bluuebunny/crossref_metadata_2025_split huggingface dataset:
Possibility of the reduction of the electromagnetic noise of the shinkansen (bullet train) by installing conducting nets
Authors: Amemiya Yoshifumi , Yamaguchi Takashi 
Published: July 2007

AbstractElectromagnetic (EM) noise is radiated when electric trains run along the Shinkansen and the VHF content causes TV receiver jamming. Currently a shared receiving method is put into practice for anti‐jamming. The jammed area extends several hundred meters to each side of the railroad, but if the noise can be reduced by 6 dB the area will be narrowed by a factor of 3 to 4. Earlier noise reduction methods were: improvement of pantograph structure, change of rubbing plate material and use of ferrite in key parts of the pantograph. However the problem on both sides of the railroad remains difficult to solve. In this paper we propose that conducting nets be installed on the supporting poles of the trolley wires. With a net three meters in width, calculation shows that the noise at 150 MHz can be reduced by 6 dB. In the calculation the noise source is taken to be a point source and the field is determined by superposing the waves diffracted from the upper and lower edges of the nets. The calculated results have been verified by experiments with a 1/70 reduced scale model.
Minimally realizable two‐dimensional transfer functions
Authors: Haratani Naomi , Takahashi Shin‐Ichi 
Published: July 2007

AbstractThe minimal realization problem of two‐dimensional transfer functions remains unsolved despite numerous efforts to solve it. Most conventional approaches have taken the form of seeking real number solutions for nonlinear equations that have system coefficients as their unknown variables and are therefore not amenable to realization. This paper presents sufficient conditions by which the possibility of minimal realization can be judged without necessarily solving nonlinear equations from the coefficients of optimally given two‐dimensional transfer functions. The sufficient conditions presented here are broad ones that include the well‐known types of separable‐denominator and separable‐numerator. We also introduce the canonical forms of state space representation for the separable denominator type and separable‐numerator type, which are very useful in practical applications, and additionally show that there are cases where realization dimensions can be reduced even for the general transfer function, which is difficult in finding the minimal realization.
Design and performance of optical fiber cord and optical cord cable
Authors: Tanaka Chihaya , Katsuyama Yutaka , Ishida Yukinori , Waki Takao , Ishihara Koushi 
Published: July 2007

AbstractThis paper describes the optical cord and stranded cable used in cable transmission systems, stations or relays. The allowable stress, bending radius and lateral load of the fiber core are explained first, and then component designs are presented that ensure these characteristics. Tensile strength requirements on the optical cable necessitate using a cord of more than 5,500 denier and a central steel wire with 1‐mm radius. On the basis of the deformation of the PVC sheath due to lateral load, the standard outer diameter of the cable is determined to be 3 mm. The buckling phenomenon of nylon pipe is discussed as it applies to a tube‐type cord, and it is shown that the Young's modulus of the pipe must be below 70 Kg/mm2. The transmission properties, strain, tensile and bending properties of cords and cables, fabricated on the basis of the above‐described design satisfy the desired objectives, confirming the effectiveness of the design.
Self‐complementary monopole‐notch array antennas
Authors: Yamamoto Katsuhiro , Sawaya Kunio , Ishizone Takayuki , Mushiake Yasuto 
Published: July 2007

AbstractThe constant impedance characteristics of self‐complementary antennas are theoretically established; however, the wideband nature of their radiation patterns is not in general assured. A number of works have been published in which widebanding of radiation patterns is attempted by creating axially symmetric self‐complementary monopole‐notch array antennas on the edge of a conductor. However, for the most part these studies are based on experimental procedures. In this paper the radiation characteristics of the self‐complementary monopole‐notch antenna are analyzed theoretically and the array structure with wideband constant gain characteristics is discussed. A monopole‐notch antenna created on the edge of an ideal semiinfinite conducting plane is first analyzed and found to possess wideband radiation characteristics. A more practical monopolenotch antenna created on a finite conducting plate is then analyzed by the induced e.m.f. method. The results show that the gain is higher for the structure with a longer edge in the main beam direction. It is also found that an antenna with constant impedance and constant gain characteristic can be obtained by setting up a monopole‐notch array on a triangular conducting plate. The validity of the theoretical analysis is experimentally confirmed and the limitation of the induced e.m.f. method is evaluated.
A method of designing multielectrode‐pair monolithic filters on high‐coupling piezoelectric plates
Authors: Watanabe Hiroshi , Shimizu Hiroshi 
Published: July 2007

AbstractIn the design of monolithic filters using multiple energy‐trapped resonators on a piezoelectric plate, the conventional method uses operating parameter theory in lumped‐element equivalent circuits. This method cannot, however, be used for designing wideband monolithic filters employing high‐coupling piezoelectric plates such as piezo‐electromagnetic material and LiTaO3 because the error introduced by the lumpedelement equivalent circuit is large. Therefore, this paper proposes a new method using the distributed‐element equivalent circuit, which is suitable for image parameter design theory. First, it is pointed out that in the design of monolithic filters based on the image parameter method which is adopted for designing multimode filters, the resonant and antiresonant arrangement method is difficult to apply to high‐coupling piezoelectric plates. Next, we point out that in order to deal with this problem a new resonant and antiresonant frequency arrangement method is suitable for high‐coupling plate filters and thus good filter properties can be obtained.
Analysis of frequency measurement of power signals with varied amplitudes
Authors: Min Y. , Ding R. J. , Song Y. H. 
Published: July 2007

AbstractFrequency is one of the most important operating parameters of a power system. Thus accurate frequency measurement plays a key role in understanding the system performance and developing effective control strategies. So far various approaches have been proposed. However, one important area, which has been neglected, is what is the effect of varied signal amplitudes on these approaches. Starting with the traditional definition of frequency, this paper analyses the basic requirements for frequency measurement, and presents new concepts for various frequency definitions. The difference between actual frequency and measured frequency by various approaches is discussed in detail. Postprocessing approach is proposed to improve the accuracy of the measurement.
Impact of decentralized wind generation in power systems reliability. Variable speed wind turbines
Authors: Morales A. B. , Trecat J. , Crappe M. 
Published: July 2007

AbstractElectricity supply is challenged from deregulation and third party access to the network. In consequence of this, dispersed generation from Independent Power Producers based on co‐generation units, renewable energies or other conventional sources increase in all countries. Wind Energy Converters is one of the different technologies in use and development. Most utility‐scale wind turbines are operated at constant speed, but there is an increasing interest in variable speed ones. In this paper, a variable speed, stall regulated wind turbine has been simulated, evaluated and compared to a fixed speed wind turbine to study the impact in power systems reliability, on the basis of classic indices and risk base capacity benefit factors, as adequacy indices. Conclusions about the maximum level of penetration are illustrated using a small test system.
Comprehensive analysis and comparative study of several sensorless control systems of asynchronous motors
Authors: Abu‐Rub H. , Hashlamoun W. 
Published: July 2007

AbstractThe aim of this work is to present a novel and inexpensive method to develop and assess sensorless control schemes of induction motors. The proposed systems operate without speed and motor voltage sensors; the rotor angular speed is calculated in different ways. The stator voltage may be determined from measured DC link voltage with information of the pulse width modulation algorithm. A voltage source inverter feeds the induction motor with hysteresis current controllers using amplitude and angular frequency of the stator current as input commands. A comprehensive analysis and comparative study of several relationships of rotor angular speed is presented. The presented idea may be treated as an improvement on the principle of nonlinear control of induction motors. Simulation results have been performed using the proposed control systems. A set of criteria to assign “figures of merit” can be used to choose the proper scheme, depending on the specific application.
Effect of injected charge on the electrification of oil flowing past the surface of composite polymers
Authors: Metwally I. A. 
Published: July 2007

AbstractThe factors affecting oil‐flow electrification (OFE) in large forced oil‐cooled electric power apparatus are experimentally investigated using a closed cycle model, and a coaxial test section comprising a charge injector. The streaming and leakage currents are measured to investigate the impact of injected charge on OFE interfaced with composite polymers. The results reveal that the magnitude and polarity of the injected charge, and the type of composite polymer and its impregnation resin, if it exits, cause evident qualitative as well as quantitative changes in the measured currents. Cellulose‐based materials give the highest leakage current. For other composite polymers, the higher the number of ketonic carbonyls and/or delocalized states in the aromatic moieties, the higher is the leakage current, and hence the lower is the streaming current. Under flow conditions, the leakage current is lower than that under a stationary condition, but the trend is reversed at high temperature, especially for the HVDC case. Under HVAC, the streaming current shows polarity reversal from negative to positive on increasing the oil temperature and/or voltage. For HVDC application, the streaming current is significantly reduced by calendering the outermost layer of the composite polymer, using fine glass as a backing material instead of using glass fabric, and impregnating the composite polymer with highly dipolar epoxy resin.
Compensation of semi‐periodic currents
Authors: Czarnecki L. S. , Chen G. 
Published: July 2007

AbstractBefore power electronics were developed, non‐periodic currents used to occur in distribution systems, apart from arc furnaces supply, mainly during switching and faults. Now, such currents are produced at normal operation of some power electronics equipment. Power electronics enables very fast control of processes and energy flow. Non‐periodic currents are by‐products of such a fast control. Non‐periodic currents in electrical power systems occur as an effect of deformation or conversion of periodic, usually sinusoidal voltage and the periodic component of the supply current is crucial for permanent transfer of energy from generators to loads. Such non‐periodic current, with a periodic or quasi‐periodic components are referred to as semi‐periodic currents in this paper. The paper provides fundamentals of semi‐periodic current compensation and discusses a control algorithm of such a compensator.
Performance of sequence directional elements on MOV protected series compensated transmission lines
Authors: Funk A. T. , Malik O. P. 
Published: July 2007

AbstractPerformance of positive and negative sequence directional elements applied to MOV (metal oxide varistor) protected series compensated transmission lines with the relay voltages measured at the line side of the capacitors is investigated in this paper. Both elements basically measure the negative of the equivalent impedance behind the relay for forward faults and the line impedance plus the impedance of the remote source for reverse faults. During faults, the equivalent impedance of MOV/series capacitor combination is generally different for each of the three phases, causing mutual coupling of the sequence components, which may affect accurate impedance measurement. Simulation results indicate that mutual coupling in the sequence domain does not significantly affect the performance of the sequence directional elements on loaded systems.
Evolving artificial neural network models for voltage contingency ranking
Authors: Singh S. N. , Srivastava K. N. 
Published: July 2007

AbstractThis paper presents four different models of artificial neural network (ANN), namely Multi‐layer feed‐forward (BP) model, Modular neural network (MNN), Hybrid neural network (HNN), and Cascade neural network (CNN) for fast voltage contingency screening and ranking. The effectiveness of the proposed method is demonstrated for contingency screening and ranking at different loading conditions on two sample power systems. One of the proposed neural networks, CNN provides fast and accurate screening and ranking for unknown patterns and would be suitable for on‐line applications at energy management center.
Tuning and parameter variation effects in MRAS based speed estimator for sensorless vector controlled induction motor drives
Authors: Wang M. , Levi E. 
Published: July 2007

AbstractA frequently applied method of speed‐sensorless rotor flux oriented control of induction machines relies on utilisation of model reference adaptive system (MRAS) based speed estimation, where the outputs of the reference and the adjustable model are selected as rotor flux space phasors. Accuracy of the method heavily depends on correct setting of the machine parameters and adjustment of the filter and Pl controller parameters within the estimator. The paper at first describes tuning of various parameters of the estimator, using purely experimental data. The speed estimator is operated in parallel with a commercially available rotor flux oriented induction motor drive with speed sensor and sampled stator voltages and currents are used to tune induction motor parameters, various filters and the Pl controller within the estimator. The procedure is described and illustrated using a comparison between the measured actual speed response during acceleration transients and the corresponding speed estimate obtained from the speed estimator. In the second part of the paper, speed estimation error that will take place in the base speed region due to incorrect setting and/or variation of the parameters of the machine (stator resistance, rotor resistance and magnetising inductance) within the speed estimator is assessed using experimentally recorded data. The experimental results are found to be in very good agreement with previously published theoretical results.
On the correlation between line outages and active losses in power transmission security assessment process
Authors: Sohtaoǧlu N. H. 
Published: July 2007

AbstractIn this paper, the correlation between transmission line outages and power transmission network losses in the corresponding network configurations have been probed in the context of electric power transmission system security assessment process. The effects of transmission line outages and active losses on power systems have been investigated, and contingency ranking of the line outages in order of importance has been performed. Masking effects on system performance index are also included. Test studies have been carried out using linearized power flow model on the IEEE 24‐Bus Reliability Test System to examine the relations between transmission line outages and total active losses, and detailed results are presented.
Application of neural networks to static equivalent networks
Authors: Müller V. , Nelles D. 
Published: July 2007

AbstractThe radial basis functions RBF are described as a special form of artificial neural networks ANN and are tested, if they are applicable as static equivalent networks for power systems. Starting out from equivalent networks for power systems with one coupling node to the internal network, the method is extended up to six coupling nodes. The accuracy of ANN‐equivalent networks will not only be considered for small deviations from the actual operating state (normal operation), also unrealistic high deviations are simulated to show that ANN‐equivalent networks are applicable for the examination of large disturbances.
Leakage field distribution of a transformer for conventional and superconducting conditions
Authors: Raitsios P. , Papadopoulos D. P. 
Published: July 2007

AbstractThe overall distribution of leakage field and current density in a transformer model with cylindrical windings in proximity to the core yokes is investigated from a different viewpoint than that of Kapp or Rogowski, i.e. by taking into consideration the conductivity of the conductive material. Using Maxwell's differential equations and the vector potential and by considering the conductivity of the conductive material, general equations are obtained for the components of the magnetic induction in a two dimensional space. From these components the leakage inductance is calculated and its application for conventional and superconducting conditions is examined. The distribution of current density in the windings is obtained from the vector potential.
A genetic approach to the optimization of automatic generation control parameters for power systems
Authors: Demirören A. , Kent S. , Günel T. 
Published: July 2007

AbstractThis paper presents a method based on genetic algorithm for the automatic generation control of power systems. The technique is applied to control a system, which includes two areas tied together through a power line. As a consequence of continuously load variation, the frequency of the power system changes with time. In conventional studies, frequency transients are minimized by using integral controllers and thus zero steady‐state error is obtained. In this paper, integral controller gains and frequency bias factors are determined by using genetic algorithm. The results of simulation reveal the application of the genetic algorithm having easy implementation to find the global optimum values of the control parameters.
Steel pipe cables with reduced operating frequency
Authors: Brakelmann H. , Rasquin W. , Steinbrich K. 
Published: July 2007

AbstractThe article describes the effects of operating frequency reduction on the transmission behaviour of steel pipe cables. In many countries the external/internal gas pressure cables as well as the oilostatic cables are of a greater interest. Retrofitting of such cables is done by exchanging the old cable cores by new cores with synthetic (e.g. XLPE‐) insulations, thus building so‐called “city cables”. Possible effects of a frequency reduction on the current ratings and losses of external gas pressure cables as well as of city‐cables are discussed. Furthermore the city‐cable is compared with a superconducting cable.
Testing of insulation systems with respect to high‐frequency voltage stress
Authors: Paede M. , Pfeiffer W. , Plessow R. 
Published: July 2007

AbstractDue to the increasing use of power electronics high frequency working voltages are occurring rather frequently. This means a very high stress for any kind of insulatation. This situation is further aggravated by decreasing dimensions due to miniaturization. Therefore this situation has to be taken into account during dimensioning and testing. Different test methods with respect to withstand and partial discharge inception are described. The necessary test equipment and the dimensioning of the test circuits are specified. The aspects of periodic non‐sinusoidal voltages are taken into account by harmonic analysis.
The role of methylnaphthalene in EHV cable oil as related to oil breakdown and discharge velocity
Authors: Al‐Sulaiman A. , Qureshi M. I. 
Published: July 2007

AbstractThis experimental investigation explores the effect of high voltage lightning surges on the insulating oil used in the oil filled extra high voltage cables that serve electric power networks worldwide. Using non‐uniform electrode configuration, the breakdown voltage and corresponding discharge propagation velocities in oil samples that are doped with trace amounts of 1‐Methylnaphthalene are investigated under both polarities of applied stresses in gap spacing of up to 10 mm. Two distinct ranges of additive concentrations are observed which effect these characteristics. Generally, the positive discharge growth decreases with increase in gap spacing while the negative ones show opposite behaviour. Anomalous behaviour of discharge growth is observed at an optimum concentration of additive, as it attains supersonic velocity which increases with the increase in gap spacing. A correlation between the positive impulse breakdown voltage and the discharge propagation velocity is also established.
A wide‐band lumped circuit model of the terminal and internal electromagnetic response of coaxially insulated windings mounted on a core
Authors: Holmberg P. , Leijon M. 
Published: July 2007

AbstractThis paper presents a wide‐band lumped circuit model of coaxially insulated windings mounted on a core. The polyphase model can be used to simulate the terminal and internal electromagnetic response in DryformerTM, a new oil‐free power transformer, and similar electromagnetic power devices. The circuit parameters are based on geometrical and material data. The simulated frequency and transient response of the lumped circuit is compared to measurements on a 20 MVA 140/6.6 kV three‐phase transformer of the DryformerTM type. The comparison shows that the model can be used to estimate resonance frequencies and transient overvoltages in the transformer, although the damping is not accurately modelled. The influence of the core is discussed and investigated.
Computer simulation of responses of earth‐return circuits to the AC and DC external excitation
Authors: Czarnywojtek P. , Machczyński W. 
Published: July 2007

AbstractThe use of the circuit simulation package SPICE (Simulation Program with Integrated Circuit Emphasis) permits the complex analysis of the EMI (electromagnetic interference) on earth‐return circuits. In the approach presented, the earth‐return circuit with excitation by AC signals and transients, as well as with DC energization is modelled as a large multinode electrical equivalent circuit. The circuit is a chain of basic circuits, which are equivalents of homogenous sections of the earth‐return circuit with uniform exposure to the primary interfering electric field associated with the inductive and the conductive influence. The application of controlled voltage and current sources in the basic circuits permit the modelling of coupling effects in systems of earth‐return circuits. Contrary to the analytical methods the SPICE simulation enables one to solve the EMI problems in practical cases connected with: topological complexity of the system considered, non‐homogeneous geometrical and electrical parameters of the earth‐return circuits, non‐homogeneous earth, application of insulating flanges, bonds, earth electrodes in a system of earth‐return circuits, non‐linearity of the system, etc. The SPICE simulation is an alternative and a useful approach to the analysis of EMI problems in earth‐return circuits, when comparing with existing analytical and numerical solutions. The usefulness of the SPICE simulation has been illustrated by examples.