stability of natural esters.
1.4.2.2 Vegetable Oils
Vegetable oils are extracted from agro seeds that are accumulated as fatty acid within the seeds. These are also called as natural esters. They are available from renewable sources and are treated as eco‐friendly and biodegradable liquids [29]. Vegetable oils have higher viscosity and high pour point, which degrades the effectiveness to serve as a coolant [31]. At present, the research in the field of natural esters is on to emphasize reduction of viscosity and pour points with improved oxidation stability.
1.4.2.3 Synthetic Ester Liquids
Synthetic esters are such organic compounds that are being developed by synthesizing acids and alcohols. Synthetic esters are available in various chemical compositions depending on the acids and alcohols used for synthesis. Synthetic esters are biodegradable and are developed for high thermal performances with low viscosity and better oxidation stability. Moreover, ester group insulation oils participate actively in hydrolysis, which resists the rate of degradation of the oil.
The complete journey of the liquid dielectrics concerning the transformer insulation technology is outlined and discussed by I. Fofana [30] and U. Mohan Rao et al. [31, 32]. Given the fact that the high demand for alternative biodegradable insulating liquids allowed researchers focus on the performance analysis and behavior of ester liquids. Researchers across the globe have reported numerous studies; this book has been framed to give a complete overview of ester liquids' performance, behavior, and compatibility for current and foreseen transformer insulation technology. To accomplish the same, various topics have been organized in the subsequent chapters of this book. Authors of different chapters aimed to discuss particular topics in a detailed manner. Some fundamental concepts concerning the ester liquids have been spanned to multiple chapters. This is due to the fact that different chapters have been prepared by different research groups. However, due care is taken not to duplicate the sections and technical viewpoints. Therefore, this book editors and authors expect that this book would be useful for transformer owners, utility engineers, and researchers concerned with transformer insulation technology.
References
1 1 Tang, Y., Zhong, J., and Liu, J. (2016). A Generation adjustment methodology considering fluctuations of loads and renewable energy sources. IEEE Transactions on Power Systems 31 (1): 125–132.
2 2 Malinowski, M., Milczarek, A., Kot, R. et al. (2015). Optimized energy‐conversion systems for small wind turbines: renewable energy sources in modern distributed power generation systems. IEEE Power Electronics Magazine 2 (3): 16–30.
3 3 Berseneff, B., Perrin, M., Quoc, T.T. et al. (2014). The significance of energy storage for renewable energy generation and the role of instrumentation and measurement. IEEE Instrumentation & Measurement Magazine 17 (2): 34–40.
4 4 Díaz, N.L., Luna, A.C., Vasquez, J.C., and Guerrero, J.M. (2017). Centralized control architecture for coordination of distributed renewable generation and energy storage in islanded AC microgrids. IEEE Transactions on Power Electronics 32 (7): 5202–5213.
5 5 Wei, W., Liu, F., Mei, S., and Hou, Y. (2015). Robust energy and reserve dispatch under variable renewable generation. IEEE Transactions on Smart Grid 6 (1): 369–380.
6 6 Wang, Z., Chen, Y., Mei, S. et al. (2017). Optimal expansion planning of isolated microgrid with renewable energy resources and controllable loads. IET Renewable Power Generation 11 (7): 931–940.
7 7 Mohan, V., Suresh, R., Singh, J.G. et al. (2017). Microgrid energy management combining sensitivities, interval and probabilistic uncertainties of renewable generation and loads. IEEE Journal on Emerging and Selected Topics in Circuits and Systems 7 (2): 262–270.
8 8 Yang, P. and Nehorai, A. (2014). Joint optimization of hybrid energy storage and generation capacity with renewable energy. IEEE Transactions on Smart Grid 5 (4): 1566–1574.
9 9 Li, N. and Hedman, K.W. (2015). Economic assessment of energy storage in systems with high levels of renewable resources. IEEE Transactions on Sustainable Energy 6 (3): 1103–1111.
10 10 Wong, S. and Pinard, J.P. (2017). Opportunities for smart electric thermal storage on electric grids with renewable energy. IEEE Transactions on Smart Grid 8 (2): 1014–1022.
11 11 Baker, K., Guo, J., Hug, G., and Li, X. (2016). Distributed MPC for efficient coordination of storage and renewable energy sources across control areas. IEEE Transactions on Smart Grid 7 (2): 992–1001.
12 12 Hill, C.A., Such, M.C., Chen, D. et al. (2012). Battery energy storage for enabling integration of distributed solar power generation. IEEE Transactions on Smart Grid 3 (2): 850–857.
13 13 Djairam, D., Morshuis, P.H.F., and Smit, J.J. (2014). A novel method of wind energy generation‐the electrostatic wind energy converter. IEEE Electrical Insulation Magazine 30 (4): 8–20.
14 14 Abdelsamad, S.F., Morsi, W.G., and Sidhu, T.S. (2015). Impact of wind‐based distributed generation on electric energy in distribution systems embedded with electric vehicles. IEEE Transactions on Sustainable Energy 6 (1): 79–87.
15 15 Wang, H. and Huang, J. (2016). Cooperative planning of renewable generations for interconnected microgrids. IEEE Transactions on Smart Grid 7 (5): 2486–2496.
16 16 Betie, A., Rao, U.M., Fofana, I. et al. (Dec. 2019). Influence of cellulose paper on gassing tendency of transformer oil under electrical discharge. IEEE Transactions on Dielectrics and Electrical Insulation 26 (6): 1729–1737.
17 17 Leila, S., Zafour, H., Rao, U.M., and Fofana, I. (2019). Regeneration of transformer insulating fluids using membrane separation technology. Energies 12 (3): 368.
18 18 Theraja, B.L. and Theraja, A.K. (2014). Electrical Technology, vol. II. New Delhi, India: S. Chand Publishers.
19 19 Kulkarni, S.V. and Khaparde, S.A. (2004). Transformer Engineering: Design and Practice. CRC Press.
20 20 ASTM (2018). D117‐18, Standard Guide for Sampling, Test Methods, and Specifications for Electrical Insulating Liquids. West Conshohocken, PA: ASTM International.
21 21 Chakravorti, S., Dey, D., and Chatterjee, B. (2013). Recent Trends in the Condition Monitoring of Transformers, 1ste. London: Springer‐Verlag.
22 22 Kassi, K.S., Fofana, I., Meghnefi, F., and Yeo, Z. (2015). Impact of local overheating on conventional and hybrid insulations for power transformers. IEEE Transactions on Dielectrics and Electrical Insulation 22 (5): 2543–2553.
23 23 Rao, U.M., Sood, Y.R., and Jarial, R.K. (2016). Physiometric and Fourier transform infrared spectroscopy analysis of cellulose insulation in blend of mineral and synthetic ester oils for transformers. IET Science, Measurement & Technology 11 (3): 297–304.
24 24 Rao, U.M., Fofana, I., Betie, A. et al. (Nov.‐Dec. 2019). Condition monitoring of in‐service oil‐filled transformers: case studies and experience. IEEE Electrical Insulation Magazine 35 (6): 33–42.
25 25 Martin, D., Saha, T., Gray, T., and Wyper, K. (2015). Determining water in transformer paper insulation: effect of measuring oil water activity at two different locations. IEEE Electrical Insulation Magazine 31 (3): 18–25.
26 26 Martin, D., Saha, T., Dee, R. et al. (2015). Determining water in transformer paper insulation: analyzing ageing transformers. IEEE Electrical Insulation Magazine 31 (5): 23–32.
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