1、Designation:D680202(Reapproved 2010)Test Method forDetermination of the Relative Content Of Dissolved DecayProducts in Mineral Insulating Oils by Spectrophotometry1This standard is issued under the fixed designation D6802;the number immediately following the designation indicates the year oforiginal
2、 adoption or,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 characterizes by spectrophotometry therelative level of d
3、issolved decay products in mineral insulatingoils of petroleum origin.While new oil is almost transparent toa monochromatic beam of light in the visible spectrum,theincreasing concentration of dissolved decay products shift theabsorbance curve to longer wavelengths.1.2 This test method is applicable
4、 to compare the extent ofdissolved decay products for oils in service.It can assess theeffectiveness of used or stored oil purification during thereclamation process,as well.1.3 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.1.4
5、 This standard 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 to determine theapplicability of regulatory limitations prior to use.2.Referenced Documen
6、ts2.1 ASTM Standards:2D923 Practices for Sampling Electrical Insulating LiquidsD1524 Test Method for Visual Examination of Used Elec-trical Insulating Oils of Petroleum Origin in the FieldD3487 Specification for Mineral Insulating Oil Used inElectrical Apparatus3.Terminology3.1 Definitions of Terms
7、Specific to This Standard:3.1.1 aged oil,nan oil that no longer complies with thestandard specifications for mineral insulating oils used inelectrical apparatus according to D3487.4.Summary of Test Method4.1 A test specimen of mineral insulating oil is placed in a10-mm path length glass cuvette,whic
8、h is installed in anUV-VIS scanning spectrophotometer.The instrument is firstzeroed with spectral grade heptane.The absorbance curve ofoil is then recorded from 360 to 600 nm.Integration of the areaunder this curve indicates the numeric value of the dissolveddecay products in the oil sample.Because
9、of the high sensi-tivity of spectral analysis,the deterioration of oil purity can beassessed in the early stages of the decay process.5.Significance and Use5.1 The content of dissolved decay products in insulatingoils is made up of a variety of compounds,such as peroxides,aldehydes,ketones,and organ
10、ic acids.Each of them is partiallyadsorbed on the large surface of paper insulation leading to thepremature aging of power transformers.The relative assess-ment of byproduct formation,therefore,can be used as anindicator of the aging of the mineral oil.6.Interferences6.1 The condition of the oil spe
11、cimen should be clearaccording to the requirement of Test Method D1524.6.2 The oil specimen,therefore,should be filtered through50-m filter paper.7.Apparatus7.1 Recording UV-Visible Automated Spectrophotometer,capable of scanning the range between 360 and 600 nm isrequired.The software should permit
12、 the calculation of areaunder the absorbance curve of the oil specimen.8.Reagents and Materials8.1 Absorption CuvettesTo determine the absorbancecurve of a mineral insulating oil,two matched glass cuvetteshaving a path length of 1-cm 6 0.01-cm should be used.1This test method is under the jurisdicti
13、on of Committee D27 on ElectricalInsulating Liquids and Gasesand is the direct responsibility of SubcommitteeD27.03 on Analytical Tests.Current edition approved June 15,2010.Published August 2010.Originallyapproved in 2002.Last previous edition approved in 2002 as D680202.DOI:10.1520/D6802-02R10.2Fo
14、r 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.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West C
15、onshohocken,PA 19428-2959.United States1 8.2 Cuvette Filling DeviceA disposable plastic dropper of2-mL capacity is recommended;however,any other suitablepipette may be used.8.3 Petroleum Spirits,of 6080C boiling range.8.4 Heptane,spectral grade.9.Sampling9.1 Obtain the oil sample in accordance with
16、Practice D923.10.Preparation of Apparatus10.1 Clean the cuvettes thoroughly with petroleum spirits.10.2 Adjust the automated spectrophotometer in accordancewith manufacturers recommendation.10.3 Carry out the testing procedure at room temperature(25 6 5C).11.Procedure11.1 Fill one glass cuvette with heptane;place it in thesample holder and zero the instrument by adjusting it to readzero absorbance.11.2 Move the heptane-filled cuvette by placing it to thereference position.11.3 Fill the second gl
