Steady state temperature distribution of high voltage bushings-analysis and measurements

A computer program is developed to perform the thermal analysis of the temperature distribution of the conductor in a high-voltage bushing under steady-state conditions. A thermal circuit for an element of length dx of the conductor is analyzed, and a differential equation representing the thermal performance is obtained. The solution of the equation can be obtained without any prior measurements of conductor temperatures. The analysis is applied to a 69 kV air-to-air bushing with one end immersed in oil as well as to an experimental bushing. Good agreement between predicted and measured temperature distribution is obtained. The locations of hot spots inside the conductor, under different loading conditions, have been calculated with good accuracy. In order to reduce the hot spots, an evaporative cooling method is applied to both bushings and the conductor thermal analysis has been modified to include the cooling effect