bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of the inductance of toroidal magnetic switches
Authors: Keet A. L. , van der Laan P. C. T.
Published: July 2010

This 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

This 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

Internal 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

This 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

In 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

The 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

To 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

The 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

The 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

Manufacturers, 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

Among 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

Since 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.
Restoration of radial distribution networks
Authors: Ciric R. , Rajakovic N.
Published: July 2010

This paper describes an efficient and robust heuristic method for restoration of radial distribution networks for the purpose of re‐constructing normal operating conditions. Due to its computational efficiency, this approach can be used in both the planning and operating environments. Important implementary aspects of methodology and results of its application to realistic distribution networks are presented.
Detection of resistive single‐phase earth faults in a compensated power‐distribution system
Authors: Leitloff V. , Feuillet R. , Griffel D.
Published: July 2010

This 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

When 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

A 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

PD 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.
Hydraulically coupled power‐plants commitment within short‐term operation planning in mixed hydro‐thermal power systems
Authors: Rakic M. V. , Markovic Z. M.
Published: July 2010

A new method for short‐term operation planning and power exchange scheduling of interconnected hydro‐thermal power systems is proposed in the paper. The criterion function is the total variable profit obtained by sales of energy to customers within the system, exchange of energy with other systems, diminished by the cost of system operation. The method is based on Lagrangian relaxation, decomposition technique and successive solution of dual and primal problems. The dual and primal problems are decomposed and solved using appropriate optimization methods, while Lagrangian multipliers are corrected using subgradient method. Dual hydro subproblems are solved using linearization and network flow method. Special modification of the algorithm is made so as to enable commitment of hydro power plants, taking into account bilogical constraints on minimal flow of water downstream of the hydro power plant. The efficiency of the method is illustrated on a test problem.
Computer‐aided design of magnetostrictive devices using terfenol‐D
Authors: Benbouzid M. E. H. , Spornic S. A. , Body C.
Published: July 2010

This paper describes a model for the non‐linear magnetomechanical coupling in new highly magnetostrictive materials. This model is devoted to the Computer‐Aided Design of magnetostrictive devices. It is based on an iterative process of successive magnetic and mechanical computations by a the Finite Element Method. Magnetic and mechanical quantities are still coupled by the iterative process. As a matter of fact, the use of experimental data through the Surface Spline Method allows the introduction of the magnetomechanical coupling. The experimental data are collected from a specially designed sample holder devoted to the static characterization of Terfenol‐D rods. Comparisons between numerical outputs from the model and the experimental data reveal that the model is quite powerful to describe the magnetomechanical coupling in highly magnetostrictive materials as Terfenol‐D. Otherwise, the proposed model has been extended to take into account the magnetostrictive effect in microsystems using highly magnetostrictive thin films. Numerical computations provide in this case coherent results and show that it is able to describe the global behaviour of highly magnetostrictive microsystems.
Simulation of complex‐valued, frequency‐dependent quantities in transients programs
Authors: Heimbach M.
Published: July 2010

Transients analysis in power systems requires for many applications an effective and accurate simulation of complex‐valued, frequency‐dependent quantities, e. g. the simulation of grounding structures. The objective of this paper is to give methods to represent complex‐valued, frequency‐dependent quantities by adequate functions and strategies to incorporate them in transients programs. This shall be done in a general manner, without focusing on a specific application. Due to the fact, that transients programs work in the time domain, methods performing the transformation from the frequency into the time domain during the run‐time simulation are mandatory. The methodology to fit the frequency response by means of rational functions is well known. In the first part methods to incorporate rational functions into transients programs are briefly introduced. In the second part three different approaches to determine accurate approximations of complex‐valued, frequency‐dependent quantities are presented. Afterwards the different strategies are tested and discussed with regard to different applications. Finally, the incorporation is validated by comparison to Fast Fourier Transform (FFT).
Probabilistic model and contacts reliability estimation method of electromagnetic AC contactors
Authors: Wróblewski Z.
Published: July 2010

In the paper a probabilistic reliability model of contacts used in low voltage AC electromagnetic contactors is presented along with the theoretical foundation of the contacts reliability estimation method which employs resulrs of the simplified conracts durability tests. The model is derived from the analysis ofphysical and chem‐ ical processes which are observed during contactor operation and may result in contacts failure. The clue of the model is the mathematical description of the contacts wear allowance deterioration which is considered as the forecasting parameter of contacts durability. The model presented appears to be more adequate and accurate than the other ones which are used for description of contacts wear‐off mechanisms. Both the model and the method proposed can be applied in analysis of influence of material and design parameters on contacts durability, in design of new contacts and arc extinguishing chambers and, first of all, in the development of new and fast durability tests which can be applied by contactor manufacturers and users.
Investigation of the transient behaviour of a superconducting magnetic energy storage (SMES) generating high power pulses
Authors: Miri A. M. , Sihler C. , Salbert H. , Vollmer K.‐U.
Published: July 2010

A method for calculating transient voltages in superconducting magnets has been developed. The prediction of over voltages is an essential requirement in avoiding insulation damages in expensive high‐power magnets. A single coil of a modular built Superconducting Magnet Energy Storage (SMES) was modelled as a strongly coupled R‐L‐C network with 8556 mutual inductances. The calculated transient behaviour of the model corresponds well to the measured unit function response of the investigated coil. The coil was designed with respect to the fast repetitive ramping of the SMES. Resonant oscillations are well damped by the mixed matrix Cu/CuNi/NbTi wire used. Due to the high safety margin of the insulation the maximum over voltages could not endanger the winding. A comparison of the results with those of large superconducting fusion coils leads to the recommendation that during the design stage of larger sized SMES a numerical investigation of the resonance behaviour of the system should be performed.
Quantities of a multiterminal circuit determined on the basis of Kirchhoff's laws
Authors: Depenbrock M.
Published: July 2010

For multiterminal electrical networks the interdependency between voltages and currents of the branches of different equivalent circuits and the corresponding terminal quantities are determined using only Kirchhoff's laws. It is shown, that the only set of voltages appertaining to the set ofn currents passing the n terminals consists of the n voltages between the terminals and their common virtual star point, the potential of which is defined to be the mean value of the potentials of all n terminals. In the general case power quantities can be reasonably determined only using pairs which consist either of a terminal current and the appertaining terminal‐to‐virtual star point voltage or of a terminal‐to‐terminal voltage and its appertaining current, the definition of which is less well known. Apparent power is defined to be equal to the physically defined active power, assuming that all terminal currents would be proportional to their appertaining voltages and would have the same collective rms value as the set of actual terminal currents. All definitions can always be applied, including single‐phase and multiphase energy supply systems with or without neutral conductor.
Wavelet‐based approach to network analysis: An introduction
Authors: Gandelli A. , Monti A. , Riva M.
Published: July 2010

Starting from recent results of signal processing theory about wavelet analysis the paper presents a proposal for a review of the electrical network theory based on these new mathematical tools. The basic idea is to find the possibility to extend closed‐form approach in the analysis of electrical systems and arrange an extension of traditional impedance parameters to new and more advanced tools.
Is there a relationship between non‐active currents and fluctuations in the transmitted power?
Authors: Willems J. L. , Ferrero A.
Published: July 2010

In this note it is shown that there is no direct relationship between fluctuations of the transmitted power and the increase of the line current, of the apparent power and of the transmission power loss. A number of benchmark situations are dealt with to support the conclusion.
New invasive method for localisation of harmonic distortion sources in power systems
Authors: Staroszczyk Z. , Mikolajuk K.
Published: July 2010

The presented paper illustrates the invasive method of power‐system identification. It is based on Czarnecki 's ideas to disturb slightly the system and observe its response to find unknown harmonic sources and equivalent linear impedances. The one‐phase system is considered, with a new signal‐processing technique in which instant measurements are based only on two adjacent signal periods. That approach allowed to move differential calculations to the time domain, and to deal with integral Fourier transform, in place of discrete, in frequency domain. The new algorithm allows to increase the S/N ratio, is insensitive to signal time‐shifts and gives correct results in a wide frequency band (5 kHz). Simulation and measurements results are presented and show how accurate the identification can be for short‐time (two periods) and 1 s long observations.
Calculating a new reference point for the iec‐flickermeter
Authors: Mombauer W.
Published: July 2010

Modern multicycle‐controlled equipment produce voltage fluctuations with repetition rates much higher than the highest frequency for type testing the IEC flickermeter under the standard IEC 61000‐4‐15. In order to equalize all flickermeters it is necessary to add an additional reference point for 33'/? Hz to the standard. The amount of d/%‐values will be evaluated. Reference values for 120‐ V/60‐Hz‐ and 230‐ V/60‐Hz systems have been added.
Arcing faults detection on transmission lines using least error squares technique
Authors: Djurić M. B. , Radojević Z. M. , Terzija V. V.
Published: July 2010

In this paper a new numerical algorithm for arcing faults detection and fault distance calculation is presented. The solution is given in the time domain and for the most frequent single‐phase to ground fault. It was derived by processing the line terminal voltages and currents. The new algorithm can be utilized for blocking the automatic reclosing. A simple square wave arc voltage model was assumed to represent the long arc in free air. The unknown model parameters (the line resistance and inductance, and arc voltage amplitude) were estimated by using “Least Error Squares Technique”. The new algorithm was successfully tested by computer‐simulated and laboratory tests.
A study of corona phenomenon on hybrid AC/DC transmission lines
Authors: Metwally I. A.
Published: July 2010

The factors affecting corona phenomenon on hybrid AC/DC transmission lines are investigated using a single‐phase AC (50 Hz)/single‐pole DC reduced‐scale model. The variation of DC corona current with DC voltage follows the same conventional formula for rod‐to‐plane gaps, where the exponent of conductor height increases with DC voltage, but is slightly affected by interspacing. While the AC corona current is inversely proportional to the conductor height with a power range from 0.7 to 0.8, it also increases with the decrease in interspacing. Afield computation program is used to model both an AC 132‐kV double‐circuit transmission line and analog hybrid lines. The results reveal that hybrid lines cause higher radio noise but the audible noise is nearly the same as or lower than that for the AC double‐circuit lines. The trend of the experimental results is in agreement with the computed number of streamers and electric field profiles.
Vectorial summation of probabilistic current harmonics in power systems: From a bivariate distribution model towards a univariate probability function
Authors: Wang Y. J. , Pierrat L.
Published: July 2010

This paper extends the investigation into the bivariate normal distribution (BND) model which has been widely used to study the asymptotic behaviour of the sum of a sufficiently large number of randomly‐varying harmonic phasors (of the same frequency). Although the BND model is effective and applicable to most problems involving harmonic summation, its main drawback resides in the computation time required to extract the probability density function of the harmonic magnitude from the two‐dimensional BND model. This paper proposes a novel approach to the problem by assimilating the generalized Gamma distribution (GGD) model to the marginal distribution (the magnitude) of the BND using the method of moments. The proposed method can accurately estimate the parameters of the GGD model without time‐consuming calculation. A power system containing ten harmonic sources is taken as an example where the comparison of the Monte‐Carlo simulation, the BND model and the GGD model is given and discussed. The comparison shows that the GGD model approximates the BND model very well.
A precise method for the impedance calculation of a power rail taking into account the skin effect and complex geometry
Authors: Wang Y. J.
Published: July 2010

The method of coupled inductance based on subdivision of conductors is employed in this paper for calculating the impedance of a power rail (also known as the conductor rail or third rail) considering the skin effect and complex geometry. The proposed method also allows the current distribution over the rail cross‐section to be determined. A numerical technique that is able to economize on the number of subconductors required to achieve a prescribed level of accuracy, is also proposed to reduce computation time and matrix dimensions.
Distribution network restoration using mix integer programming method
Authors: Ciric R. M. , Popovic D. S.
Published: July 2010

This paper describes an efficient and robust method and a developed software package for the restoration of radial distribution networks for the purpose of reconstructing normal operating conditions. The proposed methodology uses combined heuristic approach and mix integer programming for solving the network restoration problem. Due to its computational efficiency, this approach can be used in both the planning and operating environments. Important implementional aspects of the methodology and the results of its application on realistic distribution networks are presented.
A new contact design based on a quadrupolar axial magnetic field and its characteristics
Authors: Fink H. , Heimbach M. , Shang W.
Published: July 2010

Axial magnetic field (AMF) contacts are applied within vacuum interrupters especially in case of high short‐circuit current. In this paper a new AMF contact design based on a quadrupolar field arrangement and its characteristics are presented. In the first part the basic principle of the new contact design is introduced. This is followed by three‐dimensional field simulations performed with the aid of a Finite‐Element‐program. The magnitude of the axial magnetic flux density, the phase‐shift between current and magnetic flux density, and the current flow within the contact plate are investigated during arcing. The impact of quadrupolar AMF on the arc behaviour during the high current phase is analysed by high‐speed films and pictures of the contact surface after arcing. The interruption performance of the principle has been validated by short‐circuit tests up to 12 kV/63 kA.
Harmonic interaction in capacitor rectifier loads
Authors: Boix O. , Sainz L. , Pedra J.
Published: July 2010

In this paper a steady‐state model of a single‐phase power supply is presented. The model takes into account the influence of feeder harmonic voltages on the non‐linear load behaviour. With this model we can observe that, when the distorting load consumption is important, the harmonic interaction must be considered in order to obtain correct results. This model has been implemented in a harmonic load‐flow program in order to perform harmonic studies in network and industrial installation.
New testing method for the classification of contact materials for vacuum circuit breakers
Authors: Kaumanns J. , Möller K. , Weinert H.
Published: July 2010

A new testing method to classify contact materials for high‐current interruption with vacuum circuit breakers (VCB) is described. The testing effort is reduced by diminishing the contact gap and the contact area as well as by an adequate testing circuit. Consequently, the number of experiments can be increased for the benefit of a high statistical certainty in the classification of contact materials. The test results are in good agreement with the results of full‐size short‐circuit current interruption tests carried out in a high‐power testing laboratory with VCB equipped with contact materials classified in the new testing circuit.
Tests and calculations of short‐circuit forces and displacements in high‐voltage substations with strained conductors and droppers
Authors: Stein N. , Meyer W. , Miri A. M.
Published: July 2010

Forschungsgemeinschaft für Elektrische Anlagen und Stromwirtschaft FCH and DKE UK 121.2 have recently completed an extensive systematic programme of short‐circuit tests on substation bus bars of stranded conductors with and without droppers. The present test series, in continuation of the former studies, comprises 100‐kV and 400‐kV arrangements, applying the relevant parameters of the former. Apart from other variations, different current paths were studied for the arrangements with droppers. The present paper is confined to giving a survey of the 100‐kV arrangements, parameter variations, measurements and test results, as far as they presently relate to the calculation procedure oflEC, CENELEC and D/V/VDE. It is further reported on studies with the Finite‐Element Method (FEM) which show a remarkable comparative accuracy. Finally, the standardized method of IEC 60865‐1 and EN 60865‐1 for the calculation of short‐circuit tensile forces is extended onto arrangements with droppers.
Physical model of the interference immunity of electronic devices and conclusions concerning their testing and operating characteristics
Authors: Bauer H. , Hentschel G.
Published: July 2010

Switching and fault processes in power‐supply systems cause pulse‐shaped disturbances which may stress electronic devices of protection and control systems. For test purposes such disturbances can be simulated. But despite of the constant test conditions the reaction of the device on the disturbance can vary in a certain range. Assuming similar internal structures of protection and control devices the coupling path and the effects of the disturbance are described. The variation in device reaction due to the disturbance is explained on the basis of different models which imitate the impact of the disturbances especially on the logical part of the circuit. By applying sensors with constant threshold the effectiveness (function) of several EMC measures can be evaluated independently from the reaction of the special device.
Numerical modelling for investigation and optimization of a sensor for sensitive partial discharge detection on high‐voltage XLPE cables
Authors: Heinrich R. , Jobava R. , Kalkner W. , Gheonjian A.
Published: July 2010

Based on experimental investigations a theoretical model of a sensor for partial discharge (PD) detection on high‐voltage cross‐linked polyethylene (XLPE)‐insulated cables respectively joints has been developed. The model handles radial symmetric sensors and is based on the Finite‐Difference Time‐Domain (FDTD) method in which a cylindrical coordinate system is exploited. The calculation provides field values at each node of the FDTD grid. The field pattern in the cable and sensor at different time steps is used to investigate the coupling mechanism of the sensor. It is also used for parametric studies of the sensor, e. g. the dependence of the sensitivity on geometrical characteristics of the sensor, which is investigated theoretically as well as experimentally. Results of computer simulation are in a good agreement with experimental data derived for such sensors.
Ground‐fault fast transients in modern unit‐connected generators
Authors: Zielichowski M. , Fulczyk M. , Mydlikowski R.
Published: July 2010

In this paper the ground‐fault overvoltages in the circuits of unit‐connected generators during interrupted arcing ground faults in the stator winding of the generator with the neutral grounded through the ground‐fault neutraliser were analysed. Comparative simulation tests of ground‐fault voltages and currents for units with the biggest difference in parameters at the neutralisation coefficient equal to 0.6 were carried out. The currents in all the branches of the equivalent scheme of the unit, the voltage drops on its particular elements and the overvoltage danger were determined. The real changes in the resistance of the ground‐fault arc in the main insulation the stator windings and the real mechanism of its quenching were taken into account.
Improvement of interactions among facts controls
Authors: Lei X. , Buchholz B. , Lerch E. , Povh D.
Published: July 2010

Interaction among the FACTS (flexible AC transmission systems) devices in a multi‐machine system can adversely influence the damping properties of individual FACTS devices. In some critical cases, it may even amplify power swings or increase voltage deviations. This paper presents a global tuning method for the FACTS controllers in a multi‐machine system. Based on a non‐linear optimization algorithm implemented in a simulation program, the parameter settings of the FACTS controllers involved can be simultaneously optimized at transient conditions in coping with the non‐linear nature of the power system. By minimizing a non‐explicit target function in which swing characteristics between areas are included, interactions among the FACTS controls at transient conditions in the multi‐machine system are minimized. Two multi‐machine power systems equipped individually with a TCSC (thyristor‐controlled series compensator) and a SVC (static Var compensator) are applied to demonstrate the efficiency of the proposed tuning procedure. The results obtained from simulations validate the improvement in damping of overall power oscillations. The simulations also show that the optimized FACTS controllers are robust in providing adequate damping for a range of conditions on the system.
Effect of dust on discharges in rod‐rod air gaps in the presence of parallel insulating spacer
Authors: Malik N. H. , Qureshi M. I. , Al‐Arainy A. A.
Published: July 2010

Breakdown and corona are investigated experimentally in clean and dust‐polluted rod‐rod air gaps in the presence of clean and dust polluted insulating spacer placed parallel to the electrodes. Gap length and spacer distances were varied and DC voltages of both polarities were used to investigate breakdown voltage andpulsa‐tive corona characteristics. The results show that the presence of spacer tends to considerably influence the effects of dust pollution on the breakdown and corona characteristics. Possible mechanisms, which control these variations, are discussed.
Accurate fault location algorithm for power transmission lines
Authors: Sadeh J. , Ranjbar A. M. , Hadjsaid N. , Feuillet R.
Published: July 2010

In this paper we propose a new fault location algorithm for power transmission lines based on one terminal voltage and current data. A distributed time domain model of the line is used as a basis for algorithm development. The suggested technique only takes advantage of post‐fault voltage and current samples taken at one end of the line and does not require filtering of DC offset and high‐frequency components of the recorded signals, which are present during transient conditions. Another advantage of the proposed method is the application of a very narrow window of data i. e. less than 1/4 of a cycle. The paper also proposes two different algorithms for lossless and lossy line models. Computer simulations approved the accuracy of the proposed methods.
Stability improvement in power systems with non‐linear TCSC control strategies
Authors: Lei X. , Jiang D. , Retzmann D.
Published: July 2010

In this paper, a non‐linear control scheme for the TCSC (thyristor‐controlled series compensator) to dampen power oscillations and to improve the transient stability of power systems is presented. Based on an one‐machine‐infinite‐bus system, a non‐linear mathematical model is established which is proven as an affine nonlinear system. With the help of the feedback linearization technique, the affine non‐linear model is exactly transferred to a linear model, and then the control scheme is designed for the TCSC based on the global linearization, where the input signal uses local measurements only. The effectiveness and robustness of the proposed non‐linear control scheme are demonstrated with an one‐machine test system, where the TCSC modelling and power system simulations are performed by using the program system NETOMAC. In comparison with a conventional control scheme, significant improvements of dynamical performance in the test power' system are achieved by the proposed non‐linear control strategy for the TCSC.
Digital implementation of fuzzy control algorithm for shunt active filter
Authors: Singh B. N. , Singh B. , Chandra A. , Al‐Haddad K.
Published: July 2010

The paper deals with a digital‐signal‐processor (DSP)‐based implementation of a Fuzzy control algorithm for a three‐phase active filter (AF). The laboratory prototype model of the AF uses voltage source inverter (VSl) with pulse‐width modulation (PWM) current control technique. The AF is employed to compensate harmonics and reactive power of a non‐linear load. A three‐phase diode bridge rectifier with resistive‐inductive load is taken as a non‐linear load. With a view to obtain the steady‐state and transient response of the AF system, its mathematical model is developed. Experimental verification of simulated results is carried out to validate the proposed fuzzy control technique for AF systems.
One‐pot synthesis of surface‐functionalized molecularly imprinted polymer microspheres by iniferter‐induced “living” radical precipitation polymerization
Authors: Li Junyi , Zu Baiyi , Zhang Ying , Guo Xianzhi , Zhang Huiqi
Published: July 2010

This article describes for the first time the development of a new polymerization technique by introducing iniferter‐induced “living” radical polymerization mechanism into precipitation polymerization and its application in the molecular imprinting field. The resulting iniferter‐induced “living” radical precipitation polymerization (ILRPP) has proven to be an effective approach for generating not only narrow disperse poly(ethylene glycol dimethacrylate) microspheres but also molecularly imprinted polymer (MIP) microspheres with obvious molecular imprinting effects towards the template (a herbicide 2,4‐dichlorophenoxyacetic acid (2,4‐D)), rather fast template rebinding kinetics, and appreciable selectivity over structurally related compounds. The binding association constant Ka and apparent maximum number Nmax for the high‐affinity sites of the 2,4‐D imprinted polymer were determined by Scatchard analysis and found to be 1.18 × 104 M−1 and 4.37 μmol/g, respectively. In addition, the general applicability of ILRPP in molecular imprinting was also confirmed by the successful preparation of MIP microspheres with another template (2‐chloromandelic acid). In particular, the living nature of ILRPP makes it highly useful for the facile one‐pot synthesis of functional polymer/MIP microspheres with surface‐bound iniferter groups, which allows their direct controlled surface modification via surface‐initiated iniferter polymerization and is thus of great potential in preparing advanced polymer/MIP materials. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3217–3228, 2010
Synthesis of amphiphilic A3B mikto‐arm copolymers from a sugar core: Combination of hydrophobic PCL and hydrophilic glycopolymers for biocompatible nanovector preparation
Authors: Suriano Fabian , Coulembier Olivier , Dubois Philippe
Published: July 2010

Amphiphilic A3B mikto‐arm copolymers have been synthesized using a t‐butyl‐diphenyl silyl‐based methylglucoside derivative. The latter has been first used as initiator for the polymerization of ε‐caprolactone leading to three‐arm star‐shaped structures followed by several postpolymerization steps to obtain star‐shaped poly(ε‐caprolactone) macroinitiator. Atom transfer radical polymerization (ATRP) of diisopropylidene galactose methacrylate in THF at 60 °C using CuBr ligated with 1,1,4,7,10,10‐hexamethyltriethylenetetramine (HMTETA) as catalytic complex allowed the formation of A3B mikto‐arm copolymers with different compositions and molecular weights. Selective deprotection of sugar protecting groups finally generated amphiphilic mikto‐arm copolymers. The molecular characterization of those copolymers was performed by 1H NMR spectroscopy and gel permeation chromatography (GPC) analysis. The self‐assembly of the copolymers into micellar aggregates and the related critical micellization concentration (CMC) in aqueous media were determined by dynamic light scattering (DLS) and UV‐visible spectroscopy, respectively. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3271–3280, 2010
Novel long chain unsaturated diisocyanate from fatty acid: Synthesis, characterization, and application in bio‐based polyurethane
Authors: Hojabri Leila , Kong Xiaohua , Narine Suresh S.
Published: July 2010

A novel long chain linear unsaturated terminal diisocyanate, 1,16‐diisocyanatohexadec‐8‐ene (HDEDI) was synthesized from oleic acid via Curtius rearrangement. Its chemical structure was identified by FTIR, 1H NMR, 13C NMR, and HRMS. This diisocyanate was used as a starting material for the preparation of entirely bio‐based polyurethanes (PUs) by reacting it with canola diol and canola polyol, respectively. The physical properties and crystalline structure of the PUs prepared from this diisocyanate were compared to their counterparts prepared from similar fatty acid‐derived diisocyanate, 1,7‐heptamethylene diisocyanate (HPMDI). The HDEDI based PUs demonstrated various different properties compared to those of HPMDI based PUs. For example, HDEDI based PUs exhibited a triclinic crystal form; whereas HPMDI based PUs exhibited a hexagonal crystal lattice. In addition, canola polyol‐HDEDI PU demonstrated a higher tensile strength at break than that of canola polyol‐HPMDI, attributed to the higher degree of hydrogen bonding associated with the former sample. Nevertheless, lower Young's modulus and higher elongation in canola polyol‐HDEDI PU were obtained because of the flexibility of the long chain introduced by the HDEDI diisocyanate. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3302–3310, 2010
Synthesis and characterization of donor–acceptor poly(3‐hexylthiophene) copolymers presenting 1,3,4‐oxadiazole units and their application to photovoltaic cells
Authors: Wang Hsu‐Shen , Su Ming‐Shin , Wei Kung‐Hwa
Published: July 2010

We have used Grignard metathesis polymerization to prepare poly(3‐hexylthiophene)‐based copolymers containing electron‐withdrawing 4‐tert‐butylphenyl‐1,3,4‐oxadiazole‐phenyl moieties as side chains. We characterized these copolymers using 1H and 13C nuclear magnetic resonance spectroscopy, thermogravimetric analysis, and gel permeation chromatography. The band gap energy of copolymer was determined from the onset of the optical absorption. The quenching effects were observed in the photoluminescence spectra of the copolymers incorporating pendant electron‐deficient 1,3,4‐oxadiazole moieties on the side chains. The photocurrents of devices were enhanced in the presence of an optimal amount of the 1,3,4‐oxadiazole moieties, thereby leading to improved power conversion efficiencies. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3331–3339, 2010
Synthesis and properties of new aromatic polyamides with redox‐active 2,4‐dimethoxytriphenylamine moieties
Authors: Hsiao Sheng‐Huei , Liou Guey‐Sheng , Kung Yi‐Chun , Hsiung Tzu‐Jung
Published: July 2010

A new triphenylamine‐based diamine monomer, 4,4′‐diamino‐2″,4″‐dimethoxytriphenylamine (2), was synthesized from readily available reagents and was reacted with various aromatic dicarboxylic acids to produce a series of aromatic polyamides (4a–h) containing the redox‐active 2,4‐dimethoxy‐substituted triphenylamine (dimethoxyTPA) unit. All the resulting polyamides were readily soluble in polar organic solvents and could be solution cast into tough and flexible films. These polymers exhibited good thermal stability with glass transition temperatures of 243–289 °C and softening temperatures of 238–280 °C, 10% weight loss temperatures in excess of 470 °C in nitrogen, and char yields higher than 60% at 800 °C in nitrogen. The redox behaviors of the polymers were examined using cyclic voltammetry (CV). All these polyamides showed two reversible oxidation processes in the first CV scan. The polymers also displayed low ionization potentials as a result of their dimethoxyTPA moieties. In addition, the polymers displayed excellent stability of electrochromic characteristics with coloration change from a colorless neutral state to green and blue‐purple oxidized states. These anodically coloring polyamides showed high green coloration efficiency (CE = 329 cm2/C), high contrast of optical transmittance change (ΔT% = 84% at 829 nm), and long‐term redox reversibility. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3392–3401, 2010