Thermal Analysis of Cable Sealing Ends
A general analytical method for thermal analysis of high-voltate oil-filled cable sealing ends is presented. Oil flow within the conductor oil duct, longitudinal heat flow through the conductor and conductor losses variation with temperature are taken into consideration. The method is successfully applied for a sealing end of a 300 kV, 2000 mm2 integral sheath cooled oil-filled cable. A companion paper where cable joints are analyzed, is referenced.
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. >
Self-Contained Oil-Filled Cables for High Power Circuits
The self-contained oil-filled cable has been developed to meet increasing power requirements both in terms of voltage and ampacity. The paper gives details of power transmission capability for 230, 345 and 525 kV cable systems for a variety of natural and forced cooled conditions. The highest rating is obtained with internal oil cooling and at 525kV 4000 MVA can be transmitted using one cable per phase. Details are given of accessory design features that have been adopted to ensure that these components do not become a limitation to power transmission capability.