Investigating material and energy efficiency of power transformers with conventional and semi-hybrid insulation operating in low-carbon electricity grids
Traditionally, power transformers use an insulation system that comprises cellulose insulation immersed in mineral oil.
byDr. B. Das, G. Kablouti
Traditionally, power transformers use an insulation system that comprises cellulose insulation immersed in mineral oil, which limits the maximum hot spot temperature to 98 °C [1]. IEC 60076-14 [2] classified new insulation systems into different categories and specified the temperature rise limitations of each category. These are referred to as hybrid insulation systems.
A hybrid insulation system allows the loading capacity to increase substantially while reducing the long-term ageing of the insulation. Hybrid insulation systems with ester fluids are also becoming common.
This type of system is a response to mitigate fire risk and resulting environmental damage in case of fire. One of the types of hybrid insulation systems is the semi-hybrid system, where the conductor insulation may see temperatures higher than 98 °C but the other parts remain below 98 °C since they are cooled by the bulk oil flow that will not see a significant temperature increase due to the higher thermal time constant of the oil compared to the copper.
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