, are connected to the o
32、uter 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 = calibrating resistor,V ,S = shunt multiplying factor (ratio of galvanometer curre
33、ntto 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.10.2 Atwo-electrode cell suitable for making routine tests isshown in Fig. A1.
34、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 cell constant,K, can be derived from the following equation:K 5 3.6p C 5 11.
35、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 temperaturebut below 300C, use a forced-draft, thermostatically con-trolled
36、 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 wallthrough which two lengths of TFE-fluorocarbon-insulatedshielded cable will
37、 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 flooring is notinsulated from the oven.11.3 Provide a safety interlock on the
38、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 with test cables connectedis shown in Fig. 1.12. Test Temperature12.1 The tempe
39、rature 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 tempera-ture of 100C, while for routine testing, it is usually made atroom tempe
40、rature, 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 temperatures.13. Test Voltage13.1 The average electrical stress to which the specimen i
41、ssubjected 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, the stress and time ofelectrification should be mutually agreed upon by the p
42、urchaserand 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 spacing. The resistivity has been found to have a maximumvalue when the app
43、lied 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 andshield it from light. Some liquids, such as oils of petroleumorigin, undergo ch
44、anges 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.4Gnger, B., and Maier, G., “The Resistivity of Insulating Oil in a Direct Vol
45、tageField,” Brown-Boveri Review, Vol 56, October 1969, pp. 525533.5Harrison, N. L., “Resistivity of Transformer Oil at Low and Medium FieldStrengths,” Proceedings IEEE, IEEEA, Vol 115, May 1968, pp. 736741.D116902e1315. Storing Test Cell15.1 Clean and dry the test cell, when not in use, inaccordance
46、 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-tance when making resistivity measurements because of theinherent susceptibility of mo
47、st 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 be strictly observed.16.2 Dismantle the cell completely and wash all the c
48、om-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 parts thoroughlywith hot tap water, then with cold tap water, followed bys
49、everal 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 the component parts of the test cell in an ovenmaintained at 110C for a pe
