Abstract
The oil-immersed transformer is commonly used in modern electrical power systems, and it is also a crucial component in smart grids related to power efficiency and quality. Because of its complex electromagnetic characteristics, it is not viable to establish its thermal control model simply by conventional approaches, such as thermal balance, specific heat capacity and thermal field. In this paper, a dynamic thermal control model dependent on modern control theories, especially thermal-electrical analogy, will be presented. Plus, its mathematical model will be developed and explained step by step.