A New Method for Indirect Measurement of Water Content in Fibrous Electro-Insulating Materials Using Near-Infrared Spectroscopy

The article presents a new method for determining moisture of solid materials using near-infrared spectroscopy. In this method, the absorbance of a near-infrared wave passing through methanol is measured; water is extracted beforehand from the material in methanol. The mass of water extracted from the sample is determined on the basis of dependence of absorbance on the water concentration in methanol. The determined water mass to dry mass ratio of the sample allows to calculate the percentage moisture of the investigated material. This new method of water content measurement was prepared in order to determine moisture in fibrous electro-insulating materials that are applied in, e.g. power transformers. The investigations described here allow to determine the time necessary to extract water from cellulose and aramid materials. The author also compared the research results of water content obtained by means of this new method with results obtained by using the normalized Karl Fischer titration method and the weight method. It was proven, based on this comparison, that the new method can be used to measure water content in fibrous materials that are either impregnated or unimpregnated with mineral oil. According to the author, the method of measuring water content presented here can be widely applied in different branches of the industry, such as in food processing and pharmaceutical manufacture.