Long-term investigations of partial discharge and gassing behavior of ester-based insulating oils for a heated oil gap

Ester-based insulating liquids are increasingly used in transformers. Due to their short operating times, the exact understanding of their aging behaviour is missing. The aim of the presented investigations is to characterise the ester-based insulating fluids with existing diagnostic methods after a long time, where the insulating fluids impinge with simultaneous electrical and thermal stress.