Hot-spot winding temperatures in self-cooled oil-insulated transformers

IN recent years operators have wanted to know how much overload a transformer would carry for a given length of time without exceeding a safe temperature. This knowledge would enable them to obtain the most from available equipment or to install equipment which would provide reasonable overload capacity in case of emergency. In order to do this, it is necessary to be able to calculate the temperatures within windings, and to know safe operating temperatures.