Heat analysis of the power transformer bushings in the transient and steady states considering the load variations

Bushings are considered as one of the main components of the power transformers. This is due to the fact that the reliable and efficient performance of the bushings significantly influences the reliability of the transformers which, in turn, are counted as the fundamental part of the power systems. The thermal behaviour of the bushings, as a consequence of the power dissipation, significantly affects the bushing's performance and design. In this paper, a novel algorithm is proposed for the heat analysis of the bushings. This algorithm aims at specifying the hot spot temperature and the temperature distribution of the bushing. Therefore, the problem is formulated using the Joule Heating equations as the partial differential equations for both transient and steady states. Then, the finite element method is employed to solve the problem. The algorithm is implemented on an oil-impregnated paper bushing. In the steady state, the temperature distribution of the whole bushing is determined. In addition, the effects of different currents on the location and magnitude of the hot spot temperature have been investigated. In the transient state, three overload scenarios are simulated two of which are from the IEEE C57.19.100 and IEC 60076-7 standards. In addition, the effects of the wind speed and electric load on the bushing's temperature distribution for 48 h have been investigated.