Breakdown probability prediction for a new set of Eh-BN/MO-NF was performed. A comparative analysis of electrical properties such as ACBDV, DC and DDF for fresh and aged VO and NF samples was studied.
74 5.1 Schematic diagram of the accelerated thermal aging configuration 79 5.2 Schematic diagram of the exploded view of each part of the accelerated power plant. 135 8.7 UV-vis spectrum of VO and VO-NF under different aging conditions 136 8.8 AN and IFT of VO and VO-NF under different aging conditions.
List of Tables
List of Acronyms
List of Symbols
Introduction
Contents
- Introduction to the oil filled transformer
- Literature survey
- NF based TO
- Synthesis and preparation of NF
- Cooling effect of the NFs
- Electrical properties of the NFs
- Sustainable VO
- Nonedible VO
- Motivation
- Objective of the thesis
- Main contribution
- Organization of the thesis
There is no fixed surfactant that can be used to stabilize NF. The thermophysical and electrical properties of Eh-BN/MO-NF are investigated and compared with the base fluid, viz.
Thermophysical and electrical properties of the MO based NF
Introduction
Among the different types of NPs, it is observed that the titanium oxide (TiO2) increases the AC breakdown voltage (ACBDV) of MO. It is observed that exfoliated h-BN (Eh-BN) is a new batch of insulating NP, which can improve the thermal conductivity of NF.
Experimental process
- Characterization of NPs and MO
- Preparation of NF
According to TEM analysis, the average size of Eh-BN powder is 50–100 nm. It confirms that the particle size is reduced from 1 μm to 200–300 nm as shown in the figure.
Results and discussion
- Stability analysis by zeta potential
- Moisture analysis of the NF
- Viscosity
- Viscosity with temperature
- Thermal conductivity analysis
- Pour and flash point study
- Interfacial tension (IFT)
- AC breakdown voltage (ACBDV)
The improvement in thermal conductivity is due to the increase in Brownian motion of the NPs. Therefore, the ACBDV of the oil in this study was measured at a moisture content of 18 and 24 ppm.
2.6) Where the charging time constant of the NP is expressed as
Since NPs have finite conductivity, it takes limited time to deposit charges on the surface of NPs depending on the conductivity and permittivity of the particles and oil. From Figure 2.20 b it is observed that when the NP is exposed to an external electric field, positive and negative ions are generated in the upper half (0 < 𝜃 ≤𝜋.
Dielectric constant and dissipation factor
In order to realize any possible effect of aging on the dielectric properties of the investigated fluid, the closed cup oxidative test of the fluid has been performed according to the ASTM-D2440 [119] standard for 164 hours at 110oC, 50 Hz. However, the dielectric constant of the aforementioned liquids decreases after oxidative aging to resp. 2.04. The above results indicate that the dielectric constant of Eh-BN NF is higher than that of MO and the aging period leads to a smaller decrease in the dielectric constant.
The liquid dispersion factor increases with increasing aging period as shown in Figure 2.23 The formation of sludge and water during oxidative aging increases the value of tan, so the dielectric properties deteriorate. Since the dielectric constant and dissipation factor of Eh-BN/MO NF are always better than MO, by using Eh-BN NPs, the aging of the transformer oil can be minimized, which improves the lifetime of the transformer.
Summary of the chapter
Moisture and polar contaminations in MO and NF adversely affect IFT, acidity, ACBDV, dielectric constant and DDF. The lowest affinity of Eh-BN NPs towards polar contamination indicates a small deterioration of its insulating properties even after oxidative aging. Since Eh-BN NPs remove the free electrons available in the MO under excitation, the streamer initiation is stopped and hence there is an improvement in ACBDV for Eh-BN/MO-NF compared to MO.
Considering the aforementioned advantages of the Eh-BN NF over existing MO-based transformation oil, it will be the alternative insulation and coolant for distribution/power transformer. To verify the usefulness and feasibility of the practical aspect of implementing NF-based TO, an oxidative thermal aging study was performed to understand the degradation behavior of MO and insulating NF at three different aging periods in the next chapter.
Open beaker oxidative ageing analysis of MO and NF
- Introduction
- Design and development of oxidative ageing simulator
- Ageing degradation
- Oxidative ageing of MO and NFs
- Open beaker oxidative ageing
- Experimental (physicochemical and electrical) properties analysis
- Zeta Potential Analysis
- Colour
- Viscosity
- Thermal conductivity
- Moisture analysis
- Acid number
- Interfacial Tension
- AC breakdown voltage
- Dielectric constant
- Dielectric dissipation factor (DDF)
- Uncertainty analysis
- Uncertainty in thermal conductivity
- Uncertainty in ACBDV
- Summary of the chapter
Regardless of the nature of TO due to these voltages, aging occurs in the oil inside the transformer. The color of the insulating oils is an indication of possible degradation or contamination in the oil. Highly insulating Eh-BN NP plays an important role in improving the BDV of Eh-BN/MO-NF.
There are three sample groups such as MO, TiO2/MO-NF and Eh-BN/MO-NF. In the course of aging, the thermal conductivity of NF gradually declines, but Eh-BN/MO-NF even after 492 hours of aging shows minimal degradation of thermal conductivity.
Sealed beaker oxidative ageing analysis of MO and NF
- Introduction
- Sealed beaker ageing and its analysis
- Results and discussion .1 Colour characteristics
- Acid number (AN) and interfacial tension (IFT)
- Dielectric dissipation factor (DDF) and resistivity
- Thermal conductivity
- ACBDV
- ACBDV statistical analysis
- Summary of the chapter
Therefore, a sealed glass oxidative aging apparatus is used to study the thermophysical and electrical properties of both MO and Eh-BN/MO-NF aged sample. The aging characteristics and thermoelectric properties of Eh-BN/MO-NF are compared with MO at a particular aging duration. During the aging period, MO and Eh-BN/MO NFs are exposed to oxygen and heated in the presence of copper catalyst in a sealed beaker.
The resistivity of the MO and Eh-BN/MO NF for the above-mentioned aging time is studied. The mechanism for improving the thermal conductivity and ACBDV of the NF has been introduced.
Thermal ageing analysis of MO and NF impregnated solid insulation
- Introduction
- Design of thermal ageing simulator
- Accelerated thermal ageing of solid insulation
- Results and discussion
- Colour of the fresh and aged kraft paper
- ACBDV of aged kraft paper
- Mechanical strength analysis
- Degree of polymerization (DP)
- Summary of the chapter
Therefore, post-aging analyzes of the insulating kraft paper are carried out, which are explained below. The color of the fresh and aged kraft paper samples is shown in Figure 5.5. Analysis of ACBDV of the insulating kraft paper provides information about its dielectric integrity.
Therefore, a study on the tensile strength of MOIKP and NFIKP at different aging duration is carried out. Thermal aging analysis of MOIKP and NFIKP is performed in four different aging periods.
Vegetable oil based liquid dielectric for transformer
- Introduction
- Nonedible karanji oil as VO
- Extraction of oil
- Chemical processing and esterification
- Chemical characterization .1 FTIR analysis
- NMR analysis
- GCMS analysis
- Experimental process and data analysis
- Thermal conductivity
- Thermogravimetric analysis
- ACBDV analysis
- Weibull Analysis
- Summary of the chapter
The seeds from the karanji tree are now a days widely used for biodiesel production [96]. However, the thermal conductivity of KOME is not stable with the increase in temperature. KOME is derived from CKO, which has higher thermal conductivity due to the triglyceride molecular structure.
There is a 6% decrease in thermal conductivity of aged KOME compared to pure KOME. The measured ACBDV frequency of the four insulating oils is shown in Figure 6.11.
Ageing study of non-edible VO, NF and MO
- Introduction
- Oxidative ageing degradation
- Oxidative ageing reaction of NEO
- Degradation analyses of ageing
- Colour
- Moisture content
- Density
- Viscosity
- Acidity
- Interfacial tension
- Flash, fire, and pour point
- Thermal conductivity
- Fluorescence analysis of aged oil
- DC, DDF and resistivity
- ACBDV study
- ACBDV distribution
- Statistical analysis
- Summary of the chapter
Therefore, the color scale is measured for the fresh and old insulating oil sample shown in Figure 7.3. The densities of MO and aged MO are the lowest compared to fresh and aged samples of NF and NEO. The observed fluorescence of fresh and aged insulating oil is shown in Figure 7.5.
It is observed that the fluorescence maxima of the fresh and aged MO and NF samples are in the region of 379 and 398 nm with a hump. Dielectric loss degradation measurements in three insulating oils were reported.
Spectroscopic analyses of the aged VO and VO-NF
- Introduction
- Preparation of VO-NF and ageing
- Results and Discussion
- Stability of VO-NF
- Colour characteristics
- NMR analysis
- FTIR analysis
- Analysis of UV-vis
- Acid number and interfacial tension with ageing
- Fluorescence spectroscopy
- Analysis using 2D EEM spectra
- DGA study
- Electrical properties .1 ACBDV analysis
- DDF and resistivity
- Summary of the chapter
The changes in color of VO and VO-NF with aging are observed in Figure 8.3 and Figure 8.4. It can be seen from the measurement that the color of VO and VO-NF changes with ageing. These results also confirm the high stability of VO and VO-NF even under harsh environmental conditions.
In this study, the permeability of VO and VO-NF around the fingerprint area is almost unchanged with aging. It can be observed that with the progression of aging, AN in VO and VO-NF increases.
Conclusion and future research
Summary of the present work
The dielectric integrity of the NF and MO is studied by evaluating the ACBDV at a given moisture level. The physicochemical and electrical properties of the NFs are studied after completion of different aging periods and compared with MO. The physicochemical analysis of the aged oil shows that the insulating Eh-BN/MO-NF is minimal.
During the course of the aging period, there is a deterioration of the thermophysical and electrical properties of both oils. The comparative analysis of the physicochemical, thermal and electrical characteristics of the fresh and aged liquid dielectrics such as NEO, NF and MO is carried out.
Contribution of the thesis
Since chemical degradation and dielectric integrity of insulating oil are interrelated, the ACBDV of fresh and aged VO and VO-NF is measured. Since to experience chemical, electrical and thermal stresses during full charge condition, spectroscopic analysis of chemical degradation and measurement of dielectric and electrical strength in aging gives the little information of the possible effect of aging in VO and VO-NF before for use in the transformer. . Therefore, measurements are carried out in detail to justify the VO-NF for its possible application in the transformer.
Suggestions for future research
To regulate the formation of flammable and harmful gases in the aged oil, DGA is performed. It is observed that the presence of insulating NPs, the ester oil decelerates the gas formation tendency of NF compared to VO during the aging process. The frequency domain spectroscopy analysis of the fresh and aged NF and NF impregnated kraft paper can be performed.
Noise attenuation characteristics of the NF filled transformer can be investigated to evaluate the likely effect of NF in the noise reduction.
Bibliography
Cao, “Effects of conductivity and permittivity of nanoparticles on insulation performance of transformer oil: Experiment and theory,” IEEE Trans. Qi, “Recent progress in transformer oil-based nanofluids: Preparation and electrical insulation properties,” IEEE Electr. Wang, “Statistical analysis of AC breakdown voltages of ester-based transformer oils,” IEEE Trans.
Azmy “Dispersion behavior and breakdown strength of transformer oil filled with TiO2 nanoparticles”, IEEE Trans. L Bessede, “Improvement of power transformers using mixtures of mineral oil with synthetic esters,” IEEE Trans.
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