bluuebunny/crossref_metadata_2025_split huggingface dataset:
Quality of residual current‐operated circuit breakers
Authors: Cantarella G. , Carrescia V. , Tommasini R. 
Published: July 2010

AbstractIn the last few decades, residual current‐operated circuit breakers, with (RCBO) or without integral overcurrent protection (RCCB, hereafter referred to indistinctly as “residual current devices” ‐ RCD), have assumed a fundamental importance for the electrical safety of low‐voltage systems. In accordance with IEC and CENELEC International Standards, they are a necessary protection against indirect contacts in TT systems, are recommended in TN and IT systems, and are able to prevent fires due to small earth‐fault currents. RCD with a rated residual operating current Idn ≤ 30 mA also constitute the only existing active protection against direct contacts and in the case of failure of the protective or earthing conductor. Hence, it is upon their reliability that, to a large extent, the safety of persons, of livestock and property depends in the use of low‐voltage electric power. This paper presents the results of a specific research conducted in Italy on approximately 21000 RCD installed in residential and nonresidential premises. The results of the research are analyzed in the dual intent of drawing, on a statistical basis. useful indications for improving the installation, manufacturing and testing requirements of RCD.
Generalised discrete reliability model of electromagnetic AC contactors
Authors: Ablewski Z. Wrö 
Published: July 2010

AbstractIn the paper discrete reliability models of AC contactors and their functional elements are presented. The models were derived from the analysis of physical and chemical processes which are observed during contactor operation. They can be used for estimation of influence of material and design parameters as well as operating conditions on contactor durability. The models presented can also be helpful in improvement of contactor design methods and in development of new durability tests which can be applied by contactor manufacturers and users.
Convergence improving minimization technique for a modified fast decoupled load flow
Authors: Berizzi A. , Silvestri A. , Zaninelli D. 
Published: July 2010

AbstractThis paper describes an efficient and reliable algorithm that modifies the Fast Decoupled Load Flow (FDLF) in order to overcome non‐convergence troubles in solving strongly stressed power systems. The Hartkopf's algorithm for improving the Newton‐Raphson method's convergence features in ill‐conditioned cases is taken as a basis. The proposed changes to FDLF consist fundamentally in minimizing the squared power mismatches with a second order interpolation technique. The simple modification makes it possible to establish for sure whether a case of non‐convergence is owing to numerical or to physical problems, and lets the operator evaluate the system condition correctly. Several numerical examples show the remarkable behaviour of the algorithm proposed.
A new concept of combined transformers
Authors: Poljak M. , Bojanic B. , Hafner T. , Tomasevic J. 
Published: July 2010

AbstractThe basic characteristics of a new concept of combined transformers consisting of an inverse current transformer and a voltage transformer with open core, are described. The results of the research and testing of impulse and AC voltage distribution, accuracy class, influence of the current transformer on the voltage transformer and vice versa are given. Thanks to its technology and simplicity, the new concept allows the commercial manufacture of combined transformers for the highest equipment voltages up to 420 kV inclusive.
Assessment of air‐density correction for practical electrode systems
Authors: Boutlendj M. , Allen N. L. 
Published: July 2010

AbstractA survey is given of available data on the effects of air density upon pre‐discharges and sparkover for nonuniform field geometries under a variety of voltage waveshapes of both polarities. Semi‐empirical relationships describing the trends of the experimental data are presented. The correction methods set up by the IEC are reviewed and some emphasis has been given to the need to distinguish between the separate influences of pressure and temperature in the overall air‐density correction factors. The limits of applicability for density correction are also discussed. Finally, a generalised semi‐empirical equation taking into account the main atmospheric variations is proposed. This is shown to offer a good accuracy for the calculation of sparkover voltages over a wider density range than has been hitherto been possible.
An efficient identifier for synchronous machine dynamics
Authors: Hegazy Y. G. , Saleh K. I. , Badr M. A. 
Published: July 2010

AbstractThe main objective of this paper is to seek the simplest possible identification model that can simulate closely the dynamic behaviour of a synchronous generator. The successful development of such a model would be of help in devising efficient on‐line digital controllers. For this purpose, the recursive least‐squares method of identification has been used. In this respect it has been found that both a third order and a second order identifier are successful in performing this job. The remarkable finding here is the capability of such reduced models of simulating the dynamics of synchronous generators under the effect of the sub‐synchronous resonance phenomenon, where the order of the differential equations describing the system understudy is extremely high. The validity of the presented analysis and the conclusions reached are checked experimentally.
Mathematical foundations of the instantaneous power concepts: An algebraic approach
Authors: Cristaldi L. , Ferrero A. 
Published: July 2010

AbstractIn this paper a mathematical framework is proposed for defining the concepts of instantaneous real and instantaneous imaginary power in three‐phase systems. Up to now, the approach to the definition of these quantities has mainly been a geometrical approach, which is not generally convenient for the quantitative analysis of the electric system behaviour. The proposed framework is an algebraic approach, based on the innovative use of the hypercomplex number algebra, which is shown to be well suited to deal with three‐wire and four‐wire three‐phase systems. The relationship with the geometrical analysis proposed by Willems is discussed.
The oscillatory nature of the power in single‐ and polyphase circuits
Authors: Emanuel A. E. 
Published: July 2010

AbstractThis study reiterates the fact that the transfer of electric energy in AC circuits is always causing oscillations of power. It is indicated that such oscillations are supported by the energy stored in moving masses, or in the electromagnetic field, or in any type of energy storing device, such as electric batteries. Oscillations caused by an unbalanced polyphase system with purely resistive loads, or by energy storage elements, or by the integer or non‐integer harmonics injected by non‐linear loads, all of them are sustained by the same types of reservoirs of energy. This paper defines three types of oscillations and the powers associated with each type, and details the physical mechanism that controls the energy conversions that govern such oscillations.
Power theory of electrical circuits with quasi‐periodic waveforms of voltages and currents
Authors: Czarnecki L. S. 
Published: July 2010

AbstractGenerally known current and power equations of electrical circuits cannot be used in situations where the voltage and current waveforms are non‐periodic. The paper suggests that these equations could be applied to systems with quasi‐periodic waveforms, however, as approximate models of the power‐related phenomena. The concepts of the running RMS and complex RMS values, as well as the running active power are introduced for that purpose and applied for generalizing the current and power equations of the single‐phase and three‐phase circuits with time‐variant parameters. Fast iterative algorithms for calculating the running quantities make it possible to integrate the frequency‐domain and the time‐domain approaches into a kind of the time and frequency‐domain model of the power‐related phenomena in circuits with quasi‐periodic waveforms.
Application of running quantities for control of an adaptive hybrid compensator
Authors: Czarnecki L. S. , Chen G. , Staroszczyk Z. 
Published: July 2010

AbstractA control algorithm for a hybrid compensator based on a concept of running complex RMS values of the fundamental harmonic of voltages and currents is presented in the paper. The hybrid compensator is composed of an adaptive passive balancing compensator, controlled in the frequency‐domain, and a current source, controlled in the time‐domain. The algorithm used for the compensator control is rooted in a new approach to the power theory of electrical systems with quasi‐periodic waveforms. It is based on the concept of running quantities and a forward extrapolation of the power properties of a time‐variant load. Experimental results obtained using such an algorithm for controlling a laboratory prototype of the hybrid compensator are presented in the paper.
Load‐ and line identification in multi‐phase systems: A compensation‐oriented approach
Authors: Mattavelli P. , Tenti P. 
Published: July 2010

AbstractThe approach presented in this paper relays on the identification of load parameters in terms of passive impedances. It is aimed to the evaluation of unbalanced and reactive currents of an n‐phase system so as to allow load compensation by means of passive components. The paper discusses also an identification method of the line parameters, from which the maximum voltage distortion caused by an individual load can be estimated: This also results in an evaluation method of the power factor, which can be used for tariffation.
On techniques for localization of sources producing distortion in three‐phase networks
Authors: Swart P. H. , van Wyk J. D. , Case M. J. 
Published: July 2010

AbstractThis paper extends the underlying network theory defining the direction of harmonic power in single‐phase systems to three‐phase systems. By employing symmetrical component theory for multi‐frequency systems, zero‐, positive‐ and negative‐phase sequence components may be considered separately. However, the theoretical results and the modelling show that single‐point measurements for the localization of distortion‐producing sources are not practical when these sources are distributed over the network.
An approach to the analysis of power flow with time‐variant components: The switching power
Authors: Monti A. , Riva M. , Furga G. Superti 
Published: July 2010

AbstractBeginning from the previous work results, the authors present Switching Power, a new quantity very useful to comprehend energetic phenomena inside a converter. Following the definition, few theorems are presented and demonstrated, afterwards few examples are discussed to better explain the study application.
Robust control of switched power converters via sliding mode
Authors: Nicolas B. , Fadel M. , Cheron Y. 
Published: July 2010

AbstractThis paper presents a variable structure control approach for the output voltage regulation of switched power converters. The most outstanding feature of this control technique is its robustness towards load and line voltage disturbances. A control implementation for a basic down converter based on state‐space transformation wholly confirms this performance. An extension to inverter control results in reduced harmonic distortion in case of uncertain load characteristics. Analytical predictions are verified by experimental results.
Expert system for energizing bulk power systems after a blackout
Authors: Markovic M. L. 
Published: July 2010

AbstractIn this paper an expert system for energizing the hydro‐dominated Austrian bulk power system after a blackout is presented. According to general restoration guidelines and operating procedures, the expert system computes the restoration schedule (as a sequence of events) for the presumed blackout (i. e. non‐available elements are defined). The restoration schedule is concluded using a discrete event simulator where all substations are modelled at element level. The dispatcher is guided by check lists to follow this restoration schedule and the switching instructions are proposed. Subsequent faults during the restoration result in a revision of the restoration schedule. This expert system has been realized with the help of the expert system tool KEE, and is in use as a stand‐alone program. Further integration within the energy management system is under way.
Shunt active filter for four wire low‐voltage systems: Theoretical operating limits and measures for performance improvement
Authors: Furga G. Superti , Tironi E. , Ubezio G. 
Published: July 2010

AbstractA voltage‐source shunt active filter with a DC storage battery is presented. The circuit configuration and the overall working limits under ideal steady‐state conditions are discussed in detail. The effectiveness of this active filter for harmonic compensation, power factor improving, load balancing and power peak shaving is shown. Analytical relationships of the switching frequency and tracking capability versus voltage levels, current ripple and device parameters are given. A number of simulation results in the time domain and in the frequency domain under sinusoidal and non‐sinusoidal load current are presented. Design rules are also given.
Application of artificial neural networks to historical data analysis for short‐term electric load forecasting
Authors: Caciotta M. , Lamedica R. , Cencelli V. Orsolini , Prudenzi A. , Sforna M. 
Published: July 2010

AbstractThe paper illustrates two different Artificial Neural Networks (ANN) architectures for electric Short‐Term Load Forecasting (STLF). Two multi‐layer perceptron ANN using the back‐propagation learning algorithm have been implemented which provide different, although complementary, forecasting approaches (static and dynamic). In order to test the potentialities of the architectures implemented, the ANN have been applied to the Short‐Term Forecasting of Italian hourly electric load. The importance of this load (peak demands up to about 38 000 MW) requires tools for STLF which must be as more accurate and precise as possible. This fact has imposed the adoption of some algorithmic enhancements to the basic back‐propagation algorithm formulation. Since an adequate formulation of the influence exerted on hourly electric load by the main meteorological and climatic factors is not known at present, the data set used for ANN training phase has concerned only historical series of electric hourly demand. The paper illustrates the two ANN architectures as well as the computational platforms used for implementation. Finally, some results obtained from the application of the two ANN to the short‐term forecasting of Italian electric load relevant to three different weeks of the year 1993 are comparatively reported.
Approximate numerical calculation method for deriving an asymmetrical temperature distribution in a cross‐section of a gas‐blasted arc
Authors: Yokomizu Y. , Matsumura T. , Kito Y. 
Published: July 2010

AbstractA new calculation method for deriving an asymmetrical temperature distribution in a cross‐section of an SF6‐gas‐blasted arc is proposed. Side‐on profiles of radiation intensities of four S+‐ion spectra observed from two directions perpendicular to each other are used as input data to determine asymmetrical distributions of emission coefficients in the cross‐section. The emission coefficient distribution of each spectral line is assumed to be represented by a product of three expressions: one corresponding to an elliptic component, the others being two polynomials that give degree of asymmetry with respect to x‐ and y‐direction. respectively. Unknown coefficients in two polynomials are numerically determined by an iteration process. From Boltzmunn plot diagram with respect to the emission coefficients of four S+‐ion spectral lines for each spatial position, the asymmetrical temperature distribution ofSFf,‐gas‐blasted arc is estimated successfully.
Overview, current trends and latest results in estimating the effects of load modelling on power‐system damping and stability
Authors: Milanovic J. V. 
Published: July 2010

AbstractThe paper presents the overview of load modelling for power‐system dumping and stability studies with main conclusions summarized from previous research. The attempt has been made to present a cross‐section of the most exploited existing load models together with the most important conclusions drawn from their implementation in power‐system stability programs. The current trends and latest results in the domain of damping of electromechanical oscillations in power systems are also presented. The effects of toad dynamics on damping of electromechanical oscillations were analyzed on the basis of one of generic toad models proposed in the past. The recent results further encourage investigation in this area and highlights the importance of proper load modelling.
An advisory system for optimal switching of power‐system capacitors
Authors: Saha S. , Tan O. T. , Christensen J. P. 
Published: July 2010

AbstractA methodology is presented to determine the optimal sequence of capacitor switching in a power system for maintaining a desirable voltage profile over a load cycle. In the first part of the algorithm, the set point voltages of the generators are determined by a non‐linear secondary voltage controller that is emulated by a feed forward neural network. In the second part, these generator voltages constitute the starting point to determine the optimal switching of capacitors by using a dynamic program solver. The algorithm was validated on an IEEE 57 bus test system with the individual loads varying non‐uniformly between 50 % and 110% of their base values.
New approach of using evolutionary programming to reactive power planning with network contingencies
Authors: Lai L. L. , Ma J. T. 
Published: July 2010

AbstractThis paper proposes the use of evolutionary programming (EP) to reactive power planning (RPP). Several techniques have been developed to make EP practicable to solve a real power system problem and other practical problems. The proposed approach is described in detail for the IEEE‐30‐bus system. Simulation results, compared with those obtained by using a conventional gradient‐based optimization method, Broyden 's method, are presented to show that the present method is better for power system planning even under network contingencies. In the case of optimization of non‐continuous and non‐smooth function, EP is much better than non‐linear programming. The comprehensive simulation results show a great potential for applications ofEP in power system economical and secure operation, planning and reliability assessment.
A simple adaptive scheme for indirect field orientation of an induction motor
Authors: Branco P. J. Costa 
Published: July 2010

AbstractA self‐adaptive scheme is described for automatically tracking the temperature and saturation‐dependent rotor time constant T, in indirect vector control. This method is based on a monitoring signal injected into the process. A cross‐correlation function between the monitoring signal and the speed error indicates the T, changes in direction (increase or decrease) and magnitude. The proposed identification algorithm presents unique characteristics: it does not use current or voltage sensors; it is not motor‐parameter dependent; the amplitude of the monitoring signal can be reduced but with an increase on the speed‐error sensibility to control interference in drive's performance and it works either on steady‐ and dynamic transient‐state. It will need some load to operate but this condition is satisfied in all practical cases. Tests were conducted with a 1.2 kW four‐quadrant AC drive. The adaptive indirect vector‐control was implemented in a microcomputer with the motor supplied by a voltage‐source inverter with current control using IGBT. Experimental and simulated results using this adaptive digital scheme for different loads and values of model T, (representing a detuned operation) are presented showing good performances.
Modelling of rectified polyphase salient‐pole synchronous machines: Influence of end‐winding leakages on short‐circuit operation diode current
Authors: Zouaghi T. , Barret P. , Vielpeau D. , Poloujadoff M. 
Published: July 2010

AbstractAn accurate modellization method of rectified polyphase salient‐pole synchronous machines is carried out in this paper. An eleven phase rectified synchronous generator is used to supply the field windings of a large hydraulic alternator. To simulate its operation it has been necessary to develop a convenient diode model and to determine accurately the magnetic linkage parameters. The results have shown that short‐circuit operation heavily depends on the shape of the field in the end‐turn windings.
Influence of dust particles on dc discharges in symmetrical air gaps
Authors: Al‐Arainy A. A. 
Published: July 2010

AbstractBreakdown and corona are investigated in clean and dust‐polluted rod‐rod air gaps varying gap length, rod radius and voltage polarity. It is shown that similar to previous results under impulse voltages, dust pollution can significantly reduce the DC breakdown voltage values of such gaps which depends upon electrode radius, gap length and voltage polarity. These factors should therefore be considered prior to the design and application of air insulation in desert regions, where sand and dust storms can occur frequently. Possible mechanisms which control the observed behaviour are explained in detail.
Scaling and dimensioning of switched reluctance machines
Authors: Gu Q. S. , Stiebler M. 
Published: July 2010

AbstractA scaling law applying to a geometrically analogous series of switched reluctance machines (SRM), based on two‐dimensional non‐linear field analysis is presented in the paper. It highlights the fact that both linear and saturated permeances per unit axial length at different rotor positions are invariant under scaling. Based on a normalized static energy conversion loop in the electric/magnetic loading plane a quality factor is defined which serves to calculate the average specific torque. A simple analytic expression for predicting the quality factor of a SRM is derived which depends only on the linear permeances at two extreme rotor positions and the electric and magnetic loadings at the top point of the static energy conversion loop. This simplifies greatly the prediction of specific torque at an early design stage. Finally, the effects of air‐gap dimension ratios, electric loading, magnetic gear ratio and leakage flux on the quality factor and the specific torque in designing SRM having different magnetic gear ratios are discussed.
A novel configuration for a wide‐range high‐power fiber‐optic current sensor
Authors: Irace A. , Breglio G. , Luciano A. , Zeni L. , Cutolo A. 
Published: July 2010

AbstractIn this paper it is discussed a new configuration for a fiber‐optic current sensor (FOCS) which increases the linearity range of the device without decreasing its sensitivity exploiting an appropriate feedback loop; in this way the whole system behaves as a “null‐detector”. Moreover, the effect of bending‐induced linear birefringence is explicitly taken into account in the design and optimization of the sensor. It is shown that the response of the experimental apparatus is practically temperature independent and that its bandwidth gets values higher than I MHz.