Abstract
A distribution transformer is an expensive electrical apparatus utilised in power systems to either step-up or step down voltage, its insulation can be achieved using oil immersion or dry-type methods, with mineral oil or natural ester oil being preferred for their superior insulation properties, biodegradability, and fire safety. Although ester oil is considered superior, it has not been widely commercialised and has not fully replaced mineral oil in the market. This is because ester oil is more expensive than mineral oil and it is uncertain whether it offers significant benefits over the lifespan of transformers in exception to known superior properties. In this study the lifecycle cost of mineral oil and ester oil insulation in distribution transformers was examined. Ester oil was determined to provide superior technical and environmental advantages despite being more expensive. It has been found to provide advantageous returns on investment and safety advantages over mineral oil. Ester oils have advantages such as excellent electrical resistance, biodegradability, and tolerance to high temperatures. Findings suggest that it is advantageous to utilise ester oil as a form of insulation in transformers over mineral oil.