This International Standard describes methods for the determination of water in insulating liquids and in oil-impregnated cellulosic insulation with coulometrically generated Karl Fischer reagent. The method in clause 2 is applicable to water concentrations above 2 mg/kg in liquids having viscosity of less than 100 mm2 /s at 40 °C. The test method in clause 3, where water is extracted by means of a nitrogen stream, is the preferred method for insulating liquids of viscosity higher than 100 mm2 /s. Clause 4 describes methods for the determination of water content in oil-impregnated paper and pressboard over the range 0,1 % to 20 % by mass.