Connection Of Conductors Research Articles

Конденсаторная установка для сельской распределительной сети 0,4 кВ: особенности построения

Reactive power compensation based on a capacitor plant connected to a rural 0.4 kV distribution network, when using non-specialized contactors, is accompanied by the occurrence of large starting currents of capacitors. In addition, the installation of a conductor connection with load current transformers requires structural modification of the capacitor plant. In order to eliminate these disadvantages, it is proposed to use a capacitor bank controlled by a time relay and protected from inrush currents by three RL circuits. In this case, the “on-off” mode of the capacitor bank must be switched to by an internal signal of the capacitor bank setting the time interval “on-off”. Using a mathematical model, as well as a three-phase physical model with a power of 1.2 kV, the authors studied the behavior of transient and steady-state currents at various values of the parameters of RL circuits.The initial invariant parameters of the model were the reactive resistances of capacitors and inductors. The nominal value of the phase current of the capacitor bank was 2.14 A. The variable parameters were the values of the active resistances of the RL circuits, which took the values of 0, 10, 20, 30 and ∞. The oscillogram of stationary and transient current was studied. As a result, it was found that in order to match the capacitor bank to the criterion of using circuit breakers and contactors of the 0.4 kV network, the resistance value of the RL circuit resistor of each phase of a three-phase capacitor bank should be tenfold higher than the reactance of the current-limiting coil of the RL circuit and be five times less than the reactance value of the power capacitor of the capacitor bank phase. In rural 0.4 kV electric networks, a single 25 kV capacitor plant with simple autonomous control can be installed to compensate for reactive power. Several capacitor plants can compensate for reactive loads of 50 and 75 kVAr.

Интегрированные с ферритовым волноводом мультиэлектродные микроантены для возбуждения-приема спиновых волн

Multielectrode microantennas for spin waves integrated with a ferrite waveguide – yttrium iron garnet film – were fabricated and tested. Microantennas of two types were studied: with a parallel connection of conductors – “grating” and with a serial connection of conductors – “meander”. The performance of such microantennas for excitation of magnetostatic surface and backward volumec waves tens of micrometers in length has been demonstrated. It has been shown that for waves with a length of tens of micrometers, high (tens of megahertz) excitation selectivity can be achieved using the “grating” microantennas. Whereas, using the “meander” microantennas for the same wavelength range, it is possible not only to get selectivity, but also to significantly (up to 10 dB) increase the excitation efficiency compared to the microantenna with a single conductor. It is noted that the use of such microantennas for shorter spin waves can be hampered by the mutual influence of microwave fields from neighboring conductors, as well as the increasing role of ohmic losses in conductors.

Пристрої на основі сплавів з ефектом пам’яті форми для підвищення надійності розбірних електричних контактних з’єднань

Increasing reliability of bolted electrical contact connections is an important problem in power engineering. Such connections are very common and their damage can lead to serious consequences. One of the ways to increase reliability of bolted electrical connections is the use of special devices based on shape memory alloys (SMAs). This article contains an analysis of four devices that destroy films (oxides, sulfides etc.) which form on a contact surface of bolted electrical connections during operation. Destruction of such films slows down process of a contact connection degradation and, ac cordingly, extends its service life, thereby increasing reliability of a contact connection. The following devices were analyzed: a conical washer made of SMA, "Detachable connection of conductors with a contact crown nut", "Terminal lug" with shape memory effect (SME) element. These devices have SME elements which during activation increase a contact pressure in an electrical connection and, accordingly, destroy films on a contact surface. Another "Terminal lug" with SME element was also analyzed. This device has SME element which during activation displaces one contact rela tive to another. This motion cleans a contact surface from films without affecting a contact pressure. Analysis of these devices, in particular using the finite element method, which was implemented using Ansys 2020 R2 Academic software, showed the following disadvantages and features of the above-mentioned devices: the need to manufacture specially designed contact connection elements, the locality of a pressure increase on a contact surface, and the need to disassemble contact connections when installing SME elements. Based on the conducted analysis, a new design of a contact connection was proposed. This new design does not have indicated disadvantages and its principle of operation is based on a combined destruction of films on a contact surface by increasing a contact pressure and by the relative displacement of the contacts.

SERIES TERMINATION OF SINGLE-ENDED LVCMOS SIGNALS

For synchronous signals with fast edges traces on printed circuit boards are transmission lines, not just conductor connections. If the length of the PCB trace exceeds certain values, it is necessary to match its impedance with the signal source and/or receiver. Impedance mismatches would bring signal reflections from the source to the receiver and back through the trans- mission line. Such reflection or distortion of the signal is called "echo" or "ringing". It is shown in emissions and irregularities of the waveform, especially the rise and fall edge. In this article, practical guidelines for sequential termination of one-way signals are considered that would resolve such effects. The simulations were done for LVCMOS signals [1].

Hairpin Windings for Electric Vehicle Motors: Modeling and Investigation of AC Loss-Mitigating Approaches

The hairpin winding configuration has been attracting attention as a solution to increase the power density of electric vehicle motors by enhancing the slot-filling factor. However, this winding configuration brings high AC losses during high-speed operation and we require new approaches to tackle this challenge. This paper considers reducing AC losses by proposing two main methods: correct transposition of conductors in parallel paths, and enhancing the number of conductor layers in a slot. First, the proper connection of conductors in parallel paths is considered, and the essential rules for this purpose are described. Next, the paper uses a numerical approach to deal with the effect of incorrect conductor transposition in winding paths on generating additional AC losses due to circulating currents. Finally, the impact of the number of conductor layers in the mitigation of AC losses is also discussed in detail. According to the results, by increasing the number of layers, ohmic losses in the layer near the slot opening dramatically decrease. For instance, ohmic losses in the layer near the slot opening of the eight-layer setup were 82% less than the two-layer layout.

Designing of Unit EBG Cell Using Conductive Textile for Dual Band Operation

Background/Objectives: Flexible electronics have paved the way for Wireless Body Area Networks (WBAN). The main challenge in accommodating such applications is reducing the impact of radiation on the human body. The presence of body tissues may affect WBAN devices such as wearable sensors and wearable antennas, so reducing back radiations becomes an important task. Methodology: When a microstrip patch antenna is placed on a human body, the artificially formed Electromagnetic Band Gap (EBG) surface mimics the property of a Perfect Magnetic Conductor (PMC) rather than the conventional Perfect Electrical Conductor (PEC). Findings: In this work, the unique property of the EBG surface beneath the patch antenna creates a zero phase shift at the resonance, which improves the antenna’s performance and reduces back radiations as well. The proposed EBG surface structure is the simplest square-shaped structure with no conductor connections Via patch (Via-less). Novelty: The EBG structure designed and presented in this paper has zero reflections for the dual-band of operations. The resonance frequency of 2.45GHz and 5.5 GHz has been designed for the absorption of 80% and 65% respectively. This level of absorption has not yet been reported in the literature. The newly formed EBG cell integrated with the patch antenna and its performance improvements has been shown. The analysis shows that the EBG enhances the return loss by 20.35 % and gain enhances by 16.44 %, on textile materials with the advantage of most simplex EBG cell construction. Keywords: EBG; PMC; PEC; Wearable Microstrip Patch Antenna; WBAN

Монтажные провода как источник зажигания в электрических шкафах

Приведены результаты исследований монтажных проводов электрических шкафов на воспламеняемость под воздействием тока. Выделены три зоны сверхтока, имеющие отличительные особенности появления источника зажигания. Показано влияние изоляции провода на частоту появления воспламенения в местах присоединения его к элементу электрооборудования. Представлены данные о воспламеняемости поливинилхлоридной изоляции в диапазоне пожароопасных значений сверхтока. Предложено характеризовать электрический провод как потенциальный источник зажигания площадью, образованной зависимостью времени воспламенения изоляции в интервале возможных сверхтоков. Wires are widely used for internal installation of electrical cabinets. Number of fire cases caused by wires takes one of the first places in fire statistics. Application of wires in the cabinets has its own fire-prone aspects peculiarities as concerns initiation of electrical nature ignition source. It appears both at single wire laying and at laying in cords where wires touch each other also in connection points of electrical apparatuses and devices located in the cabinet. The article considers issues of ignition source appearance in wires taking into account specifics of their installation in electrical cabinets. Ignition source appearance in a single wire and in wires contacting each other has a difference. There are given experimental data on inflammation frequency of wire insulation material at single wire laying and also at higher resistance in electrical elements connection points. Zones that differ in characteristic features of wire as an ignition source are given in the range of possible overcurrents. Zone A is characterized by insulation ignition with low probability due to low current density that is not enough to heat the wire up to the critical temperature Т, at which thermal decomposition products of wire insulating polymeric cover ignite. Zone B is designated in the range of overcurrent ratio from 2,5 to 18 compared with the long term permissible current value, in which insulation inflammation is observed due to fast conductor heating taking into account the influence of connection points with devices and apparatuses where increased transient resistance is present. It is experimentally confirmed that with the increase in transient resistance at the point of conductor connection with electrical equipment elements, the inflammation frequency of wire insulation increases. At the same time, the overcurrent range where ignition source appears reduces. It is proposed to use the area limited by the dependence of the time before insulation inflammation from the minimum to the maximum current value at which ignition occurs as a characteristic of the wire as an ignition source.

Towards Electrothermal Optimization of a HVDC Cable Joint Based on Field Simulation

Extruded high-voltage direct current cable systems transmit electric power over long distances. Numerical field simulation can provide access to the internal electrothermal behavior of cable joints, which interconnect cable sections. However, coupled nonlinear electrothermal field simulations are still a challenge. In this work, a robust numerical solution approach is implemented and validated. This approach allows for efficient parameter studies of resistively graded high-voltage direct current cable joint designs. It is assessed how the dielectric stress distribution between the conductor connection and the grounded cable sheath is influenced by nonlinear field and temperature dependent electric conductivity of the field grading material. Optimal field grading material parameters, which fulfill the field grading and power loss requirements, are suggested based on the simulation studies.

New method for fast coupled magnetic field-circuit simulation of power transformers based on a semi-analytical approach

A novel mesh-free methodology for the coupled magnetic field-circuit simulation of power transformers is presented in this paper. The proposed methodology employs equivalent models for the conductors and the iron core, which are based on the field produced by elementary geometric configurations and boundary conditions derived from Ampere's and Faraday's laws. Power losses in the windings due to circulating currents are calculated with the proposed method and the Finite Element Method (FEM). A 25 MVA transformer is investigated as a case study and the effect of the conductor connections within the windings is considered through its incidence matrix. The windings losses obtained by applying the proposed methodology are compared with the losses estimated from the short circuit test showing an excellent agreement. The computational performance is also compared with FEM. It has been found that the proposed method is about 9 times faster than FEM retaining the level of precision required for transformer design purposes.

Detection of Slackening of Conductor Connection in Circuit Breakers Using Conducted Emission

Detection of Slackening of Conductor Connection in Circuit Breakers Using Conducted Emission

Optimal Design Method to Improve the Magnetic Field Distribution of Multiple Square Coil Systems

Power electronic equipment regulated by the International Thermonuclear Experimental Reactor (ITER) organization must be tested in a relevant steady-state magnetic field immunity test, and the test area is generally required to be a cube shape. For this reason, a multiple square coil system structure is used. In this article, a Taylor expansion and an optimization program are used to determine the optimal parameters of a coil system with different groups. For a three-coil system, the effects of the conductor cross-section, conductor spacing, helical structure, and conductor connection on the magnetic field uniformity are analyzed. A clear understanding of the influence degree of the error helps design an actual coil system. ITER organization is currently conducting research on magnetic field generator for electronic devices in large scientific devices. The design method proposed in this article can reduce the design difficulty and provide theoretical support.

Тестовий контроль знань учнів із фізики

Controlling learners’ educational achievements in our time performs the most important function of learning. Scientists and methodologists argue that the test control of students’ academic achievement meets the requirements of quantitative and objective measurement of learners’ knowledge, skills and abilities. The relevance of the test controlling method of learners’ academic achievements is dictated also by the introduction of the independent external evaluation (IEE) as a final certification of school leavers. With the emergence of computer classes, the use of tests became available and appropriate. The use of computers in the testing process greatly enhances the benefits of this type of control. This paper is aimed at studying experimentally the impact of the controlling testing on enhancing learners’ educational achievements in Physics and managing learners’ cognitive activity. We have been prepared the system of test questions on the following topics: “We begin to study Physics”, “Mechanical work. Units of work”, “Power and its units”, “Electric current. Conductor Resistance”, “Serial and Parallel Conductor Connection”, “Ideal Gas Laws”, “Atomic Physics. Spectrums”. The tests were developed in order to identify the students’ acquisitions of the main issues constituting the educational material / programme, as opposed to revealing some amount of information from the learner's side. In our opinion, it is important for students to master the level of education that would become the basis for further self-improvement of their own education, their own opportunities to overcome the challenges that the life postures to him / her in today's society. Therefore, the main task while developing the test tasks was the formation of certain subject and life-oriented competences. We conducted a pedagogical experiment to introduce the test control of learners' knowledge in Physics. A series of lessons were conducted using the test survey in the experimental class, but no tests were used in the control class. Using the example of testing 8th grade schoolchildren in Physics it was detected that the use of a systematic test control of knowledge acquisition at corresponding lessons Physics allowed the students to demonstrate better knowledge of certain topics at sufficient and high levels. Keywords: testing control, learners’ self-educational competence in Physics, creative thinking.

Preparation and Properties of Graphene Anticorrosive Coatings for Transmission Towers

The transmission tower is one of the largest equipment facilities in the transmission and distribution line network. It is mainly used to support the connection of overhead conductors to ensure the safe and stable transmission of power transmission lines. Due to the vast territory of China and the wide distribution of transmission towers, the operating environment faced by transmission towers is also extremely complex. In addition to the pulling force given by the transmission line, rain, snow, dust, salt spray, acid rain and other substances cause erosion and corrosion on the transmission tower. The use of anti-corrosion coatings is an effective way to avoid erosion and corrosion of transmission tower. Therefore, it is very important to prepare an anti-corrosion coating suitable for transmission towers for the safe operation of transmission towers. Graphene is a new type of functional nano-material that attracts attention. Its special layered structure can effectively shield the material, reduce the internal stress of the coating, and improve the adhesion, mechanical properties, anti-corrosion effect and other properties of the coating.

IEEE Access Special Section Editorial: Wirelessly Powered Networks: Algorithms, Applications, and Technologies

Wireless Power Transfer (WPT) is, by definition, a process that occurs in any system where electrical energy is transmitted from a power source to a load without the connection of electrical conductors. WPT is the driving technology that will enable the next stage in the current consumer electronics revolution, including battery-less sensors, passive RF identification (RFID), passive wireless sensors, the Internet of Things and 5G, and machine-to-machine solutions. WPT-enabled devices can be powered by harvesting energy from the surroundings, including electromagnetic (EM) energy, leading to a new communication networks paradigm, the Wirelessly Powered Networks.

Влияние способов охлаждения токовводов с высокотемпературными сверхпроводниками на их тепловое состояние

The article considers the practically import antissue of the oretically modeling current leads containing high-temperature superconductors (HTSC current leads) with a view to determine the lead thermal state in response to changes of different operating parameters. The modeling procedure is based on subdividing the current inlets into individual segments differing from each other in the nature of their electrical resistance (conductor, superconductor, and contact connection of the conductor and superconductor) and in their cooling conditions, which are determined by the cooling medium aggregative state (whether the cryoagent is in liquid or gaseous state), or when the segments are thermally insulated. The chosen principle for subdividing the currentl ead sinto segment was used asabasistoobtain and present in systematic form the analytic equations describing the distribution of temperature and heat flux in individual segments having different thermal and electrical characteristics. The boundary conditions and the thermal matching conditions of the selected segments make it possible to obtain an integer current lead mathematical model. The use of the proposed procedure is illustrated on the example of carrying out a comparative analysis of the temperature and heat fluxes variation patterns in current leads fitted with single- and two-stage cooling in changing the cooling gases (helium and nitrogen) flowrate.

A Thermal Probability Density–Based Method to Detect the Internal Defects of Power Cable Joints

Internal defects inside power cable joints due to unqualified construction is the main issue of power cable failures, hence in this paper a method based on thermal probability density function to detect the internal defects of power cable joints is presented. First, the model to calculate the thermal distribution of power cable joints is set up and the thermal distribution is calculated. Then a thermal probability density (TPD)-based method that gives the statistics of isothermal points is presented. The TPD characteristics of normal power cable joints and those with internal defects, including insulation eccentricity and unqualified connection of conductors, are analyzed. The results indicate that TPD differs with the internal state of cable joints. Finally, experiments were conducted in which surface thermal distribution was measured by FLIR SC7000, and the corresponding TPDs are discussed.

СОЕДИНЕНИЕ АВТОМОБИЛЬНЫХ ПРОВОДНИКОВ МЕТОДОМ УЛЬТРАЗВУКОВОЙ СВАРКИ. ПОЖАРНАЯ ОПАСНОСТЬ

Introduction. Nowadays ultrasonic welding of metals including conductors is widely used. The con­nection of copper conductors by ultrasound is based on high-frequency oscillations. Materials and methods. Copper stranded conductors interconnected by ultrasonic welding were chosen as the materials for the study. The study of these samples was carried out in the laboratory by metallographic analysis. Results and discussion. In case of a poor contact at the connection point, a large transient resistance may occur when an electric current passes through a given point and cause fire. To establish the involvement of a poor adhesion to the occurrence of a fire, it is necessary to conduct metallographic studies of the compound. With qualitatively performed welding, fusion of individual sections of wires at the junction site is observed, while in the case of a “poor” connection, clearly defined boundaries are observed. A very long exposure to ultrasound in the welding process on the connected conductors leads to a de­crease in the plasticity of the conductor, which in turn leads to the fracture of the veins near the junction and, as a consequence, to the emergence of local current overload. Where the places of rupture after the fire are melted and smoked, indicates that the test conductor was damaged even before the ignition of the vehicle. Conclusion. Thus, the possibility of vehicle combustion as a result of a poorly executed connection of conductors by ultrasonic welding is shown. It is noted that the fire can be caused by uncompleted welding (“non-fusion” of the conductors), or vice versa when an impact of ultrasonic waves on the conductors to be connected has been too long. It is necessary to withdraw this connection directly at the seat of fire for further laboratory metallo­graphic research.

Sub-micro-Newton resolution thrust balance.

Herein is described a sensitive vacuum balance for measuring the thrust produced by small (∼0.5 kg) thrusters typically employed in microsat station-keeping. The balance is based on a torsion design but incorporates jewel-pivot bearings instead of the more typical torsion spring bearings. Novel tilt control allows maintenance of true verticality of the bearing axis even while under vacuum. The low moment of inertia design allows it to measure small thrusts from high-voltage devices without direct wire conductor connections. Calibration by several means is described including use of a previously calibrated dielectric barrier discharge thruster.

Electrohydrodynamic Direct-Write Multi-Layer Micro Circuit on Flexible Substrate

Electrohydrodynamic Direct-Writing (EDW) provides a simple and rapid way to print micro/nanostructures from viscoelastic solution, which meets the demand in the development of all-printed organic electronics. Overlapped printing of different functional materials to build up multi-layer devices displays excellent advantages in the flexible electron. The 3D multi-layer devices as well as flat interconnection can be fabricated on the flexible substrate directly via EDW technology. The technology of EDW utilized stable charged jet to print orderly conductive and insulator micro/nanostructure. Silver ink is used to print conductor connection, and polyvinylpyrrolidone (PVP) solution is used to fabricate insulator layer. Multi-layer interconnection can be printed layer by layer on the polyimide (PI) flexible insulator substrate. The resistance of top and bottom conductor connection was 6.1Ω and 5.9Ω, respectively. The insulator layer demonstrated excellent insulation characteristics between the bottom and top silver interconnection.

A note on the nucleation with multiple steps: Parallel and series nucleation

Parallel and series nucleation are the basic elements of the complex nucleation process when two saddle points exist on the free-energy landscape. It is pointed out that the nucleation rates follow formulas similar to those of parallel and series connection of resistors or conductors in an electric circuit. Necessary formulas to calculate individual nucleation rates at the saddle points and the total nucleation rate are summarized, and the extension to the more complex nucleation process is suggested.