Partial Discharge Characteristics of Palm Fatty Acid Ester for Dissolved Gas Analysis

Currently, natural ester insulating oil is widely used in transformers because of its fire safety and environmental sustainability. Natural ester insulating oil has high viscosity and poor oxidation stability compared with mineral oil. Therefore, the modified ester palm fatty acid ester (PFAE) has been developed, which has a monoester structure. PFAE has a lower viscosity and greater oxidation stability than mineral oil. In this paper, the characteristics of partial discharge lasted for 120 h were compared between PFAE and mineral oil using needle-plane and creepage discharge electrodes. The dissolved gas production characteristics for different discharge durations were analysed. The test results showed that the discharge was large in the PFAE compared with mineral oil for needle-plane electrode. And for creepage, discharge was comparable in two oils. The main gases produced under the discharge were H2 and CO for both oils, and C2H6 was not produced significantly in PFAE. The amounts of generated hydrocarbon gases in PFAE were lower than that in mineral oil for similar discharge energies. The basic gas ratios method and the Duval pentagon showed that the fault type in both oils were PD and D1.