Aaltodoc Repository :: Browsing by Author "Mansour, Diaa Eldin A."

Browsing by Author "Mansour, Diaa Eldin A."

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Condition Assessment of Natural Ester–Mineral Oil Mixture Due to Transformer Retrofilling via Sensing Dielectric Properties
(MDPI AG, 2023-07) Karaman, Hesham S.; Mansour, Diaa Eldin A.; Lehtonen, Matti; Darwish, Mohamed M.F.; Department of Electrical Engineering and Automation; Power Systems and High Voltage Engineering; Benha University; Egypt-Japan University of Science and Technology
Mineral oil (MO) is the most popular insulating liquid that is used as an insulating and cooling medium in electrical power transformers. Indeed, for green energy and environmental protection requirements, many researchers introduced other oil types to study the various characteristics of alternative insulating oils using advanced diagnostic tools. In this regard, natural ester oil (NEO) can be considered an attractive substitute for MO. Although NEO has a high viscosity and high dielectric loss, it presents fire safety and environmental advantages over mineral oil. Therefore, the retrofilling of aged MO with fresh NEO is highly recommended for power transformers from an environmental viewpoint. In this study, two accelerated aging processes were applied to MO for 6 and 12 days to simulate MO in service for 6 and 12 years. Moreover, these aged oils were mixed with 80% and 90% fresh NEO. The dielectric strength, relative permittivity, and dissipation factor were sensed using a LCR meter and oil tester devices for all prepared samples to support the condition assessment performance of the oil mixtures. In addition, the electric field distribution was analyzed for a power transformer using the oil mixtures. Furthermore, the dynamic viscosity was measured for all insulating oil samples at different temperatures. From the obtained results, the sample obtained by mixing 90% natural ester oil with 10% mineral oil aged for 6 days is considered superior and achieves an improvement in dielectric strength and relative permittivity by approximately 43% and 48%, respectively, compared to fresh mineral oil. However, the dissipation factor was increased by approximately 20% but was at an acceptable limit. On the other hand, for the same oil sample, due to the higher molecular weight of the NEO, the viscosities of all mixtures were at a higher level than the mineral oil.
Emerging applications of IoT and cybersecurity for electrical power systems
(Institution of Engineering and Technology, 2023-10) Darwish, Mohamed M.F.; Elsisi, Mahmoud; Fouda, Mostafa M.; Mansour, Diaa Eldin A.; Lehtonen, Matti; Department of Electrical Engineering and Automation; Power Systems and High Voltage Engineering; Benha University; Idaho State University; Egypt-Japan University of Science and Technology
Evaluating transient behaviour of large-scale photovoltaic systems during lightning events using enhanced finite difference time domain method with variable cell size approach
(Institution of Engineering and Technology, 2024-06) Hetita, Ibrahim; Mansour, Diaa Eldin A.; Han, Yang; Yang, Ping; Wang, Congling; Darwish, Mohamed M.F.; Lehtonen, Matti; Zalhaf, Amr S.; Department of Electrical Engineering and Automation; Power Systems and High Voltage Engineering; University of Electronic Science and Technology of China; Tanta University; Benha University
Photovoltaic (PV) arrays are usually installed in open areas; hence, they are vulnerable to lightning strikes that can result in cell degradation, complete damage, service disruption, and increased maintenance costs. As a result, it is imperative to develop an effective and efficient lightning protection system by evaluating the transient behaviour of PV arrays during lightning events. The aim is to evaluate the transient analysis of large-scale PV systems when subjected to lightning strikes using the finite difference time domain (FDTD) technique. Transient overvoltages are calculated at various points within the mounting system. To optimise the FDTD method's execution time and make it more suitable for less powerful hardware, a variable cell size approach is employed. Specifically, larger cell dimensions are used in the earthing system and smaller cell dimensions are used in the mounting system. The FDTD method is utilised to calculate the temporal variation of transient overvoltages for large-scale PV systems under different scenarios, including variations in the striking point, soil resistivity, and the presence of a metal frame. Simulation results indicate that the highest transient overvoltages occur at the striking point, and these values increase with the presence of a PV metal frame as well as with higher soil resistivity. Furthermore, a comparison is performed between the overvoltage results obtained from the FDTD approach and the partial element equivalent circuit (PEEC) method at the four corner points of the mounting systems to demonstrate the superior accuracy of the FDTD method. Besides, a laboratory experiment is conducted on a small-scale PV system to validate the simulation results. The calculated overvoltages obtained from the FDTD and PEEC methods are compared with the measured values, yielding a mean absolute error of 5% and 11% for the FDTD and PEEC methods, respectively, thereby confirming the accuracy of the FDTD simulation model.
Influence of Mineral Oil-Based Nanofluids on the Temperature Distribution and Generated Heat Energy Inside Minimum Oil Circuit Breaker in Making Process
(MDPI AG, 2023-06-27) Karaman, Hesham S.; El Dein, Adel Z.; Mansour, Diaa Eldin A.; Lehtonen, Matti; Darwish, Mohamed M.F.; Department of Electrical Engineering and Automation; Power Systems and High Voltage Engineering; Benha University; Aswan University; Egypt-Japan University of Science and Technology
The enhancement of the thermal properties of insulating oils has positively reflected on the performance of the electrical equipment that contains these oils. Nanomaterial science plays an influential role in enhancing the different properties of liquids, especially insulating oils. Although a minimum oil circuit breaker (MOCB) is one of the oldest circuit breakers in the electrical network, improving the insulating oil properties develops its performance to overcome some of its troubles. In this paper, 66 kV MOCB is modeled by COMSOL Multiphysics software. The internal temperature and the internally generated heat energy inside the MOCB during the making process of its contacts are simulated at different positions of the movable contact. This simulation is introduced for different modified insulating oils (mineral oil and synthetic ester oil) with different types of nanoparticles at different concentrations (0.0, 0.0025, 0.005, and 0.01 wt%). From the obtained results, it is noticed that the thermal stress on the MOCB can be reduced by the use of high thermal conductivity insulating oils. Nano/insulating oils decrease internal temperature and generate heat energy inside the MOCB by about 17.5%. The corresponding physical mechanisms are clarified considering the thermophoresis effect.
A new technique for fault diagnosis in transformer insulating oil based on infrared spectroscopy measurements
(Institution of Engineering and Technology, 2024-04) Darwish, Mohamed M.F.; Hassan, Mohamed H.A.; Abdel-Gawad, Nagat M.K.; Lehtonen, Matti; Mansour, Diaa Eldin A.; Department of Electrical Engineering and Automation; Power Systems and High Voltage Engineering; Benha University; Egypt-Japan University of Science and Technology
Condition monitoring of the insulating system within power transformers has a massive importance according to the electrical utilities. Dissolved gas analysis (DGA) is frequently used for this purpose. However, DGA lacks the necessary level of accuracy to identify all equipment faults, particularly in their initial stages of degradation. Also, it does not have the capability for real-time monitoring and relies on manual sampling and laboratory testing, causing potential delays in fault identification. Additionally, the interpretation of DGA data necessitates specialised expertise, which may pose difficulties for smaller entities that have limited access to resources. Therefore, the contribution of this research is to use infrared spectroscopy measurements as a new effective technique substituting the DGA method for fault diagnosis in insulating oil. The inception faults that were considered in this study were the electrical fault (discharges of high energy) and the thermal fault (300°C < Temperature <700°C). Regarding that, two test cells were crafted especially for serving the simulation processes inside the laboratory for both types of inception faults. Subsequently, six samples of pure paraffinic mineral oil were taken to be degraded in the laboratory. Following that, all of them besides another sample that were not subjected to any kind of faults were taken to be examined by Fourier transform infrared (FTIR) spectroscopy to obtain an overview of the oil's behaviour in each fault case. After that, the FTIR analysis was initially verified utilising the DGA method. Then, for further affirmation, the dielectric dissipation factor (DDF) for all samples was measured. In the final analysis, the verification tests provide experimental evidence about the outperformance of this new optical technique in detecting the transformer's inception faults in addition to proving its potential for being a superior alternative to the well-known traditional diagnostic techniques.
A Novel Polyester Varnish Nanocomposites for Electrical Machines with Improved Thermal and Dielectric Properties Using Functionalized TiO2 Nanoparticles
(MDPI AG, 2023-10) Ahmed, Hanaa M.; Abdel-Gawad, Nagat M.K.; Afifi, Waleed A.; Mansour, Diaa Eldin A.; Lehtonen, Matti; Darwish, Mohamed M.F.; Department of Electrical Engineering and Automation; Power Systems and High Voltage Engineering; Benha University; Egypt-Japan University of Science and Technology
Recently, there has been a growing interest in polymer insulating materials that incorporate nanoscale inorganic additives, as they have shown significantly improved dielectric, thermal, and mechanical properties, making them highly suitable for application in high-voltage insulating materials for electrical machines. This study aims to improve the dielectric and thermal properties of a commercial polyester varnish by incorporating different concentrations of titanium dioxide nanoparticles (TiO2) with proper surface functionalization. Permafil 9637 dipping varnish is the varnish used for this investigation, and vinyl silane is the coupling agent used in the surface functionalization of TiO2 nanoparticles. First, nanoparticles are characterized through Fourier transform infrared spectroscopy to validate the success of their surface functionalization. Then, varnish nanocomposites are characterized through field emission scanning electron microscopy to validate the dispersion and morphology of nanoparticles within the varnish matrix. Following characterization, varnish nanocomposites are evaluated for thermal and dielectric properties. Regarding thermal properties, the thermal conductivity of the prepared nanocomposites is assessed. Regarding dielectric properties, both permittivity and dielectric losses are evaluated over a wide frequency range, starting from 20 Hz up to 2 MHz. Moreover, the AC breakdown voltage is measured for varnish nanocomposites, and the obtained data are incorporated into a finite element method to obtain the dielectric breakdown strength. Finally, the physical mechanisms behind the obtained results are discussed, considering the role of nanoparticle loading and surface functionalization.
On Highlighting the Merits of Gas-to-Liquid Transformer Oil Under Accelerated Thermal Aging and Faults: Electrical and Physio- Chemical Properties
(IEEE, 2024) Badawi, Mohamed; Ibrahim, Shimaa A.; Mansour, Diaa Eldin A.; Ward, Sayed A.; El-Faraskoury, Adel A.; Ghali, Mohsen; Mahmoud, Karar; Lehtonen, Matti; Darwish, Mohamed M.F.; Department of Electrical Engineering and Automation; Power Systems and High Voltage Engineering; Benha University; Tanta University; Egyptian Electricity Holding Company; Egypt-Japan University of Science and Technology
Mineral (MO) oil has long been utilized as a dielectric and cooling medium in high-voltage power transformers due to its low cost and availability. Recently, there has been a great trend toward the use of gas-to-liquid (GTL) oil due to its purity, chemical consistency, and better performance than conventional oils. This study aims to investigate the normal and abnormal thermal impacts on GTL and MO oil types. In this regard, this paper presents two parts. Firstly, it studies a comprehensive evaluation of the aging characteristics under normal conditions of GTL oil in comparison to conventional MO. Aged oil samples were obtained using a laboratory-based accelerated aging test, for simulating the thermal stress during the transformer's operation. Hence, the two oil types are subjected to different aging durations (i.e., 3, 6, and 10 days). These aged and fresh samples were tested for AC breakdown voltage, dielectric dissipation factor, permittivity, and resistivity as electrical testing. Additionally, as chemical and physical testing, moisture and acidity are measured for fresh and aged samples of two of these oil types. Besides, optical spectroscopy measurements have been used for insulating oil assessment; these kinds of measurements point out the existence of overall aging byproducts, including sludge formation, which can negatively impact the oil properties including physio-chemical and electrical properties. The used optical techniques include Ultraviolet-visible absorption and photoluminescence tests. Secondly, thermal faults impact as abnormal conditions is generally evaluated through dissolved gas analysis as a chemical test, where it is utilized to measure the gas concentrations for the two oils under abnormal conditions test after the thermal heating test. This study concluded that the electrical and physio-chemical properties of GTL oil with aging have superior results compared to MO oil.
PVC nanocomposites for cable insulation with enhanced dielectric properties, partial discharge resistance and mechanical performance
(2020-08-01) Abdel-Gawad, Nagat M.K.; El Dein, Adel Z.; Mansour, Diaa Eldin A.; Ahmed, Hanaa M.; Darwish, Mohamed M.F.; Lehtonen, Matti; Department of Electrical Engineering and Automation; Power Systems and High Voltage Engineering; Benha University; Aswan University; Tanta University
The current study aims to develop polyvinyl chloride (PVC) nanocomposites with enhanced electrical and mechanical properties by incorporating titanium oxide (TiO2) nanoparticles within PVC chains. Different loading of nanoparticles and different nanoparticle surface states were considered. The surface states are unfunctionalised, functionalised using vinyl silane and functionalised using amino silane. The choice of a most suitable surface state was a critical factor that guarantees a good dispersion of nanoparticles and consequently enhances the compatibility between TiO2and PVC matrix. The process followed in the PVC/TiO2nanocomposites preparation, loaded with different wt.% of TiO2nanoparticles, was the solvent method. The dielectric properties measured here were the relative permittivity (ϵr), dielectric loss (tano), breakdown strength (AC and DC under uniform field) and the internal partial discharges (PDs) within insulation cavity. All measurements have been performed under room temperature and at frequency ranged from 20 to 1.0 MHz. Furthermore, the mechanical properties of the samples like elongation, elasticity modulus and tensile strength were also studied. Vinyl silane showed better improvements in both electrical and mechanical performances compared to the amino silane, especially in cases of high weight fractions of TiO2. This is because of the improvement in the PVC-TiO2interfacial region arise from the similarity of polarity and surface tension values of vinyl silane with that of PVC matrix and TiO2nanoparticles.
Reliable Estimation for Health Index of Transformer Oil Based on Novel Combined Predictive Maintenance Techniques
(IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2022-03-02) Badawi, Mohamed; Ibrahim, Shimaa A.; Mansour, Diaa Eldin A.; EL-Faraskoury, Adel; Ward, Sayed A.; Mahmoud, Karar; Lehtonen, Matti; Darwish, Mohamed M.F.; Department of Electrical Engineering and Automation; Power Systems and High Voltage Engineering; Benha University; Tanta University; Egyptian Electricity Holding Company
Transformer oil insulation condition may be deteriorated due to electrical and thermal faults, which may lead to transformer failure and system outage. In this regard, the first part of this paper presents comprehensive maintenance for power transformers aiming to diagnose transformer faults more accurately. Specifically, it aims to identify incipient faults in power transformers using what is known as dissolved gas analysis (DGA) with a new proposed integrated method. This proposed method for DGA is implemented based on the integration among the results of five different DGA techniques; 1) conditional probability, 2) clustering, 3) Duval triangle, 4) Roger's four ratios refined, and 5) artificial neural network. Accordingly, this proposed integrated DGA method could improve the overall accuracy by 93.6% compared to the existing DGA techniques. In addition, the second part used for predictive maintenance is based on determining the health index for five new transformers and an aged power transformer (66/11 kV, 40 MVA) filled with NYTRO 10XN oil by evaluating the breakdown voltage, DGA, moisture content, and acidity for the oil. In the breakdown voltage test, two practical types of transformer oil; NYTRO 10XN and HyVolt III alongside their mixtures are estimated and compared. In addition, aged oil samples extracted from a real case study in-service transformer during operation with different aged durations; 9, 10, 11, 12, and 13 years, are tested for breakdown voltage, and then compared with fresh oil samples. For DGA, a temperature rise test is performed on the five new transformers with a comparison between dissolved gases before and after the temperature rise. In addition, winding resistance is measured after the temperature rise. Also, acidity and moisture are measured for oils extracted from the new five transformers and from the 13-year in-service transformer for studying their health index. The health index of the transformer insulation system is examined using only DGA and DGA plus breakdown voltage (BDV), moisture, and acidity. The results show that by using DGA plus BDV, moisture, and acidity, the health index provides reliable estimation results compared to using only DGA.

Browsing by Author "Mansour, Diaa Eldin A."

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