Preparation, characterization and feasibility analysis of methyl ester of Sesbania seeds oil (MESSO) as alternate liquid dielectrics in distribution transformers

Abstract

The methyl ester of Sesbania seed oil (MESSO) was prepared using the transesterification method. The conditions for obtaining the maximum yield of the ester were optimized. The yield was 93.3% (v/v) at reaction time of 24 h, catalyst concentration of 4.5 wt% and methanol to oil volume ratio of 6 : 1. MESSO was characterized by adopting TG-DTA and FT-IR methods. The physical, chemical and electrical properties were measured as per International Standards for assessing its suitability as an insulating liquid in transformers. The kinematic viscosity of the ester is 0.98 × 10^-11 mm² S^-1, which is far less than the viscosity of the raw oil. The low acid/neutralization value (0.001 mg of KOH per g) for MESSO offers high oxidation stability. The high flash point (260 °C) and fire point (345 °C) values of MESSO provide operational safety to the transformers when they are filled with the developed insulating fluid. The saturated fatty acid content in MESSO provides a high thermal and oxidation stability for the transformers. The high dielectric constant values for MESSO in comparison to the mineral oil are attributed to the polar groups present in the ester. These results confirm that MESSO can be developed as an alternative to mineral oils for insulation and cooling in transformers. MESSO has merits of low cost, bio-degradability, ecofriendliness and preparation from renewable sources.

Fig. 1. (a) Sesbania grandiflora plant, (b) Sesbania seed pods and (c) Sesbania seeds.

Fig. 2. Purification of oil.

Fig. 3. Transesterification process.

Fig. 4. (a) Effect of reaction time. (b) Effect of catalyst loading on the % yield of MESSO.

Fig. 5. GC-MS spectra of Sesbania oil.

Fig. 6. TGA-DTA analysis of MESSO.

Fig. 7. FTIR spectrum of MESSO.

Fig. 8. Shear rate vs. viscosity.

Fig. 9. Temperature vs. moisture content.

Fig. 10. log f vs. dielectric constant.

Fig. 11. log f vs. log(dielectric loss factor).