Analysis of Temperature Dependences of the Loss Factor of Transformer by Method FDS

The paper presents an experimental and mathematical analysis of the temperature dependence of the loss factor of the 110/3 kV traction transformer by the method of frequency dielectric spectroscopy (FDS). To prevent inaccuracies in determining the exterior temperature of the transformer caused by its slow oil temperature stabilization, a high-voltage transformer with drained oil was chosen for assessing insulation condition through the FDS method. The entire dielectric system, consisting of oil-paper insulation with minimal remaining oil, responded promptly to abrupt temperature changes. For a better visual comparison of the curves, two separate frequency graphs with temperature dependencies were chosen, namely the graph for very low frequencies up to 0.01 Hz with higher values of the loss factor and the graph for frequencies of 0.1 Hz, 2 Hz or 50 Hz, with lower loss factor values at which frequencies transformer insulation analysis is commonly used. The use of these curves enables a reasonably accurate assessment of the insulation condition of the transformer using the loss factor and capacity even at temperatures other than those measured.