The chemical structures of ester liquids are more polar than mineral oil. Polarity has an impact on the moisture saturation limit, power factor and insulation resistance in a transformer. The gases that emerge from ester liquids (hydrogen, methane, ethane, ethylene, acetylene, carbon monoxide and carbon dioxide) are the same as in mineral oil, but their gas behavior is different. IEEE C57.155 specifies required information on the gas behavior of ester liquids. There are differences in the dielectric and thermal behavior of ester liquids compared to mineral oil. Leading transformer manufacturers are aware of these differences and take this information into account when designing transformers. Users should be careful when using the limits set for mineral oil-filled transformers for an ester-filled transformer in tests such as power, insulation resistance and DGA.
Benefits of Using Ester in Transformers
The main reasons for considering an ester as a transformer dielectric fluid include high fire safety and better environmental friendliness. Additionally, esters have high moisture tolerance, which can extend the life of the insulation system. These features are explained below.
Fire security
Dielectric liquids are classified according to their Fire Point and Net Calorific Value in accordance with the IEC 61039: 2008 “Classification of insulating liquids” standard.
Class K liquids are known as “Less Flammable Liquids” which allow for closer spacing between a transformer and its surroundings when installed indoors or outdoors. For example, distances between a less flammable liquid insulated transformer with improved protection and an adjacent transformer or building can be reduced from 15.2 m to 1.5 m.
In accordance with FM Global guidelines, savings in space, concrete and construction time can be achieved.
Eco-Friendly
Ester liquids are considered environmentally friendly as they are known to be “easily biodegradable”. Biodegradation occurs when organic matter is broken down sufficiently by enzymes in soil or water to process it back into hydrogen and carbon.
