Potential of coconut oil as a dielectric liquid in distribution transformers

The installation of distribution transformers in environmentally sensitive areas is a growing concern of electric utilities, and everywhere it sees a strong local resistance. Special and costly measures must be taken to address this concern, for example, by reducing the risk of transformer oils being inadvertently released into the environment. To solve this problem, promising natural esters based on edible oil-seeds were studied in the last few decades to ascertain their suitability based on industry-recognized standards. Some common natural esters available today in the transformer oil market are mostly produced from seeds of soybean, rapeseed, sunflower, and others [1–5]. However, due to the inherent disadvantage of high pour point, coconut oil has been sidelined for many years. Recent research on the coconut oil indicates that this can be used as a dielectric liquid at a distribution level transformer in a tropical region. Unlike main seed oil, the use of coconut oil in a transformer has not yet started despite its superior dielectric and physicochemical properties. It is a totally biodegradable and edible vegetable oil. Prototype transformers filled with coconut oil are in operation in Sri Lanka since 2001 where it has been studied satisfactorily by the researchers [6]. The superior oxidation stability, non-toxicity, and good dielectric properties of coconut oil are previously well known but no detailed comparison has been published on the electrical, thermal, and physicochemical properties of coconut oil, commercial natural esters, and mineral oil. This paper aims to present a comparison of the relative advantages, limitations, and scope of coconut oil for use in a transformer.