Single Transformer Research Articles

Parameter Estimation of Single Phase Core Type Transformer Using Bacterial Foraging Algorithm

The electrical circuit equivalents of magnetic device structures such as transformer require an exact knowledge of its parameters. Efficient parameter estimation technique is essential to obtain the equivalent circuit parameters of transformer because the parameters are used to manipulate parasitic elements and to obtain the enhanced circuit performance. In this paper, Bacterial Foraging Algorithm (BFA) has been applied to estimate the equivalent circuit parameters of single phase core type transformer. The information of open Circuit (OC) and Short Circuit (SC) tests has been utilized in BFA algorithm. The effectiveness of the proposed approach has been tested with a sample transformer and the simulation results are compared against the conventional method. The numerical results show that the proposed approach outperforms the conventional method in the aspects of solution quality.

Thermal seawater desalination: Possibilities of using single effect and double effect absorption heat transformer systems

Water and energy are two inseparable items that govern our lives and promote civilisation. The provision of fresh water is becoming an increasingly important issue in many areas in the world. Absorption heat transformer systems are attractive to use solar energy, geothermal energy and waste heat from industrial process as heat source and delivering thermal energy to higher temperature than the temperature of the fluid by which they are fed. In this paper a comparative study between single effect and double effect absorption heat transformer systems used for seawater desalination is carried out. The mathematical formulation will be based on mass, energy and exergy equations and conditions of thermodynamic equilibrium, considering lithium bromide–water as working mixture. Simulation results were used to study and to compare the influence of the absorber temperature and the intermediate heat source temperature (evaporator and generator temperatures) on the energy efficiency, exergy efficiency, and fresh water production of the two systems. The numerical results obtained will serve like a tool to predict the possibilities and limits of application of absorption heat transformers coupled to seawater desalination system.

Performance modelling of single and double absorption heat transformers

Absorption heat transformers (heat pump Type II) enable the temperature of a low heat source to be raised to a higher level. This process takes place by means of the absorption of a vaporized working fluid into a substance which has strong affinity for the vapor. The temperature lift and the coefficient of performance (a measure of the efficiency of the process), are important design parameters which depend on the thermodynamic properties of the working pair and also on the configuration of the equipment. In order to investigate the performance of readily available, not expensive and environmentally friendly fluids in heat transformers, the systems H 2O/CaCl 2 and H 2O/LiCl were studied, by using a Fortran program. The theoretical performance of both systems in a single stage absorption heat transformer (SSHT), was derived and compared to results obtained previously for the system H 2O/CaCl 2 on a double absorption unit (DAHT).

ELECTRICAL PROPERTIES OF PIEZOELECTRIC TRANSFORMER USING PSN-PMN-PZT CERAMICS

ABSTRACT In this study, Pb(Sb1/2Nb1/2)O3-Pb(Mn1/3Nb2/3) O3-Pb(Zr0.49Ti0.51)O3 (abbreviated as PSN-PMN-PZT) composition ceramics was sintered at 1230∼1270°C for developing the composition for piezoelectric transformer. At the ceramic composition sintered at 1250°C, Density, electromechanical coupling factor (kp) and mechanical quality factor (Qm) showed the excellent values of 7.78[g/cm3], 0.59 and 1931, respectively, suitable for piezoelectric transformer application. The single layer Rosen-type piezoelectric transformers were also sintered at the sintering temperature of 1250°C and manufactured with the size of 48 × 10 × 2 mm3, respectively, using the composition ceramics. And then, their electrical properties were investigated according to the variations of frequency and load resistance. At the load resistance of 150 kΩ, the voltage step-up ratio of the transformers showed the maximum values at the vicinity of 68.4KHz. And also, at that load resistance, piezoelectric transformers showed the temperature rises of about 6°C at the output power of 5W. At transformer with high effective electromechanical coupling factor(keff) and high piezoelectric constant(d33), lower temperature increase was relatively appeared. And also, the piezoelectric transformer was reviewed for the voltage down of igniter type energy harvesting piezoelectric device.

Energy and exergy analyses of seawater desalination system integrated in a solar heat transformer

Abstract Among the numerous options to improve the energy efficiency of desalination plants stands out the absorption heat transformer. A heat transformer is a device, which can deliver heat at a higher temperature than the temperature of the fluid by which it is fed. Solar thermal energy can be used as heat input for single effect heat transformer while the high grade thermal energy delivered by the heat transformer can be used as heat source for water desalination. In this paper, an attempt has been made to study the combination: flat plate solar collectors, a single effect heat transformer and desalination system (distillation process) used to provide a beach house located in Skikda (East of Algeria; Latitude 36.52°N, Longitude 6.57°E) with drinking water. This system produces about 500 l of drinking water per day in July. Mathematical models of the solar flat plate collectors (FPC), absorption heat transformer (AHT) operating with the water/lithium bromide solution and the overall desalination system (WP) were developed to simulate the performance of this combination system. The energy and exergy analyses are carried out for each component of the system. All exergy losses that exist in this solar desalination system are calculated. Energy and exergy efficiencies are estimated.

Supercomponentes Contingency Modeling for Security Assessment in Power Systems

The utilization of the power systems to its maximum capacity is a condition that produces economic benefits to all agents involved in the chain of energy supply and thus to society. However, under these conditions, operators can take risks that could cause the loss of system stability and, in the worst case, blackouts. Thus, operators require analysis tools that give them information in order to take preventive and corrective actions, to operate the system in a reliable way and to check the behaviour of the same. Generally, in this type of analysis, simple component's contingencies are used. However, the practice has shown that more than one component (generation unit, circuit line, single transformer, among others) of the system can fail, either by simultaneous outages; events in cascade or by a major outage that means a complete installation with several components gets out of service. So, a super component refers to complex electrical facilities as: substations, generation plants and multiple circuit transmission lines. An outage of the super component implies the multiple and simultaneous outages of many elements. These kinds of events are not, generally, considered in the mentioned analyses; however, it would be very important to keep them in mind in the security evaluation of power systems. This paper presents a methodology to evaluate the severity of this kind of contingencies in the operative planning scenario. The super components that are taken into account are the multiple circuit lines (in the same structure), generation plants and substations. The impact of contingency on power system security is evaluated in a 24-hour ?day ahead? planning horizon through the computation of the energy not supplied, the number of overloaded lines and the percentage of load loss The Energy not supplied is computed as function of a load shedding based on operator's rules.

Three-Phase 4-Wire Isolated Wind Energy Conversion System Employing VSC with a T-Connected Transformer for Neutral Current Compensation

This paper presents a voltage and frequency controller (VFC) for a 4-wire stand-alone wind energy conversion system (WECS) employing an asynchronous generator. The proposed VF con-troller consists of a three leg IGBT (Insulated Gate Bipolar Junction Transistor) based voltage source converter and a battery at its DC bus. The neutral terminal for the consumer loads is created using a T-connected transformer, which consists of only two single phase transformers. The control algorithm of the VF controller is developed for the bidirectional flow capability of the active power and reactive power control by which it controls the WECS voltage and frequency under different dynamic conditions, such as varying consumer loads and varying wind speeds. The WECS is modeled and simulated in MATLAB using Simulink and PSB toolboxes. Extensive results are presented to demonstrate the capability of the VF controller as a harmonic eliminator, a load balancer, a neutral current compensator as well as a voltage and frequency controller.

Dual-mode magnetoelectric effect in laminate composite of Terfenol-D alloy and PMN–PT transformer with double output ports

The magnetoelectric effect of a laminate composite made by sandwiching a Rosen-type Pb(Mg1/3Nb2/3)O3–PbTiO3 (PMN–PT) single crystal transformer between two length-magnetized magnetostrictive Tb0.3Dy0.7Fe1.92 (Terfenol-D) alloy plates has been investigated. An additional giant sharp longitudinal–longitudinal (L–L) mode resonant magnetoelectric voltage coefficient of 15.6 V Oe−1 due to the transformer voltage gain effect was observed besides the longitudinal–transverse (L–T) mode magnetoelectric voltage coefficient of 4.0 V Oe−1. Moreover, our novel dual-mode (L–L and L–T) laminate can provide two independent output ports, which makes the composite a promising material for multifunctional application in magnetic sensors and magnetoelectric transducers.

Large-Scale Distribution Planning—Part I: Simultaneous Network and Transformer Optimization

This paper is the first of two and presents a planning methodology for low-voltage distribution networks. Combined optimization of transformers and associated networks is performed, considering the street layout which connects the different consumers. In this first part, micro-optimization, the planning zone is divided into small zones, mini-zones, which are optimized independently. A repetitive procedure is used in order to locate transformers using clustering techniques. Optimum capacity, customers to be satisfied, the optimum network to be used and losses associated to this network are determined for each location. The methodology is applied over an area of 12.9 km <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> with nearly 20 215 consumers. In the second paper, two macro-optimization methodologies are discussed based on the planning results for each mini-zone, one based on the Voronoi polygons in order to improve load grouping into mini-zones and the other based on the combination of neighboring networks into a single transformer by means of a Tabu search. Finally, the methodology is applied to a zone with a surface of 2118 km <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> and approximately 1300 000 customers.

An Improved Modeling of Vector Magnetic Properties of Electrical Steel Sheet for FEM Application and Its Experimental Verification

This paper presents an improved vector magnetic property model of anisotropic electrical steel sheet taking account of both the modeling accuracy and the computational cost when combined with finite element (FE) formulation. The reluctivity and hysteresis coefficients in the model are calculated using Fourier series expansion of measured B - and H -waveforms, which are obtained by using a self-developed double-excitation type 2-D measuring apparatus. The time-stepping FE formulation considering the improved vector magnetic property model is derived and applied to magnetic field analysis of a single phase transformer core model made of Grain-oriented silicon steel sheet. The convergence characteristic of non-linear FE analysis is discussed, and the effectiveness of the proposed magnetic property model in comparison with the experimental results is investigated.

Factors Affecting Transformer Plant Species Distribution in Tallgrass Prairie National Preserve

The distribution of transformer plant species, defined as harmful species that substantially modify ecosystems, was generally localized in Tallgrass Prairie National Preserve, Kansas (TPNP). Surveys for transformer species were conducted along line transects (n=301) in September 2006. Nine of 16 transformer plant species (81.8%) revealed significant positive associations with riparian forests or with cultivated land. These preferences are likely confounded in that the soils most suitable for cultivation lie in the vicinity of riparian forests. In contrast, a single transformer species revealed a significant positive association with roads. Agricultural areas and riparian forests appear to be more highly invaded than annually burned and grazed prairie in TPNP. Consequently, targeting early detection efforts in or near agricultural areas and riparian forests rather than the more extensive prairie will likely yield higher detection rates of transformer species.

Single stage and double absorption heat transformers in an industrial application

An industrial application of the single stage and double absorption heat transformer (AHT) systems using water–lithium bromide solutions with water as the refrigerant was analyzed. First, a basic single stage AHT system was described, the operating sequence was explained and thermodynamic system analysis was presented. Next, an application of the single stage AHT system to an industrial company was analyzed. A computer code was prepared to determine the effect of different parameters on the AHT system performance and the results were presented in graphical form. Additionally, the series and parallel double absorption AHT systems were introduced, the operating sequences were explained and thermodynamic system analysis was included. All results were presented in tabular form for comparison. It is concluded that about 50% of the waste heat can be utilized and the hot process water and vapor could be produced by applying single stage and double AHT systems, respectively. The parallel double AHT system could generate more vapor than the series double AHT system. Copyright © 2009 John Wiley & Sons, Ltd.

Improving Understanding of Single Phase Transformer Behaviour through a Multimedia Tool

Many civil engineering students may show little motivation for a course in electrical machinery, because they consider it unexciting and of little importance to their professional practice. Therefore, the use of interactive computer graphics and animations can be a complementary tool for teaching these topics. This paper describes the use of Multimedia MATLAB Graphical User Interface (GUI) for studying the electric single phase transformer at undergraduate level. This Multimedia tool integrates: a description of its structural features; a video recorded in the laboratory showing the open circuit and short circuit tests; and a simulation module that allows us to perform these transformer tests and to analyse voltage regulation and the efficiency of the transformer. This GUI helps students not only to get a better understanding of the advantages and limitations of computer simulation, but also to get a better feel for the physical concepts they study in the lecture and laboratory parts of the course.

Star-hexagon transformer and non-isolated three-leg VSC based three-phase four-wire DSTATCOM

A new three-phase four-wire DSTATCOM (distribution static compensator) is proposed for power quality improvement in the distribution system. The DSTATCOM is based on a star/hexagon transformer and three-leg VSC (voltage source converter). It compensates harmonic current, reactive power and balances the load along with neutral current compensation. Each of the three single phase transformers has three windings and the secondary windings are connected in star/hexagon configuration for interfacing to a three-phase four-wire power distribution system. The IGBT (insulated gate bipolar transistor) based VSC is a capacitor supported and it is controlled for the required compensation of load currents. The DC bus voltage of the VSC is regulated even during dynamic load variations. The DSTATCOM is tested for power factor correction and voltage regulation along with neutral current compensation, harmonic elimination and load balancing under linear loads as well as non-linear loads. The performance of the three-phase four-wire DSTATCOM is validated using MATLAB software with its Simulink and SimPower System (SPS) tool boxes.

A Reliable, Low-Cost Igbt Gate Drive Circuit

A new isolated gate driver for insulated gate bipolar transistors (IGBTs) is introduced, which features low cost, small size and high immunity to dv/dt transients. It has short propagation delays and creates near optimum gate drive waveforms with a negative gate bias in the off state. It incorporates a single two-winding transformer for isolation and requires no secondary side power supply.

Design parameter based method of partial discharge detection and location in power transformers

Insulation defect detection in time ensures higher operational reliabi- lity of power system assets. Power transformers are the most critical unit of power systems both from economical and operational front. Hence it becomes necessary to have knowledge of the actual insulation condition of transformer to increase dependability of the system. The performance and ageing of the transformer insulation is mainly affected by Partial discharges (PD). Proper diagnosis in terms of amplitude and location of partial discharge in a power transformer enables us to predict well in advance, with much confidence, the defect in insulation system, which avoids large catastrophic failures. In this work a 20kVA, 230/50kV single phase core type transformer is used for evaluation of the transfer function-based partial discharge detection and location using modeling of the winding, using design data. The simulation of capturing on-line PD pulses across the bushing tap capacitor is done for various tap positions. Standard PD source model is used to inject PD pulse signal at 10 tap locations in the winding and corresponding response signatures are captured at the bushing tap end (across 1000pF). The equivalent high frequency model of the winding is derived from the design parameters using analytical calculations and simulations in packages such as MAGNET and ANSOFT. The test conditions are simulated using ORCAD-9 and the results are evaluated for location accuracy using design parameter based PD monitoring method.

An Improved Engineering Model of Vector Magnetic Properties of Grain-Oriented Electrical Steels

This paper presents an improved magnetic reluctivity model for vector magnetic properties of anisotropic electrical steel sheet based on Chua-type model using Fourier series expansion of measured <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">B</i> and <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">H</i> waveforms in the viewpoint of engineering application. In the modeling, B-spline surface interpolation is adopted to obtain smooth approximation of measured data. The accuracy of the proposed magnetic reluctivity model is verified by comparing its modeling results with experimentally measured <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">B-</i> and <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">H</i> -waveforms with 30 PG110 grain-oriented silicon steel sheet. The nonlinear finite element (FE) formulation is also derived to incorporate the proposed reluctivity model, and applied to magnetic field analysis of a single phase transformer core model. By comparing the numerical results with experimental ones, the effectiveness of the reluctivity model and FE formulation is investigated.

On the Effects of Subsynchronous Interharmonic Voltages on Power Transformers: Three Phase Units

The effects of subsynchronous interharmonic voltages (SIVs) on three phase power transformers are presented and discussed. In a companion paper, the results of an experiment study a single phase transformer highlighted the need for accurate modeling of the magnetization curve. This study focuses on the magnetizing currents, rms values, and spectral components in the presence of SIVs. A suitable time domain model based on the physical phenomena, as well as a circuit analysis, is presented for both three and five limbs core configurations. The model is experimentally validated and the results of numerical simulations, carried out for different power transformers, are utilized to determine the SIV effects for a variety of magnetizing curves, core geometries, SIV magnitudes, frequencies, and symmetrical components. A compact index able to give a first quantitative estimation of the SIV effects is introduced.

On the Effects of Subsynchronous Interharmonic Voltages on Power Transformers: Single Phase Units

The effects of subsynchronous interharmonic voltages (SIVs) on three phase power transformers are presented and discussed. In a companion paper, the results of an experiment study a single phase transformer highlighted the need for accurate modeling of the magnetization curve. This study focuses on the magnetizing currents, rms values, and spectral components in the presence of SIVs. A suitable time domain model based on the physical phenomena, as well as a circuit analysis, is presented for both three and five limbs core configurations. The model is experimentally validated and the results of numerical simulations, carried out for different power transformers, are utilized to determine the SIV effects for a variety of magnetizing curves, core geometries, SIV magnitudes, frequencies, and symmetrical components. A compact index able to give a first quantitative estimation of the SIV effects is introduced.

Conceptual Design of a 5 MVA Single Phase High Temperature Superconducting Transformer

HTS transformers are being developed by one of 21st Century Frontier R&D Programs in Korea. The final target of the program for the HTS transformer is to develop a 3 phase 100 MVA HTS power transformer. Before then, we proposed a single phase 5 MVA HTS transformer using 2 G wires. It is not for commercialization but for the preliminary research for fabricating the 100 MVA HTS transformer. We supposed volt per turn of 100. It has primary, secondary and tertiary windings. Its size is almost same with that of a 33 MVA single phase HTS transformer in previous work. AC losses due to the winding methods and the variations of other parameters are analysed.