Alternative Liquid Dielectrics for High Voltage Transformer Insulation Systems. Группа авторов
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СКАЧАТЬ Tension (IFT)

      The IFT value of insulating liquids provides important information for detection of impurities or polar contaminations in the oil. The poor value of the IFT leads to drop in the quality of the oil, which is caused by the generation of oxides and peroxides in the insulating oil during its service. The value of IFT is measured in accordance with the standard ASTM D971. IFT is determined by the differences of the interactions between the molecules of one fluid to another fluid [66]. It is also observed that the IFT of NEO is lower than that of MO because of the molecular structure of NEO, which contains unsaturated fatty acid chains and the moisture content present in the oil. The NEOs have variances in the fatty acid structure which differ in their carbon chain lengths and in the number of double bonds or unsaturation. IFT is a physical attribute that is closely associated with the molecular configuration. The number of unsaturated fatty acids and the length of the fatty acid hydrocarbon chain affect the IFT value and the tension also increases when the chain length increases.

      2.4.3.4 Thermal Conductivity

      One of the most significant characteristics to understand the heat transfer property of any insulating oil is thermal conductivity. In order to understand this property of cooling in the transformer, thermal conductivity is measured by using the device KD2 pro at room temperature. Single probe transient hot‐wire method is used to observe the thermal conductivity. The governing equation for thermal conductivity is

      (2.9)k equals StartFraction q Over 4 pi left-parenthesis upper T 1 minus upper T 2 right-parenthesis EndFraction ln StartFraction t 1 Over t 2 EndFraction

Schematic illustration of the comparison of viscosity values of different oil samples.

      where “k” is the thermal conductivity, “q” is the heat flow per unit length of the source, and “T1” and “T2” are the temperatures of the heat source at times “t1” and “t2”, respectively [67]. The thermal conductivity of natural ester is higher than MO because it contains the triglyceride molecular structure.

      2.4.3.5 Viscosity

      (2.11)StartLayout 1st Row normal upper R bullet plus normal upper O 2 right-arrow upper R upper O Subscript 2 bullet Baseline 2nd Row upper R upper O Subscript 2 bullet Baseline plus upper R upper H right-arrow upper R upper O upper O upper H plus normal upper R bullet EndLayout right-brace modifying above a with caret € f with hook upper P r o p a g a t i o n

      (2.12)StartLayout 1st Row upper R upper O upper O upper H right-arrow upper R upper O bullet plus upper O upper H bullet 2nd Row upper R upper O bullet plus upper R upper H plus normal upper O 2 right-arrow upper R upper O upper H plus upper R upper O Subscript 2 bullet Baseline 3rd Row upper O upper H bullet plus upper R upper H plus normal upper O 2 right-arrow normal upper H 2 normal upper O plus upper R upper O Subscript 2 bullet Baseline EndLayout right-brace modifying above a with caret € f with hook upper C h a i n modifying above upper A with caret upper R e a c t i o n

StartLayout 1st Row normal upper R bullet colon r a d i c a l 2nd Row upper R upper O Subscript 2 bullet Baseline colon p e r o x y minus r a d i c a l EndLayout

      (2.15)normal upper C 3 normal upper H 8 left-parenthesis upper O upper H right-parenthesis left-parenthesis upper O upper O upper C upper R right-parenthesis Subscript 2 Baseline plus normal upper H 2 normal upper O left-right-arrow ModifyingBelow normal upper C 3 normal upper H 8 left-parenthesis upper O upper H right-parenthesis Subscript 2 Baseline left-parenthesis upper O upper O upper C upper R right-parenthesis With presentation form for vertical right-brace Underscript upper M o n o g y l c e r i d e Endscripts plus normal upper R minus upper C upper O upper O upper H