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Background. There are currently no thermal self-diagnostics systems of instrument transformers operating in real time, as opposed to power ones, and thermal inspections are often carried out according to a maintenance schedule, which affects the reliability of electrical equipment. Therefore, an important task is to create such systems for digital instrument combined current and voltage transformers based on resistive dividers, which determine temperature values at several points, including the most heated element. The aim of this study is to obtain experimental data on the thermal state of a resistive divider exposed to environmental factors and voltage for developing a self-diagnostics system. Materials and methods. The results are obtained by physical simulation of thermal conditions of the transformer and its elements in highand low-voltage climatic chambers. The effects of the following factors of critical importance have been simulated: electric voltage, insolation, temperature and speed of the ambient air. Data processing was performed using the methods of probability theory and mathematical statistics. Results. The time needed for the thermodynamic system to move to a steady heat exchange mode, and also the temperatures on the lower resistors and on the surface of the voltage transformer insulation cover have been determined. It has been established that thermal conditions are more significantly affected by the simulated voltage than by insolation. The study has shown that even in the most severe emergency operating modes, heating in the lower resistor does not exceed the critical value. It has been found that the thermal state of the transformer is significantly influenced by the simulated factors including directional insolation, which is not taken into account in the existing methods of calculating the thermal state of the instrument electrical equipment. Conclusions. The reliability of the obtained results is ensured by the fact that the simulation took into account significant factors. The results of the experiment will be used to develop a thermal self-diagnostics system for the digital transformer, which will improve the reliability of operation of such instrument equipment by allowing the personnel’s to give a rapid response to real-time information about the transformer thermal state.

A laboratory study of environment and voltage effects on the thermal state of resistive voltage divider