bluuebunny/crossref_metadata_2025_split huggingface dataset:
ChemInform Abstract: A Study of Mesoionic Thiatriazoles, Oxatriazoles and Tetrazoles by Multinuclear Magnetic Resonance Methods
Authors: JAZWINSKI J. 
Published: July 2010

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
Experimental research on the behaviour of hv cap and pin insulator strings with failed units
Authors: Bonzano R. , Ricca M. , Garbagnati E. , Marrone G. , Pigini A. 
Published: July 2010

AbstractElectric, mechanical, environmental stresses, or vandalism can cause porcelain or glass insulator string units to fail during service. This paper presents the results of an experimental research aimed at assessing the influence of failed units on the performance of glass cap and pin insulator strings. Special attention was devoted to 420 kV overhead line configurations. Afterwards, using a statistical approach, the situations of damaged strings were determined that can jeopardize the service reliability of the line and therefore require to start maintenance works. Finally, live line maintenance was considered, with reference to the practice applied in Italy in which operators remain at ground potential while using suitable insulating tools. Taking into account the safety conditions defined by the specific recommendations, the highest number of failed insulators in a string was assessed that would still permit its maintenance by live line works.
Digital simulation of fault arcs in power systems
Authors: Kizilcay M. , Pniok T. 
Published: July 2010

AbstractFaults in power transmission systems often take place through long arcs in air. Therefore, the dynamic interaction between a fault arc and the power network is extremely important in relation to the single‐ or three‐pole autoreclosure and to the system protection relaying. Using the theory of constrained switching arc a new dynamic black box model of a long fault arc is developed. Power system transients caused by arcing faults are successfully simulated using the version ATP (Alternative Transients Program) of the universal Electromagnetic Transients Program (EMTP).
Digital simulation of slip energy recovery induction motor drives using efficient machine and converter models
Authors: Vovos N. A. , Giannakopoulos G. B. 
Published: July 2010

AbstractThis paper presents a computationally efficient technique for digital simulation of slip energy recovery induction motor drives. A machine model that significantly simplifies the machine equations, by eliminating the dependence of the inductance matrix on the ever‐changing rotor angle, is used. Combining this model with a flexible technique to represent the varying topology of the converters, the state equations corresponding to any operating condition of the drive system are automatically formulated. To validate the proposed simulation method, results concerning the transient performance of the drive system are given.
Dynamic behaviour of electromagnetic actuators
Authors: Asche G. 
Published: July 2010

AbstractThis paper describes a numerical method of calculating the dynamic behaviour of electromagnetic actuators supplied by a voltage of any waveform. Moving parts, eddy currents caused by the time variable field and the relative velocity to the field as well as saturation of the magnetic circle are taken into account. The numerical method is based on the finite difference method and the time stepping method according to Crank‐Nicolson. To consider the voltage equation a double iterative solution is used. An example of application with comparison of calculation and measurements is given.
Time chararacteristics of the vacuum breakdown under impulse stress
Authors: Gollor M. 
Published: July 2010

AbstractThe model of the explosive electron emission presents a good explanation for the complete development of a vacuum breakdown. Major aspects are the delay time and the fall time of the voltage collapse with their dependencies on gap spacing and residual gas pressure. Some simple mathematical expressions present a realistic description of the vacuum breakdown by the use of empirical derived correction factors. Measurements with steep fronted and lightning impulse voltages are in good agreement with the results of numeric investigations according to the micro explosion model.
Interactive power system data preparation and verification using a pc‐editor
Authors: Linke K. , Rumpel D. 
Published: July 2010

AbstractFor computerized power system operation, all objects of the network must be mapped in a data‐model. For this task, the „Grid Data Language”︁ (GDL) does not apply format‐bound source data, but describes the objects using a format‐free source text. To handle such texts, an editing‐ and verification‐system was implemented. This paper reports its application when describing an extra‐high voltage network for use in a training simulator. In that way, the full content of a dispatcher EHV data‐model could be converted to GDL, requiring a work of 15 to 20 man‐days.
Shielding of an oscillating dipole field by permeable and conducting sphere‐shaped shields
Authors: Baum E. 
Published: July 2010

AbstractIn this paper the shielding matrix for a sphere‐shaped permeable and conducting shield of arbitrary thickness is derived. With the help of this result the shielding efficiency of a double shield consisting of two hollow spheres is determined. The inner hollow sphere is of finite dimensions and composed of permeable nonconducting material while the outer is conductive and stretches out to infinity. The validity of the analytical computations was checked by a comparison with a Finite‐Element (FE) Analysis for a special case.
Influence of network frequency oscillations on synchronous motors driving masses with great moment of inertia
Authors: Uhlir I. 
Published: July 2010

AbstractIn this paper an influence of network frequency oscillations on exciting of hunting synchronous machines coupled with masses of great moments of inertia is shown. It solves the maximum permissible value of a moment of inertia on the shaft of a synchronous machine in respect to an oscillation of network frequency.
Protection of insulator strings against high‐power Arcs
Authors: Strnad A. 
Published: July 2010

AbstractArcs with high current amplitudes and long duration can cause severe damage or destruction of insulator strings installed in overhead lines or substations. This paper describes the effects to be expected and the range of thermal loads which include a risk if no arcing protective fittings are used. Furthermore, it describes the requirements which arcing protective fittings must meet, the forces which act on the arc, and how the excess pressure inside the plasma channel of the arc shaft can be used for an effective control of the arc.
Exact transformed decoupled optimal power flow
Authors: Ghoneim M. Z. , El Arini M. M. , Rumpel D. 
Published: July 2010

AbstractIn a recently published paper of the authors („On an Exact Transformed Decoupled Load Flow”︁: Electr. Power a. Energy Syst. 13 (1991) no. 1, pp. 28‐32) the method of an exact transformed decoupled power flow (ETD) was presented which can almost achieve the speed of a decoupled power‐flow computation while maintaining the benevolent performance of a Newton power flow in ill‐conditioned cases. The present paper introduces this method to an optimal power‐flow solution. It can be shown that a speed‐up of about the factor three is achieved as against a standard Dommel/Tinney version.
New algorithm for determining critical flashover voltage and standard deviation from flashover probability data
Authors: Gouda O. E. , Zeitoun A. G. , Eisawy E. A. 
Published: July 2010

AbstractThe paper deals with the determination of critical flashover voltage and standard deviation from flashover probability data. A new and simple algorithm is suggested for the analysis of flashover data. In this algorithm the critical flashover voltage and standard deviation of the flashover of a given insulation are determined by interpolation of the data assuming a cumulative normal distribution of variation. The algorithm uses very simple equations permitting much faster evaluation for the critical flashover and standard deviation. Computational difficulties that arise in the two methods (Maximum Likelihood and Graphical Method) are avoided. The algorithm has been applied to several examples, the calculated values are very close to those obtained by using the two methods, the degree of imprecision introduced is usually negligible. A computer program based on the new algorithm is presented to perform all the computations.
A pattern recognition approach for steady‐state security evaluation of an electrical power system
Authors: Gagliardi F. , Chiodo E. , Menniti D. , Testa A. 
Published: July 2010

AbstractA new pattern recognition approach to steady‐state security evaluation of electrical power systems is presented. Such approach is based upon a combined use of the „nearest‐neighbour”︁ method and of an opportune system model ‐ previously proposed by the authors ‐for the basis of knowledge generation. In the first part of the paper, the definition of steady‐state security and the problems arising from its on‐line evaluation are briefly recalled. Then, the pattern recognition approach proposed is described in some detail, and its ability in order to overcome the computational drawbacks of traditional methods is illustrated. Afterwards, some remarks on the system model utilized are reported. Finally, a numerical experiment with reference to the AEP 14 bus test system is presented, showing very encouraging results.
Transient recovery voltage in short‐circuit tests on low‐voltage circuit‐breakers
Authors: Bottauscio O. , Crotti G. , Farina G. 
Published: July 2010

AbstractIn the paper the transient recovery voltages (TRV) that can be experienced in actual installations are compared with those obtainable in short‐circuit tests following the IEC Standards indications. The differences, put in evidence by the experimental investigation, suggest that a measurement campaign on different conditions of distribution and utilization circuits is necessary in order to provide TRV data, such that specific values can be selected for the relevant Standards.
Microbending optoelectronic sensor for on‐line temperature measurements in high‐power electrical systems
Authors: Cutolo A. , Gallo M. 
Published: July 2010

AbstractRelying on well known technology for microbending sensors largely used in high sensitivity pressure measurements, an optoelectronic sensor for temperature measurements was devised and successfully tested. It can prove extremely useful for on‐line and real‐time diagnostics of high‐power electrical systems. The major advantages of this sensor are low cost, easy handling, high electromagnetic compatibility and good precision: Some preliminary experimental results confirm the feasibility of the device. Although the results have been finalized to the real‐time diagnostics of temperature profiles in high‐power electrical systems, their extension to other fields is straightforward.
Eddy currents, current density and induction in slots with two parallel bars
Authors: Fritz W. 
Published: July 2010

AbstractTwo parallel bars in the slot above a current carrying conductor are the elementary arrangement of strands in stator windings of electrical high power machines. The first step consists of the calculation of the magnetic field strength and induction in the slot as general solution; a special solution is gained by the application of the necessary boundary conditions. After that the eddy currents and the eddy current losses of such an arrangement are investigated and discussed.
Determination of time constants with regression equations
Authors: Harcks G. 
Published: July 2010

AbstractThis contribution presents a procedure for the determination of thermal conditions' parameters for electrical machines using regression equations. The determination of the parameters of thermal processes is based on the evaluation of heating and cooling‐down values which are measured depending on time. The procedure introduced in this contribution is equally suitable for the determination of parameters of heating and cooling‐down processes, in particular of the thermal time constants, on the basis of the two‐component model. The basis of the model is a multi‐parametric exponential function that is transferred into a linear regression equation by means of an appropriate transformation.
Parametrizing the power‐plant and load models of a stand‐alone training simulator
Authors: Rumpel D. , Ader T. 
Published: July 2010

AbstractIn order to train an operator in the context of his „own „ power system, a stand‐alone training simulator should be capable to replicate any real power system and to display its performance in its proper operational terms. This purpose can be achieved with a relatively minor effort using the GDL (Grid Data Language) data system, and automatically deriving an operation‐like user interface from the data‐model. A previous paper in ETEP (no. 6, pp. 311‐316: „Database/Power‐Flow Interlinkage of a Stand‐Alone Power System Training Simulator”︁) described, how the power flow of the simulator is interlinked and parametrized via the GDL‐source. The present paper details, how the same tools are applied for parametrizing the power plant and load models.
Is there yet an explanation of ball lightning?
Authors: Arnhoff G. 
Published: July 2010

AbstractA singular solution of Helmholtz equation is described, which delivers a spherical field of radiation. This field is surrounded by an infinite number of ball sockets. These spherical areas are separated by surfaces, which, by special arrangement of the field strengths, cannot be penetrated by their own radiation. A further aspect of this field is, that it does not expand with time. On the surface of the central sphere, being a characteristic of Helmholtz equation, an other solution, which is decreasing continually toward great distances, may be attached. So one receives afield of radiation, which could be used for the explanation of ball lightning. According to this theory thus ball lightning is a self‐restricted field of radiation. Numerical results of the distribution of field strengths for a particular example are given and for the energy of ball lightning to be expected during thunderstorms.
Temperature calculation in electrical machines
Authors: Farschtschi A. 
Published: July 2010

AbstractIt is possible to give a complete description of the temperature behavior of electrical machines by building the heat‐source network. The temperature characteristics of the components can be taken into account by the relevant heat transfer paths in the form of convection, conduction and radiation. The thermal response of the components of an electrical machine as a typical multiple mass problem differs from place to place. The interaction between the neighboring parts results in it no longer being possible to describe the thermal time characteristics of most components by an e‐function. The time each component requires to reach its thermal equilibrium can be determined. This computer program allows the temperature to be determined at any desired point within the claw‐pole generator. The influence of design, material and flow changes can be investigated.
Diagnostic possibilities with short‐circuit protected transistor inverter for electric drives with high reliability
Authors: Weisgerber V. 
Published: July 2010

AbstractIn this paper diverse diagnostic possibilities for transistorized voltage source inverters are presented. As shown, it is possible to test the power circuit for well function and the load for short circuit and unsymmetry. The basis for the test‐routines are power switches, which are protected against overcurrent and short circuit by the base drive circuit. In case of an error an error message is sent back to the main control. Several possibilities for detecting an overcurrent are presented. The principle of monitoring an overcurrent by measuring‐the saturation state of the transistor is explained. The design and the function of the realized base drive circuit are described. Measuring results on short circuit and overcurrent power transistor modules rated to 150 A and 400 A are shown.
Reference power network for the harmonic propagation analysis
Authors: Capasso A. , Lamedica R. , Manigrasso R. , Sani G. , Superti Furga G. , Tironi E. 
Published: July 2010

AbstractThe paper presents the theoretical and experimental work carried out to define a „ reference power network”︁ to study the phenomena of harmonic propagation. This means a network which firstly presents ‐ as a consequence of the presence of a resonance frequency ‐ critical behaviour from the point of view of the correct representation of the components, and secondly is defined through measurements and from investigations among the consumers, in such a way that it might be used for subsequent calculations and surveys pertaining to the models of the various components. The measurements have been carried out with non invasive techniques by using a source of harmonics (AC/DC railway conversion substation) allowing disturbances, controllable in amplitude, to be injected over a programmable period of time. By the end of the investigation the simulation analysis had identified the elements of arbitrariness and the limits of the actual modelling, thus pointing out some possible lines of research to be developed in this area.
Treeing inception of xlpe at lightning impulse voltage
Authors: Rittner K. , Borner G. 
Published: July 2010

AbstractThis paper deals with investigations of the treeing inception of polyethylene insulation under lightning impulse voltage. The experimental results of investigations with XLPE samples in a needle‐plane arrangement will be presented and the influence of various parameters will be discussed. A strong dependence of tree inception voltage on the polarity of the needle‐electrode was found whereas time between the impulses, form of impulses and type of experiments show a small or no influence. Moreover, it will be shown that with lightning impulse voltage ignited trees can reliably be detected by means of PD‐measurement at alternating voltage.
Structure of high performance switched reluctance machines and their power feeding circuitries
Authors: Amin B. 
Published: July 2010

AbstractThe performance of switched reluctance machines (SRM) is strongly structure‐dependent. The layout of the power feeding circuitry of the machine depends, in turn, upon the structure of the motor. This paper discusses the problems of the machine structure: number of phases, number of poles per phase, number of teeth on the rotor and on the stator, etc. Several power circuitries are examined and the advantages and drawbacks of each of them are discussed. Four‐quadrant drive, dynamic and regenerative braking mode of functioning are reviewed.
Design of state observers for linear time‐variant systems
Authors: Solenski N. 
Published: July 2010

AbstractA synthesis method for solving the state observer problem for a special class of time‐variant processes is presented. This method which may be regarded as an extension of pole assignment known from time‐invariant systems, starts from a general state space description for linear time‐variant systems. However, stability is not guaranteed, therefore the properties of Hermitean matrices are used for stability analysis. They permit a simple stability test of the closed loop to complete the synthesis. Applicability and transient behaviour of the controlled system is explained by two examples which include time‐variant parameters.
Influence of loads representation in load‐flow studies for ac/dc industrial electrical systems
Authors: Gagliardi F. , De Martinis U. , Fantauzzi M. , Maraniello M. , Lauria D. 
Published: July 2010

AbstractThe paper deals with loads representation when AC/DC industrial electrical systems are considered and load‐flow studies have to performed on. For such systems studies the importance of a proper load representation is pointed out; some numerical applications are then presented in order to give an idea of the advantages that a proper loads representation may have for an AC/DC industrial load‐flow study.
Interaction between non‐linear loads and synchronous generators
Authors: Gagliardi F. , De Martinis U. , Fusco G. , Lauria D. 
Published: July 2010

AbstractIn this paper the problem of the interaction between synchronous generator and non‐linear load is considered. The problem taken into account is the determination of voltage and current waveforms as well as the calculation methodologies related to it. The following paper ends with a relative numerical application.
Three‐dimensional calculation of linear magnetic fields of not axisymmetrical winding arrangements in transformers
Authors: Janisch T. H. , Buchgraber G. 
Published: July 2010

AbstractWhenever asymmetrical winding arrangements of transformers are to investigate, the use of three‐dimensional calculation methods is essential. In this paper an alternative method to the classical Finite Element formulation is used, based on reduced and total scalar potentials. The basic equations of this method are presented in a short form. Applied on the example of a helical winding arrangement, the results and the influence of winding parameters are discussed.
A 10‐kW‐quasi‐resonant‐converter using igbt as battery charger
Authors: Gao Y. 
Published: July 2010

AbstractThe application of resonant converters in the switched‐mode power supply (SMPS) is very popular due to its high efficiency and compact construction. But because of the limited switching ability of the available power transistor in case of relatively high frequencies, their application is most of all limited to SMPS with smaller power. For the middle power SMPS over 1 kW the realization is most complicated. By using the new power semiconductor switches IGBT, it is possible to build a battery charger according to the quasi‐resonant converter principle with simple driver circuits. The output power amounts up to 10 kW (200 V/50 A).
Analysis of the voltage harmonics of PWM voltage fed inverters using high switching frequencies and different modulation functions
Authors: Van Broeck H. Der 
Published: July 2010

AbstractThis paper presents different methods to determine the harmonics of pulse width modulated patterns by means of a minimum on mathematical equations. The first solution is based on a FFT algorithm and allows detailed investigations for a low frequency ratio of the PWM. The second solution consists of a single expression by which any harmonic based on a high switching frequency can be determined. It can, however, also be applied at low frequency ratios above z 15 and takes different modulation schemes into account. Starting from the pure sinusoidal PWM a third harmonic can be injected, the space vector modulation can be applied or the flat top modulation can be considered. The third approach calculates the most important harmonics of the PWM by a simple equation which can be solved without numerical help. The results of the paper are suitable for three phase PWM transistor inverters in electrical drives or in line converters.