Article
Polymer Science
Cristina Fernandez-Diego, Alfredo Ortiz, Isidro A. Carrascal, Inmaculada Fernandez, Carlos J. Renedo
Summary: Comparing the aging of cellulose board samples immersed in mineral oil and synthetic ester, it was found that synthetic ester leads to less degradation in the insulation system. Using mechanical properties to quantify the degradation of the cellulose board through kinetic models provides information about the different behavior exhibited by PSP 3055 with different fiber direction angles considered.
Article
Energy & Fuels
Mateusz Cybulski, Piotr Przybylek
Summary: The research analyzed the application of molecular sieves in the drying process of transformer insulation systems, including the study and analysis of water sorption isotherms of various electro-insulating liquids, and the evaluation of the temperature effect on drying dynamics.
Article
Energy & Fuels
Pawel Zukowski, Przemyslaw Rogalski, Tomasz N. Koltunowicz, Konrad Kierczynski, Marek Zenker, Alexander D. Pogrebnjak, Matej Kucera
Summary: This study investigated the conductivity and permittivity of electrical pressboard-insulating liquid-water composites and compared them to water. The presence of water increased the permeability of the composites below 100 Hz, and the conductivity of the composites exponentially increased with increasing water content. The activation energy of the composites' DC conductivity was higher than that of liquid water, and the dielectric relaxation times of the composites were significantly longer than those of water.
Article
Energy & Fuels
Teresa Nogueira, Jose Carvalho, Jose Magano
Summary: This research compares the effects of ester fluid insulation and mineral oil insulation on power transformers. Ester fluids have advantages in electrical performance, but they increase load-losses, mass, and manufacturing costs. However, ester fluids contribute to improved environmental safety and are an eco-friendly option.
Article
Chemistry, Physical
Zaid B. Siddique, Soumen Basu, Prasenjit Basak
Summary: This paper focuses on studying the dielectric behavior of a mixture of natural ester oil and mineral oil blend dispersed with TiO2 and ZnO nanoparticles. The results show an overall enhancement in the dielectric properties of nanofluids, with improved breakdown voltage compared to pure mineral oil, pure ester oil, and the oil-blend. These nanofluids can be used as insulating oils in transformers, offering better cooling performance as well.
JOURNAL OF MOLECULAR LIQUIDS
(2021)
Review
Engineering, Electrical & Electronic
Marina N. Lyutikova, Sergey M. Korobeynikov, U. Mohan Rao, Issouf Fofana
Summary: Due to growing environmental concerns, synthetic and natural esters have become the focus for high-voltage equipment insulation in the past two decades. These ester liquids are biodegradable, non-toxic, safe for the environment and human health, and derived from renewable sources with high fire resistance. However, their use is limited in electrical equipment due to factors such as high cost, viscosity and density, electrostatic charge, and faster propagation of streamers in an inhomogeneous electric field. This article presents a comprehensive review on the blend of mineral oil and alternative dielectric fluids, discussing research progress, challenges, and tutorial elements. This is valuable for researchers, utilities, and transformer owners concerned with ester liquids and retrofilling.
IEEE TRANSACTIONS ON DIELECTRICS AND ELECTRICAL INSULATION
(2022)
Article
Energy & Fuels
Hubert Moranda, Jaroslaw Gielniak, Ireneusz Kownacki
Summary: This research demonstrates the relationship between the concentration of mineral oil and the density of the mixture, as well as the capacitance of a capacitor immersed in it. The study provides two methods for measuring oil concentration in the mixture and recommends the capacitance method as the easier option, especially for online applications.
Article
Engineering, Electrical & Electronic
Jose E. Contreras, Josue Rodriguez, Carlos Gaytan
Summary: Currently, the use of new biodegradable dielectric liquids as an alternative to conventional mineral oil in transformers is being considered. However, the higher viscosity of ester liquids compared to mineral oil requires modifications in the impregnation process of insulation materials.
IEEE TRANSACTIONS ON DIELECTRICS AND ELECTRICAL INSULATION
(2022)
Article
Engineering, Multidisciplinary
M. H. A. Hamid, M. T. Ishak, N. S. Suhaimi, J. Adnan, N. Hashim, M. Ariffin, N. I. A. Katim, Rahisham Abd Rahman
Summary: This paper investigates the dielectric properties and AC breakdown voltage behavior of Palm Oil (PO) and Rice Bran Oil (RBO). It is found that RBO has better insulating oil capability than PO, and PO has advantages in terms of stress distribution. RBO has the highest breakdown voltage, followed by PO, while MO shows the lowest breakdown voltage.
ALEXANDRIA ENGINEERING JOURNAL
(2022)
Article
Chemistry, Analytical
Ruimin Song, Weigen Chen, Ziyi Wang, Zhixian Zhang, Yingzhou Huang, Jianxin Wang
Summary: This study presents a novel approach using dual-enhanced Raman spectroscopy for sensing liquid components. The method employs a centrifugal extractor for selective enhancement of targeted components, and utilizes a liquid-core fiber to optimize laser transmission and Raman signal collection efficiency. The system demonstrates fast, stable, and adaptable performance, suitable for the detection of a wide range of liquid ingredients.
ANALYTICAL CHEMISTRY
(2023)
Article
Energy & Fuels
Piotr Przybylek
Summary: Currently, synthetic ester is gaining a bigger market share, being used in both new and operated transformers filled with mineral oil. This article presents a new method using near-infrared spectroscopy to determine the concentration of mineral oil in a mixture with synthetic ester, with higher accuracy compared to previous methods described in the literature.
Article
Engineering, Electrical & Electronic
Feipeng Wang, Liangxuan Ouyang, Chao Song, Zijian Yang, Shi Li, Yang Xu, Jian Li
Summary: In this study, the natural ester insulating oil (FR3) is blended into the synthetic tetra-ester insulating oil (KA) through mixing and oscillating. The physicochemical and electrical properties of the ester blends indicate that the flash point, fire point, and ac breakdown voltage of KA can be increased, and the dissipation factor of KA can be reduced by the addition of FR3. The optimized ester blend (85% KA: 15% FR3) demonstrates high flash point, low pour point, low dissipation factor, high ac breakdown voltage, and high DSC onset temperature.
IEEE TRANSACTIONS ON DIELECTRICS AND ELECTRICAL INSULATION
(2023)
Article
Engineering, Electrical & Electronic
Obaidur Rahman, Tarikul Islam, Aqueel Ahmad, Shaheen Parveen, Neeraj Khera, Shakeb A. Khan
Summary: This paper proposes a cross capacitance sensor for on-site testing of transformer oil that overcomes limitations of traditional sensors. Through finite element analysis, the sensor is simulated to estimate the concentration of insulation degradation by-products in oil. Experimental validation shows that the sensor's response is linear and highly sensitive.
IEEE SENSORS JOURNAL
(2021)
Article
Green & Sustainable Science & Technology
Anu Kumar Das, Dayal Ch Shill, Saibal Chatterjee
Summary: This paper examines the application of natural esters and new vegetable oils as alternatives to conventional mineral oils in the electric utility. It focuses on the dielectric performance and environmental safety of coconut oil, and discusses its sustainability and market potential.
RENEWABLE & SUSTAINABLE ENERGY REVIEWS
(2022)
Article
Engineering, Electrical & Electronic
U. Mohan Rao, Issouf Fofana, Pawel Rozga, Patrick Picher, Dilip K. Sarkar, Rajan Karthikeyan
Summary: The focus of this study is on the oxidation aspects (gelling) of natural esters and its impact on the performance of transformer insulation systems. Even though natural esters are not suitable for breathing units, the scenario considered simulates a defect in the sealing system, allowing direct contact with atmospheric air. Commercially available natural ester liquids are thermally degraded under controlled aging conditions to observe the formation of sol and gel. The influence of sol and gel on the insulation is analyzed through physicochemical and electrical characterizations.
IEEE TRANSACTIONS ON DIELECTRICS AND ELECTRICAL INSULATION
(2023)
Article
Engineering, Electrical & Electronic
Shafqat Nabi Mughal, Yog Raj Sood, R. K. Jarial
Summary: This study aims to predict global solar radiation by developing time series based neural network models. The results show that nonlinear autoregressive models are a good choice for predicting solar radiation, with the best performance achieved in hourly prediction.
IETE JOURNAL OF RESEARCH
(2023)
Article
Energy & Fuels
Beki Sekongo, Stephan Brettschneider, U. Mohan Rao, Issouf Fofana, Marouane Jabbari, Patrick Picher, Zie Yeo
Summary: This article investigates the breakdown behavior of ester fluids under prolonged usage conditions and evaluates important characteristics. It is found that ester liquids generally perform better than mineral oil in many cases. Additionally, the radius of curvature and thermal aging have an impact on the performance of ester fluids.
Article
Environmental Sciences
S. Nabi Mughal, Y. R. Sood, R. K. Jarial
Summary: In this research, a hybrid model combining nonlinear autoregressive neural networks and empirical models is used to predict global solar radiations on tilted surfaces. The proposed model shows an average 9% increase in global solar radiation reception on tilted surfaces compared to horizontal surfaces. A comparison with other empirical models also indicates that the proposed hybrid model has less error in estimating global solar radiations.
INTERNATIONAL JOURNAL OF ENVIRONMENTAL SCIENCE AND TECHNOLOGY
(2023)
Article
Automation & Control Systems
Anant Kumar Verma, Chandrasekaran Subramanian, Raj Kumar Jarial, Pedro Roncero-Sanchez
Summary: This article presents a robust single-phase phase-locked loop (PLL)-less frequency, phase, and amplitude estimation technique that does not require a rigorous design and tuning process for better stability. The improved discrete-time oscillator involves a comb filter for better dc-offset rejection capability and transient response time. The introduction of imaginary zeros ensures better harmonic removal ability compared to a known nonadaptive discrete-time oscillator. The proposed scheme reduces real-time implementation complexity by using an open-loop frequency estimation technique and avoiding inverse trigonometric functions.
IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS
(2022)
Article
Engineering, Multidisciplinary
Bhumaiah Jula, Raj Kumar Jarial, Anant Kumar Verma, Pedro Roncero-Sanchez, Josep M. Guerrero, Tiago Davi Curi Busarello, Hafiz Ahmed
Summary: This article proposes a robust and enhanced three-phase fundamental frequency estimation algorithm for the electric aircraft grid, which has been experimentally validated to be effective and practical.
Article
Computer Science, Information Systems
Anant Kumar Verma, Chandrasekaran Subramanian, Raj Kumar Jarial
Summary: This paper proposes a nonadaptive error demodulation technique for tracking the amplitude, phase, and frequency information of grid voltage in single-phase applications. The nonadaptive Lyapunov filter has good bandpass filtering characteristics for quickly rejecting DC offset and harmonics. Additionally, the open-loop phase angle deviation algorithm accurately compensates estimated amplitude and phase angle information under off-nominal frequency conditions.
IEEE SYSTEMS JOURNAL
(2022)
Article
Engineering, Multidisciplinary
Manish Kumar, Raj Kumar Jarial, Anant Kumar Verma, Chandrasekaran Subramanian, Ravindra Nath, Panos C. Kotsampopoulos, Claudio Burgos Mellado
Summary: This article presents a scheme for fast and accurate tracking of single-phase grid voltage parameters under distorted grid voltage conditions. The proposed scheme uses a half-cycle moving-window discrete Fourier transform (HC-MWDFT) based pre-filter to ensure stability and orthogonal signal generation. By combining a positive feed-forward comb filter and a fractional complex resonator, odd-order harmonics can be attenuated and fundamental components can be extracted quickly. Unlike traditional phase-locked loop (PLL) techniques, the grid frequency is estimated indirectly using a simple open-loop frequency detector, avoiding the need for complicated controller tuning and external phase/frequency feedback loops.
Article
Engineering, Electrical & Electronic
Kandala N. V. P. S. Rajesh, U. Mohan Rao, I. Fofana, P. Rozga, Ashish Paramane
Summary: This article investigates the influence of data balancing approaches on transformer DGA fault classification, highlighting the importance of selecting suitable data sampling methods and machine learning algorithms for efficient classification.
IEEE TRANSACTIONS ON DIELECTRICS AND ELECTRICAL INSULATION
(2023)
Article
Engineering, Electrical & Electronic
Suchandan Das, Ashish Paramane, Soumya Chatterjee, U. Mohan Rao
Summary: This article proposes a novel and accurate fault classification framework using gas ratios as features obtained from the DGA data of power transformers. The DGA data was balanced using SMOTE and the best features were selected using RFE. Three ML classifiers, namely KNN, SVMs, and XGBoost, were used for fault classification. The proposed method achieved high detection accuracy on both the local power utility data and the benchmark IEC TC-10 database, demonstrating its reliability in diagnosing incipient faults in power transformers.
IEEE TRANSACTIONS ON DIELECTRICS AND ELECTRICAL INSULATION
(2023)
Article
Engineering, Electrical & Electronic
Manish Kumar, Raj Kumar Jarial, Anant Kumar Verma, Ravindra Nath, Miguel Torres, Catalina Gonzalez-Castano, Pedro Roncero-Sanchez
Summary: Fast and precise tracking of grid voltage attributes is crucial for controlling and operating grid-side converters. This study proposes a discrete Fourier transform-based bandpass filter to extract the fundamental frequency positive sequence component from unbalanced and distorted grid conditions. A simple frequency estimator and a curve-fitting based error correction technique are also developed to accurately estimate the amplitude and phase-angle of the fundamental component. Experimental results validate the effectiveness of the proposed scheme.
INTERNATIONAL JOURNAL OF ELECTRICAL POWER & ENERGY SYSTEMS
(2023)
Proceedings Paper
Green & Sustainable Science & Technology
Bhumaiah Jula, Raj Kumar Jarial, Anant Kumar Verma, Claudio Burgos-Mellado, Miguel Torres, Samir Gautam, Hafiz Ahmed, Pedro Roncero-Sanchez
Summary: This article evaluates the suitability of non-adaptive orthogonal signal generation (OSG) approaches for single-phase electric aircraft (EA) grids. Improved filtering capability can enhance the reliability of single-phase grid voltage signals and improve the performance of phase-locked loops (PLLs) and frequency-locked loops (FLLs) under distorted voltage conditions. However, not all OSG approaches are suitable for single-phase EA grids due to wider frequency variations.
2022 IEEE 10TH POWER INDIA INTERNATIONAL CONFERENCE, PIICON
(2022)
Proceedings Paper
Engineering, Electrical & Electronic
U. Mohan Rao, I Fofana, P. Rozga, A. Beroual, J. Malde, R. Martin, Feipeng Wang, Edward Casserly, M. Pompili, L. Calcara
Summary: This article presents the research activities of the IEEE technical committee on liquid dielectrics (TC-LD), with a focus on aging phenomena, condition monitoring, and diagnostic testing of dielectric liquids. The article highlights the importance of environmental and sustainability factors in the study of dielectric liquids. A planned working group within the TC-LD is aimed at understanding and summarizing the challenges and potential of using ester liquids for liquid-filled high-voltage apparatuses, with the objective of improving their workability as high-performance insulating liquids.
2022 IEEE 21ST INTERNATIONAL CONFERENCE ON DIELECTRIC LIQUIDS (ICDL)
(2022)
Proceedings Paper
Engineering, Electrical & Electronic
Jayasree Thota, U. Mohan Rao, I Fofana, P. Picher, S. Brettschneider
Summary: This paper investigates the water behavior of three low pour point insulating liquids and examines the influence of water content on gas generation and breakdown failure probability under high voltage conditions.
2022 IEEE 21ST INTERNATIONAL CONFERENCE ON DIELECTRIC LIQUIDS (ICDL)
(2022)
Review
Engineering, Electrical & Electronic
Marina N. Lyutikova, Sergey M. Korobeynikov, U. Mohan Rao, Issouf Fofana
Summary: Due to growing environmental concerns, synthetic and natural esters have become the focus for high-voltage equipment insulation in the past two decades. These ester liquids are biodegradable, non-toxic, safe for the environment and human health, and derived from renewable sources with high fire resistance. However, their use is limited in electrical equipment due to factors such as high cost, viscosity and density, electrostatic charge, and faster propagation of streamers in an inhomogeneous electric field. This article presents a comprehensive review on the blend of mineral oil and alternative dielectric fluids, discussing research progress, challenges, and tutorial elements. This is valuable for researchers, utilities, and transformer owners concerned with ester liquids and retrofilling.
IEEE TRANSACTIONS ON DIELECTRICS AND ELECTRICAL INSULATION
(2022)
Proceedings Paper
Materials Science, Multidisciplinary
R. K. Jarial, Shafqat Nabi Mughal, Yog Raj Sood
Summary: This paper proposes an optimized design procedure for Photovoltaic system and a Autoregressive Neural Network model for predicting PV power output. The proposed model performs well and outperforms other time-series models according to the comparison results.
MATERIALS TODAY-PROCEEDINGS
(2022)
