Research on Fire Safety and Environmental Characteristics of Green Synthetic Ester

In recent years, retrofilling has attracted widespread attention both domestically and internationally, and more and more distribution transformers and power transformers have successfully been retrofilled with esters. However, as an emerging technology, retrofilling still faces numerous challenges in practical applications. Due to process limitations, it is difficult to completely remove and replace the mineral oil in the cellulose paper and core gaps after retrofilling, which may have a negative impact on the fire performance and environmental performance of esters. In this study, synthetic ester and mineral oil were used to prepare mixed insulation fluids with mineral oil content ranging from 0 % to 10 %. Fire safety and environmental safety experiments were conducted in the laboratory. The experimental results indicate that when the mineral oil content reaches 3.5 %, the fire safety level of the synthetic ester drops below Class K. In addition, the biodegradation and toxicity tests conducted on the mixture with 3.5 % mineral oil show that even with a small amount of residual mineral oil, the synthetic ester mixed insulation liquid maintains good biodegradability and extremely low toxicity.