1.0 Introduction
1.1 Background of the Study
Electrical faults that occur in power transfers accounts for over fifty percent of transformer failure's expenditures . Fifty percent of transformer failure's expenditure is caused by insulation, dielectric, and oil-related faults [1]. The need for better dielectrics and transformer oils for insulation is unequivocal. In a liquid-filter transformer, the insulator liquid plays an important function by providing both the electrical insulation and the means of transforming thermal losses to the cooling system. Insulating oil in a transformer must ensure the transfer of heat. This function is realized both by thermal conductivity and convection [2].
Nowadays, transformers can be filled with three basic types of insulating liquids:
- Mineral oils,
- Synthetic oils or
- Natural esters [3].
The use of each type is fortified by the application. However, in the face of increasing demand for the use of environmentally friendly products in the industry, more and more companies are working towards developing the use of esters and specifically natural esters for use in the majority of their products.
Transformers have been filled with mineral oil for more than one century. This type of oil is a petroleum based product, essentially composed of hydrogen and carbon atoms. Carbon and hydrogen are assembled in different structures: napthenic (CnH2n), paraffinic (CnH2n+2) and aromatic (CnH2n-6)[3]. The distribution of carbons in napthenic and paraffinic structures define the type of mineral oil. This distribution is controlled by the crude oil and the refining processes used. Because of its wide availability, good properties and low cost, mineral oil is the fluid most used in the electric power transformer industry. New mineral oils have to be in accordance with the IEC 60296 or ASTM D3487.
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