Calculating model of insulation life loss of dry- type transformer based on the hot-spot temperature

The mechanism of thermogenesis and thermolysis of transformer was analyzed in this paper, the position of the hot-spot temperature was also analyzed. By calculating winding average surface temperature rising, a hot-spot temperature calculating model of dry -type transformer was established, and the calculating model of insulation life loss of dry-type transformer was established based on the hot-spot temperature calculating model. In the end, according to a practical example, the winding hot-spot temperature was calculated, the ageing rate of transformer winding under rated load was calculated by the calculating model, and the insulation life loss of the transformer was evaluated. The result shows that the hot-spot temperature of LV coil is higher than HV coil; the winding has a smaller aging rate and insulation life loss when less than rated load.