Effect of Electrical Field on Conductivity of Synthetic Ester Induced by Space Charge Accumulation

Synthetic ester has emerged as an alternative in applications where mineral oil has traditionally been used. Furthermore, their new applications in areas such as converter transformers and battery energy storage systems are currently being investigated. Conductivity of insulating materials is a crucial parameter for such new applications. This paper investigates the impact of electrical field on the conductivity of synthetic ester through a combination of experimental and simulation studies. The experimental results indicate short-term conductivity increases while long-term conductivity exhibits a non-linear trend with applied electrical field. The simulation results show that the increase in the measured short-term conductivity is due to field-enhanced charge dissociation while the non-linear trend in the measured long-term conductivity is a combined effect of space charge accumulation and field distortion. Furthermore, the simulation model incorporating space charge accumulation and charge injection is used to explain electrical field dependent conductivity phenomena, and key parameters and formulae describing field enhanced intrinsic and injected charge density are identified for synthetic ester and compared with those of mineral oil.