ASTM_D_2300_-_08.pdf

Designation:D230008Standard Test Method forGassing of Electrical Insulating Liquids Under ElectricalStress and Ionization(Modified Pirelli Method)1This standard is issued under the fixed designation D2300;the number immediately following the designation indicates the year oforiginal 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 measures the rate at which gas isevolved or absorbed by insulating 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 concerns,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 ASTM Standards:2D924 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.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 pressure 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 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 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 molecules pres-ent in insulating liquids are largely responsible for thehydrogen-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 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 testconditions,the activating gas hydrogen,in contrast to othergases,for example,nitrogen,enhances the discrimination ofdifferences in the absorption-evolution patterns exhibited bythe insulating liquids.Insulating liquids shown to have gas-absorbing(H2)characteristics in the test have been used toadvantage 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 operatingperformance of the equipment.This test method is not con-cerned with bubble evolution,which may arise from physicalprocesses associated with super-saturation of gases in oil orwater vapor bubbles evolving from wet insulation.1This test method is under the jurisdiction of ASTM Committee D27 onElectrical Insulating Liquids and Gasesand is the direct responsibility of Subcom-mittee D27.05 on Electrical Test.Current edition approved June 1,2008.Published July 2008.Originally approvedin 1968.Last previous edition approved in 2000 as D2300 00.DOI:10.1520/D2300-08.2For 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.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 of this paper iscontained in“Minutes of the Meeting of the Insulated Conductors Committee of theAmerican Institute of Electrical Engineers,”Nov.