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

Statistical analysis of the impact of FeO3 and ZnO nanoparticles on the physicochemical and dielectric performance of monoester-based nanofluids

This article deals with a comparative study of the physicochemical and electrical properties of monoesters of castor oil compared with their counterparts based on FeO₃ and Z_nO nanoparticles. The results are also compared with those in the literature on triesters, and also with the recommendations of the IEEE C 57.14 standard. The data is analysed statistically using a goodness-of-fit test. The analysis of the viscosity data at 40 °C shows an increase in viscosity. For concentrations of 0.10 wt%, 0.15 wt% and 0.20 wt% these are respectively 5.4%, 9.69%, 12.9% for F_eO₃ NFs and 7.6%, 9.91% and 12.7% for Z_nO NFs. For the same concentrations, the increase in acid number is respectively 3.2%, 2.9%, 2.5% for FeO3 samples and 3.18%, 2.0%, 1.2% for Z_nO samples. For the same concentrations, the fire point shows an increment of 4%, 3% and 2% for F_eO₃ samples and a regression of 8.75%, 6.88% and 5.63% for Z_nO samples. As for the breakdown voltage, for the same concentrations we observe respectively an increment of 43%, 27%, 34% for the F_eO₃. The results show an improvement on partial discharge inception voltage with FeO3 of 24%, 8.13% and 15.21% respectively for the concentrations 0.10 wt%, 0.15 wt% and 0.20 wt%.

Effect of the relaxation time of mineral oil and monoesters on the fractal dimension and mutual information of creeping discharges propagating along a pressboard

This paper presents a new method for analysing creeping discharges based on information theory as it applies to medical imaging. The analysis of information surface data is used to determine the impact of relaxation time on the characteristic parameters of creeping discharges. The same information is used to make a comparative study of the morphology of discharges propagating in palm kernel oil methyl ester (PKOME) and in mineral oil (MO). Other comparative methods based on fractal analysis and normality hypothesis tests associated with Anderson Darling (AD), Kolmogorov-Smirnoff (KS) and Shapiro-Wilk (SW) statistics are used. The results show that very short relaxation times increase the error on the measurement of the fractal dimension and the maximum extension of the discharges. A growth of the mutual information between 0 and 60% is observed for relaxation times varying between 60s and 420s respectively. For the same time interval, the P-value increases from 0.027 to 0.821 according to the AD statistic, from 0.01 to more than 0.150 according to KS and from 0.083 to more than 0.1 according to SW. This result indicates that the data are from a normal distribution. After 420s of relaxation, the error on the maximum extension measurement is reduced by 94% in PKOME and 92% in MO. Similarly, the error on the mean fractal dimension in MO is reduced by 86.7% for a relaxation time between 301s and 420s, and by 84.6% in PKOME for a time between 180s and 420s. These different results imply that the impact of the discharge can be predicted when it is in its initial phase during which the number of discharge occurrences is reduced. On the other hand, the physicochemical characteristics of the insulating liquid used dictate the relaxation time to be allowed for the laboratory measurements.

Micro-physical parameter dynamic evolution behaviour of a natural ester molecular chain under a changing electric field and its correlation mechanism with lightning impulse discharge: theoretical analysis

The lightning impulse breakdown properties of natural esters are very important for their further applications. This paper focuses on the discharge mechanism investigation of a natural ester insulating liquid under a lightning impulse electric field. Based on density functional theory (DFT), the configuration, electron structure, ionization and electron affinity process, excitation process and molecular orbital of natural ester molecules were calculated under different electric field strengths. A correlation mechanism between the micro-physical parameters of ester insulating liquid molecules and discharge was proposed. The molecular electrostatic potential was used to predict the active point of discharge. The results show that the molecular structure of triglycerides shows yield behaviour under electric field action. The electrons are redistributed in the direction of the source of the electric field. Among the four triglycerides, the ionization and electron affinity process, excitation process and molecular orbital of glycerol tripalmitate were least affected by the electric field. The microscopic properties of other triglycerides were significantly affected by the electric field. According to the electrostatic potential (ESP) result of natural ester molecules, it can be predicted in the experiment that the surface of H atoms of the triglyceride ester group easily forms electron traps to bind electrons, while the surface of an O atom at the ester of a triglyceride undergoes electron collisions resulting in an electrical discharge. The proportion of palmitic acid in natural esters could be increased or pure glycerol tripalmitate could be used as an insulating oil to solve the problem of the low lightning impulse breakdown voltage of natural esters.

Extraction and Characterization of Sesbania cannabina (Retz.) Pers. (Dhaincha) Seed Oil for Potential Engineering Applications

Sesbania cannabina (Retz.) Pers. (Dhaincha) is a member of family Fabaceae spread over several countries in tropical and subtropical regions of the world. Sesbania aculeata, Sesbania drummondii, Sesbania grandiflora, Sesbania rostrata, Sesbania sesban, and Sesbania speciosa are other members of this family. The agricultural, nutritional and pharmaceutical applications of Sesbania species are known to farmers, villagers, and the tribes since ages and are well studied by researchers. However, the significance of Sesbania as an industrial crop has not been recognized till now. The objective of this study was extraction and characterization of Sesbania cannabina seed oil (SCSO) for potential engineering applications. The seed oil was extracted with hexane in a Soxhlet extractor. Yield was only 2.32% w/w due to long storage at high temperature in seed house. Sesbania cannabina seed oil methyl ester (SCSOME) was prepared via esterification and transesterification for analysis of fatty acid composition of extracted oil. SCSO has high iodine value (118 g I₂/100 g) and high saponification value (185.79 mg KOH/g) making the oil suitable for use as candle stocks or in soap making. However, these applications were ruled out on account of being insignificant for oil available in limited quantity. The oil has high viscosity index (174.19), high onset (382°C) and offset (450°C) decomposition temperatures, endothermic nature, and shear rate thickening behaviour. These properties make SCSO a good candidate for application as specialty lubricant required under severe operating conditions of high temperature and high shear rate or as insulating and cooling transformer oil.

Significantly Enhanced Electrical Performances of Eco-Friendly Dielectric Liquids for Harsh Conditions with Fullerene

The eco-friendly vegetable liquid is increasingly used because of the growing demand for environmentally friendly dielectric liquid. A vegetable liquid/fullerene nanofluid was fabricated via ultrasonic processing with good dispersion of the fullerene nanoparticles. It was observed that a small amount of fullerene (~100 mg/L) can significantly improve the electrical properties of vegetable insulating liquid (dissipation factor decreased by 20.1%, volume resistivity increased by 23.3%, and Alternating Current (AC) dielectric breakdown strength increased by 8.6%). Meanwhile, the trace amount of fullerene is also able to improve the electrical performances (i.e., dissipation factor and electrical resistivity) of the vegetable nanofluid under harsh conditions of long-term thermal aging compared with the blank contrast. The reduced acid values (25%) and dissolved decomposition gases (58.2% for hydrogen) in the aged vegetable nanofluid indicate the inhibition of molecule decomposition of vegetable liquid with fullerene. The improved electrical performances and thermal resistance of the vegetable nanofluid contribute to the electron affinity of fullerene proved by calculation of electron density distribution on the surface. The thermogravimetric analysis of the nanofluid under different atmospheres interprets that the oxygen absorbed inevitably in the fullerene contributes to the performance deterioration of the nanofluids during the initial aging. This work provides a potential method towards eco-friendly dielectric liquid with great electrical performances for harsh environments.