Electric Power Devices Research Articles

A smart antenna system for remote supervision

This paper presents a switched smart antenna system, designed to provide a reliable communication between a Center for Integrated Operation of a distributor of electric power and automation devices such as electrical switches remotely controlled. The smart antenna system is controlled by an electronic device which sets de direction of the main lobe of an antenna array to the automation device. Network of power distribution automation devices are used as switches, remotely controlled and su- pervised by a Center for Integrated Operation (COI, from Portuguese Centro de Operacao Integrado). The communication between the COI and the automation devices can be performed by various forms of media such as dial-up, cellular, satellite and radio link in the UHF band. In the case of UHF radio link, the system consists of a base station that communicates with all devices in the area, focuses the information and sends it to the COI. The base station is usually located at a substation of the electricity Distribution Company, and devices on poles. At the base station, an antenna array of collinear dipoles is used which produces an omnidirectional radiation pattern with gain of about 6 dBi. The distance,terrain, vegetation and buildings in the path between the devices and the base can disrupt radio communication, leaving these devices in shadow regions. An increase in signal intensity would be sufficient to overcome various obstacles and reestablish communication path, eliminating the shadow regions. This could be achieved by the omnidirectional dipole array, but at the expenses of a great number of dipoles which in the end would be unpractical. This paper describes a smart antenna switched system installed at the base station that focuses the main lobe towards the automation device with a higher gain than the one of the original system. This would reestablish communication and also would be able to spread the communi- cation with more devices to be installed for further expansion. As far as the authors are concerned, no similar application of a smart antenna array has been reported yet.

A dc plasma source for plasma–material interaction experiments

A new device has been constructed for the investigation of interactions between engineered materials and a plasma in regimes relevant to electric propulsion and pulsed power devices. A linear plasma source, consisting of a hollow cathode, cylindrical anode, and axial magnetic field, delivers a 3 cm diameter beam to a biased target 70 cm away. The ion energy impacting the surface is controlled by biasing the sample from 0 to 500 V below the local plasma potential. This paper discusses the major aspects of the plasma source design and presents measurements of the plasma parameters achieved to date on argon and xenon. Experiments show that splitting the gas injection between the hollow cathode and the anode region provides control of the discharge voltage to minimize cathode sputtering while providing ion fluxes to the target in excess of 1021 m−2 s−1. Sputtering rate measurements on a non-textured molybdenum sample show close agreement with those established in the literature.

Silicone insulators of power transmission lines with a variable inorganic load concentration: Electrical and physiochemical analyses

Polymeric insulation is an increasing tendency in projects and maintenance of electrical networks for power distribution and transmission. Electrical power devices (e.g., insulators and surge arresters) developed by using polymeric insulation presents many advantages compared to the prior power components using ceramic insulation, such as: a better performance under high pollution environment; high hydrophobicity; high resistance to mechanical, electrical and chemical stresses. The practice with silicone insulators in polluted environments has shown that the ideal performance is directly related to insulator design and polymer formulation. One of the most common misunderstandings in the design of silicone compounds for insulators is the amount of inorganic load used in their formulation. This paper attempts to clarify how the variation of the inorganic load amount affects physicochemical characteristics of different silicone compounds. The physicochemical evaluation is performed from several measurements, such as: density, hardness, elongation, tensile strength. In addition, the evaluation of the physicochemical structure is carried out using infrared test and scanning electronic microscopy (SEM). The electrical analysis is performed from the electric tracking wheel and erosion test, in agreement with the recommendation of the International Electrotechnical Commission (IEC).

Development of Low AC Loss TFA-MOD Coated Conductors

TFA-MOD process is expected to be promising for future applications since it can produce high performance YBCO coated conductors (CCs) with low cost. Applying YBCO CCs to the power electric devices such as transformers and power cables, the reduction of alternating current (AC) loss for long wire is necessary. Multi-filamentation process, which is one of the most effective approaches for AC loss reduction, has been developed by the scribing process. We have developed the filamentation process using chemical etching. MOD derived CCs are, however, easily damaged in the chemical etching process due to existence of pores in a YBCO layer, resulting in critical current (Ic)-degradation and weak delamination strength. Consequently, it is difficult to scribe MOD derived CCs into 1mm-wide filaments for long length using the chemical etching process. Accordingly, we have studied a scribing process using an excimer laser without chemical etching. We defined P’ value in this study as a function of irradiated laser power [J] divided by processing speed[m/s]. We studied relationship between the P’ value and the results of scribing. It was found that we could scribe the C.C. with a sufficient depth in the condition of large P’ value. Furthermore, we found that the Ic was degraded with further increase of the P’ value. A 5mm wide short sample was divided into 10 filaments by the excimer laser scribing process at the P’ of 9[J/(m/s)]. The sample revealed reduction of the hysteresis loss down to 1/10 which could be expected from a theoretical prediction using the numbers of the filaments. Ic-degradation was suppressed as 28%, which was smaller than that of the scribed sample using chemical etching (Ic degradation was 38%). Subsequently, we applied the technique to a 100m long YBCO CC. The hysteresis loss of the 100m long MOD derived CC was reduced down to 1/10 (1/the number of filaments) after the multi-filamentation.

Energy Harvesting from Electromagnetic Waves and its Application

Power supply is one of the key challenges for perpetual operation of electrical devices in Internet of Things (IoT) era. Low power electrical devices used at home are usually powered by coin cell batteries. However, the battery charging for such devices result in significant increases in operation cost. In this paper, we discuss feasibility of harvesting and storing a small amount of energy from ambient electromagnetic waves. A combination of an antenna and rectifier can be used to collect a few hundreds of microwatts of energy from several energy sources such as TV towers and microwave ovens. By accumulating this energy over time by a capacitor, it is possible to provide power to low-power devices and realize perpetual operation of such devices.

デバイス用ダイヤモンドウェハのUVアシスト研磨に関する研究

デバイス用ダイヤモンドウェハのUVアシスト研磨に関する研究

Needs of High Temperature Superconductivity in Technology Development of Advanced Electric Power Devices

Needs of High Temperature Superconductivity in Technology Development of Advanced Electric Power Devices

A hybrid electric power device for simultaneous generation and storage of electric energy

We herein report on an entirely new kind of electric power device. In the hybrid device, chemical energy is directly converted into electric energy, which is capacitively stored within a singular contrivance. The device is built based on dual-function electrodes, viz. discrete electrodes manifesting simultaneous electrocatalytic and charge-storage features.

The influence of ultrasound signal parameters on sonoluminescence light intensity

Abstract Topics of this article concern the study of the fundamental nature of the sonoluminescence phenomenon occurring in liquids. At the Institute of Electrical Power Engineering at Opole University of Technology the interest in that phenomenon known as secondary phenomenon of cavitation caused by ultrasound became the genesis of a research project concerning acoustic cavitation in mineral insulation oils in which a number of additional experiments performed in the laboratory aimed to determine the influence of a number of acoustic parameters on the process of the studied phenomenona. The main purpose of scientific research subject undertaken was to determine the relationship between the generation of partial discharges in high-voltage power transformer insulation systems, the issue of gas bubbles in transformer oils and the generated acoustic emission signals. It should be noted that currently in the standard approach, the phenomenon of generation of acoustic waves accompanying the occurrence of partial discharges is generally treated as a secondary phenomenon, but it can also be a source of many other related phenomena. Based on our review of the literature data on those referred subjects taken, it must be noted, that this problem has not been clearly resolved, and the description of the relationship between these phenomena is still an open question. This study doesn’t prove all in line with the objective of the study, but can be an inspiration for new research project in the future in this topic. Solution of this problem could be a step forward in the diagnostics of insulation systems for electrical power devices based on non-invasive acoustic emission method.

Three-Dimensionally Ordered Mesoporous (3DOm) Carbon Materials as Electrodes for Electrochemical Double-Layer Capacitors with Ionic Liquid Electrolytes

Compared to rechargeable batteries, electrochemical double-layer capacitors (EDLCs) are normally considered to be higher power but lower electrical energy density charge storage devices. To increase the energy density, one can enlarge the interfacial area between electrodes and electrolyte through the introduction of nanopores and employ electrolytes that are stable over wider voltage ranges, such as ionic liquids. However, due to the relatively high viscosity of ionic liquids and large ion sizes, these measures can result in diminished power performance. Here, we describe the synthesis of carbon electrodes that overcome these limitations and simultaneously provide high specific energies and high specific powers in EDLCs using the ionic liquid EMI-TFSI as an electrolyte. A colloidal crystal templating method was optimized to synthesize three-dimensionally ordered mesoporous (3DOm) carbons with well-defined geometry, three-dimensionally interconnected pore structure and tunable pore size in the range from ...

Analysis of Acoustic Signals Interfering Diagnostic Measurements of Electric Power Transformer Tap Changers

Subject matter of this paper applies to improvement of acoustic emission method used in the diagnosis of on load tap changers of high power transformers. During measurement of acoustic emission signals generated by damages or defects, which can appear in insulation system and in the power transformer tap changers, various forms of noise signals may occur. Interferences occurring during measurements under laboratory and under industrial conditions can be generated either by sources placed inside the studied electric power device or they can be emitted in their immediate vicinity. Sources of interfering signals are physical phenomena of a mechanical, electrical or acoustical nature. Interferences appearing during measurement of acoustic emission pulses generated by electrical discharges and other types of defects that overlap the measured waveforms may result in their distortion. As part of the research conducted, the results of which are presented in this paper, following was subjected under consideration: measurements of acoustic noise signals generated by partial surface discharges occurring on support and bushing insulators were performed.

Interfacial band configuration and electrical properties of LaAlO3/Al2O3/hydrogenated-diamond metal-oxide-semiconductor field effect transistors

In order to search a gate dielectric with high permittivity on hydrogenated-diamond (H-diamond), LaAlO3 films with thin Al2O3 buffer layers are fabricated on the H-diamond epilayers by sputtering-deposition (SD) and atomic layer deposition (ALD) techniques, respectively. Interfacial band configuration and electrical properties of the SD-LaAlO3/ALD-Al2O3/H-diamond metal-oxide-semiconductor field effect transistors (MOSFETs) with gate lengths of 10, 20, and 30 μm have been investigated. The valence and conduction band offsets of the SD-LaAlO3/ALD-Al2O3 structure are measured by X-ray photoelectron spectroscopy to be 1.1 ± 0.2 and 1.6 ± 0.2 eV, respectively. The valence band discontinuity between H-diamond and LaAlO3 is evaluated to be 4.0 ± 0.2 eV, showing that the MOS structure acts as the gate which controls a hole carrier density. The leakage current density of the SD-LaAlO3/ALD-Al2O3/H-diamond MOS diode is smaller than 10−8 A cm−2 at gate bias from −4 to 2 V. The capacitance-voltage curve in the depletion mode shows sharp dependence, small flat band voltage, and small hysteresis shift, which implies low positive and trapped charge densities. The MOSFETs show p-type channel and complete normally off characteristics with threshold voltages changing from −3.6 ± 0.1 to −5.0 ± 0.1 V dependent on the gate length. The drain current maximum and the extrinsic transconductance of the MOSFET with gate length of 10 μm are −7.5 mA mm−1 and 2.3 ± 0.1 mS mm−1, respectively. The enhancement mode SD-LaAlO3/ALD-Al2O3/H-diamond MOSFET is concluded to be suitable for the applications of high power and high frequency electrical devices.

The Review of Dynamic Voltage Restorer in Power System

Dynamic Voltage Restorer, as an important electric power device, used to deal with the voltage sag. In the front of the article, the voltage sag is introduced firstly, and then shows the basic structure and principle of Dynamic Voltage Restorer, research status, existing problems. Finally I will try to give the development trend of Dynamic Voltage Restorer.

Biofuel Cells for Biomedical Applications: Colonizing the Animal Kingdom

Interdisciplinary research has combined the efforts of many scientists and engineers to gain an understanding of biotic and abiotic electrochemical processes, materials properties, biomedical, and engineering approaches for the development of alternative power-generating and/or energy-harvesting devices, aiming to solve health-related issues and to improve the quality of human life. This review intends to recapitulate the principles of biofuel cell development and the progress over the years, thanks to the contribution of cross-disciplinary researchers that have combined knowledge and innovative ideas to the field. The emergence of biofuel cells, as a response to the demand of electrical power devices that can operate under physiological conditions, are reviewed. Implantable biofuel cells operating inside living organisms have been envisioned for over fifty years, but few reports of implanted devices have existed up until very recently. The very first report of an implanted biofuel cell (implanted in a grape) was published only in 2003 by Adam Heller and his coworkers. This work was a result of earlier scientific efforts of this group to "wire" enzymes to the electrode surface. The last couple of years have, however, seen a multitude of biofuel cells being implanted and operating in different living organisms, including mammals. Herein, the evolution of the biofuel concept, the understanding and employment of catalyst and biocatalyst processes to mimic biological processes, are explored. These potentially green technology biodevices are designed to be applied for biomedical applications to power nano- and microelectronic devices, drug delivery systems, biosensors, and many more.

Ultra-small Fe3O4 nanoparticle decorated graphene nanosheets with superior cyclic performance and rate capability

Advanced anode materials for next generation lithium ion batteries have attracted great interest due to the ever increasing demand for powerful, light-weight, and compact electrical devices. In this work, graphene nanosheets decorated with ultra-small Fe3O4 nanoparticles (USIO/G) were synthesized via a facile hydrothermal method. Compared with other reported Fe3O4-based anode composites, USIO/G demonstrated superior cyclic ability and excellent rate capability owing to its ultra-small size of active lithium storage sites, Fe3O4, with an average diameter less than 5 nm. Furthermore, graphene nanosheets played an important role in the overall electrochemical performance of the composite by enhancing the electrical conductivity, forming a flexible network, and providing extra lithium storage sites. The obtained composites were tested for electrochemical performance for a total number of 2120 cycles: a rate capability test with current densities ranged from 90 to 7200 mA g(-1) for 920 cycles, followed by a cycling test at 1800 mA g(-1) for 1200 cycles. For the rate capability test, steady reversible capacities were delivered under each current density with final reversible capacities of 1177, 1096, 833, 488, 242, and 146 mA h g(-1) at 90, 180, 900, 1800, 3600, and 7200 mA g(-1), respectively. The subsequent cyclic test demonstrated the superior cyclic stability of USIO/G and a reversible capacity of 437 mA h g(-1) at the 2120(th) cycle was delivered.

The Effect of Hydrogen on the Fatigue Properties of Austenitic Stainless Steel

ABSTRACTHydrogen can be used as an environmentally friendly fuel to power vehicles, electric devices, and spacecraft with water vapor as the only emission. One associated challenge is the development of safe hydrogen storage systems. Hydrogen tanks and other hydrogen infrastructure elements will be exposed to both high-pressure hydrogen and cyclic stresses. In our work, 304 stainless steel specimens were precharged with hydrogen and subjected to rotational bending fatigue with a maximum stress amplitude of 90 ksi. A diffusion model was solved to approximate the concentration of hydrogen in the specimen at the time of the test. Contrary to our previous work with simple bending fatigue tests, hydrogen precharging actually increased rotational bending fatigue life from 28,074 (Sx = 7,430, N = 103) cycles to 91,513 (Sx = 40,209, N=32) cycles, a factor of approximately 3.25. This result demonstrates that the effect of hydrogen on fatigue life can be highly situational, and great care should be taken when designing systems that will be exposed to high-pressure hydrogen under fatigue conditions.

Role of Dislocation Movement in the Electrical Conductance of Nanocontacts

Dislocation is a lattice imperfection of crystalline materials. Dislocation movement is induced during plastic deformation and influences the mechanical properties. Although the role of dislocation in mechanical properties has been well understood, the role of dislocation in electrical properties is completely lacking. Only Matthiessen's rule addresses the electrical influence of dislocations at the macroscale. Here, we show that the electrical conductance change due to dislocations and show their movements through in situ observation of a gold nanocontact. The density of the dislocations in the gold nanocontact did not affect the electrical conductance. The repeated and discrete dislocation movements resulted in an electrical conductance oscillation. Our results demonstrate how dislocations and their movements affect electric conductance at the nanoscale. This instability issue will cause a big problem for future electric devices such as ultra low power electric devices and nanowire photovoltaic devices.

실측에 의한 특고압수용가의 전력품질 분석

Recently, due to the expansion of electric power demands, nonlinear load such as converters and inverters connected to the electric power distribution system, and extensive application of harmonic generation sources with power electric devices, disturbance of the electric power system and its influences on industries have been continuously increasing. In this research, power quality was analyzed for 11 extra-high voltage customers by considering voltage unbalance condition, power factor, THD and TDD. This research will be utilized as fundamental data to improve power quality for power utility.

AC Loss Properties of Laser-Scribed Multi-Filamentary GdBCO Coated Conductors with Artificial Pinning Centres

RE 1 Ba 2 Cu 3 O 7-∂ (RE: Rare Earth, Gd, Y and so on) coated conductors have a large aspect ratio and also anisotropy in critical current density. For practical application of REBCO tapes, we evaluated J c and ac loss properties in a wide range of temperature and magnetic field. The induced ac losses due to the perpendicular magnetic field to a tape face are considerably huge. Therefore, in case that REBCO coated conductors are applied electric power machines and devices, ac loss induced in the windings should amount to a great part of the total heat load. We proposed an ac loss reduction method, which is combined with a laser scribing technique and a special winding process into a multi–filamentary structure. Additionally, we are trying to enhance critical current density J C, by doping artificial pinning centre. In this study we investigated the ac loss properties of multi-filament structural GdBCO tapes with BZO nano–lods as artificial pinning centers. We measured ac losses of 5, 10, 20-filament GdBCO tapes by using a saddle-shaped pickup coil. Consequently we confirmed the ac loss decreased in inverse proportion to the number of filaments even in the GdBCO tapes with enhanced J C by introducing artificial pinning centers.

AC loss reduction of TFA-MOD coated conductors in long length by laser scribing technique

Abstract TFA-MOD process is expected to be promising for future applications since it can produce high performance YBCO coated conductors with low cost. Applying YBCO coated conductors to the power electric devices such as transformer, cable, motors, reduction of AC loss for long wire is necessary. Multifilamentation, which is one of the effective approaches for AC loss reduction, has been developed by the scribing process. YBCO coated conductors produced by our standard TFA-MOD process delaminated into two parts by the laser scribing. The delamination was clarified to occur within the superconducting layer caused by the defects such as pores in the superconducting layer. In order to reduce the defects in the superconducting layer, we modify the heat treatment profile performed on the decomposed precursor films by applying the interim annealing(550-600°C) before crystallization heat treatment(740-770°C). The interim annealed samples had much less and smaller pores than the standard processed ones. The peel strength measured by transverse tensile test was as high as the PLD derived coated conductors which was successfully scribed into five filaments resulting in 1/5 AC loss. A 50m long YBCO coated conductor with the characteristics of 398A/cmwidth was obtained and cut into 5 mm width, followed by the laser scribing process into five filaments. The multifilamentation process was successfully performed without delamination throughout the wire. The hysteresis loss was down to 1/N (N: number of filaments), as we aimed. The IC properties of the filaments were 29±4A, indicating the wire was uniformly fabricated.