bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electromagnetism, short‐circuit forces and strains in elbow sections of phase‐isolated, metal‐enclosed generator busbars
Authors: Knopf R. , Cupsa A. 
Published: July 2010

AbstractThe electromagnetic relationships (currents, field and current distribution, forces) in three‐dimensional right‐angle arrangements are determined using numerical processes. As a next stage, the short‐circuit strength is investigated with due regard given to the non‐linear material properties. The three‐dimensional calculations required for the field variables and the mechanical loads are then obtained using finite element methods. The individual influencing factors are discussed on the basis of the calculation variants. It is shown that a non‐linear, time‐dependent calculation is required for high loads. The processes presented can be used to calculate steady‐state and transient states in cables and gas‐insulated transmission routes.
Training the restoration of electricity supply systems in the netherlands
Authors: Van Ommeren P. , Van Son P. , Rumpel D. , Litzinger A. 
Published: July 2010

AbstractUsing a stand‐alone training simulator developed at the Gerhard‐Mercator‐ University Duisburg/Germany, a sequence of training seminars was staged in cooperation between KEMA‐ECC, the Power Systems Institute of the University, and with support of the Dutch Electricity Generating Board (Sep). A group of twelve utility operators of Sep and the different regional transport and production companies attended each seminar, with the aim of getting experience on the performance of their systems under the adverse conditions of network‐restoration. For that aim, the simulator models the Dutch 380 kV/220 kV transmission grid and eight connected subtransmission networks on 150 kV and 110 kV.
An effort to find near‐optimal bandpass filter characteristics for use in partial discharge measurements
Authors: Satish L. , Zaengl W. S. 
Published: July 2010

AbstractQuantification of apparent charge is the primary goal of most Partial Discharge (PD) measuring systems and is achieved by the quasi‐integration method using bandpass filters. Past investigations have shown that commercially available PD detectors incorporate widely varying bandpass filter characteristics and so the final results obtained from two different PD measuring systems for similar input conditions were completely different. The authors feel that traceability in PD measurements can be brought about if a uniform bandpass filter characteristic can be found which may be considered as optimal for conventional applications. It so happens that even concerned international standards do not specify any such characteristics. In this short contribution, simulation studies are carried out in an attempt to find the optimal bandpass filter characteristics which yield minimum integration errors and possess short pulse resolution times.
Wettability and thermally stimulated depolarisation current spectra of naturally aged silicone rubber insulators
Authors: Wankowicz J. G. , Gubanski S. M. 
Published: July 2010

AbstractInvestigations are reported on high‐ and low‐temperature vulcanized silicone rubber composite insulators that were exposed to service for three, nine and eleven years under industrial or marine pollution conditions. Wetting angles and thermally stimulated depolarization (TSD) current spectra were measured. Microscopic observations of selected insulator surfaces were carried out as well. The prolonged services cause gradual and inhomogeneous losses of hydrophobicity on surfaces and inside of insulator housing materials. It is shown that there exists a correlation between the measured TSD current spectra and the wettability changes. In addition, the spectra also allow to predict an ability to support a process of hydrophobicity recovery at a housing surface. It seems that TSD measurements may be applied as a complementary test method during performance assessment of silicone rubber composite insulators.
A novel isolated, compensated darlington base‐drive configuration
Authors: Enslin J. H. R. 
Published: July 2010

AbstractThis paper will introduce a new isolated version of the compensated base drive for high‐power bipolar transistor switches. A unique pulse transformer is used to drive a high‐power bipolar transistor by means of a compensated Darlington pair. This Darlington pair consists of an insulated gate bipolar driving transistor (IGBT) and a high‐current single bipolar transistor. In high‐efficient, high‐power bridge applications of high‐current switches, the saturation voltage should be ultra‐low, which implies a high‐power bipolar transistor in deep saturation. This isolated base‐drive circuit is described and evaluated in these applications.
Definition and measurement of the earth resistance of an electrode covering a large area
Authors: Corbellini G. , Corbellini U. 
Published: July 2010

AbstractThe measurement of the earth resistance of an electrode by means of an auxiliary current electrode is affected by a systematic error with respect to the theoretical value, measured picking up the current at an infinite distance, due to the interaction between the two electrodes. The error increases with the ratio of the size of the test electrode to its distance from the auxiliary electrode. This paper suggests a method for the correction of the systematic error when the usual simplifying assumptions are made. The method itself is based on the replacement of the actual electric field, generated during the measurement, by the ideal electric field produced by punctiform electrodes. Its use allows the measurement of the earth resistance even with very short distances between the auxiliary electrode and the test electrode, taking into account the equivalent hemispherical electrodes.
Performance of a three‐phase induction motor fed from a non‐ideal single‐phase supply
Authors: Abdel‐Halim I. A. M. , Slama M. M. , Hamed H. G. 
Published: July 2010

AbstractThe effect of supply reactance on the performance of a three‐phase induction motor fed from a non‐ideal single‐phase supply, using a capacitor phase converter, is investigated. Equations for predicting the performance of the motor are derived, with the effect of the single‐phase supply reactance taken into consideration. Star‐and delta‐connected motors are considered in deriving the performance equations. Computed results for the motor‐performance characteristics obtained when the motor is fed from a non‐ideal single‐phase supply are compared with those obtained when the motor is fed from a non‐ideal three‐phase balanced supply having the same supply reactance as that of the single‐phase supply.
Critical review of the scientific background underlying the generalized machine theory and correlation theorems in the space‐phasor theory
Authors: Serrano‐Iribarnegaray L. 
Published: July 2010

AbstractSteady‐state studies in electrical machines are based, since Steinmetz's work, on the use of time phasors on the one hand and on dividing the total flux into common and leakage flux on the other. Transients studies, however, developed many years later, have lacked analytical tools analogous to the time phasors, and have been carried out resolving the flux into self and mutual flux (Generalized Machine Theory). This paper analyzes the arguments supporting this change of focus and concludes that Steinmetz 's approach can also be extended very successfully to transients analysis, replacing the time phasors by space phasors. This results in the modern Space‐Phasor Theory, whose advantages become especially clear when using the new and powerful physical interpretation of the current and voltage phasors as well as the correlation theorems. These theorems show in what a simple and direct way the space phasors (that symbolize internal quantities) can be related to the machine external quantities during any steady or transient state.
A parameter‐identification‐based diagnosis for detecting static air‐gap eccentricity
Authors: Bradatsch T. , Filbert D. 
Published: July 2010

AbstractA new method for predicting static eccentricity in an induction machine with a non‐uniform air gap is described. This procedure is based on a suitable system mode I for which the model parameters have to be identified. Under certain conditions, the mathematical model of the machine leads to an equation depending on speed, voltage, current and their derivatives. The parameters of the machine can be identified by a least‐square algorithm. The basic concept of the identification method is that the mathematical parameters will be influenced by the static eccentricity because a non‐uniform air gap will increase the inductance in all three phases of the machine. Practical results of air‐gap eccentricity detection of a low‐power motor are presented.
Contribution to iron‐loss evaluation in electrical machines
Authors: Amin B. 
Published: July 2010

AbstractThis paper will show that a simple formulation, similar to that used for the evaluation of the copper loss, can be used to calculate the iron loss of an electrical machine. The analytical method used in the present contribution for evaluating the iron loss of almost all types of electrical machines remains valid for any periodic, quarter‐wave symmetry‐applied voltage waveform. Accurate direct measurements of iron loss concerning five types of industrial electrical machines are presented and analyzed. These data concern two field‐excited and one permanent magnet‐excited DC commutator motors, a high‐speed, 400 Hz, induction motor used in the aeronautical industry and a permanent magnet (PM) synchronous motor used in robotics. These measurements come to support the validity of the proposed formulation and to check each specific aspect of the presented analysis.
Analysis of the inductance of toroidal magnetic switches
Authors: Keet A. L. , van der Laan P. C. T. 
Published: July 2010

AbstractThis paper describes a method to calculate inductances of magnetic switches, toroidal coils wound on ring‐shaped cores of non‐linear magnetic material. To check the described theory, measurements have been carried out on the inductance of magnetic switches in the saturated state. Most text books give expressions for the inductance, but for the critical applications presented here a better approximation is required. Therefore to calculate the inductance of a toroid, the main and three additional types of flux have been taken into account. As a result of this study, a remarkable agreement between the measured and calculated values is found for a large range of turns. For a toroid with a large number of turns the main flux is large compared to the secondary fluxes. For small numbers of turns however, the main flux and the secondary flux contribute equally to the total flux.
Comparison of a forced switching and a quasi‐resonant series chopper with regard to radio‐frequency noise emission
Authors: Scheich R. , Roudet J. 
Published: July 2010

AbstractThis paper presents a short introduction to problems of conducted noise emission encountered in power electronic converter and their measurement. Furthermore, it proposes a methodology based on modular modelling enabling a rapid obtainment of results with satisfactory accuracy. Differential and common mode noise signals are treated separately, each one emitted by its corresponding noise source, and trespassing a particular propagation path, both of which are modelled. After a numeric application of this methodology to a quasi resonant chopper, a comparison of the results obtained with noise levels emanating from a forced switching chopper is provided. Interesting conclusions on the noise behaviour of both converter topologies and on conceptual decisions may thus be drawn.
Prevention of tank rupture of faulted power transformers by generator circuit breakers
Authors: Culver B. , Fröhlich K. , Widenhorn L. 
Published: July 2010

AbstractInternal fault arcs in power step‐up transformers occasionally occur at different locations inside the tank. In this study it has been investigated to what extent generator circuit breakers (GCB) between generator and transformer may prevent explosion or severe damage due to pressure rise caused by the fault arc. Using sources from literature, study of fault cases that occurred in the past, and research of arc‐current and arc‐voltage conditions, a procedure was established to check the probability to what extent a GCB may reduce severe transformer damage and increase safety by prevention of fire. Following this procedure some actual fault‐case studies show that GCB are effective in saving the transformer tank with a probability up to more than 80 %. Comparison with failure data verify the calculations.
Multifrequency analysis with time‐domain simulation
Authors: Usaola J. , Mayordomo J. G. 
Published: July 2010

AbstractThis paper presents a novel method for harmonic analysis that uses techniques both in the time and the frequency domain. The linear parts of a network are modelled in the frequency domain, while the non‐linear ones (converters, saturable transformers, etc.) can be modelled more easily in the time domain. Harmonic balance equations in the multi‐frequency domain are set, and solved by a Newton‐Raphson iterative procedure, with which it is easier to study cases with problems of convergence.
Fast and accurate method to measure interharmonics in power systems
Authors: Dai X. , Gretsch R. 
Published: July 2010

AbstractIn order to improve the resolution of spectrum analysis, the traditional method is to take more sampling periods, e. g. 50 sampling periods corresponding to the spectrum interval of 1 Hz. This method is not suitable to the inter‐harmonic measurement, because most interharmonics vary rather quickly with the time and so the analysis results based on long time sampling may be useless. In this paper the zero‐padding technique with short sampling time is used to resolve interharmonics, and the zoom FFT is used to decrease the computation time in order to meet the needs of real‐time measurement. The simulating computation shows that the resolution for two adjacent frequency components is usually sufficient to measure harmonics and interharmonics in power systems with acceptable short sampling and computation time. This method is also suited to analyse harmonics and interharmonics when there exists an undesirable asynchronous deviation between the sampling period and the signal period.
Evaluation of earth resistivity for grounding systems in non‐uniform soil structure
Authors: Ghourab M. E. 
Published: July 2010

AbstractThe variation in soil resistivity have a considerable influence on the performance of most grounding systems, affecting both the value of ground resistance, the ground potential rise, the step and touch surface potentials. This paper presents a suggested mathematical model to examine the behavior of earthing system in non‐uniform three‐layer soil conditions. The study of the apparent soil resistivity of a driven ground rod as well as the value obtained by the four‐point Wenner method has been done and its dependence on the characteristic of each layer is discussed. A comparison between the two methods is emphasized. Finally, the results demonstrate that there is a predicable relationship between the calculated results obtained by these two methods.
Improving the economic competitiveness of small‐load long‐distance AC transmission systems by the use of static compensators at the receiving end
Authors: Ceraolo M. 
Published: July 2010

AbstractTo supply small loads located very far from low‐cost generation areas local Diesel generation or transmission from the generation areas to loads are the alternatives to be considered. The competitiveness of the latter solution can be improved by the use of static devices, able to compensate active and/or reactive powers, installed in suitable locations of the transmission system. In this paper the possibility of installing at the Receiving End either a Static War Compensator (SVC) or a Static Watt‐Var Compensator (SWVC, that is a device able to work in the four quadrants of the P‐Q plane) is discussed. A possible operating strategy is proposed for both devices, the loadability limits of various options are determined, and an economical comparison of the schemes without compensators and with SVC or SWVC is also carried out in a practical case of application.
Instantaneous power measurement in time‐frequency domain
Authors: Andria G. , Attivissimo F. , Savino M. 
Published: July 2010

AbstractThe paper deals with an original application of the Short‐Time Fourier Transform (STFT) to instantaneous power measurements. This technique can be easily implemented in a dedicated instrument to perform accurate time‐frequency analysis of the time‐varying harmonic contents of network powers (in their active and imaginary components), which are typically non‐stationary signals. Moreover, new algorithms have been examined carefully and developed to attain high levels of accuracy, flexibility and efficiency through STFT‐PD (Power Distribution). Particularly, optimized interpolation formulas were used, derived from the windowing theory to reduce the negative effects due to leakage during instantaneous frequency changes. The effectiveness of the suggested technique and, particularly, the high level of accuracy achieved in time‐varying amplitude and frequency measurements of the analysed components of instantaneous powers and currents has been proven by means of suitable simulations.
The gabor transform as a power‐system analysis tool
Authors: Case M. J. , Swart P. H. 
Published: July 2010

AbstractThe analysis of power‐system distortion has mainly been based on Fourier analysis in various forms. This has been done despite the fact that Fourier analysis requires repetitive waveforms, which certainly is not the situation prevailing on real power systems. The Gabor Transform is a mathematical approach which facilitates the evaluation of non‐repetitive waveforms. This paper introduces the Gabor Transform, and shows how Ms method recovers information that otherwise would be lost in the Fourier Analysis.
Measurement of the electric power quality and related problems
Authors: Ferrero A. , Menchetti A. , Sasdelli R. 
Published: July 2010

AbstractManufacturers, customers and the International Standards are paying more and more attention to the concept of “quality” of an industrial product. In particular, the definition and measurement of the electric power quality is destined to become a big problem. Under sinusoidal, symmetric and balanced conditions, the power‐quality problem is basically a loading quality problem; otherwise, it may be also a supplying quality problem. The paper discusses the measurement of some electric power‐quality indices. It also considers the problem of separating the utility's contribution to the power quality deterioration from the customer's one.
A new method using two triacs for control of single‐phase induction motor
Authors: Abdel‐halim M. A. , Kamal I. K. 
Published: July 2010

AbstractAmong the conventional methods there is no one method by which single‐phase induction motors can be started, speed‐controlled and reversed. The paper develops a new method for controlling single‐phase induction motors with two symmetrical stator windings by placing two bidirectional solid‐state switches (triacs), one in series with the main winding and the other with the auxiliary winding. Such a connection will perform all the required jobs namely: starting, speed control and reversing the direction of rotation. A motor representation in the d, q, 0 reference frame is presented. A state‐space mathematical model has been developed to describe the system taking care of the discontinuities introduced by the triacs. Computer results for transient and steady‐state conditions are presented. Also, experimental verification has been done.
Coordination of surge protective devices using the current data from lightning field measurements
Authors: Heidler F. 
Published: July 2010

AbstractSince about 15 years the electric and magnetic fields radiated by lightning have been measured in the region of Munich/Germany. From these measurements the maximum current steepness of positive and negative return strokes to ground were derived. It was found that the positive return strokes contain higher current steepness than the negative ones. In low‐voltage power distribution systems the concept of lightning protection zones requires that surge protective devices are installed, whenever an electrical line crosses the boundary between two zones. Because the maximum current steepness of negative strokes is lower than for positive strokes, it can be concluded that for the coordination of the surge protective devices only the negative return stroke currents have to be considered.
Detection of resistive single‐phase earth faults in a compensated power‐distribution system
Authors: Leitloff V. , Feuillet R. , Griffel D. 
Published: July 2010

AbstractThis paper proposes several algorithms to detect very resistive, permanent (i. e. non‐transient) single‐phase earth faults in compensated MV distribution systems and to identify the faulty feeder. These algorithms analyse the variation of the parameters of the system and of its electric steady‐state quantities, in particular the residual currents of the feeders. In a first part, the impact of a resistive earth fault on these quantities is deduced. The algorithms enable a detection of permanent resistive earth faults of up to 100 k and identify the concerned feeder. A verification of these algorithms was possible by experiences.
Sliding mode control for a combined active‐passive power‐conditioning equipment
Authors: Furga G. Superti , Tironi E. , Ubezio G. 
Published: July 2010

AbstractWhen compared with ideal conditions, the implementation of active shunt filtering exhibits shortcomings caused by the generation of switching ripple, the limited frequency of filtering and the non‐ideal behaviour of both network and load. It is hence necessary to deal with high harmonics by means of passive filtering elements. The power conditioning equipment put forward in this paper consists of an active filter combined with a passive LC filter. The sliding mode control proposed is particularly rugged and capable of achieving the desired line current with a distorting load and over a wide variation range of network parameters. Numerical simulations and experimental results are reported.
Ac chopper with harmonics elimination and phase control
Authors: Ad'doweesh K. 
Published: July 2010

AbstractA switching strategy for the A C chopper is presented. With this strategy, it is possible to control the phase angle of the output voltage, besides the possibility of controlling the output voltage magnitude. Furthermore, selected lower order harmonics can be eliminated. Profiles of switching angles of the proposed technique are given. Theoretical analysis of the performance of the A C chopper under this strategy along with experimental results verifying the analysis is detailed.
Apparent charge measurement in gis by modern diagnostic methods
Authors: Wanninger G. 
Published: July 2010

AbstractPD measurements are used to ensure the reliability of a CIS. A risk evaluation is only possible, if the emitted PD signal at the defect, the transfer behaviour of the GIS and the coupling of the signals are well‐known. Diagnostic measuring techniques are mentioned as well as the problems of determining a transfer function for these methods. Experimental and theoretical studies on realistic PD currents show the limits of the diagnostic techniques for quantitative measurements.