bluuebunny/crossref_metadata_2025_split huggingface dataset:
Digital simulation of fault arcs on long‐distance compensated transmission systems with particular reference to adaptive autoreclosure
Authors: Song Y. H. , Aggarwal R. K. , Johns A. T. 
Published: July 2010

AbstractThere is an increasing demand for more detailed and accurate modelling of fault arcs on Extra‐High Voltage (EHV) transmission systems. This is particularly so in relation to the design and development of alternative and improved equipment such as adaptive autoreclosure schemes and new protection techniques. This paper discusses in some detail techniques that have been developed to model fault arcs more realistically, including a time‐dependent dynamic resistance model of the primary arc and significant improvements that have been made in the dynamic conducting characteristic of secondary arcs. The statistical character of the secondary arc has been sufficiently taken into account by the dynamic conducting and reignition voltage characteristics. The new techniques are then employed for the simulation of fault transients on a long‐distance compensated system. In this respect, the evaluation of shunt compensation is also outlined, because special compensation schemes are essential for reducing the secondary arc current and recovery voltage to levels commensurate with rapid extinction in long‐distance lines. The paper concludes with a study of the implications of the simulation results in respect of the design of adaptive autoreclosure schemes by identifying interesting features of the waveforms.
Transient behaviour of the EMTP‐calculation method analyzed with the Z‐tyansformation
Authors: Linnert U. , Hosemann G. 
Published: July 2010

AbstractTo simulate power circuits there is the difference admittance method DLV as well as the synchronised difference admittance method SDLV with factorised eigenvalues of the network branches. For all methods, deviations depending on the step size are generally unavoidable. Here, these deviations will be analysed by simple, single‐phase examples with the help of the Z‐transformation. With large step sizes, the standard DLV is falsified by oscillations, but not the SDLV. In contrast to DLV series connections of elements with SDLV does not lead to the same result as the simulation of the entire element. Nevertheless, the results achieved with SDLV3 are more precise than those with DLV.
On the calculation of ripple factor
Authors: Gluskin E. 
Published: July 2010

AbstractA simple formula which connects the ripple factors of the “half‐wave” and “full‐wave” rectified functions, both obtained from the same T‐periodic function f(t) which possesses the property f(t + T/2) = ‐f(t) and is non‐negative within half the period, is presented.
Transformer model for application in load‐how analysis
Authors: Vlachogiannis J. G. , Xypteras J. , Bakirtzis A. G. 
Published: July 2010

AbstractThis paper gives a closed formula which expresses the variation of the leakage reactance of transformers as a function of the transformer tap position. The derivation of the formula is based on the analysis of the distortion of the leakage field as portions of the winding are cut out by means of tappings. Three cases are examined, depending on whether taps are cut out: ‐ asymmetrically at the end of a winding, ‐ at the electrical centre of a winding or ‐ symmetrically at the end of a winding. The validity of the derived model is tested by comparison with existing transformer impedance correction data. Finally, test results from the incorporation of the model in a load‐flow program are presented.
Dynamic combination of impedance calculating distance‐protection algorithms
Authors: Lönard D. 
Published: July 2010

AbstractNon‐ideal input signals lead to incorrect results of distance‐protection algorithms. A method to combine several parallel algorithms will be presented, showing possibilities to mix different types of principles to achieve an improved behaviour. One example of the so called filter‐combination algorithm will be discussed. Simulations have been carried out on a PC 486, using a digital signal‐processing model. The results proof the robust behaviour of the presented method.
Linear‐programming‐based method for optimum schedule of reactive power sources in power systems
Authors: Abdel‐Salam M. M. , El‐Sadek M. Z. , Hussein A. I. , Hussein A. A. 
Published: July 2010

AbstractThis paper proposes a linear‐programming optimization‐based method for reactive power scheduling using generator terminal voltages and reactive outputs, transformer tap‐settings and switchable reactive power sources as control variables. Dual linear programming is applied to minimize a composite objective function consisting of the cost of the adjusted control variables and the system transmission losses. The proposed composite objective function is more economical than that of the minimum total adjustment of the control variables and calls for less adjustments of var sources to meet the desired voltage limits. The proposed method is applicable to practical transmission and distribution networks, 500 kV to 11 kV, of small and large sizes.
High‐dynamic AC machine control without speed or position sensor
Authors: Zimmermann W. 
Published: July 2010

AbstractIn many applications inverter‐fed A C machines with high dynamic performance are needed, but position control is not required. Conventional field‐oriented control fulfils the dynamic requirements, but usually needs a costly position or speed sensor. Simple voltage‐frequency control avoids these sensors, but will only achieve a moderate dynamic performance. For such applications a self controlled scheme based on the measured flux vector may be used. In this paper a flux phase control loop and a method of backing the flux model with an observer to improve the behaviour at low stator frequencies are described.
A step‐down frequency‐modulated zero‐current switching quasi‐resonant converter‐fed DC drive
Authors: Reddy S. Rama , Lakshmikanth A. , Raj V. Babu , Chellamuthu C. 
Published: July 2010

AbstractThe simulation and implementation of a step‐down frequency‐modulated zero‐current switching quasi‐resonant converter (FM‐ZCS‐QRC)fed DC drive are presented. A parallel resonant QRC is used for the speed control of a DC motor. The FM‐ZCS‐QRC‐fed DC drive is modelled and simulated. A microprocessor‐based prototype system is also implemented for controlling the drive speed and the results predicted by simulation are verified experimentally. It is found that the FM‐ZCS‐QRC‐fed DC drive has several advantages over those fed from phase‐controlled converters, DC choppers and PWM converters.
Design of a linear robust PSS for optimal damping of multimode‐oscillations
Authors: Huwer R. , Kocher P. , Nelles D. , Wache M. 
Published: July 2010

AbstractThere is a simple rule to design a robust linear Power‐System Stabilizer (PSS) which is optimal independent of the network structure and operation point. Only the setting of voltage regulator determines the adjusting parameters. The paper shows the behaviour of such a PSS if two different modes of power swings occur. Both are damped as quickly as possible if the load angle of the generator does not become negative or larger than 90°.
Design of a small, axial‐flux permanent‐magnet motor
Authors: van Dessel M. , Belmans R. , Hanitsch R. , Hemead E. A. 
Published: July 2010

AbstractThe paper deals with the design of a disc‐type motor excited by permanent magnets. The main flux is oriented in the axial direction, yielding a pan‐cake type arrangement. The outer diameter is about 45 mm, the axial length about 15 mm. After the introduction, the motor design is explained. On the basis of these general design considerations, the average flux density at no‐load in the materials is approximated using an analytical, one‐dimensional approach. An accurate analysis of the axial flux machine requires a 3D finite‐element calculation. The 3D model design needed for this, is explained. The motor characteristics (induced voltage and torque), obtained from the 3D calculation are described and compared with measurements.
EMC analysis for grounding structures in power systems
Authors: Heimbach M. 
Published: July 2010

AbstractEMC analysis of power systems requires the knowledge of the dynamic behaviour of extended grounding structures during electromagnetic transients. This paper presents an approach, which permits to determine the electromagnetic field distribution in the surroundings of the grounding system. In the first part a model for linear conductors based on the transmission‐line approach is described. The second part deals with a procedure, which allows to calculate the electromagnetic field from the results of the transmission‐line representation. Both the transmission‐line model and the field calculation are implemented in the Electro‐Magnetic Transients Program (EMTP). The interfacing with the EMTP permits not only the computation of the grounding system, but also of entire power systems as the latter can be simulated by the EMTP and connected to the grounding system.
Steady‐state analysis of soft and hard‐switched DC/DC converters
Authors: Pinola L. , Rotta E. , Testa L. , Varoli V. 
Published: July 2010

AbstractA methodology for the accurate steady‐state analysis of soft‐switched (quasi‐resonant) DC/DC converters is described. It consists in a two‐steps procedure: a simplified analysis provides the initial values to an iterative algorithm which improves the accuracy of the results up to the required level. Symbolic mathematics packages make it possible to apply a rigorous approach also to the high‐order networks typical of quasi‐resonant converters. The procedure is validated by comparison of its outputs to experimental results.
About an improved evaluation of results by the standardized salt‐fog procedure for composite insulators
Authors: Schmuck F. , Barsch R. , Pilling J. 
Published: July 2010

AbstractBased upon long‐term experiences with accelerating ageing tests of polymeric materials and composite insulators, the authors give a contribution to an improvement of the reproducibility and results' validity of the salt‐fog procedure. The following parameters and criteria standardized are critically evaluated: the magnitude of the fog conductivity and the continuous test duration taking at least 1000 h. Using a modified Inclined‐Plane Test, the partial discharge burning time is determined as additional diagnostic value. Summarizing, a modified salt‐fog procedure and further diagnostic values are suggested.
Short‐circuit performance of a stretched transformer winding with regard to its actual mechanical characteristics
Authors: Kozlowski M. , Pewca W. 
Published: July 2010

AbstractThe impact of heterogeneous mechanical structure of a transformer winding: existence of the turn insulation and the inner axial cooling ducts will be shown with regard to the actual mechanical characteristics of copper and insulation materials using a newly developed calculation method. For the distribution along the coil width of the wire permanent set values of the wires will be presented and the consequences discussed. The reason for settlement of the proper limits for permissible tensile stresses in the winding will be shown also.
An example for dynamic compensation of non‐active power in the case of non‐linear active loads
Authors: Staudt V. 
Published: July 2010

AbstractA lot of different definitions for active and non‐active quantities and their compensation are known in case of single‐ or polyphase systems under steady‐state conditions. In practice the load as well as the source of such a system is varying with time. This requires compensation methods which are ready to deal with dynamic conditions. In the most general case the load may be non‐linear and even change from passive to active and vice versa. This paper presents a control scheme for a series compensator (series active filter) in a single‐phase circuit which can handle a wide range of passive and active non‐linear loads under dynamic conditions. No information about the character of the source and the load is required, as long as load and source current can be controlled by appropriate voltages.
Assessment of unbalance emission level produced by loads using the apparent power components
Authors: Mayordomo J. G. , Beites L. F. , Gutierrez J. L. 
Published: July 2010

AbstractThis paper proposes the application of the unbalanced fundamental power as a merit figure to establish a prediction method of the voltage unbalance emission levels produced by the connection of unbalanced loads. The total apparent power, as criterion for optimal compensation, is discussed when it is applied to loads which are sensitive to voltage unbalances such as generators and motors. The analysis of these aspects is made according to recommendations for voltage unbalances.
The problem of harmonic compensators location
Authors: Mikolajuk K. 
Published: July 2010

AbstractCurrent harmonics can be eliminated in each individual load. Such a compensation generally must be expensive. Harmonics are partly compensated between individual consumers. Therefore, the compensation of group of consumers seems to need lower cost than individual compensation. In the case of group compensation there are two possible approaches. The first approach uses compensators controlled by a current in common buses supplying a cluster of consumers. In the second approach a voltage waveform is chosen as a control data, the compensator should maintain a sinusoidal voltage. Such an approach needs not many compensators to ensure a proper quality of energy delivered. The purpose of the presented paper is to formulate the optimization problem for compensators location in power systems. It is shown that the problem leads to combinatorial optimization. The Travelling Salesman Problem and 0‐1 Knapsack Problem are related to the presented combinatorial problem, but it seems, that there is not solved the combinatorial optimization problem which is identical to the considered one.
Principal peculiarities of ceramic and composite insulators for overhead EHV/UHV power transmission lines: Electrical characteristics, performance, reliability and application areas
Authors: Tikhodeev N. N. 
Published: July 2010

AbstractAreas of rational application of cap‐and‐pin and rod line insulators manufactured of various materials (porcelain, glass and polymers) are discussed in terms of ensuring high reliability and adequate performance of strings on EHV and UHV AC and DC overhead power transmission lines. It is shown that the most critical characteristics of both cap‐and‐pin and rod units are their quality in terms of annual in‐service failure rates and their polluted dielectric strength at long‐duration exposure to the operating voltage. Additional features of importance for HVDC lines are high resistivity of the dielectric and good dielectric strength of each individual unit.
Accelerated ageing tests on composite hollow insulators under DC voltages
Authors: Petruseh W. , Week K.‐H. 
Published: July 2010

AbstractInvestigations are reported on two specimen of silicone rubber hollow insulators at a DC voltage of‐100 kV. Leakage current measurements are performed under natural pollution conditions and with artificial wetting. On the surface of naturally polluted insulators energised with DC voltage several types of simple microbes were found, which may influence the leakage current performance. It is also shown that accelerated ageing procedures using salt fog for creating surface discharges are not representative for inland sites with a low degree of pollution. Ageing performance of non‐ceramic insulators should be checked in general with respect to the UV‐strength of the material used. Accelerated ageing tests regarding pollution performance are necessary only if the site conditions will create surface discharges on the non‐ceramic material chosen for the insulator. A test procedure, based on the IEC1000 h test, with constant discharge activity over a selected duration is proposed for further investigation. There is no advantage regarding creepage distance dimensioning of non‐ceramic insulators in comparison to porcelain insulators for sites with surface discharges under natural conditions. The use of non‐ceramic insulators for areas with very heavy or extreme pollution seems to be questionable.
A highly efficient method for optimum electrode contour determination
Authors: Kato K. , Hikita M. , Hayakawa N. , Kito Y. , Okubo H. 
Published: July 2010

AbstractA new algorithm has been developed, which enables to determine an electrode contour with an optimum electric field distribution, using‐a personal computer. The algorithm is based on the charge simulation method (CSM) and uniquely determines the optimum electrode contour from electric field distribution in the whole field space. In addition, the algorithm is capable of estimating quantitatively a target of the optimum electrode contour at the initial stage of the optimization process. Consequently, the estimation of the target electrode contour proved to need minimum number of modification to reach the optimum electrode contour. The new algorithm for optimization eminently raised the convergence of iterative calculation, resulting in a particularly efficient technique for electric field optimization.
A new application of ferrite and high‐frequency signals to power system protection
Authors: Lai L. L. , Ndeh‐Che F. , Chu K. H. , Yokoyama R. , Zhao M. 
Published: July 2010

AbstractThis paper reports a new scheme where ferrite materials and high‐frequency signals are used to detect power system faults. The ferrite acts as a broad band dissipater. The attenuation properties of ferrite beads on high‐frequency signals is studied and are then used on a 10 m long single‐phase transmission line model to investigate their use as a primary detection device in a non‐unit protection scheme which possesses unit protection properties. The results show that the ferrite beads attenuate the high‐frequency noise quite effectively. But the picking up of high‐frequency noise has to be considered as well.
Electromagnetic spectrum radiated from gas discharges and its relation to partial‐discharge characteristics
Authors: Okubo H. , Yamashita H. , Hayakawa N. , Ueda T. , Hikita M. 
Published: July 2010

AbstractElectromagnetic spectrum radiated from partial discharges (PD) andflashover occurring in air have been measured for needle‐plane electrodes. The experimental results showed that the gain of the electromagnetic wave for both PD andflashover decrease with an increase of the distance from the discharge source in the frequency range from 30 MHz to 300 MHz. The results were discussed in terms of a model assuming that electromagnetic wave radiation from a small dipole antenna simulated that from the PD source. Consequently, the distance characteristics of the signal gain proved to agree well with the theoretical calculation in the frequency range from 35 MHz to 75 MHz. An attempt was also made to separately measure the electromagnetic spectrum caused by positive and negative PD pulses, according to AC applied voltage phase. A t the same time, PD pulses were measured with a computer‐aided measuring system. The relationship between the PD statistical characteristics and the electromagnetic spectrum has been discussed.
Irreversibility of dielectric strength of vacuum interrupters after switching operations
Authors: Osmokrovic P. , Lazarevic Z. 
Published: July 2010

AbstractThe irreversibility of dielectric strength of commercial vacuum interrupters after a large number of consecutive switching operations is investigated in order to find out how dielectric performance of a vacuum interrupter degrades during its service life. Three types of commercially available vacuum interrupter were tested. Two of these devices were with transverse and one with axial magnetic field, all having CuCr contacts. Breakdown voltage data are measured in appropriate experiments in which type of tested interrupters and arcing conditions are varied.
Emergency assist mode of the coordinated secondary voltage control in case of voltage instability
Authors: Popovic D. S. , Gorecan Z. A. 
Published: July 2010

AbstractThis paper presents the performance analysis of different operation modes of the coordinated secondary voltage control in case of voltage instability. It was found that the basic pilot‐bus voltage control mode is not suitable in case of an already initiated voltage instability process, so that the new emergency assist mode of operation is proposed. Finally, the performance of the basic and the proposed emergency assist modes are studied on the test example of the power system.
The GDL data transmission experiment
Authors: Rumpel D. , Proske D. , Kempinski W. , Hummel M. 
Published: July 2010

AbstractThe experiment was designed to demonstrate the data transmission capabilities of a language‐oriented data system (GDL). In a realistic simulation, an unknown computer‐controlled substation was connected to a control centre. By inquiry to the substation, the control centre computer got informed on the stock of objects and the topological connections in this substation, then designed interactive diagrams for its switchyards. Finally, this substation was controlled as for switching and transformer tapping by an operator. The time required to couple the previously unknown substation to the control system amounted to 100 s.
Numerical and experimental investigations into transverse flux induction heating
Authors: Mohring J.‐U. , Leßmann H.‐J. , Mühlbauer A. , Nacke B. 
Published: July 2010

AbstractInduction heating of flat metal products can be carried out using the magnetic transverse flux or the longitudinal flux. Transverse flux induction heating offers advantages particularly in the case of thin strip material. A program package is described, which enables the numerical simulation of the current and temperature distributions in transverse flux induction heating arrangements, to investigate the physical correlations. The calculation methods for the current distribution are based on the boundary element method (BEM) and those for the temperature distribution on the finite difference method (FDM). Taking into account the installation‐specific symmetries, the calculations can be carried out on generally available computers like PC or workstations. The numerical modelling and the evaluation of the results are presented using an industrial pilot plant as an example. A transverse flux laboratory model is used for the experimental verification of the electromagnetic (EM) calculation method. The temperature distribution in the strip during the passage through the industrial pilot plant is recorded with the aid of an infrared measuring system and compared with the calculation results.
Measuring system for fast transients monitoring in gas‐insulated substations
Authors: Osmokrovic P. , Petkovic D. , Markovic O. , Kartalovic N. , Vukic D. 
Published: July 2010

AbstractIn this paper the results of testing and calibration of measuring systems for very fast transients (VFT) in gas‐insulated substation (GIS) are presented. The general principles for the construction of measuring systems for recording and transmission of VFT are also discussed. The paper describes in detail the constructions of four measuring probe types adjusted for VFT monitoring in 123 kV SF6‐insulated substation. The primary construction requirement was the ability to monitor VFT in 123 kV SF6‐insulated substation containing frequencies 200 MHz without distortion in both frequency and voltage domains. For the purpose of the measuring system testing and calibration an experimental facility was developed based on the computer experimental modelling technique. The verified experimental facility was then used for testing and calibration of measuring probes type. During the test, various effects on the measuring system response quality were noted with respect to the applied constructional solutions, with different kinds of dielectric material used for the low‐voltage capacitor and different diameters of the sensor probe. The obtained results are explained and the possibilities of further improvement of SF6, VFT measuring system characteristics suggested.