Electric Current System Research Articles

Research on Electrical Automation Control System and Design Based on Geographic Information Technology

As the pace of power plant construction accelerates, higher requirements are placed on the application performance of the control system. From the current development status of the current electrical control system, it reflects the characteristics of multi-function, miniaturization and intelligence, and provides an important guarantee for the reliable operation of the electrical system. This paper analyzes and studies GIS in geographic information technology and power system application. The structure and function of electric power GIS system are designed. According to the structure and particularity of distribution network, a new distribution network database model is established. The overall planning and design of the network information database are carried out. The design idea of electric automation control system is discussed, and the development trend of electric automation control system in the future is prospected.

Use of the Frequency Response Technique to Analyze the Impact of Improving the Power Factor in the Electrical Networks

Current electrical systems tend to have low power factors that are often accompanied by high levels of harmonic distortion of voltage and current, which have been growing by the increase of the loads no line in the electrical systems, infringing the limits established by the norms and regulations in force. These operating conditions affect the stability of the network and the bad functioning of the equipment, presenting high costs of billing and sanctions imposed by the state. Therefore, the need to analyze the electrical systems before the ingredient of non-linear loads arises in order to guarantee the correct operation and the quality of the power according to the normative requirements. This article presents a typical case study; The installation of capacitor banks to improve the power factor, which fulfil their main task, but serious problems such as the generation of resonances in parallel in the natural response of system, deformation of the waveforms of tension and current, and increase of the harmonic distortion individual and total of tension and current. for which a frequency response or frequency-scanning analysis is presented using ETAP as an additional analysis tool.

Using a physical model to determine the hydrodynamic dispersion coefficient of a solution through a horizontal sand column

Miscible displacement can be understood as a physical process in a porous medium whereby two or more fluids fully dissolve into each other when a fluid mixes and goes into the pore space occupied by other fluids without the existence of an interface. A physical model was made in Can Tho University, which included an electrical current system connecting nine groups of four-electrode probes for measuring the electrical conductivity of a potassium chloride solution flowing through a horizontal sand column placed in a firm frame. The experiments were performed with different volumetric flow rates and three types of sand (fine, medium and coarse). The breakthrough curves were analysed, and then the hydrodynamic dispersion coefficients were calculated. The hydrodynamic dispersion coefficient was one of the hydraulic and solute transport parameters used to design a constructed subsurface flow wetland. The research proves that the flows were laminar, and that mechanical dispersions dominated over molecular diffusions and that the dispersions were large enough to cause combined mixing and flowing processes.

High current variable temperature electrical characterization system for superconducting wires and tapes with continuous sample rotation in a split coil magnet.

A new state-of-the-art electrical transport measurement system was developed for the characterization of industrially produced coated conductors (CCs). The current leads are rated to a conduct current of up to 1000 A, which opens up the possibility of measuring the critical current Ic of tapes at a wide range of temperatures. The setup operates in a He-gas flow cryostat that provides stable temperatures between 1.8 and 200 K. The setup is equipped with a split-coil magnet that can apply fields of up to 6 T. A continuous rotation of the sample with respect to the magnetic field with an angular resolution of 0.5° enables characterization of anisotropic Ic of different tapes. In the measured voltage-current curves, weak sample heating mostly occurs from the dissipation in the tape during the Ic transition. It is demonstrated that the system can provide reliable data on the properties of CCs at temperatures lower than 77 K for a magnet design and other applications. The results allow the study of vortex pinning for further prospects of engineering the microstructure of the superconducting layer as well as to assess the performance of various tapes with different architectures to achieve optimum performance at different operating temperatures and magnetic fields.

Techno-Economic Analysis of Rural 4th Generation Biomass District Heating

Biomass heating networks provide renewable heat using low carbon energy sources. They can be powerful tools for economy decarbonization. Heating networks can increase heating efficiency in districts and small size municipalities, using more efficient thermal generation technologies, with higher efficiencies and with more efficient emissions abatement technologies. This paper analyzes the application of a biomass fourth generation district heating, 4GDH (4th Generation Biomass District Heating), in a rural municipality. The heating network is designed to supply 77 residential buildings and eight public buildings, to replace the current individual diesel boilers and electrical heating systems. The development of the new fourth district heating generation implies the challenge of combining using low or very low temperatures in the distribution network pipes and delivery temperatures in existing facilities buildings. In this work biomass district heating designs based on third and fourth generation district heating network criteria are evaluated in terms of design conditions, operating ranges, effect of variable temperature operation, energy efficiency and investment and operating costs. The Internal Rate of Return of the different options ranges from 6.55% for a design based on the third generation network to 7.46% for a design based on the fourth generation network, with a 25 years investment horizon. The results and analyses of this work show the interest and challenges for the next low temperature DH generation for the rural area under analysis.

Complex-demand scheduling problem with application in smart grid

We consider the problem of scheduling complex-valued demands over a discretized time horizon. Given a set of users, each user is associated with a set of demands representing different power consumption preferences. A demand is represented by a complex number, a time interval, and a utility value obtained if it is satisfied. At each time slot, the magnitude of the total selected demands should not exceed a given generation capacity. This naturally captures the supply constraints in alternating current (AC) electric systems. In this paper, we consider maximizing the aggregate user utility subject to power supply limits over a time horizon. We present approximation algorithms characterized by the maximum angle ϕ between any two complex-valued demands. More precisely, a PTAS is presented for the case ϕ∈[0,π2], a bi-criteria FPTAS for ϕ∈[0,π-ε] for any polynomially small ε, assuming the number of time slots in the discretized time horizon is a constant. Furthermore, if the number of time slots is part of the input, we present a reduction to the real-valued unsplittable flow problem on a path with only a constant approximation ratio. Finally, we present a practical greedy algorithm for the single time slot case with an approximation ratio of 12cos⁡ϕ2 and a running time complexity of only O(Nlog⁡N), N standing for the aggregate number of user demands, which can be implemented efficiently in practice.

The magnetic field of a plane current sheet with piecewise uniform electrical conductivity, with results for three insertions

A system of N coupled linear boundary Fredholm integral equations of the second kind is derived to describe the electric current system and the magnetic field distribution in space for an infinite plane electrical conducting sheet with N non-overlapping insertions, permeated by a uniform parallel electric field. The cases of one or two insertions obtained earlier are recovered. The system for three insertions is derived and solved numerically to provide solutions for new problems involving elliptic or square insertions. The lines of current are plotted and the results for each case are discussed to assess the efficiency of the numerical method. The solved problems provide a detailed study of the complex behaviour of harmonic functions in space and in the plane, represented, respectively, by the magnetic scalar potential and the current function, at lines of discontinuity of the electrical conductivity. It is noted that the case of holes can be treated equally well. The method and the obtained results allow to evaluate the magnetic field on the Earth’s surface on and around a multitude of islands. They may be useful in non-destructive testing of current sheets through magnetic field measurement. The tackled problems display different types of discontinuities of the magnetic field components. The numerical results indicate that the case of three or more insertions may differ qualitatively from that of one or two insertions, namely the possibility of existence of current loops.

Alternating current and direct current-based electrical systems for marine vessels with electric propulsion drives

The initial widespread electrification of marine vessels primarily used alternating current (AC)-based systems as they were prevalent in the electrical distribution infrastructure for land-based systems. At present, there are marine vessels that operate based on a hybrid diesel-electric system, in which the on-board diesel engines generate AC power to a common AC bus, which in turn supplies power to the electrical propulsion drives and other service loads. Recently, there has been an active interest in a transition to direct current(DC)-based electrical distribution system with diesel-electric hybrid propulsion systems for marine vessels due to potential improvements in electrical performance and fuel consumption. This paper evaluates the improvement in the move to DC-based distribution system for marine vessels in terms of electrical performance and fuel efficiency. An overview of a typical AC electrical system currently in use is provided, and modifications of the system to a DC-based system is presented. The power factor, total harmonic distortion, and voltage regulation are discussed. Both symmetrical and asymmetrical generator scheduling are examined and the potential fuel savings for an example diving support vessel is presented. A discussion on the recommendations to shift towards DC-based systems is then provided based on the findings of this paper.

Особенности оптимизации подсистемы электроснабжения электрической тяги на железнодорожном транспорте

Objective: To assess the basic factors, innovative technologies, on the basis of which an integrated network of electrified lines of high-speed rail is to be created in Russia. Methods: Optimization of the traction power supply system according to characteristic criteria of resources and energy efficiency minimization. Results: Quality indices of power supply of hauling operations, voltage level of collectors for different electric propulsion systems with direct and single-phase alternating current were analyzed. The key factors, significantly influencing the performance indices, are the voltage level and type of current of an electric powered network. It was shown that the system of electric propulsion is a promissory system and possesses the best competitiveness indices, as its electric power supply subsystem is functioning on high-voltage direct current with the use of a 24 kW direct current electric stock on the basis of a new multipurpose generation converting complex. Practical importance: The suggested justification method of electrification variant by means of a dependence diagram depicting spacing between substations and catenary wire section makes it possible to justify a competitive high-voltage direct current electric propulsion system during the design of electric power infrastructure for busy railway lines.

Intermittency spectra of current helicity in solar active regions

We analyse the spatial distribution of current helicity in solar active regions. A comparison of current helicity maps derived from three different instruments (Helioseismic and Magnetc Imager on board the Solar Dynamics Observatory, SDO/HMI, Spectro-Polarimeter on board the Hinode, and Solar Magnetic Field Telescope at the Huairou Solar Observing Station, China, HSOS/SMFT) is carried out. The comparison showed an excellent correlation between the maps derived from the spaceborne instruments and moderate correlation between the maps derived from SDO/HMI and HSOS/SMFT vector magnetograms. The results suggest that the obtained maps characterize real spatial distribution of current helicity over an active region. To analyse intermittency of current helicity, we traditionally use the high-order structure functions and flatness function approach. The slope of a flatness function within some range of scales - the flatness exponent - is a measure of the degree of intermittency. SDO/HMI vector magnetograms for 3 ARs (NOAA 11158, 12494, and 12673) were used to calculate the flatness exponent time variations. All three ARs exhibited emergence of a new magnetic flux during the observational interval. The flatness exponent indicated the increase of intermittency 12-20 hours before the emergence of a new flux. We suppose that this behaviour can indicate subphotospheric fragmentation or distortion of the pre-existed electric current system by emerging magnetic flux.

Impact assessment of DG in distribution systems from minimization of total real power loss viewpoint by using optimal power flow algorithms

This paper presents the enhancement and impacts of the system losses, voltage profile and cost by using distributed generations (DGs) of different size in distribution network. Distributed Generation (DGs) is expected to play a key role in the residential, commercial and industrial sectors of the power system. Distributed Generation (DG) provides an alternative to the traditional electricity sources and can also be used to enhance the current electrical system. DG produces a series of important influence on the distribution network. It mainly introduces four effect areas, namely, distribution network real power loss, voltage, distribution grid planning and relay protection. In this analysis, load flow method is used for optimization of objective function for minimization of total real power loss and reactive power loss of the system. The work is focused on analyzing the impact of DG installation on distribution network operation including system voltage profile analysis, real and reactive power losses and cost of the system. First, various sizes of DG penetration levels and the impact of distributing the DG across the bus where load is maximum are explored. Secondly, the real power losses of the system are analyzed. Thirdly, the voltage profile and cost of the system are analyzed. The proposed methodology has been tested for IEEE-14 bus distribution test system. This work is also helpful for practitioner whose are working in the fields of renewable energy sources.

An MBSE Tool to Support Architecture Design for Spacecraft Electrical Power System

Since difficulty and complexity of spaceflight missions are increasing, current electric systems in the spacecraft become increasingly complicated challenging the spacecraft electrical power system ...

100% 에너지자립 제로에너지주택을 위한 비용효과적 신재생 설비시스템 최적구성에 관한 연구

Purpose: The domestic thermal insulation standard value has significantly increased to realize the Zero Energy House and many passive houses or zero energy houses are being built recently. Passive technology, which is represented by high thermal insulation and high density, shows relatively stable implementation by development of building materials and accumulated construction experience. On the other hand, there are not matured technologies for heating and cooling, hot water supply and ventilation including new and renewable energy. This study investigated the possibility of constructing optimal renewable energy and facilities system in terms of cost and effectiveness for zero energy houses that can achieve 100% of energy independence rate at current level. Method: The target building is a single story house with a floor area of 100 ㎡ located in Gyeonggi-do. Outer wall and roof floor are composed of 200mm SIP (Structural Insulation Panel) structure and window is vacuum window with U = 0.5 w/㎡℃. As a building equipment, this study considered following systems: ground source heat pump (GSHP), air source heat pump (ASHP), electric heating boiler (EHB), electric cable heating (ECH), electric air conditioner (EAC), solar domestic hot water system (DHWS), and solar PV. Finally, this study selected four combinations of systems (GSHP, ASHP+EAC, EHB+EAC, ECH+EAC) for the investigation. Result: This study assumed that all the loads in the building are covered by electric energy, and the calculation of the annual energy cost was based on the current electric charge system. Therefore, all loads are supplied by domestic electricity except GSHP. In addition, this study assumed that all renewable energy facilities for 100% energy self-reliance are supplied by solar power and then calculated the capacity to cover all household electricity with PV to derive the range of required PV capacity. Finally, this study calculated the initial investment cost range for each system configuration and the investment payback period, and determined the cost effective system configuration.

Current Systems in the Earth's Magnetosphere

AbstractThe basic structure and dynamics of the primary electric current systems in the Earth's magnetosphere are presented and discussed. In geophysics, the word current is used to describe the flow of mass from one location to another, and its analog of electric current is a flow of charge from one place to another. An electric current is associated with a magnetic field, and they combine with the Earth's internally generated dipolar magnetic field to form the topology of the magnetosphere. The concept of an electric current is reviewed and compared with other approaches to investigate the physics of the magnetosphere. The implications of understanding magnetospheric current systems are discussed, including paths forward for new investigations with the robust set of observations being produced by the numerous scientific and commercial satellites orbiting Earth.

RETRACTED ARTICLE: Smart city information acquisition system based on internet of things

In order to develop an information acquisition system and apply to smart city, the information acquisition system using four-meter centralized reading is designed. At present, all provinces and municipalities in the country are vigorously promoting the construction of household electricity, water, gas and heat, and remote meter reading technology of electricity, water, gas and heat is also becoming more mature. In particular, the electricity information acquisition system pioneered by the State Grid Corporation of China (SGCC) has already realized the full coverage of the remote meter reading network of residents, and laid the foundation for the integrated acquisition of electricity, water, gas and heat by family. However, from the present point of view, the management of electricity, water, gas and heat is self-organized. Though there are many similarities in the problem of meter reading, due to the reasons of industry management, resource sharing cannot be formed. The basic structure of the current electric information acquisition system, the remote and local communication technology, and the benefit produced by the meter are introduced. A technical scheme for collecting four kinds of meter meters by using the existing power information collection network is put forward. The use of four-meter centralized reading shows that the technical plan about four-meter centralized reading is in line with the direction and requirements of sharing and building the resource-saving society. Compared with the other system, it is in the leading position. In conclusion, this new smart technology has achieved certain effect in the practical application and the application prospect is very wide.

A spatial electricity market model for the power system: The Kazakhstan case study

Kazakhstan envisions a transition towards a green economy in the next decades, which poses an immense challenge as the country's economy and energy system depends heavily on hydrocarbon resources. Here, it lacks inclusive and transparent tools assessing technical, economic, and environmental implications resulting from changes in its electricity system. We present such a tool: our comprehensive techno-economic unit-commitment model determines the hourly least-cost generation dispatch, based on publicly available data on the technical and economic characteristics of the system. It accounts for particularities of the Kazakh electricity system by representing combined heat and power, and endogenously determining line losses. Model results examine two typical weeks: winter (annual peak load) and summer (hour of lowest annual load) presenting regionally and temporally disaggregated results for power generation, line utilization, and nodal prices. In an application to market design, the paper compares nodal and zonal pricing as two possible pricing schemes in Kazakhstan for the envisioned strengthening of the day-ahead market. The model analyze the current Kazakh electricity system and can be easily expanded to assess the sector's future development. Possible applications include investment in generation and transmission infrastructure, policy assessment for renewables integration, carbon pricing, emission reduction, and questions of market design.

Tracing Electric Currents That Flow Along Earth’s Magnetic Field

A new study uses satellite data to examine a worldwide system of electric currents in greater detail than ever before.

The Geomagnetic Effects of Solar Activity as Measured at Ouagadougou Station

The coronal mass ejections (CMEs) produce by Sun poloidal magnetic fields contribute to geomagnetic storms. The geomagnetic storm effects produced by one-day-shock, two-days-shock and three-days-shock activities on Ouagadougou station F2 layer critical frequency time variation are analyzed. It is found that during the solar minimum and the increasing phases, the shock activity produces both positive and negative storms. The positive storm is observed during daytime. At the solar maximum and the decreasing phases only the positive storm is produced. At the solar minimum there is no three-days-shock activity. During the solar increasing phase the highest amplitude of the storm effect is due to the one-day-shock activity and the lowest is produced by the two-days-shock activity. At the solar maximum phase the ionosphere electric current system is not affected by the shock activity. Nevertheless, the highest amplitude of the storm effect is caused by the two-days-shock activity and the lowest by the one-day-shock activity. During the solar decreasing phase, the highest amplitude provoked by the storm is due to the three-days-shock activity and the lowest by the one-day-shock activity.

Approximation Schemes for Two Non-Linear Knapsack Problems and Their Applications in Alternating Current Electric Systems

The purpose of this paper is to study the approximability of two non-linear Knapsack problems, which are motivated by important applications in alternating current electrical systems. The first problem is to maximize a nonnegative linear objective function subject to a quadratic constraint, whilst the second problem is a dual version of the first one, where an objective function is minimized. Both problems are $\np$-hard since they generalize the unbounded Knapsack problem, and it is unlikely to obtain polynomial-time algorithms for them, unless $\p=\np$. It is therefore of great interest to know whether or not there exist efficient approximation algorithms which can return an approximate solution in polynomial time with a reasonable approximation factor. Our contribution of this paper is to present polynomial-time approximation schemes (PTASs) and this is the best possible result one can hope for the studied problems. Our technique is based on the linear-programming approach which seems to be more simple and efficient than the previous one.

Possibilities for Estimating Horizontal Electrical Currents in Active Regions on the Sun

Part of the “free” magnetic energy associated with electrical current systems in the active region (AR) is released during solar flares. This proposition is widely accepted and it has stimulated interest in detecting electrical currents in active regions. The vertical component of an electric current in the photosphere can be found by observing the transverse magnetic field. At present, however, there are no direct methods for calculating transverse electric currents based on these observations. These calculations require information on the field vector measured simultaneously at several levels in the photosphere, which has not yet been done with solar instrumentation. In this paper we examine an approach to calculating the structure of the square of the density of a transverse electrical current based on a magnetogram of the vertical component of the magnetic field in the AR. Data obtained with the Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamic Observatory (SDO) for the AR of NOAA AR 11283 are used. It is shown that (1) the observed variations in the magnetic field of a sunspot and the proposed estimate of the density of an annular horizontal current around the spot are consistent with Faraday’s law and (2) the resulting estimates of the magnitude of the square of the density of the horizontal current $$ {j}_{\perp}^2 $$ = (0.002− 0.004) A2/m4 are consistent with previously obtained values of the density of a vertical current in the photosphere. Thus, the proposed estimate is physically significant and this method can be used to estimate the density and structure of transverse electrical currents in the photosphere.