bluuebunny/crossref_metadata_2025_split huggingface dataset:
ChemInform Abstract: Acetone Chemical Ionization Mass Spectrometry
Authors: PRABHAKAR S. , VAIRAMANI M. 
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.
ChemInform Abstract: Investigations of Intramolecular Hydrogen Bond by Nitrogen Magnetic Resonance Methods
Authors: SCHILF W. , STEFANIAK L. 
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.
Economic comparison of VSC HVDC and HVAC as transmission system for a 300 MW offshore wind farm
Authors: Van Eeckhout B. , Van Hertem D. , Reza M. , Srivastava K. , Belmans R. 
Published: July 2010

AbstractVoltage source converter high voltage direct current (VSC HVDC) is a relatively new technology which allows the connection of islanded power systems. As such, it can form a connection between large‐scale future offshore wind farms and the onshore transmission grid. In this paper, the VSC HVDC solution is proposed as a promising alternative for high voltage alternating current (HVAC). The choice for a transmission technology is primarily based on economic considerations. Therefore, the economic value of VSC HVDC is investigated in this paper. VSC HVDC has important technical advantages for submarine installation compared to HVAC. The aim is to monetize these advantages in an economic comparison. Possible wind farm topology simplifications and optimizations due to the use of VSC HVDC are taken into account. Depending on the ownership of the transmission cable, the break‐even cable length, above which the HVDC option is chosen, varies. A sensitivity analysis is included in this paper. Copyright © 2009 John Wiley & Sons, Ltd.
Optimizing choppers and inverters by controlling cross currents with overlapping operation in the bridge legs
Authors: Klug Rolf‐Dieter 
Published: July 2010

AbstractThe paper describes a method that improves the current polarity changes of DC‐choppers and voltage source inverters and that increases the maximum output voltage by avoiding the switching dead time in the bridge legs. The resulting cross currents are controlled by an overlapping operation of the active power semiconductors. The two degrees of freedom of the bridge leg are used to contol nearly independently the load current by the modulation ratio and the cross current by the overlap ratio. Experimental results with a 4‐quadrant DC‐chopper with high switching frequency show the improvement coming from the elimination of the switching dead time problems.
Mechanical stress in high‐voltage switchgear with flexible single conductors under short‐circuit current load
Authors: Böhme H. , Golletz F. , Fiebiger C. 
Published: July 2010

AbstractHigh‐voltage switchgear with flexible conductors can be exposed to high mecanical loads during short‐circuits. These loads are caused by the reaction of the flexible conductors to the electromagnetic force. Using the 110 kV supports as a part of a disconnector, the stress in the high voltage switchgear as shown does not respond quasi‐statically to the dynamic force in the flexible conductors which means, that the mechanical‐dynamic properties of the device determine the critical stress. Moreover, simple models well‐known in the system theory are used to describe the mechanical‐dynamic properties.
Modelling of induction motor loads in power‐system voltage stability studies
Authors: Brucoli M. , La Scala M. , Sbrizzai R. , Trovato M. 
Published: July 2010

AbstractIn planning an interconnected power network, it is very important to assess whether a voltage collapse occurs during a prefixed operating condition. However, it has been often found that voltage phenomena occur in a real system at a load condition different from the one predicted by simulation studies. One of the causes that makes the use of present procedures unreliable is the lack of adequate models for dynamic loads. To overcome this difficulty, the paper presents a practical approach which analyses the influence of dynamic load modelling on the voltage stability limits of interconnected power systems. Five different representations of induction motor loads are considered and the degree of accuracy of each model is investigated. Simulation studies on a sample power system clearly show that voltage stability limits can be strongly affected by the adopted representation.
Electromagnetic field above the earth's surface due to a buried three‐phase high‐voltage power‐line
Authors: Neelakanta P. S. , Lordan R. , Ungvichian V. , Wahid P. F. 
Published: July 2010

AbstractA closed form formulation to calculate the quasistatic magnetic field above the earth's surface induced by an underground, three‐phase high‐voltage power‐line is derived. Computed results are compared with measured data.
Validity of narrow and broadband pd‐measurements on power transformers; pulse deformations
Authors: Kachler A. J. , Maier R. , Nieschwietz H. 
Published: July 2010

AbstractExtensive investigations of partial discharge (pd) pulse winding response characteristics have revealed considerable physical insight into the mechanics of pulse transfer from within the windings to the externally accessable points of measurement. Based on the IEC charge measuring method, pd‐pulse response profiles were investigated on both, layer‐ and disc‐type transformers of different original size (25 MVA, 40 MVA and 1100 MVA) by means of internal pd‐pulse injections at geometrically and electrically differing sites. The winding design and the pd‐source locations influence significantly the externally measurable pd‐magnitude and pulse form. By no means and by neither broad band (BB) or narrow band (NB) method of detection is it possible to correlate externally measured apparent charge values with the dissipated charge at the pd‐source location. NB and BB instruments are equally applicable, with some preference to NB for pd‐measurements on power transformers.
Performance characteristics of the thyristor divert automatic voltage regulator
Authors: Abdel‐Halim M. A. 
Published: July 2010

AbstractFast response automatic voltage regulators utilizing static semi‐conductor elements are widely used in the systems of synchronous generators which are either isolated or connected to a large scale electric network. This paper presents an accurate circuit model for a rather recently used thyristor divert automatic voltage regulator, TDAVR. The tensor technique has been employed to develop a mathematical model describing the regulator. By the aid of this model, the performance and control characteristics of this regulator have been accurately determined. The effects of some different parameters of the regulator circuit upon its performance have been investigated. It is possible now to integrate this accurate circuit model with the already used circuit models of the synchronous generators and their exciters in place of the approximate transfer function model. Also, the model, being a detailed one, helps in proper design of the power and control circuit components of the studied A VR.
Theory and practice of energy measurement of non‐sinusoidal and asymmetrical currents and voltages
Authors: Gyarfas J. , Rapant S. 
Published: July 2010

AbstractThis paper deals with the evaluation of views on electric power and energy relations in one‐ and three‐phase systems by non‐sinusoidal currents and voltages. Pragmatic approach to the valuation of relations in the network with higher harmonics and by asymmetrical three‐phase systems are derived by means of an increased loss coefficient. Results of measurement of representative large users of electric power and the practical consequences are shown.
Appreciable cable conductor losses by axial magnetic fields?
Authors: Braun A. 
Published: July 2010

AbstractThis paper deals with the losses occuring in the cable conductor by the axial magnetic field, which is produced by the single copper wires of the outer shield in case of bonding both sides of the shield. A theoretical consideration determines the losses in copper‐ and aluminium conductors for commonly used frequencies depending on the shield characteristics. For an exemplary chosen cable configuration the additional losses are calculated.
Investigations on the rotary motion of internal ares in single phase sf6 ‐insulated switchgear
Authors: Munch R. 
Published: July 2010

AbstractAn internal arc in single phase sf6‐insulated switchgear implies the risk that the outer arc root stabilizes on a spot and punctures the enclosure after a short time. however, the burn‐through times increase considerably if a rotary motion of the arc around the centre electrode takes place. this paper presents results of experimental research on the rotary motion of fault arcs and measures influencing this movement. in addition to fundamental investigations two possibilities were worked out in order to guarantee a rotary motion at definite positions of a coaxial gis.
Method of calculating the magnetic flux density and forces in contact‐free magnetic bearings
Authors: Baatz M. , Hyrenbach M. 
Published: July 2010

AbstractTo mount electrical machines intended to work a very long time without maintenance, there are offered magnetic bearings. This article describes the physical fundamentals of calculating the magnetic flux density and the forces in magnetic bearings, in consideration of radial and axial displacement of the parts of the bearing, and the derived program. Subsequently the conclusions for the construction of magnetic bearings are summed up.
A new flexible electronic overload protective relay
Authors: El‐Sayed I. F. 
Published: July 2010

AbstractThis paper describes and implements an electronic relay scheme which protects industrial loads against overload and unbalance. The scheme works on a principle of integrating a pulse train. The strength of these pulses depends on the excess of current over the nominal value. It is shown that the presented scheme is capable of having variable overload protection characteristics. The relay design is directed to attain optimum overload protection that provides maximum use of motor and minimum waste operation time. The electronic circuit is described in details and different operating modes are studied. Experimental and analytical results are given and discussed.
Instrument for the registration of small and fast variations in the rms values of an alternating voltage
Authors: Nielsen N. H. 
Published: July 2010

AbstractIt is now possible to register small and fast voltage variations in the supply network by means of a recently developed measuring instrument. Within the fields of both measuring technique and automatic control technique, there is often a need for a simple apparatus capable of a fast transformation of the instantaneous difference between the RMS value of an alternating voltage and a fixed reference value into an analog output signal. With the chosen construction, the time response of the instrument allows for the measurement of the RMS of every consecutive period consisting of two successive half periods. The accuracy of the measurement is higher than the accuracy obtainable by means of a peak‐to‐peak measurement made on an oscillogram. The new instrument, which makes allowance for any distortion of the curve form, processes the signal analogically.
Thermal resistances of cables with corrugated sheaths
Authors: Brakelmann H. , Honerla J. , Rasquin W. 
Published: July 2010

AbstractFor corrugated cable sheaths the additional thermal resistances between the insulation respectively the screening surface and the sheath are examined. The results show that the air gap between the cable insulation and the corrugated sheath causes a considerably additional thermal resistance if the corrugated sheath is not in direct contact with the electric insulation. In case of an air gap thickness of 5 mm, this thermal resistance already comes up to that of the total electric insulation of an XLPE‐insulated extra‐high voltage cable. For such cases it is therefore advisable to supplement the IEC publication 287 accordingly.
Modelistic investigation of multi‐stress ac‐dc endurance of pet films
Authors: Gubanski S. M. , Montanari G. C. 
Published: July 2010

AbstractIn the paper, the results of life tests performed on polyethylene terephtalate (PET) films, subjected to electrical and thermal stresses simultaneously applied (multi‐stress), under AC and DC voltage, are presented and discussed, with a modelistic viewpoint. It is found that the AC electrical life lines at different temperatures drawn in semilog plot tend to show upward curvature at low electrical stresses, while fairly linear behavior is detected for the majority of life lines in bilog plot. Among the two sets of DC data, obtained in different laboratories, one behaves quite similarly to the AC results, i. e. provides clear threshold in semilog plot and straight lines in bilog plot, while the other gives straight life lines both in semilog and bilog plots. Life models able to fit the AC and DC data, based on both the inverse power and the exponential laws, are presented and checked by experimental results, in order to achieve the most suitable models for the explanation of the behavior of the tested insulating material. On the basis of these models, generalized probability distribution functions are derived, which can provide life percentiles at selected failure probabilities. Moreover, the temperature dependence of the life‐model parameters is investigated, to the aim of explaining the electrical life models in the range of test and extrapolation temperatures.
Capacitive loads by a voltage‐source active filter
Authors: Tuttas C. 
Published: July 2010

AbstractUsually the filter current of an active filter (VSI‐type) is controlled by a two‐step controller and the disturbance (load current) is added to the control circuit. This method becomes unstable, if capacitive loads have to be compensated. It is shown in this paper, that the algorithm can be stabilized by additional filter capacitors. So the control circuit remains stable also at the compensation of capacitive loads.
Energy considerations for partial discharges in voids
Authors: Kurrat M. 
Published: July 2010

AbstractDegradation of material is directly related to energy conversion. Information about the state of energy during partial discharges in voids is thus necessary to evaluate degradation of solid insulation. In this paper, measurable quantities are related to partial discharges energies. For spherical voids in polyethylene, these measurable quantities are compared with calculated ones. In conclusion, energy conversion in voids is discussed to estimate the relevance of different measurable quantities.
Calculation of magnetic field of a switched reluctance motor using a microcomputer
Authors: Stiebler M. , Li R. 
Published: July 2010

AbstractThe paper is concerned with the determination of the magnetic field distribution and the static torque of a switched reluctance motor by means of the finite element method (FEM). In a simplified approach two different models are described, and a microcomputer is used to compute the field of an example motor. The analysis is extended to compute the static torque from the rate of change of magnetic co‐energy with respect to angular displacement; the results are compared with measurements.
Digital measurement system for high‐voltage impulse tests on transformers
Authors: Scheltinga L. , Vaessen P. T. M. 
Published: July 2010

AbstractMore information from test data can be obtained when digital measuring techniques are used. A description of a tailor made measurement system in use by a Dutch high‐voltage laboratory is presented. Schematic diagrams of the test setup and the measurement system are shown and the precautions taken to avoid electromagnetic compatibility (EMC) problems are described. Software facilities and their realization are described together with algorithms for waveshape determination. The use of a digital signal processor board for transfer function calculations is explained. Examples of tests with full and chopped lightning impulses are presented both in time and frequency domain.
Power measurement of periodic current and voltage by digital signal processing
Authors: Marganitz A. 
Published: July 2010

AbstractFor measuring the electric power the two‐pole parameters current and voltage must be picked up and processed to the power value. So the most important problem of power measurement is the processing of signals. Solutions therefor exist from all kind of signal processing techniques. Especially the digital signal processing with a signal processor shows a short measuring time, also if current and voltage are non‐sinusoidal. For this case, algorithms and measurement structures are presented for the different power terms as active power, reactive power and apparent power.
Harmonic insertion in PWM inverter drive schemes
Authors: Theocharis J. , Petridis V. 
Published: July 2010

AbstractThe procedure of harmonic insertion is generalized in this paper. Analytical expressions of the voltage spectra are derived. The insertion of the 3rd harmonic to the modulating signal, which is of particular interest, is considered as a special case. It is demonstrated in this case that the fundamental harmonic component of the phase and the line‐to‐line voltage is not affected by the insertion of the 3rd harmonic for sufficiently high values of the chopping ratio. However it has been shown that the higher harmonic spectrum is significantly improved as compared to the case of pure sinusoidal modulation. For different values of the fundamental component the optimal values of the amplitude of the third harmonic to be inserted have been calculated so that the distortion factor of the higher harmonic spectrum is minimized. Other cases of harmonic insertion are also considered which provide spectrum efficiency improvement. Experimental results are given which have been obtained by means of a microcomputer controlled PWM generator constructed for this purpose.
Factors affecting the discharge parameters of small positive rod‐plane gaps in atmospheric air
Authors: Pyrgioti E. , Menemenlis C. 
Published: July 2010

AbstractRod‐plane gaps below 55 cm with various terminations of the rod were tested with positive impulse voltages of various forms. The complete breakdown probability distributions as well as the histograms of the time‐to‐breakdown were deduced. The results indicate that while for gaps longer than 30 cm the specific breakdown voltage Em stabilizes around the value of approximately 4.5 kV/cm, below this length Em increases rapidly as the gap length decreases. Non‐Gaussian distributions of the breakdown voltages were detected and factors leading to non‐Gaussian distributions were investigated. The implications of a non‐Gaussian distribution of the breakdown in the design of air insulation of electrical installations of lower voltages were also examined.
Compensation effect in thermal aging investigated according to eyring and arrhenius models
Authors: David P. K. , Montanari G. C. 
Published: July 2010

AbstractThe study of the compensation effect applied in the domains of reaction rate constant as well as of time‐to‐failure in thermal endurance characterization of insulating materials is developed in the paper. In particular, the compensation effect is defined on the basis of both Arrhenius and Eyring relationships, and new life models are consequently derived. It is found that for the whole amount of investigated materials both models fit very well the experimental results and then are valid for material characterization.
Fast quadratic programming approach for large scale reactive power optimization
Authors: El‐Sayed M. A. H. , Abdel‐Rahman T. M. , Mansour M. O. 
Published: July 2010

AbstractA fast quadratic programming approach has been developed to control the reactive power (VAR) generation in dispatching centers. The main objective of VAR control is to minimize the transmission losses taking into consideration the voltage constraints at each node of the network. The developed approach utilizes the decomposition of whole system into smaller subsystems and coordination of different subsystem solutions to obtain the optimal VAR control in the large scale systems. The smallest practical size of the decomposed subsystems is the one‐generator‐bus subsystem. The fast and non‐iterative VAR optimization of the decomposed subsystems is obtained based on considering only one active constraint at a time by solving the quadratic programming sub‐problems. The numerical test results of IEEE‐118 and 200 buses power system have indicated that the speed and accuracy of the proposed approach are adequate for real‐time applications on large‐scale systems. This approach is also applicable for large system deviations from its normal conditions and needs small memory size.
Non‐active power compensation using time‐window method
Authors: Blajszczak G. 
Published: July 2010

AbstractThe paper deals with simultaneous compensation of all components of non‐active power: reactive power, higher harmonics and an asymmetry in a three‐phase network. A new control method which allows to eliminate any non‐active components with considerably reduced delay time is proposed. In this paper a new configuration of a compensator power circuit is also proposed. The compensation ability of the new system was verified experimentally.
Standard data transmission protocols in process control applications
Authors: Funk G. 
Published: July 2010

AbstractThe paper describes a standard data transmission protocol that is widely used in telecontrol systems and in field‐bus systems for process control applications. The described standard is based on an asynchronous data transmission method that is used for character transmission in office automation systems. The described code guarantees Hamming distance 4 as protection against undetectable message errors. Furthermore, the article describes extensions of the standard code that achieve Hamming distances 6 and 8. The increased data integrity levels of the described data transmission protocols are achieved by defining product codes with single parity check codes and BCH codes and by defining special sync characters.
Computation of magnetic field in a switched reluctance motor using a quadratic hybrid biem‐eem method
Authors: Omekanda A. , Broche Ch. , Baland R. 
Published: July 2010

AbstractThe Switched Reluctance Motor (SRM) is a simple and robust electrical machine which is finding application over a wide speed and power range. The design optimization and reliability assurance of its behaviour require accurate prediction of the magnetic field distribution in its active regions. Numerical methods must be used to compute the magnetic field for several combinations of rotor positions and excitation current intensities. In that case, it is necessary to develop numerical techniques giving a better degree of precision to meet requirements of the electromagnetic quantities calculation.In this paper, a numerical hybrid method coupling Boundary Integral Equation Method (BIEM) and Finite Element Method (FEM) is presented. The development of this two‐dimensional hybrid method is founded upon the nodal approximation of the magnetic vector potential. This nodal approximation exploits one‐ and two‐dimensional finite elements of Lagrange's family. The quadratic hybrid method coupling BIEM and FEM permits to take advantages of each of two numerical methods. The BIEM‐FEM method is used to calculate the magnetic flux distribution, magnetization curves, and torque in a 7.5 kW SRM prototype. It provides an accurate analysis of the magnetostatic field and gives precise values of the electromagnetic quantities.