1、Designation: D 2300 08Standard Test Method forGassing of Electrical Insulating Liquids Under ElectricalStress and Ionization (Modified Pirelli Method)1This standard is issued under the fixed designation D 2300; the number immediately following the designation indicates the year oforiginal adoption o
2、r, 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.1. Scope1.1 This test method measures the rate at which gas isevolved or absorbed by insul
3、ating liquids when subjected toelectrical stress of sufficient intensity to cause ionization incells having specific geometries.1.2 This test method is not concerned with bubbles arisingfrom supersaturation of the insulating liquid.1.3 This standard does not purport to address all of thesafety conce
4、rns, if any, associated with its use. It is theresponsibility of whoever uses this standard to consult andestablish appropriate safety and health practices and deter-mine the applicability of regulatory limitations prior to use.For specific precautions see 5.1.4 and 8.4.2. Referenced Documents2.1 AS
5、TM Standards:2D 924 Test Method for Dissipation Factor (or Power Factor)and Relative Permittivity (Dielectric Constant) of Electri-cal Insulating Liquids3. Summary of Test Method33.1 After being saturated with a gas (usually hydrogen), theinsulating liquid is subjected to a radial electrical stress.
6、 Thegas space above the insulating liquid film is ionized due to theelectrical stresses and therefore the insulating liquid surface atthe insulating liquid-gas interface is subjected to ionic bom-bardment. The evolving or absorbing of gas is calculated involume per unit of time from changes in press
7、ure with timefrom two specimens run on the same sample.3.2 This test method indicates whether insulating liquids aregas absorbing or gas evolving under the test conditions.4. Significance and Use4.1 For certain applications when insulating liquid isstressed at high voltage gradients, it is desirable
8、 to be able todetermine the rate of gas evolution or gas absorption underspecified test conditions. At present time correlation of suchtest results with equipment performance is limited.4.2 In this test method, hydrogen (along with low molecularweight hydrocarbons) is generated by ionic bombardment
9、ofsome insulating liquid molecules and absorbed by chemicalreaction with other insulating liquid molecules. The valuereported is the net effect of these two competing reactions. Thearomatic molecules or unsaturated portions of moleculespresent in insulating liquids are largely responsible for thehyd
10、rogen-absorbing reactions. Both molecule type, as well asconcentration, affects the gassing tendency result. Saturatedmolecules tend to be gas evolving. The relation betweenaromaticity and quantity of unsaturates of the insulating liquidand gassing tendency is an indirect one and cannot be used fora
11、 quantitative assessment of either in the insulating liquid.4.3 This test method measures the tendency of insulatingliquids to absorb or evolve gas under conditions of electricalstress and ionization based on the reaction with hydrogen, thepredominant gas in the partial discharge. For the test condi
12、-tions, the activating gas hydrogen, in contrast to other gases,for example, nitrogen, enhances the discrimination of differ-ences in the absorption-evolution patterns exhibited by theinsulating liquids. Insulating liquids shown to have gas-absorbing (H2) characteristics in the test have been used t
13、oadvantage in reducing equipment failures, particularly cablesand capacitors. However, the advantage of such insulatingliquids in transformers is not well defined and there has beenno quantitative relationship established between the gassingtendency as indicated by this test method and the operating
14、performance of the equipment. This test method is not con-cerned with bubble evolution, which may arise from physical1This 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
15、.Current edition approved June 1, 2008. Published July 2008. Originally approvedin 1968. Last previous edition approved in 2000 as D 2300 00.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volu
16、me information, refer to the standards Document Summary page onthe ASTM website.3The original Pirelli method is described by Guiseppe Palandri and UgoPellagatti in the paper. “Gli Oli Isolanti per Cavi Elettrici” (Insulating Oils forElectric Cables), Elettrotecnica (Milan) Jan. 8, 1955. Translation
17、of this paper iscontained in “Minutes of the Meeting of the Insulated Conductors Committee of theAmerican Institute of Electrical Engineers,” Nov. 15 and 16, 1955.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.processes associated w
18、ith super-saturation of gases in oil orwater vapor bubbles evolving from wet insulation.5. Apparatus5.1 The apparatus for making gassing tests where theinsulating liquid is saturated in the same cell that is usedthereafter to electrically stress the insulating liquid is shown inFig. 1. The apparatus
19、 consists of the following:5.1.1 Gassing Cell and Buret Assembly, as shown in Fig. 1,with dimensions as given in Fig. 2. The gassing cell consists ofthe following two components:5.1.1.1 Cell made of borosilicate glass with the part understress constructed of 16 mm inside diameter and 18 mm outsidedi
20、ameter truebore tubing. This cell has an outer (ground)electrode of painted or plated silver with a vertical slit forobserving the insulating liquid level, and a metal conductorband for ground connection.5.1.1.2 Hollow High-Voltage Electrode made of 10 60.1-mm outside diameter center-less-ground and
21、 polished No.304 stainless steel seamless tubing and containing an 18-gagestainless steel capillary tubing as a gas passage. The electrodeshall be supported and centered by a precision-machined 24/40recessed TFE-fluorocarbon plug.A18-in. needle valve (E) withgas inlet is on top of the electrode.5.1.
22、2 Gas Buret (Fig. 1) made of 7-mm outside diameterborosilicate glass tubing with an etched scale, tapered glassjoint (G) for connecting to the gassing cell, a bypass stopcock(D), and three glass bulbs, (A, B, and C).5.1.3 Oil Bath with thermostatic control to maintain thebath at test temperature 60.
23、5C. The bath shall be equippedwith a stirrer, a heating arrangement capable of maintaining thenecessary temperature control, a suitable support for thegassing test cell assembly, and a thermometer graduated in0.1C divisions. As the test is temperature sensitive, it isimportant that the calibration i
24、s traceable to a standard, such asNIST.5.1.4 Transparent Safety Shield to protect the operator fromcontact with high voltage.5.1.5 High-Voltage Transformer, providing a test voltagehaving a frequency in the range of 45 to 65 Hz. Thetransformer and its controlling equipment shall be of such sizeand d
25、esign that with the test specimen in the circuit, the voltagewave shape shall approximate a sinoid with both half cyclesclosely alike. The ratio of peak-to-rms values should be equalto the square root of two within 65 % while maintaining 10RV 62%.6. Reagents and Materials6.1 Hydrogen, oxygen-free. S
26、ee Note 1.6.2 Dibutyl Phthalate, reagent grade.6.3 2-Propanol, reagent grade.6.4 Low vapor pressure grease, such as high vacuumsilicone grease.6.5 Unless otherwise indicated, it is intended that all re-agents shall conform to the Committee on Analytical Reagentsof the American Chemical Society.NOTE
27、1Hydrogen normally is the saturating gas but other gases, suchas nitrogen, carbon dioxide, argon, or air may be used.7. Preparation of Apparatus7.1 Clean the glass cell by first rinsing it inside and outsidewith a suitable hydrocarbon solvent such as heptane or othersolvent suitable for the dielectr
28、ic liquid test tested. Then fill thecell with the hydrocarbon solvent and scrub to remove waxydeposits from previous tests. Clean the tapered joint, takingcare that none of the grease enters the cell. Again rinse withhydrocarbon solvent and blow dry with clean compressed air.Check the silver electro
29、de and repair if necessary.7.2 Clean the hollow electrode by blowing a suitable hy-drocarbon solvent through the capillary tube with compressedair, rinsing the insulating liquid off the entire electrode with asuitable hydrocarbon solvent, such as heptane, and wiping offany waxy deposit with tissue p
30、aper. Polish the surface with a2-propanol soaked towel. If there are visible marks on thestainless steel shaft of the electrode, they should be polishedwith a suitable device, such as a buffing wheel, wiping off theFIG. 1 Schematic Diagram of Cell and Manometer AssemblyFIG. 2 Detailed Dimensions of
31、the Glass Cell and the Inner (High-Voltage) ElectrodeD 2300 082buffing compound carefully with tissue paper moistened with asuitable hydrocarbon solvent such as heptane.7.3 Apply a light coat of low vapor pressure silicone greaseto the stopcock (D) and the standard-taper joint (G) andassemble the gl
32、ass cell and buret, but do not insert the electrodeinto the glass cell.7.3.1 Caution: Do not allow silicone grease to contaminatethe inside of the buret, gassing cell, electrode, or oil.7.4 Fill the buret to the half-full mark with dibutyl phthalate.8. Procedure8.1 Introduce 5 6 0.1 mL of the insula
33、ting liquid sampleinto the glass cell by means of a hypodermic syringe.8.2 Lightly coat the TFE-fluorocarbon plug of the electrodewith the test insulating liquid or low vapor pressure siliconegrease and insert the electrode into the glass cell.NOTE 2It has been found helpful to place a few drops of
34、the testinsulating liquid on top of the TFE-fluorocarbon plug to act as a gas-seal.If there is a leak, use of the oil may help detect it through the appearanceof gas bubbles at the top of the Teflon plug.8.3 Bring the oil bath up to 80C (for some applications itmay be desirable to use 60C; in either
35、 case, report testtemperature as indicated in 10.1.1). Suspend the gassing celland buret assembly in the oil bath at the level indicated in Fig.1, and connect the lead from the outside electrode to ground.8.4 Attach the gas inlet and outlet connections. When usinghydrogen, the gas outlet should lead
36、 outside the building, eitherdirectly or through a fume hood.8.5 Close the stopcock (D) and open the valve (E) to allowthe saturating gas to bubble through the test insulating liquidand the buret liquid at a steady rate (about 3 bubbles/s) for 10min.8.6 Open the stopcock (D) and continue bubbling th
37、esaturating gas through the test insulating liquid for an addi-tional 5 min.8.7 After a total of 15 min of gas bubbling, close the firstvalve (E) and then the stopcock (D), making certain the liquidlevels in the two legs of the buret are equal.8.8 Connect the high-voltage lead to the center electrod
38、e.8.9 Place the transparent safety shield in position and takethe buret reading after checking the bath temperature.NOTE 3To facilitate reading the buret, it has been found helpful toilluminate the buret scale and to use a magnifying glass or a small opticalmagnifying device.8.10 Turn on the high vo
39、ltage and adjust to 10 kV. Recordthe time and voltage, as well as the buret level, and check theobservation slit on the outer electrode for onset of the gassingreaction.8.11 After 10 min, record the buret level, voltage, and bathtemperature.8.12 After an additional 50 min, again record the buretleve
40、l, voltage, and bath temperature, and turn off the voltage.8.13 To ensure the equipment is operating correctly it isrecommended that the buret level be read every 10 min untilthe test is terminated.Aplot of the readings versus time shouldgive a reasonably straight line. If the data are widely scatte
41、red,the equipment should be checked and the test rerun.8.14 For oils with very low gassing tendencies, it may benecessary to stop the test to vent the manometer. The total gasabsorbed is the sum of the gas absorbed before and afterventing.8.15 Repeat the procedure on a fresh test specimen, 8.1-8.13.
42、9. Calculation9.1 Calculate the gassing tendency as follows:G 5 B602 B10!K/Twhere:G = gassing tendency, L/min,B60= buret reading, mm, at 60 min of test,B10= buret reading, mm, at 10 min of test,K = buret constant = L/mm buret reading, (see Appen-dix X2) andT = test time of computed gassing rate,min
43、= 60 10 = 50 min.NOTE 4This will result in an answer which will be positive ( + ) if gasis evolved, and negative () if gas is absorbed.9.2 Take the average of the two values of G. If the averagevalues are different by more than 0.3 + 0.26 |X|, then the testshould be repeated. Where |X| is the absolu
44、te value of duplicatedeterminations in microliters per minute. Duplicate analysesare performed because it is difficult to detect when a problemoccurs during a test. The equation to determine when duplicateanalysis are acceptable is based on general experiences and isnot derived from a round-robin pr
45、ogram for this test method.9.3 See Appendix X1 to determine the electrical stress forthe electrode system and dielectric liquids.10. Report10.1 Report the following:10.1.1 Test temperature,10.1.2 Test voltage and frequency,10.1.3 Saturating gas,10.1.4 Test period, and10.1.5 Average gassing rate in m
46、icrolitres per minute.11. Precision and Bias11.1 The precision of this test method is based on aninterlaboratory study of D 2300-01, Standard Test Methods forGassing of Electrical Insulating Liquids Under Electrical Stressand Ionization (Modified Pirelli Method), conducted in 2006.One laboratory tes
47、ted two different materials. Every “testresult” represents the average of two determinations. Thelaboratory obtained ten replicate test results for each material.4See Table 1.11.1.1 ReapeatabilityTwo test results obtained within onelaboratory shall be judged not equivalent if they differ by morethan
48、 the “r” value for that material; “r” is the intervalrepresenting the critical difference between two test results forthe same material, obtained by the same operator using thesame equipment on the same day in the same laboratory.4Supporting data are available from ASTM International Headquarters. R
49、equestRR: D27-1019.D 2300 08311.1.2 ReproducibilityTwo test results shall be judged notequivalent if they differ by more than the “R” value for thatmaterial; “R” is the interval representing the difference be-tween two test results for the same material, obtained bydifferent operators using different equipment in different labo-ratories.11.1.2.1 Reproducibility was not determined as part of thisstudy.11.1.3 Any judgment in accordance with these two state-ments would have an approximate 95 % probability of beingcorrect.11.2 BiasAt the time of the study, there was
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