Mohamed A. Izzularab

Bio: Mohamed A. Izzularab is an academic researcher from Menoufia University. The author has contributed to research in topics: Fault (power engineering) & Transformer oil. The author has an hindex of 13, co-authored 43 publications receiving 577 citations.

Modeling and experimental verification of high impedance arcing fault in medium voltage networks

Abstract: A high impedance arcing fault due to a leaning tree in medium voltage (MV) networks is modeled and experimentally verified. The fault is represented in two parts; an arc model and a high resistance. The arc is generated by a leaning tree towards the network conductor and the tree resistance limits the fault current. The arcing element is dynamically simulated using thermal equations. The arc model parameters and resistance values are determined using the experimental results. The fault behavior is simulated by the ATP/EMTP program, in which the arc model is realized using the universal arc representation. The experimental results have validated the system transient model. Discrete wavelet transform is used to extract the fault features and therefore localize the fault events. It is found that arc reignitions enhance fault detection when discrete wavelet transform is utilized

DWT-Based Detection and Transient Power Direction-Based Location of High-Impedance Faults Due to Leaning Trees in Unearthed MV Networks

Abstract: Electrical faults due to leaning trees are common in Nordic countries. This fault type has been studied in and it was found that the initial transients in the electrical network due to the associated arc reignitions are behavioral traits. In this paper, these features are extracted using the discrete wavelet transform (DWT) to localize this fault event. Wireless sensors are considered for processing the DWTs on a residual voltage of different measuring nodes that are distributed in the network. Therefore, the fault detection is confirmed by numerous DWT processors over a wide area of the network. The detection security is also enhanced because the DWT responded to a periodicity of the initial transients. The term for locating the faulty section is based on the polarity of a specific frequency bandpower computed by multiplying the DWT detail coefficient of the residual current and voltage at each measuring node. The fault due to a leaning tree occurring at different locations in an unearthed 20-kV network is simulated by the alternate transients program/electromagnetic transients program and the arc model is implemented using the universal arc representation. Test cases provide evidence of the efficacy of the proposed technique.

The role of interfacial zone in dielectric properties of transformer oil-based nanofluids

Abstract: Transformer oil-based nanofluids have unexpected and distinctive dielectric properties that are different from properties of constituting components. This is believed to be attributed to the effect of interfacial zone between oil and nanoparticles. Accordingly, this paper aims to investigate the role through which the interfacial zone affects the dielectric properties of transformer oil-based nanofluids. Oil-based nanofluids are prepared with two different types of nanoparticles having different surface charging polarity. These types are alumina (Al 2 O 3 ) nanoparticles with cationic surface and titania (TiO 2 ) nanoparticles with anionic surface. For each type of nanoparticles, two groups are prepared with and without a surface modifier, which is called surfactant. Each group consists of four samples having nanoparticles weight fractions of 0.01, 0.04, 0.07 and 0.1 g/L. Surfactant is chosen with charge opposite to that of nanoparticle surface charge to be adsorbed on the nanoparticle surface. For each nanofluid sample, surfactant is distributed through the oil using magnetic stirrer, and then, nanoparticles are mixed and homogenized using magnetic stirrer and ultrasonic processing. After preparation, dielectric properties including breakdown strength and dielectric constant are measured. Based on the obtained results, the role of interfacial zone could be clarified in conjunction to that developed in solid nanodielectrics.

Effect of nanoparticles on transformer oil breakdown strength: experiment and theory

Abstract: This study presents theoretical as well as experimental studies in order to obtain interpretations about the role of nanoparticles in the breakdown mechanism of transformer oil. The published breakdown mechanisms for nanofilled transformer oil are briefly discussed in order to highlight the points of agreement and disagreement with these mechanisms. Moreover, a proposed breakdown mechanism for nanofilled oil is presented depending on a proposed particle charging mechanism that is theoretically discussed and experimentally validated. Finally, the obtained experimental results prove the efficacy of the proposed theoretical mechanisms.

Effect of temperature on AC breakdown voltage of nanofilled transformer oil

Abstract: Studying the effect of adding nanosized ZrO2 to mineral transformer oil on the AC breakdown voltage is presented. The study is carried out considering different concentration levels of nanosized ZrO2. These concentrations are 0, 0.001, 0.002, 0.003 and 0.006%w. The AC breakdown voltage of both nanofilled and base oil is measured according ASTM D1816 standard at room temperature. The evaluation is carried out based on AC breakdown voltage for the nanofilled and base oil considering average and Weibull statistical techniques. Both 50 and 10% breakdown voltage probabilities are obtained and analysed for all samples. Also, the effect of temperature (to take the effect of real operating conditions) on breakdown voltage of base and nanofilled oil is experimentally evaluated. The studied temperatures are 50, 80 and 130°C. The obtained results show that the performance of nanoparticles is significantly affected by increasing the temperature of nanofilled transformer oil. Finally, a proposed mechanism for the effect of temperature on the nanofluids breakdown strength is introduced.

Interface design for high energy density polymer nanocomposites

Abstract: This review provides a detailed overview on the latest developments in the design and control of the interface in polymer based composite dielectrics for energy storage applications. The methods employed for interface design in composite systems are described for a variety of filler types and morphologies, along with novel approaches employed to build hierarchical interfaces for multi-scale control of properties. Efforts to achieve a close control of interfacial properties and geometry are then described, which includes the creation of either flexible or rigid polymer interfaces, the use of liquid crystals and developing ceramic and carbon-based interfaces with tailored electrical properties. The impact of the variety of interface structures on composite polarization and energy storage capability are described, along with an overview of existing models to understand the polarization mechanisms and quantitatively assess the potential benefits of different structures for energy storage. The applications and properties of such interface-controlled materials are then explored, along with an overview of existing challenges and practical limitations. Finally, a summary and future perspectives are provided to highlight future directions of research in this growing and important area.

Microgrid Protection Using Communication-Assisted Digital Relays

Abstract: Microgrids have been proposed as a way of integrating large numbers of distributed renewable energy sources with distribution systems. One problem with microgrid implementation is designing a proper protection scheme. It has been shown that traditional protection schemes will not work successfully. In this paper a protection scheme using digital relays with a communication network is proposed for the protection of the microgrid system. The increased reliability of adding an additional line to form a loop structure is explored. Also a novel method for modeling high impedance faults is demonstrated to show how the protection scheme can protect against them. This protection scheme is simulated on a realistic distribution system containing a high penetration of inverter connected Distributed Generation (DG) sources operating as a microgrid. In all possible cases of operation the primary and secondary relays performed their intended functions including the detection of high impedance faults. This system is simulated using Matlab Simulink's SimPowerSystems toolbox to establish the claims made in this paper.

Detection of High Impedance Fault in Power Distribution Systems Using Mathematical Morphology

Abstract: A high impedance fault (HIF) is characterized by a small, nonlinear, random, unstable, and widely varying fault current in a power distribution system. HIFs draw very low fault currents, and hence are not always effectively cleared by conventional overcurrent relays. Various schemes are proposed to detect such faults. This paper presents a method to detect HIFs using a tool based on mathematical morphology (MM). The method is implemented alongside the conventional overcurrent relay at the substation to improve the performance of this relay in detecting HIFs. It is rigorously tested on standard test systems using PSCAD/EMTDC® to generate test waveforms, and Matlab® to implement the method. Simulation results show that the proposed method is fast, secure, and dependable.

High Impedance Fault Identification on Distribution Networks

Abstract: This paper presents a transient-based algorithm for high-impedance fault identification on distribution networks. It uses the discrete wavelet transform to monitor high- and low-frequency voltage components at several points of the power system, being able to indicate the most likely area within which the disturbance has occurred, without requiring data synchronization nor the knowledge of feeder or load parameters. The proposed algorithm is evaluated through electromagnetic transients program simulations of high-impedance faults in a 13.8 kV system modeled from actual Brazilian distribution grid data. Solid faults, capacitor bank switching, and feeder energization are also simulated, considering the system with and without distributed generation. Obtained results show that the algorithm significantly reduces the search field of the high-impedance fault, reliably distinguishing it from other disturbances.