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. . OIL TESTINGr Dielectric Strength ASTM 0.877 � The most critical test of insulating oil is the dielectric strength,because it tells if the oil is capable of providing the °:::F. electrical insulation required.The test y"` --- result is the voltage at which the oil breaks down and allows an electrical ilk arc to pass between two electrodes.A poor dielectric test(25 KV or less,21 KV the minimum)would indicate a high presence of contaminates such as water,carbon or dirt particles. Color ASTM D-1500 This test is a comparison of the color of :Alio a sample to a chemical standard. New , ,,I "• a Oil will have a color number of.5 or less. � ' A number of 4.0 would be considered to a ;' ) t be unacceptably high for transformer oil r with a naphthenic base.Parafenic t'al" based oil will be darker. ; ' .....4 ;#110,,i''' Acidity ASTM D•974 The acid content of insulating oil is a -T measure of its deterioration and of its '.4 ,r�'�'' o< tendency to form sludge.The term N 1,. neutralization number is employed to ,..,-: : u _iii.„,,,. express the acidity of the oil. It is the �� quantity of potassium hydroxide(KOH) -----�'- ,.4..'�x in milligrams needed to neutralize one s , gram of insulating fluid.A .- recommended minimum neutralization number for new transformer oil is less than 0.1. (i.e. 0.1 mg KOH/g.) 4 Interfacial Tension ASTM D:971 '`� .-4 z This test is a measure of strength of the surface film of the oil in contact with water.The test is performed on an Interfacial Tensiometer. This test measures polar contaminants in the oil, giving an overall indication of changes in AteAllH .- , the insulating oil without being selective as to the cause. New oil may have an _ interfacial tension as high as 50 dynes �4's per centimer, while badly aged oil may ; be below 15 dynes per centimeter. ...•,... Gas Chromatography ----- --- Deterioration of a transformer -- insulation system will cause certain 3 - n 1 _x ;, I combustible gases to form.It is . y : ■ . estimated that 25% of transformers in �'t i �, �I- g lk �,, use have combustible gases being _ ° °t �� • ••generated.Various conditions of 1 .,,; p: a v,'• •• transformer heating or arcing will generate acetylene,hydrogen,methane, i - ''l .:. I ethane and ethylene.t Heating of _m.= cellulose present in transformers will - produce carbon monoxide. Detection of these gases,the identification and rate of generation can ® _ be helpful in determining the health of a // transformer.The gases are extracted from the oil or head space and then analyzed by our chemist using a gas • chromatograph.