ASTM D1169-2011 Standard Test Method for Specific Resistance (Resistivity) of Electrical Insulating Liquids《电绝缘液体电阻率(电阻系数)的标准试验方法》.pdf

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1、Designation: D1169 11Standard Test Method forSpecific Resistance (Resistivity) of Electrical InsulatingLiquids1This standard is issued under the fixed designation D1169; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of l

2、ast 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 determinat

3、ion 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.1

4、.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 stan

5、dard 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 warn

6、ing statement.2. Referenced Documents2.1 ASTM Standards:2D150 Test Methods for AC Loss Characteristics and Per-mittivity (Dielectric Constant) of Solid Electrical Insula-tionD257 Test Methods for DC Resistance or Conductance ofInsulating MaterialsD923 Practices for Sampling Electrical Insulating Liq

7、uidsD924 Test Method for Dissipation Factor (or Power Factor)and Relative Permittivity (Dielectric Constant) of Electri-cal Insulating Liquids3. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 specific resistance (resistivity), nthe ratio of the dcpotential gradient in volts per

8、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 the liquid.The units are ohm-centi

9、metres.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 low concentra-tion of conductive co

10、ntaminants.5. General Considerations5.1 Theory and measuring equipment pertaining to thismethod shall be in accordance with Test Methods D257.5.2 Where both ac loss characteristic (dissipation factor orpower factor) and resistivity measurements are to be madeconsecutively on the same specimen, make

11、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. For repeatable results makethese test

12、s 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 having an adequate rangefor accurate

13、ly 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 D27.05 on Electrical Test.Current edi

14、tion approved May 1, 2011. Published May 2011. Originallyapproved in 1951 as as D1169 51 T. Last previous edition approved in 2009 asD1169 09. DOI: 10.1520/D1169-11.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Bo

15、ok of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 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. Upo

16、n 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 test results.5.4.3 Undue length of time required for the test specimen inthe cell to attain the desir

17、ed 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. Instrumentation6.1 Instrumentation listed in Test Methods D257 is suitable,with the exception of the Voltage R

18、ate-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 % or better, oper-ated in the upper one third of its scale range for measuring thevoltage supply.6.1.2 C

19、urrent-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 new or used liquids will besatisfactory. For currents greater than 109A an Ayrton shuntand galvanometer

20、, 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 divisions for the applicableAyrton shunt ratio. For currents less than 109A an electronicpicoammeter has

21、 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, accurate to 0.5 s, for measur-ing the time of electrification.6.1.4 Batteries or other stable direct-voltage

22、 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 current to equal or exceed the dc current being measured.The ac component of current is equal to 2 p tim

23、es 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 is 100 kHz, and the ripple voltage is 5 mV (0.001 % ofa 500 V test voltage), the alternating component

24、 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 leakage is minimal. Tothis end, mount the transfer switches on polystyrene orTFE-fluorocarbon insula

25、tion 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 flux can result in spuriousthermal emfs that will cause erroneous indications.7.3 Completely shield the

26、 test circuit. Make connections tothe current-measuring instrument with shielded leads. TFE-fluorocarbon-insulated shielded 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

27、 accordance withPractices D923. When possible, obtain samples for testingthrough a closed system. If exposed to atmospheric 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

28、 109A replace 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 (Resistivit

29、y) of ElectricalInsulating LiquidsD1169 112and processes in the sampling, and these will be found in thegoverning procedures. 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 C

30、alibration 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 of zero are equal whenthe galvanometer is energized with “direct” and “reverse”polarities of the test p

31、otential.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 outer electrode of thetest cell.9.2 The galvanometer sensitivity, Gs, in amperes per divi-sion, is used

32、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 currentto total current), andD = galvanometer deflection, in divisions.10. Test Cells10.1 The design of test

33、 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. A1.1. A brief description of this cell is given inthe Annex.10.3 Because the configuration of the electrode

34、s 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 11.3Cwhere:K = test cell constant, cm, andC = capacitance, pF, of the electrode system with air as thediele

35、ctric. (For methods of measuring C, see TestMethods D150).11. Test Chamber11.1 When the tests are to be made above room 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 t

36、he 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 pass to make electrical connection from themeasuring equipment and voltage source, respectively, to thet

37、est 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 door of the testchamber so that the electrical circuit supplying voltage to thetest cell will be broken w

38、hen 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 temperature at which a referee test is made shall bemutually agreed upon between the purchaser and the seller.

39、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 temperature, 85, or 100C. In some research investiga-tions, tests may be made at considerably higher temperatu

40、res,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 issubjected shall be not less than 200 V/mm (5 V/mil) nor morethan 1200 V/mm (30 V/mil). The upper limit h

41、as 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 purchaserand the seller. The time of electrification in general usage is 1min.NOTE 4The dc volume resistiv

42、ity 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 applied electrical stress is about 50 V/mil; electricalstresses either below or above this critical value yi

43、eld lower values ofvolume resistivity.3 ,414. Conditioning14.1 Store the sample in its original sealed container andshield 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 thet

44、est is to be made, for a sufficient period of time to permit thesample to attain room temperature before it is opened.15. 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

45、 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 the3Gnger, B., and Maier, G., “The Resistivity of Insulating Oil in a Direct VoltageField,” Brown-Boveri Review, Vol 56, October 1

46、969, pp. 525533.4Harrison, N. L., “Resistivity of Transformer Oil at Low and Medium FieldStrengths,” Proceedings IEEE, IEEEA, Vol 115, May 1968, pp. 736741.D1169 113inherent susceptibility of most insulating liquids to contami-nating influences of the most minute nature. For this reasonclean and dry

47、 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 com-ponent parts thoroughly with a technical grade of a suitablesolvent (such as acetone or pentane). Wash

48、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 byseveral rinsings with distilled water. Take extreme care duringthe washing and rinsing of the test cell sho

49、wn 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 period of not less than 60 min. Donot dry test cells made of Monel at this elevated temperaturefor more th