Thermal measurement of an ester-filled power transformer at ultra-low temperatures: steady state

摘要

At arctic ambient temperatures, the viscosity of cooling fluids for power transformers reaches extreme levels. This leads to a change of fluid flow and cooling performance, which is even more critical in case of ester fluids and cooling by means of radiators. To ensure reliable operation even under such conditions, a power transformer has been tested under different loads at ambient temperatures ranging from -50癈 to -30癈. In this report, we concentrate on the measurement results for overall cooling performance in steady state. We demonstrate such surprising results as a temperature increase when outside temperature is reduced or when fans are activated for improved cooling. Both effects are due to a change of effectively used cooling surface.