Abstract. The purpose of the work is to modify the known transformer oil moisture meter by mounting a thermostat on the desorption column with the possibility of raising the temperature and to study the degree of completeness of water extraction from the oil matrix. The principle of operation of the moisture meter is based on the electrochemical method, which includes several successive stages: extraction of water molecules from the oil matrix by dry gas in a desorption column at elevated temperature, transfer of the vapor-gas phase by dry gas to a sensitive element, and subsequent electrolysis of water. A measure of the water content in oil is the current strength required for the electrical decomposition of water absorbed per unit time. The modified moisture meter (desorption column with thermostat), in contrast to the standard version of the device (desorption column without thermostat), allows one to measure the mass fraction of water in old oxidized oils from existing high-voltage transformers with higher accuracy. Results of performed research show that heating a liquid dielectric sample to 80 °C leads to a decrease in the viscosity of transformer oil. This fact contributes to the most complete extraction of water from the matrix of the insulating liquid. Reliable measurement of the mass fraction of water in a liquid dielectric is one of the important tasks in diagnosing the state of the insulation system of expensive high-voltage transformers.

Keywords: mineral insulating oil, Karl Fischer method, moisture content, electrochemical method for water determination

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