bluuebunny/crossref_metadata_2025_split huggingface dataset:
Modelling of permanent magnet synchronous motors with spatial harmonics
Authors: Bonet‐Madurga J. , Díez‐González A. 
Published: July 2007

AbstractA mathematical model of the permanent magnet synchronous motor with spatial harmonics is presented. The model equations are expressed in a stator reference frame and in a field‐oriented d‐q reference frame. They have been derived applying the space‐phasor theory, which allows the analysis of transients and of spatial harmonics. The spatial distribution of the stator windings, the square‐type induction wave of the magnets and an airgap of variable length have been considered. Expressions for the airgap permeance, inductances, flux linkages, electromagnetic torque and the voltage equations have been obtained. The validity of the model is confirmed by previous experimental works.
Determinination of the ARC extinction time on power lines using voltage signals
Authors: Djurić M. , Radojević Z. , Zorić K. 
Published: July 2007

AbstractThis paper presents a simple algorithm for the overhead lines secondary arcing fault detection and determination of the exact arc extinction time. The algorithm is based on the bus voltage signals only. It uses the method of Least Error Square Technique based on the calculation of the relative error between the modelled voltage sine signal and the measured bus voltage signal. The algorithm was successfully tested with the signals recorded on the real power system and signals obtained through laboratory tests. The test results demonstrate the ability of this algorithm to detect reliably secondary arcing faults and the ability to determine the exact arc extinction time. The algorithm can be used for defining the reclosing dead time and blocking automatic reclosing of overhead lines with permanent faults.
Long arc in free air elongation effects modeling and simulation
Authors: Terzija V. V. , Koglin H.‐J. 
Published: July 2007

AbstractIn the paper the elongation effects on the long arc in still air are investigated and modelled. Arc is initiated under laboratory conditions in the high power test laboratory FGH‐Mannheim (Germany). Based on the analysis of laboratory arc voltage and current wave forms, the new dynamic arc model, taking into account the arc length variation, is derived. An example of arc computer simulation using the new model is given. The main features of the simulated arc are presented. The main features of both the real and the simulated arc are given in the time and the spectral domains.
Steady state of the cascaded doubly‐fed induction machine
Authors: Hopfensperger B. , Atkinson D. J. , Lakin R. A. 
Published: July 2007

AbstractA cascaded doubly‐fed induction machine (CDFM) is a connection of two wound rotor induction machines. The rotors of the two individual machines are electrically and mechanically coupled so that brushes for the rotor sliprings are no longer required.This paper describes the steady state behaviour of such a cascaded machine arrangement. Frequency and slip values are defined. A per‐phase equivalent circuit, based on the common induction machine equivalent circuit, helps to gain understanding of the machine quantities. Measurements on a CDFM confirm simulations with the equivalent circuit experimentally. Saturation effects are discussed to show the limitation of the simple equivalent circuit model. By studying the power flow within the CDFM and taking machine utilisation into consideration allows to suggest that a CDFM has to consist of two identical machines.
Cable model with frequency dependent parameters calculated by using subconductors
Authors: Hofmann L. 
Published: July 2007

AbstractA cable model with frequency dependent parameters in the time domain for the simulation of transients in the short time range is presented. The model is based on the division of the transmission line into m short lossless delay line segments of length Δxk = l/m, which are connected to each other by damping‐networks consisting of constant ohmic resistances and by distortion‐networks simulating the frequency dependence of the series impedance per unit length. The damping‐networks consider ohmic line losses as well as leakage losses by shunt conductances. The distortion‐networks are represented by state space equations in the time domain. One advantage of the model in comparison to generally used models is the direct determination of the model parameters from the geometrical dimensions of the line‐ground configuration. This model also provides a fast and accurate algorithm.
DSTRP: A new algorithm for high impedance fault detection in compensated neutral grounded M.V. power systems
Authors: Ruz F. , Quijano A. , Gómez E. 
Published: July 2007

AbstractThe detection algorithms depend on the network topology, the neutral grounding of the secondary winding in H.V./M.V. transformers being one of the main factors to consider. In compensated distribution systems, we need complex detection algorithms based on network parameters estimation. The neutral voltage is the most sensitive magnitude to detect an unusual situation but it is not a selective parameter. In this paper we present the new DSTRP that calculates the influence of each feeder asymmetry in neutral voltage. We also analyze the measurement errors influence that limits the sensitivity threshold of this algorithm.
Nonlinear disturbance attenuation control of static phase shifter in sense of L2‐gain
Authors: Mei S. , Guan T. , Lu Q. , Song Y. H. , Goto M. 
Published: July 2007

AbstractStatic phase shifters (SPS) have the abilities to optimize power flow and to improve transient stability of power systems. In this paper, improving transient stability of the power system using the static phase shifter is considered. First, a nonlinear robust model of the power system including SPS is established. Then a Backstepping method is used to construct the storage function, and a disturbance attenuation controller in the sense of L2‐gain is achieved consequently. The controller reflects the nonlinearity of the system and attenuates disturbances explicitly. Simulations have proved the effectiveness of the nonlinear disturbance attenuation controller.
A new probabilistic load‐flow method for radial distribution networks
Authors: Golkar M. A. 
Published: July 2007

AbstractProbabilistic load flow is a technique which recognizes the probabilistic nature of the input parameters and takes account of the uncertainties and random variations of generation and load within one computer run. Many formulations have been presented to implement this technique. The majority have assumed either a linear model to represent the load flow equations, or the output random variables to be normally distributed. In this paper, a new probabilistic method for the load flow study of radial distribution system is presented. To increase the accuracy of the method, a new linearization method specific for radial distribution feeders has been developed. As the manipulations required in this method are much less than conventional methods, it is very fast. The method has been used for analyzing some practical networks and the result shows the superiority of the method to conventional ones.
Probabilistic approach of description of thyristor converter faults due to parasitic impulses
Authors: Masmoudi N. , Sellami F. 
Published: July 2007

AbstractThis paper presents a study method of faults linked to parasitic impulses in thyristor converters. In the proposed method control signals are presented in vector form allowing the generalization of parasitic signals. An evaluation of probability of correct operation becomes systematic both in the study of evolution of the system and in the detection of malfunction. An example is given to illustrate the implementation of the method.
Review of the basic insulation level for 400 kV oil‐filled cable systems: Switching and temporary overvoltages (TOV)
Authors: Probert S. A. , Song Y. H. , Basak P. K. , Ferguson C. P. 
Published: July 2007

AbstractThis paper investigates the switching impulse and temporary overvoltage (TOV) duty for 400 kV underground power cables using ATP. This work together with the work reported in [1], investigates the full range of transient overvoltages due to lightning, switching and other temporary overvoltages (TOVs) using ATP. [1] re‐assesses the basic insulation level (BIL) for 400 kV oil‐filled cables. The objective of this work was to check the impact of switching surges on the choice of BIL and to re‐assess the switching impulse insulation level (SIL) and TOV withstand level for 400 kV cables. A comprehensive study of the transient overvoltages experienced by cables within National Grid's transmission system has been performed. This paper provides an argument, for reducing the BIL and SIL for 400 kV cables.
Evaluation of electromagnetic interference on telecommunication cables from an AC railway line: Measurements and calculations
Authors: Lucca G. , Moro M. , Ferrero C. , Giunta M. 
Published: July 2007

AbstractThe paper describes the main results of a field measurement campaign of the electromagnetic interference produced by a 25 kV ‐ 50 Hz railway line on nearby telecommunication cables; the results of the measurements were compared with the results of calculations based on suitable circuit models for studying the inducing and induced systems. The results of the comparison were deemed satisfactory.
A new power electronic converter for switched reluctance motor
Authors: Faiz J. , Salehi M. R. , Hosseini S. H. 
Published: July 2007

AbstractThis paper presents a new topology of bridge converter for a four‐phase switched reluctance motor (SRM). It consists of a four‐quadrant conventional bridge converter and extra switches for selecting phases of the motor. The converter is capable to control the phases of SRM properly and to operate similar compared to the conventional converter with different torques and speeds. There is a minimum number of passive elements and the rated voltage and current of solid‐state components are also minimum. This converter is very convenient for a four‐phase (in general even‐phases) SRM with high voltage and torque. Different modes of operation of SRM are analyzed using the proposed converter and simulation results for a typical 8/6 SRM are presented.
Waveform distortion caused by high power adjustable speed drives part I: High computational efficiency models
Authors: De Rosa F. , Langella R. , Sollazzo A. , Testa A. 
Published: July 2007

AbstractWaveform distortion caused by high power adjustable speed drives is considered and two high computational efficiency models are proposed. Both models are essentially based on the switching function theory and on a new simplified control system representation. The first refers to the solution based on the Line Commutated Inverters, the second to the case of the Pulse Width Modulated Inverters. Models' accuracy and computational efficiency are demonstrated. In a companion paper, the proposed models are applied inside a simulation procedure for the probabilistic analysis of waveform distortion on both the supply and motor sides of the two types of Adjustable Speed Drives here considered.
Waveform distortion caused by high power adjustable speed drives part II: Probabilistic analysis
Authors: Castaldo D. , De Rosa F. , Langella R. , Sollazzo A. , Testa A. 
Published: July 2007

AbstractWaveform distortion caused by high power adjustable speed drives is considered in a probabilistic scenario. In a companion paper, two high computational efficiency drive models, one using the Line Commutated Inverter and the other the Pulse Width Modulated Inverter, have been proposed. These models are used inside a simulation procedure for the probabilistic analysis of waveform distortion on both the supply and motor sides of the two kinds of drives considered. The results obtained considering both mechanical and supply voltage variability are presented and commented.
Effect of tall instrumented towers on the statistical distributions of lightning current parameters and its influence on the power system lightning performance assessment
Authors: Borghetti A. , Nucci C. A. , Paolone M. 
Published: July 2007

AbstractStatistical distributions of lightning current amplitude, time‐to‐peak and other lightning current parameters used in power system insulation coordination are based on experimental data obtained by means of tall instrumented towers. It is, however, generally accepted that these distributions, which we will call ‘classical’ ones, are affected by the presence of the tower, as the tower ability to attract lightning flashes tends to increase for flashes with larger currents. Current amplitudes are thus biased towards higher values with respect to those which refer to flashes at ground. In this paper, we adopt a procedure recently proposed by the authors to infer the statistical distributions of lightning current parameters at ground level starting from those obtained from data measured using tall instrumented towers. The procedure is first applied to classical statistical distributions of lightning current parameters to quantify the tower bias, and this for various models that have been proposed in the literature to represent the exposure of the tower to direct strokes. Then, the statistical distributions at ground, calculated by applying the proposed procedure, are used to calculate the indirect‐lightning performances of an overhead line above an ideal and a lossy ground. The results are also compared with those obtained using the original distributions of lightning current parameters, i.e. by neglecting the bias introduced in the distributions by the presence of the instrumented tower, and a significant difference is found.
Quality of supply management by means of interruption statistics and voltage quality measurements
Authors: Kjølle G. H. , Seljeseth H. , Heggset J. , Trengereid F. 
Published: July 2007

AbstractQuality of supply regulation is a growing area of interest in liberalized energy markets. An important basis for the quality of supply regulation and management is the documentation of existing quality levels. The documentation should be based on standardized terms for recordings and measurements. In Norway the interruption recordings are standardized from 2000 by using the fault and interruption collection tool FASIT. Voltage quality measurements are based on EN 50160. This paper presents results from six years of mandatory interruption recordings in Norway as well as results from the national voltage measurement program going on since 1992.
Embedded generation planning under uncertainty including power quality issues
Authors: Carpinelli G. , Celli G. , Pilo F. , Russo A. 
Published: July 2007

AbstractIn the last years there has been a considerable growing interest in connecting generation to distribution systems. Thus, Embedded Generation is predicted to play an increasing role in the future electric systems. For this reason, distribution system engineers should properly take into account its impact in the system studies. On the other hand, power quality has recently become an important concern for utility, facility and consulting engineers since the electric disturbances have significant economic consequences. In this paper a three step procedure, based on Genetic Algorithm and Decision Theory, is applied to obtain the best generation sizing and siting on a medium voltage distribution network, considering in the objective function and in the constraints the power quality disturbances and taking into account the unavoidable uncertainties that the Embedded Generation production introduces. A numerical application to a simple distribution test system gives evidence of the power quality and uncertainty influence.
Evaluation methods and accuracy in probabilistic harmonic power flow
Authors: Caramia P. , Carpinelli G. , Esposito T. , Varilone P. 
Published: July 2007

AbstractSome evaluation methods to obtain the probability density functions of voltage and current harmonics in multi‐convertor power systems are presented. The approaches are based on Monte Carlo simulation applied to the non linear and linear harmonic power flow equations, on convolution process and on Pearson distributions. These methods are compared in terms of time execution and accuracy in the evaluation of harmonic probability density functions, and in particular of their 95 percentiles and maximum values, being these quantities the statistical measures of greatest interest in many International harmonic Standards and Recommendations. Several numerical applications are presented and discussed with reference to a multiconvertor test system.
Effect of adverse weather on the voltage dip mitigation capability of a static transfer switch
Authors: Sannino A. , Bollen M. H. J. 
Published: July 2007

AbstractThis paper discusses the effect of time‐varying failure rates due to adverse weather on the voltage dip mitigation capability of a static transfer switch (STS). A model that takes into account the increase in both failure rate and repair time due to adverse weather is proposed. Applicabilty of the model and additional effort needed in collecting data are discussed. Sensitivity of the model to uncertainties in the data is assessed.
Valuing reductions in on‐the‐job illness: ‘presenteeism’ from managerial and economic perspectives
Authors: Pauly Mark V. , Nicholson Sean , Polsky Daniel , Berger Marc L. , Sharda Claire 
Published: July 2007

AbstractThis paper reports on a study of manager perceptions of the cost to employers of on‐the‐job employee illness, sometimes termed ‘presenteeism,’ for various types of jobs. Using methods developed previously, the authors analyzed data from a survey of more than 800 US managers to determine the characteristics of various jobs and the relationship of those characteristics to the manager's view of the cost to the firm of absenteeism and presenteeism. Jobs with characteristics that suggest unusually high cost (relative to wages) were similar in terms of their ‘absenteeism multipliers’ and their ‘presenteeism multipliers.’ Jobs with high values of team production, high requirements for timely output, and high difficulties of substitution for absent or impaired workers had significantly higher indicators of cost for both absenteeism and presenteeism, although substitution was somewhat less important for presenteeism. Copyright © 2007 John Wiley & Sons, Ltd.
Selection criteria for a microeconometric model of labour supply
Authors: Blundell Richard , Meghir Costas 
Published: July 2007

AbstractThe wide variety of observed behaviour that is displayed in survey data suggests that microeconometric models should allow a reasonable degree of flexibility in specification. However, since these models are generally used for policy analysis they are required to satisfy some degree of theoretical consistency. This requirement has generally led to the adoption of rather simple ‘inflexible’ models based on additive preferences or linear labour supply responses. We estimate and test a sequence of models for the labour supply of married working women, emphasizing the importance of testing both the thecretical and statistical assumptions underlying the models.
A Bayesian approach to assessing the robustness of hedonic property value studies
Authors: Atkinson Scott E. , Crocker Thomas D. 
Published: July 2007

AbstractHedonic price models are widely employed to estimate implicit prices for bundled attributes. Residential property value studies dominate these applications. Using a representative cross‐sectional property value data set, we employ Bayesian methods to translate a range of priors in covariate selection typical of hedonic property value studies into a range of posterior estimates. We also formulate priors regarding measurement error in individual covariates and compute the ranges of resulting posterior means. Finally, we empirically demonstrate that a greater and more systematic use of prior information drawn from one's own data and from other studies can break the collinearity deadlock in this data.
On estimating dynamic factor demands
Authors: Mahmud S. F. , Robb A. L. , Scarth W. M. 
Published: July 2007

AbstractMany recent empirical studies on inter‐related factor demands involve factor demand functions whose arguments depend on the researcher's arbitrary normalization rule. This paper shows how sensitive the estimated elasticities are to the various normalizations that are possible. Alternatives that are not dependent on a normalization are suggested.
The performance of coal‐burning electric generating units in the United States: 1960–1980
Authors: Joskow Paul L. , Schmalensee Richard 
Published: July 2007

AbstractThis paper studies determinants of the thermal efficiency and reliability of coal‐burning electric generating units using a new, comprehensive, unbalanced panel data set. For two major technological groups consistent and efficient estimates are obtained of the effects of unit age, vintage, scale, operating practices, and coal quality. Large utilities integrated into design and engineering appear to obtain superior unit performance. Implications of our results for life‐cycle generation costs, regulators' performance norms, and the complex pattern of technological change in this industry are discussed.
Empirical evidence on the sign of the slope of the hazard rate from unemployment from a fixed effects model
Authors: Alaouze Chris M. 
Published: July 2007

AbstractEmpirical evidence on the sign of the slope of the hazard rate from unemployment is obtained from a fixed effects model based on the gamma distribution for unemployment duration. The data used are pairs of unemployment spells for adult males in the control and experimental groups of the Denver Income Maintenance Experiment. The sample selection issue involved in selecting the pair of spells used in the empirical work is discussed. The empirical results suggest that for these samples the hazard function is monotone decreasing and support the assumptions that the first two spells of unemployment are identically distributed and can be modelled using the gamma distribution.
Semiparametric econometrics: A survey
Authors: Robinson P. M. 
Published: July 2007

AbstractSemiparametric econometric models contain both parametric and nonparametric components, reflecting in some fashion what has been learned from economic theory and previous empirical experience, and what remains unknown. They raise such questions as how well the parametric component can be estimated, and how to construct rules of inference with good statistical properties. The paper attempts to survey the econometric and most relevant statistical literature on semiparametric inference, and includes a partial bibliography.
Formation of firms' production decisions in finnish manufacturing industries
Authors: Rahiala Markku , Teräsvirta Timo 
Published: July 2007

AbstractBusiness survey data have recently been used in several studies to shed light on the formation of firms' plans and expectations. The main tool for analysis has been the multivariate conditional log‐linear model. The trichotomous answers in a typical business survey have an ordering. This makes it possible to analyse firms' production decisions with a categorized version of Cox's proportional hazards model. In this paper the production decisions of Finnish firms are investigated using data from the Finnish business survey. The results obtained are largely in accord with the implications of the production smoothing model of Blinder (1982).