bluuebunny/crossref_metadata_2025_split huggingface dataset:
Voltage sags mitigation on distribution utilities
Authors: Tosato F. 
Published: July 2007

AbstractVoltage sags are important to industrial reliability. Modern process controls are often sensitive to voltage sags, that may cause significant production outages. World‐wide experience proves that a main origin of voltage sags affecting customers are short circuits on utility lines, with special reference to the overhead radial distribution ones. Since the voltage sag during the fault is proportional to the short‐circuit current, an effective fault‐current limitation by means of a device connected at the beginning of the most exposed radial feeders will limit the expected voltage sag amplitude and improve the system power quality. In the paper a proposal for a simple but effective fault‐current limiter is given and discussed.
Single‐phase three‐level rectifier with high power factor
Authors: Lin B.‐R. , Lu H.‐H. 
Published: July 2007

AbstractA new control scheme for the single‐phase rectifier with three‐level voltage pattern is proposed. A power‐factor corrector to improve the power quality is presented. A hysteresis current control (HCC) is adopted to control the line current with high power factor and low harmonic distortion. The line current command is derived from a DC link voltage regulator and an output power estimator. The major advantage of using three‐level instead of two‐level voltage pattern is that the blocking voltage of each power device is clamping to half of the DC link voltage. Based on the region detector of the line voltage, capacitor compensator and hysteresis comparator, the proposed control scheme is used to drive the line current with high power factor and low current distortion. The proposed scheme is verified by software simulations and experimental results from a laboratory prototype.
Load modelling for analysis of power‐system harmonics under unbalanced conditions
Authors: Sainz L. , Clua J. , Jordi O. 
Published: July 2007

AbstractThis paper analyses the load‐harmonic modelling under unbalanced conditions. It presents a harmonic characterization of linear three‐phase loads (three‐phase P‐Q consumptions) for different impedance configurations and analytical models for an ideal six‐ and twelve‐pulse converter supplied by unbalanced voltages, too. The models of these linear and non‐linear loads are incorporated to the three‐phase harmonic load‐flow formulation. A 15‐bus network is presented to study the different load behaviour.
Analytical model for assessment of the line harmonic currents generated by a variable speed drive
Authors: Miègeville L. , Guérin P. 
Published: July 2007

AbstractWith the widespread use of static power converters in many industrial applications, it requires to characterise more accurately the harmonic content injected on electrical networks. The present paper proposes an analytical method to obtain the model of the harmonic currents produced by a variable speed drive. The bridge rectifier is assumed to operate in the continuous mode. In addition, both the AC and DC side impedances are taken into account. Firstly, the validity of the analytical model is demonstrated by comparison both to the results of the time simulations and experimental measurements. Secondly, a detailed comparative survey between the present modelling and some earlier ones is carried out to define the application fields of the analytical model and to point out its interest in describing the harmonics generated by the rectifier for high DC current ripples.
Experimental evaluation of parameter variation effects in indirect rotor‐flux oriented induction‐motor drives
Authors: Sokola M. , Levi E. 
Published: July 2007

AbstractThe paper investigates detuning effects, caused by parameter variations, in an indirect current‐fed rotor‐flux oriented induction motor drive aimed at operation in both the base speed region and the field‐weakening region. Rotor resistance variation and magnetising inductance variation are elaborated. In contrast to the existing studies, where these detuning effects are analysed using appropriate induction machine models, the approach undertaken in this paper is purely experimental. Detuning is evaluated based on measured speed response in transient operation and measured stator current fundamental component in steady‐state operation. Detuning during steady‐state operation in the field‐weakening region is additionally characterised with measured stator voltage fundamental component.
ETEP‐Information on European Dissertations
Authors: Wang X. H. , Song Y. H. , Ferguson C. P. 
Published: July 2007

AbstractThe paper reports on the experimental characterisation and subsequent development of an electrical model for cable oversheath faults under AC voltages. The characteristics can be represented by a combination of linear resistance and capacitance below a threshold voltage and a non‐linear resistance above the threshold voltage. The proposed model was then incorporated into ATP (Alternative Transient Program). The simulation results clearly show satisfactory similarity between the model and the experimental results. The developed electrical model may therefore be used to accurately simulate sheath‐to‐earth fault conditions in buried cable systems.
Achievements of the esprit IV project 22297 electronet ‐ a project closing report
Authors: Dreyer T. , Giannini M. , Lambrecht D. , Laresgoiti I. , Selvik E. , Weber Th. 
Published: July 2007

AbstractThe ESPRIT IV (European strategic programme for research and development in information technology)project ElectroNet aimed at defining a European data model suitable for planning applications of HV (high voltage) and EHV (extra high voltage) power systems by applying the ISO‐STEP‐methodology. For three years thirteen partners from seven European countries worked on this project which was finally completed by the end of September 1999.This paper presents the innovative concepts developed for ElectroNet. Finally an outlook of a subsequent planned project EPSIM is given.
High frequency modal analysis of lossy non‐uniform three‐phase overhead lines taking into account the catenary effect
Authors: Brand Faria J. A. ÄO 
Published: July 2007

AbstractThe catenary effect determines that overhead transmission lines are non‐uniform structures. Most often this effect is assumed to be negligible and the problem is circumvented by simply assigning a constant average height to each line conductor. In order to assess the adequacy of this standard procedure different transmission‐line sections with different sag values have been dealt with, from a modal analysis viewpoint. Each line section has been discretized into a large number of uniform elemental cells; the chain transfer matrix has been computed and the modal characteristics of the structure determined. Computation results clearly show that the average height standard approach is inappropriate for the evaluation of the high frequency modal propagation properties. Frequency scans reveal that the catenary effect gives rise to noticeable resonance phenomena: abrupt variations being observed in the modal propagation characteristics for all modes, the ground mode specially.
Energy functions analysis in voltage collapse
Authors: Jurado F. , Carpio J. 
Published: July 2007

AbstractTime‐domain approach examines the behaviour of the system, one determines whether stability has been maintained or lost. In contrast to the time‐domain approach, direct methods determine system stability based on energy functions. The basis of direct methods for the stability assessment of a system is knowledge of the stability region. During the last decade, many researches have thoroughly analysed the use of energy functions for the direct stability assessment of networks. Energy function analysis offers a different geometric view of voltage collapse. The Transient Energy Function, a technique based on Lyapunov stability theory and originally developed for direct stability analysis of power systems, has been successfully used as a voltage stability index for collapse studies. In this paper the simulation results are on the IEEE 173‐bus test system.
A novel node ordering approach for parallel load flow analysis
Authors: Chen S.‐D. , Chen J.‐F. 
Published: July 2007

AbstractThe bordered block diagonal form(BBDF) of the Jacobian matrix is quite suitable for parallel processing implementation. Balance loading on all processors is essential to ensure the success of any parallel approach. To achieve this objective, a novel approach involving the node ordering method is proposed in this study on the basis of calculating the maximum number of fill‐in and the degree of every node as the cutset block nodes. Simulation results of the IEEE 118–bus system and the Taiwan Power Company (TPC) 288–bus system are presented to demonstrate the performance of the proposed algorithm and its capability to implement parallel computing for the load flow analysis.
On the compensation of non‐active current components of three‐phase loads with quickly changing unsymmetry
Authors: Staudt V. , Wrede H. 
Published: July 2007

AbstractSome types of loads, like arc furnaces, present a special challenge to compensation strategies. They vary quickly and have a very high rated power. For example the arcs of an arc furnace are not burning continuously especially when starting the melting process. This causes variations of the line voltage with frequencies well below the line frequency commonly known as voltage flicker. Because of cost efficiency the energy storage capability of compensators for the mitigation of voltage flicker effects can still only be small compared to the energy taken by the arc furnace during one period of the line voltage. This paper discusses the use of a compensation tool which quickly detects negative sequence current components in comparison to the calculation of an equivalent conductance using the so‐called FBD method (Fryze‐Buchholz‐Depenbrock method). Simulations are used to demonstrate the advantages and disadvantages of the tool for detecting negative sequence current components. It is shown that the quick detection and compensation of negative sequence current components can reduce the amount of voltage flicker considerably.
A thermodynamic approach to the instantaneous non‐active power
Authors: Morando A. P. 
Published: July 2007

AbstractHaving schematically run through the transition from single‐phase to three‐phase relationships, the energy balance is formalised using Park vector notation. The imaginary power notation emerges. Leading back, in the sinusoidal case, to the usual reactive power, it generalises its specific contents in the case of variable states, explaining in particular a typical aspect of three‐phase networks: the energy bouncing from one phase to another. This aspect can be seen as an index of power quality. At last, these same considerations are obtained by means of Lagrangian and thermodynamic approaches that lend a deeper meaning to the energy related quantities.
On the characterization of voltage and current transducers in steady‐state distorted conditions
Authors: Sasdelli R. , Muscas C. , Peretto L. , Tinarelli R. 
Published: July 2007

AbstractThe traceability of measurements performed to gauge information about the operation of electrical power systems under nonsinusoidal conditions is an important and live issue, usually neglected by the technical Standards. A generalized definition of the “composite error” is proposed in this paper as a meaningful index for the metrological characterization of voltage and current transducers in steady‐state nonsinusoidal conditions. In this connection, the relationship among the composite error, the classical ratio and phase‐angle errors and other parameters characterizing the waveforms of the transduced quantities are pointed out. Finally, problems involved in the measurement of the composite error in steady‐state distorted conditions are dealt with and the results of some experimental work are presented.
Poynting vector and the quality of electric energy
Authors: Ĉakareski Ẑ. , Emanuel A. E. 
Published: July 2007

AbstractThis paper expounds on electric energy quality issues using the Poynting Vector (PV). It is shown that components that do not contribute to a net energy transfer, are attributed to the nonactive components of the PV that are associated with three situations: 1. Phase displacement, 2. Current harmonics injection, 3. Load unbalance. The nonactive PV components can be viewed as carriers of polluting energy that negatively affects the energy transfer process and its conversion at the end‐user. The developed analysis helps visualize the flow of electric energy in poly‐phase systems and provides a theoretical base for the resolution of apparent power for three‐phase systems with nonlinear and unbalanced loads.
Investigation of the circuit breaker reignition overvoltages caused by no‐load transformer switching surges
Authors: Popov M. , van der Sluis L. , Paap G. C. 
Published: July 2007

AbstractWhen an unloaded transformer or motor is switched under certain conditions, the circuit breaker can be exposed to a re‐strike effect that leads to voltage escalation. The effect of reignition depends not only on the type of circuit breaker, but also on the surrounding network.In this paper we describe a detailed model of all system components, which is extended where necessary, for the calculation of transients caused by the vacuum circuit breaker switching surges. Especially the transformer modelling is explained in detail for a broad frequency range because of a very complex transient behaviour. The system configuration consisting of a circuit breaker, a cable, a transformer and arresters is observed and modelled by means of some provided measured data. The results of some models are compared with measurements. The models have been imbedded into the Alternative Transient Program (ATP). The program developed here can be widely used for studies of transient recovery overvoltages caused by interruption of transformer steady‐state and inrush currents if the measured data and parameters for the system components are known.
Measurements on electrical power systems under bi‐tone conditions by using the virtual time‐domain approach
Authors: Peretto L. , Sasdelli R. , Tinarelli R. , Rossi C. 
Published: July 2007

AbstractThe virtual time‐domain approach is very convenient for the characterization of multi‐tone signals, both quasiperiodic and periodic with very low fundamental frequency. Measurements on a three‐phase load controlled by an inverter have been performed by means of a digital method implementing that approach. The results are reported and discussed also in comparison with those provided by a validation procedure.
A self‐tuning harmonic and interharmonic processing technique
Authors: Gallo D. , Langella R. , Testa A. 
Published: July 2007

AbstractMeasurement and analysis experiences have highlighted great difficulties in detecting and measuring interharmonics due to their small amplitudes and their consequent vulnerability to spectral leakage of harmonic tones. A new approach that has a general validity and results fully compatible with the latest IEC standard draft is presented. This approach is based on a self‐tuning technique aimed at performing the spectral analysis on a time window whose width is as near as possible to an integer number of the actual period of the fundamental component, so minimizing the effects of spectral leakage on interharmonic estimation. The approach proposed is successfully applied to both numerical and experimental tests.
Circuits with semi‐periodic currents: Main features and power properties
Authors: Czarnecki L. S. 
Published: July 2007

AbstractThe active, reactive, scattered and unbalanced currents and powers, the RMS value and harmonic components are defined only for periodic quantities. Unfortunately, non‐periodic variation of load parameters or their periodic variation but with a frequency different than the frequency of the voltage produced by power generators, causes non‐periodic currents. Such non‐periodic currents, however, are often much lower than periodic components and consequently, the entire current can be considered as semi‐periodic. The notion of semi‐periodic voltage has similar meaning. This paper discusses the main properties of semi‐periodic currents, it provides their classification and introduces a concept of primary, secondary, coperiodic, non‐coperiodic components as well as the concept of interharmonic noise and quasi‐harmonics. The paper investigates how circuits with semi‐periodic voltages and currents could be described in power terms.
The contribution of oil‐flow electrification to the leakage current of multi‐point gaps under direct and alternating voltages
Authors: Metwally I. A. 
Published: July 2007

AbstractThis paper demonstrates the effect of oil‐flow electrification (OFE) on the leakage current in oil‐cooled electric power apparatus using a closed cycle model. The current in multi‐point gaps is measured as a function of oil‐flow velocity and temperature, type and polarity of the applied voltage, number of points and their interspacing, and type of the solid insulating material used in such composite insulation system. The results reveal that OFE phenomenon exists for both energized and unenergized cases. It causes a polarity reversal for the current under positive direct voltage, while it augments that current for negative voltage case. The measured current increases exponentially with temperature and/or voltage. Higher number of points or interspacing between points leads to higher current under both direct (both polarities) and alternating voltages for both stationary and flowing conditions. Also, the experimental results are interpreted and discussed in the light of electric field computation using a package based on the charge simulation method. The electric field profiles, corona inception voltage and number of streamers are invoked to explain the trend of the experimental results.
Application of a self‐tuning to automatic generation control in power system including smes units
Authors: Demirören A. 
Published: July 2007

AbstractIn this study, a self‐tuning control scheme is proposed and applied to automatic generation control (AGC) in power system with superconducting magnetic energy storage (SMES). The system is assumed consisting of two areas. The proposed self‐tuning control scheme is used to implement the automatic generation control adding to conventional control configuration. The performance of the system for load changes in the areas in the interconnected power system is studied. A comprehensive performance evaluation of the system is presented. The computer simulation of the interconnected power system with two areas shows that the proposed self‐tuning control scheme is very effective in damp out of oscillations caused by load disturbances.
Sensorless MRAS‐based induction motor control with parallel speed and stator resistance estimation
Authors: Vasić V. V. , Vukosavić S. N. 
Published: July 2007

AbstractThis paper proposes a novel MRAS‐based speed controller for the induction motor drive without shaft sensor, with the integral adaptation mechanism for on‐line tuning of the stator resistance (Rs). For an accurate estimate of the shaft speed (ω) even at near zero speeds, proposed Rsestimator running parallel in order to compensate for the RS thermal variation. In an intent to accurately estimate the ω at low speeds, without deterioration the drive performance, parallel with the ω estimation the Rsis also estimated to compensate Rsthermal variation. The reference and adjustable models of MRAS‐based ω estimator change their roles in the Rsestimator context. The dynamics of the ω derivation and the Rsestimation are investigated for a wide range of operating conditions and straightforward design procedure is proposed, derived from the hyperstability theory. Extensive computer simulations prove the effectiveness of the proposed solution.
Power system load‐model identification through simulation of field measurements
Authors: Milanovic J. V. , Halley A. J. , Piekutowski M. 
Published: July 2007

AbstractThe paper describes some of the simulations of measurements taken using EMTDC to estimate power system load models. It shows how different load structure and non‐ideal conditions in power systems influence results of the measurements. On the basis of simulations performed different load models are proposed for various classes of load compositions. An example of load parameter estimation from measured results is given.
Digital algorithm for distance relay including grounding impedance at fault place
Authors: Radojević Z. M. , Popović Lj. M. 
Published: July 2007

AbstractThe influence of the fault place grounding impedance in algorithms for ground faults distance relay is not usually taken into account. The fault place grounding impedance depends on design characteristics of the ground wire and towers footing resistance. This paper shows a possibility of taking into account the fault place grounding impedance in the algorithm for the ground fault distance relay. The algorithm taking into consideration the fault place grounding impedance has better accuracy and only slightly greater complexity.
Influence of conductor coating and bundling on corona phenomenon of hybrid AC/DC transmission lines
Authors: Metwally I. A. 
Published: July 2007

AbstractThis paper presents theoretical and experimental investigations of the factors affecting corona phenomenon on hybrid AC/DC transmission lines using a single‐phase AC (50 Hz)/single‐pole DC reduced‐scale model. A field computation program is used to model both an AC 132‐kV double‐circuit transmission line and an analog hybrid line. The results reveal that the corona inception voltage of DC conductors is much higher than that of AC conductors, where it augments with increasing number of bundles, coating thickness and/or permittivity. Conductor coating and/or bundling causes a drastic reduction in both audible‐ and radio‐noise profiles, but there is no effect of bundle orientation. The trends of the experimental results are in agreement with the computed corona inception voltage, number of streamers and electric field. Increasing the number of bundles and/or DC voltage reduces the AC corona current, and so does the number of streamers. Both the interspacing between AC and DC conductors, and the relative amplitude of applied voltages determine the variation of AC corona current. Conductor coating gives an economical solution to increase the corona inception voltage, and reduces the number of streamers at the conductor surface. For thinner coatings, the AC corona current is unchanged while the DC corona current increases.
On the segmentation method used for analyzing nonuniform transmission lines: Application to the exponential line
Authors: Brand Faria J. A. ão 
Published: July 2007

AbstractThis paper addresses the topic of nonuniform transmission line modeling with emphasis on the determination of the high‐frequency propagation parameters. A well‐known tool for analyzing nonuniform line structures, the segmentation method is characterized by modeling the line by a cascade of uniform segments. However, such an approach seems to have a flaw, as it apparently does not include the series‐impedance and shunt‐admittance space‐derivative terms appearing in the wave equations. The importance of that problem is investigated here. A double‐section exponential single‐phase line structure, for which exact closed‐form results are derived, is analyzed using the segmentation method. The approximate results obtained are compared with exact ones. Comparison shows that for typical line geometrical dimensions the segmentation method performs excellently. Further, it is shown that besides the limitations inherent to the line discretization process no other formal limitations to the segmentation method do really exist.