bluuebunny/crossref_metadata_2025 huggingface dataset:
Long‐span installation machine for optical cables
Authors: Harada Kazuhiro , Saegusa Kentaro , Nakahira Mizuho , Tsuchiya Yuzo , Saito Takeo , Kurashima Takeshi
Published: July 2007

Long‐span installation of optical cables is realizable by virtue of their light weight, small outer diameter, lower transmission line loss due to reduction of the number of splices, effective installation operations, etc. The authors have developed a novel long‐span installation machine for optical cables and a practical method of installation using this machine. The machine is found to be applicable in practice based on its fundamental composition of a pair of upper and lower caterpillars and a drive motor. The machine is distinguished by the following performance characteristics and functions: (i) it can pull cables of different OD and a pulling rope with a constant speed; (ii) the maximum pulling load is 300 kgf; (iii) the small, light‐weight equipment can be installed in any kind of manhole; (iv) the equipment can be operated by a utility power supply or portable generator; (v) there are control provisions for pulling force limitation and cable slack detection to facilitate automatic cable installation. Another advantage is the “distributed pull system,” wherein the pulling force needed for cable installation is distributively loaded over the cable length. In combination with these features, 14 optical cable sections were actually installed in a duct section of 18 km length. The average section length was 1,300 m and the maximum was as long as 2,500 m. As a result, the practical applicability of the above equipment was proved, showing that they satisfy the design criteria and functions and that there is no significant increase in cable losses after the installation operations.
Performance of millimeter‐wave detector using hot carriers in semiconductor
Authors: Kikuchi Kazuo , Furukawa Seijiro
Published: July 2007

This paper confirms in practice the wideband property of hot‐carrier microwave and millimeter‐wave detectors based on one of the high‐field effects in semiconductors. The dectection sensitivity as related to the diode structure and material is clarified. A p‐type Ge hot carrier diode is fabricated and its detection properties in the 10 GHz and 100 GHz bands investigated. Experiments show that the detection output is close to the value predicted from the structure and that the critical field of the semiconductor is obtainable from the bias‐voltage dependence of the detection characteristics. Finally, the figure of merit of materials for hot carrier bias is defined and guidlines for selection of materials are presented.
Reliability analysis and light preventive maintenance for a two‐unit parallel redundant system with bivariate exponential failure distribution
Authors: Sugasawa Yoshio , Kaji Ikuo
Published: July 2007

The degree of reliability is analyzed for the case where the preventive maintenance is applied to a parallel redundant system with two mutually related and repairable units. The bivariate exponential distribution (BVE) is introduced to describe the failure time distribution of two units that are not independent and mutually related. The reliability analysis of a repairable two‐unit parallel redundant system assuming a BVE failure distribution has already been reported. In this report, two methods of preventive maintenance are considered in the system with the BVE failure distribution. (1) Mutually related preventive maintenance is applied to the system only when both units obey the BVE distribution in failure time distribution. (2) Simultaneous preventive maintenance is applied to two units at prescheduled times. In the reliability analysis, the limiting availability of the system is calculated by using an extended regeneration point method in Markov renewal processes (MRP). In numerical examples, actual figures are assigned to each distribution and the time ratio of preventive maintenance for the two units is defined. Then the relationship between variations of the time ratios and the limiting availability is shown.
A new realization of a digital filter using a number theory transform
Authors: Edanami Takafumi , Tsujii Shigeo
Published: July 2007

With the number theory transform it is possible to perform a high‐speed convolution operation without multiplication and without numerical errors. For this reason, applications of the number theory transform to FIR digital filters have drawn attention. However, when the number theory transform is applied to digital filters, the operating word length becomes extremely large to prevent overflow at the output and this becomes a serious problem in actual hardware implementation. A method is proposed for expanding the dynamic range of the input and output in which the higher order difference of the impulse response is made another impulse response. It is shown that the proposed technique can greatly expand the input and output dynamic ranges. The method can also be combined with other techniques to improve its effectiveness.
Electromagnetic fields in twisted coordinate system
Authors: Yabe Hatsuo , Mushiake Yasuto
Published: July 2007

This paper introduces the twisted coordinate system and presents theoretical investigations of the existence of EM fields whose polarization plane rotates helically. First, concrete expressions for vector operations are derived and the vector wave equations in homogeneous and isotropic media are given in terms of covariant and contravariant components. Then the EM wave whose polarization plane rotates with the coordinate axis is investigated. The results show that propagating rotating polarized wave fields do not exist if the electric field has only a single twisted coordinate component and that the TEM wave exists only as circular‐polarized plane wave fields. By combining two circular‐polarized waves propagating in opposite directions, parallel electric and magnetic fields exist. The Hertz vectors suitable for this type of coordinate are derived and general equations for TE and TM mode EM fields are obtained.
Image bandwidth compression by pre‐compensative interpolation
Authors: Yanaka Kazuhisa , Saeki Norio , Saito Tadao , Inose Hiroshi
Published: July 2007

In the interpolative coding method, the pixels constituting the image are divided into “transmitted points” and “interpolated points,” and the former only are transmitted to the receiving end from the sending end. The latter are reconstructed by interpolation at the receiving end. Commonly, the original image values have been used for the transmitted point values as they are, or, the original image values have been properly lowpass filtered for the transmitted point values. However, judging from the entire image transmission system, the problem of how to determine the transmission point values at the sending end is closely related to the interpolation method at the receiving end.

In this paper, we propose a pre‐compensative interpolation coding method such that given the interpolation method at the receiving end, the transmission point values at the sending end are determined so that the sum of the squared error between the transmitted points and interpolated points is minimized. We introduce two kinds of pre‐compensative interpolation coding methods for the case where the interpolation at the receiving end is linear, that is, a locally pre‐compensative interpolation coding method and a globally pre‐compensative interpolation coding method. According to a simulation using a standard image, the following effects have been recognized: the improvement of the SN ratio in comparison with existing simple linear interpolation which uses the original image values as the transmitted point values, and the decrease of the image quality degradation which seems to be caused by noise.
Edge effects in dipole phased arrays
Authors: Tokumaru Shinobu , Miyamoto Takuji
Published: July 2007

In the conventional analysis of the phased array, the array structure is considered infinite. This kind of approach is effective only for the investigation of the pattern from the centrally located elements and is not applicable for edge elements. In this paper, the edge effect of the dipole phased array is studied by introducing virtual generators in the analysis. The analysis method is applied for the calculation of the element pattern, current distribution, and active impedance of edge elements.
10 × 10 optical matrix switch
Authors: Yamamoto Hisao , Yokoyama Masaaki , Ogiwara Haruo
Published: July 2007

The design and test results of low‐loss optical matrix switches capable of switching between input and output of many fibers are described. Regarding the lens system, it is pointed out that if a large switching system is designed with the conventional optical collimating system used in small‐scale switches, loss due to caliber eclipse or mode conversion appears. However, if the telescopic lens system is used, it is theoretically possible to design a large‐scale switching method that the angular errors and pointed out regarding the optical path switching method that the angular errors and parallel motion errors of the optical lines after the optical paths are switched may possibly be reduced by using a pentagonal prism flexibly supported at an appropriate position and pushing it to a plane. Finally, a design method and the test results for a trial 10 × 10 matrix switch designed in accordance with this method are discussed.
Measurements and imaging method of blood flow profile in human heart
Authors: Chihara Kunihiro , Sakurai Yoshifumi , Matsuo Hirohide , Kitabatake Akira , Abe Hiroshi
Published: July 2007

Measurement and imaging of medical information invisible directly to human eyes are indispensable to improved diagnoses and to the delivery of quality medical care. This paper discusses development of a multichannel Doppler flowmeter for noninvasive measurement of blood flow in the human heart and the use of a computing system for visual representation of the blood flow profile. Data acquisition from multiple sites of the human body has been greatly simplified by the use of multichannel data acquisition systems developed through research. Also, a new method for discriminating the direction of blood flow, which is far better suited to digital computer processing, is here proposed and methods for displaying the flow using a color/gray level displaying system and a graphic terminal as a data output device are discussed to represent the flow information in a three‐dimensional and dynamic manner. Since it has been said in general that Doppler flowmetry is to some extent quantitatively inadequate the accuracy of the developed measuring method is determined by a simulated experiment. Although the data acquired from the measuring system are as yet processed off‐line, real‐time processing seems to be feasible if an arrow processor is employed.
Design of Pel adaptive DPCM coding based upon image partition
Authors: Saitoh Takahiro , Harashima Hiroshi , Miyakawa Hiroshi
Published: July 2007

Pel Adaptive DPCM Coding is an encoding method in which an appropriate DPCM coding loop is selected for every picture element. This is done by referring to only the past decoded values in the previously available multiple coding loops. Since each DPCM loop has been determined experimentally, it has been difficult to achieve efficient encoding, and the location of its compression limit remains unclear. In this paper, we have modified the previously proposed Block Adaptive DPCM coding method based on image partition and introduced a Pel adaptive DPCM coding method using multiple DPCM coding loops. In this method, nonhierarchical cluster analysis plays an important role. The coding performances of a Pel adaptive DPCM coding method differ depending on the subject images. The Pel adaptive DPCM designed by the above method yields a maximum performance advantage of 2.9 dB for the Girl and Couple images, 1.5 dB for the Aerial image, and none for the Moon. This is an improvement over the optimally designed block adaptive DPCM coding method proposed previously by the authors.
Synthesis and Properties of Tetrasubstituted 1,10‐Phenanthrolines and Their Ruthenium Complexes
Authors: Schäfer Bernhard , Görls Helmar , Meyer Susann , Henry William , Vos Johannes G. , Rau Sven
Published: July 2007

The synthesis and the photophysical properties of a series of tetrasubstituted phenanthroline (phen) ruthenium complexes of the type [Ru(tbbpy)2(phen‐R4)]2+ (tbbpy = 4,4′‐di‐tert‐butyl‐2,2′‐bipyridine; phen = 1,10‐phenanthroline; R represents the substitution at 3‐, 5‐, 6‐ and 8‐positions with phenyl, 4‐tert‐butylphenyl and para‐biphenyl) and of a homoleptic [Ru(phen‐R′4)3]2+ (R′ = 4‐tert‐butylphenyl) are described. The phen‐R4 ligands were obtained in high yields usingSuzuki‐type coupling reactions. The solid‐state structure of 3,5,6,8‐tetraphenylphenanthroline is reported. The investigation of the photophysical properties of the free ligands reveals a pronounced effect of the aryl substitution on absorption and emission properties. These properties are mirrored in the corresponding complexes, which possess room‐temperature emission lifetimes of up to 2833 ns.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
On the Synthesis and Reactivity of Enantiopure Azetidines
Authors: Banide Emilie , Lemau de Talancé Vincent , Schmidt Grégory , Lubin Hodney , Comesse Sébastien , Dechoux Luc , Hamon Louis , Kadouri‐Puchot Catherine
Published: July 2007

β‐Amino alcohols with an (E)‐vinylsilane moiety were cyclized in the presence of N‐bromosuccinimide to afford diastereomerically pure azetidines. The chemo‐ and stereoselectivities of this bromocyclization are discussed. AM1 calculations support the observed chemoselectivity. The reactivity of the azetidines towards fluorinated reagents was studied. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
Synthesis and Solid‐State Fluorescence Properties of Structural Isomers of Novel Benzofuro[2,3‐c]oxazolocarbazole‐Type Fluorescent Dyes (Eur. J. Inorg. Chem. 22/2007)
Authors: Ooyama Yousuke , Kagawa Yusuke , Harima Yutaka
Published: July 2007

The cover picture shows photophysical properties of structural isomers of novel benzofuro[2,3‐c]oxazolo[4,5‐a]carbazole‐type (3) and benzofuro[2,3‐c]oxazolo[5,4‐a]carbazole‐type fluorophores (4), which differ in the position of the oxygen and nitrogen atoms on the oxazole ring. Considerable differences in the absorption and fluorescence spectra were observed between structural isomers both in solution and in the solid state. The background shows the “Itsukushima Shinto Shrine” (in the UNESCO World Heritage List) in Hiroshima, Japan, where the research reported in the article by Y. Harima et al. on p. 3613 ff was performed.
Voltage sags mitigation on distribution utilities
Authors: Tosato F.
Published: July 2007

Voltage sags are important to industrial reliability. Modern process controls are often sensitive to voltage sags, that may cause significant production outages. World‐wide experience proves that a main origin of voltage sags affecting customers are short circuits on utility lines, with special reference to the overhead radial distribution ones. Since the voltage sag during the fault is proportional to the short‐circuit current, an effective fault‐current limitation by means of a device connected at the beginning of the most exposed radial feeders will limit the expected voltage sag amplitude and improve the system power quality. In the paper a proposal for a simple but effective fault‐current limiter is given and discussed.
Single‐phase three‐level rectifier with high power factor
Authors: Lin B.‐R. , Lu H.‐H.
Published: July 2007

A new control scheme for the single‐phase rectifier with three‐level voltage pattern is proposed. A power‐factor corrector to improve the power quality is presented. A hysteresis current control (HCC) is adopted to control the line current with high power factor and low harmonic distortion. The line current command is derived from a DC link voltage regulator and an output power estimator. The major advantage of using three‐level instead of two‐level voltage pattern is that the blocking voltage of each power device is clamping to half of the DC link voltage. Based on the region detector of the line voltage, capacitor compensator and hysteresis comparator, the proposed control scheme is used to drive the line current with high power factor and low current distortion. The proposed scheme is verified by software simulations and experimental results from a laboratory prototype.
Load modelling for analysis of power‐system harmonics under unbalanced conditions
Authors: Sainz L. , Clua J. , Jordi O.
Published: July 2007

This paper analyses the load‐harmonic modelling under unbalanced conditions. It presents a harmonic characterization of linear three‐phase loads (three‐phase P‐Q consumptions) for different impedance configurations and analytical models for an ideal six‐ and twelve‐pulse converter supplied by unbalanced voltages, too. The models of these linear and non‐linear loads are incorporated to the three‐phase harmonic load‐flow formulation. A 15‐bus network is presented to study the different load behaviour.
Analytical model for assessment of the line harmonic currents generated by a variable speed drive
Authors: Miègeville L. , Guérin P.
Published: July 2007

With the widespread use of static power converters in many industrial applications, it requires to characterise more accurately the harmonic content injected on electrical networks. The present paper proposes an analytical method to obtain the model of the harmonic currents produced by a variable speed drive. The bridge rectifier is assumed to operate in the continuous mode. In addition, both the AC and DC side impedances are taken into account. Firstly, the validity of the analytical model is demonstrated by comparison both to the results of the time simulations and experimental measurements. Secondly, a detailed comparative survey between the present modelling and some earlier ones is carried out to define the application fields of the analytical model and to point out its interest in describing the harmonics generated by the rectifier for high DC current ripples.
Experimental evaluation of parameter variation effects in indirect rotor‐flux oriented induction‐motor drives
Authors: Sokola M. , Levi E.
Published: July 2007

The paper investigates detuning effects, caused by parameter variations, in an indirect current‐fed rotor‐flux oriented induction motor drive aimed at operation in both the base speed region and the field‐weakening region. Rotor resistance variation and magnetising inductance variation are elaborated. In contrast to the existing studies, where these detuning effects are analysed using appropriate induction machine models, the approach undertaken in this paper is purely experimental. Detuning is evaluated based on measured speed response in transient operation and measured stator current fundamental component in steady‐state operation. Detuning during steady‐state operation in the field‐weakening region is additionally characterised with measured stator voltage fundamental component.
ETEP‐Information on European Dissertations
Authors: Wang X. H. , Song Y. H. , Ferguson C. P.
Published: July 2007

The paper reports on the experimental characterisation and subsequent development of an electrical model for cable oversheath faults under AC voltages. The characteristics can be represented by a combination of linear resistance and capacitance below a threshold voltage and a non‐linear resistance above the threshold voltage. The proposed model was then incorporated into ATP (Alternative Transient Program). The simulation results clearly show satisfactory similarity between the model and the experimental results. The developed electrical model may therefore be used to accurately simulate sheath‐to‐earth fault conditions in buried cable systems.
Achievements of the esprit IV project 22297 electronet ‐ a project closing report
Authors: Dreyer T. , Giannini M. , Lambrecht D. , Laresgoiti I. , Selvik E. , Weber Th.
Published: July 2007

The ESPRIT IV (European strategic programme for research and development in information technology)project ElectroNet aimed at defining a European data model suitable for planning applications of HV (high voltage) and EHV (extra high voltage) power systems by applying the ISO‐STEP‐methodology. For three years thirteen partners from seven European countries worked on this project which was finally completed by the end of September 1999.

This paper presents the innovative concepts developed for ElectroNet. Finally an outlook of a subsequent planned project EPSIM is given.
High frequency modal analysis of lossy non‐uniform three‐phase overhead lines taking into account the catenary effect
Authors: Brand Faria J. A. ÄO
Published: July 2007

The catenary effect determines that overhead transmission lines are non‐uniform structures. Most often this effect is assumed to be negligible and the problem is circumvented by simply assigning a constant average height to each line conductor. In order to assess the adequacy of this standard procedure different transmission‐line sections with different sag values have been dealt with, from a modal analysis viewpoint. Each line section has been discretized into a large number of uniform elemental cells; the chain transfer matrix has been computed and the modal characteristics of the structure determined. Computation results clearly show that the average height standard approach is inappropriate for the evaluation of the high frequency modal propagation properties. Frequency scans reveal that the catenary effect gives rise to noticeable resonance phenomena: abrupt variations being observed in the modal propagation characteristics for all modes, the ground mode specially.
Energy functions analysis in voltage collapse
Authors: Jurado F. , Carpio J.
Published: July 2007

Time‐domain approach examines the behaviour of the system, one determines whether stability has been maintained or lost. In contrast to the time‐domain approach, direct methods determine system stability based on energy functions. The basis of direct methods for the stability assessment of a system is knowledge of the stability region. During the last decade, many researches have thoroughly analysed the use of energy functions for the direct stability assessment of networks. Energy function analysis offers a different geometric view of voltage collapse. The Transient Energy Function, a technique based on Lyapunov stability theory and originally developed for direct stability analysis of power systems, has been successfully used as a voltage stability index for collapse studies. In this paper the simulation results are on the IEEE 173‐bus test system.
A novel node ordering approach for parallel load flow analysis
Authors: Chen S.‐D. , Chen J.‐F.
Published: July 2007

The bordered block diagonal form(BBDF) of the Jacobian matrix is quite suitable for parallel processing implementation. Balance loading on all processors is essential to ensure the success of any parallel approach. To achieve this objective, a novel approach involving the node ordering method is proposed in this study on the basis of calculating the maximum number of fill‐in and the degree of every node as the cutset block nodes. Simulation results of the IEEE 118–bus system and the Taiwan Power Company (TPC) 288–bus system are presented to demonstrate the performance of the proposed algorithm and its capability to implement parallel computing for the load flow analysis.
On the compensation of non‐active current components of three‐phase loads with quickly changing unsymmetry
Authors: Staudt V. , Wrede H.
Published: July 2007

Some types of loads, like arc furnaces, present a special challenge to compensation strategies. They vary quickly and have a very high rated power. For example the arcs of an arc furnace are not burning continuously especially when starting the melting process. This causes variations of the line voltage with frequencies well below the line frequency commonly known as voltage flicker. Because of cost efficiency the energy storage capability of compensators for the mitigation of voltage flicker effects can still only be small compared to the energy taken by the arc furnace during one period of the line voltage. This paper discusses the use of a compensation tool which quickly detects negative sequence current components in comparison to the calculation of an equivalent conductance using the so‐called FBD method (Fryze‐Buchholz‐Depenbrock method). Simulations are used to demonstrate the advantages and disadvantages of the tool for detecting negative sequence current components. It is shown that the quick detection and compensation of negative sequence current components can reduce the amount of voltage flicker considerably.
A thermodynamic approach to the instantaneous non‐active power
Authors: Morando A. P.
Published: July 2007

Having schematically run through the transition from single‐phase to three‐phase relationships, the energy balance is formalised using Park vector notation. The imaginary power notation emerges. Leading back, in the sinusoidal case, to the usual reactive power, it generalises its specific contents in the case of variable states, explaining in particular a typical aspect of three‐phase networks: the energy bouncing from one phase to another. This aspect can be seen as an index of power quality. At last, these same considerations are obtained by means of Lagrangian and thermodynamic approaches that lend a deeper meaning to the energy related quantities.
On the characterization of voltage and current transducers in steady‐state distorted conditions
Authors: Sasdelli R. , Muscas C. , Peretto L. , Tinarelli R.
Published: July 2007

The traceability of measurements performed to gauge information about the operation of electrical power systems under nonsinusoidal conditions is an important and live issue, usually neglected by the technical Standards. A generalized definition of the “composite error” is proposed in this paper as a meaningful index for the metrological characterization of voltage and current transducers in steady‐state nonsinusoidal conditions. In this connection, the relationship among the composite error, the classical ratio and phase‐angle errors and other parameters characterizing the waveforms of the transduced quantities are pointed out. Finally, problems involved in the measurement of the composite error in steady‐state distorted conditions are dealt with and the results of some experimental work are presented.
Practical aspect of active and generating powers in nonsinusoidal situations: Some questions
Authors: Emanuel Alexander E.
Published: July 2007

Many modern apparent power resolutions are based on the Fryze's active power as well as on the generating power. This paper scrutinizes the usefulness of Fryze's active power subcomponents and the very existence of the generating power in real life electrical systems.
Poynting vector and the quality of electric energy
Authors: Ĉakareski Ẑ. , Emanuel A. E.
Published: July 2007

This paper expounds on electric energy quality issues using the Poynting Vector (PV). It is shown that components that do not contribute to a net energy transfer, are attributed to the nonactive components of the PV that are associated with three situations: 1. Phase displacement, 2. Current harmonics injection, 3. Load unbalance. The nonactive PV components can be viewed as carriers of polluting energy that negatively affects the energy transfer process and its conversion at the end‐user. The developed analysis helps visualize the flow of electric energy in poly‐phase systems and provides a theoretical base for the resolution of apparent power for three‐phase systems with nonlinear and unbalanced loads.
Investigation of the circuit breaker reignition overvoltages caused by no‐load transformer switching surges
Authors: Popov M. , van der Sluis L. , Paap G. C.
Published: July 2007

When an unloaded transformer or motor is switched under certain conditions, the circuit breaker can be exposed to a re‐strike effect that leads to voltage escalation. The effect of reignition depends not only on the type of circuit breaker, but also on the surrounding network.

In this paper we describe a detailed model of all system components, which is extended where necessary, for the calculation of transients caused by the vacuum circuit breaker switching surges. Especially the transformer modelling is explained in detail for a broad frequency range because of a very complex transient behaviour. The system configuration consisting of a circuit breaker, a cable, a transformer and arresters is observed and modelled by means of some provided measured data. The results of some models are compared with measurements. The models have been imbedded into the Alternative Transient Program (ATP). The program developed here can be widely used for studies of transient recovery overvoltages caused by interruption of transformer steady‐state and inrush currents if the measured data and parameters for the system components are known.
Measurements on electrical power systems under bi‐tone conditions by using the virtual time‐domain approach
Authors: Peretto L. , Sasdelli R. , Tinarelli R. , Rossi C.
Published: July 2007

The virtual time‐domain approach is very convenient for the characterization of multi‐tone signals, both quasiperiodic and periodic with very low fundamental frequency. Measurements on a three‐phase load controlled by an inverter have been performed by means of a digital method implementing that approach. The results are reported and discussed also in comparison with those provided by a validation procedure.
A self‐tuning harmonic and interharmonic processing technique
Authors: Gallo D. , Langella R. , Testa A.
Published: July 2007

Measurement and analysis experiences have highlighted great difficulties in detecting and measuring interharmonics due to their small amplitudes and their consequent vulnerability to spectral leakage of harmonic tones. A new approach that has a general validity and results fully compatible with the latest IEC standard draft is presented. This approach is based on a self‐tuning technique aimed at performing the spectral analysis on a time window whose width is as near as possible to an integer number of the actual period of the fundamental component, so minimizing the effects of spectral leakage on interharmonic estimation. The approach proposed is successfully applied to both numerical and experimental tests.
Circuits with semi‐periodic currents: Main features and power properties
Authors: Czarnecki L. S.
Published: July 2007

The active, reactive, scattered and unbalanced currents and powers, the RMS value and harmonic components are defined only for periodic quantities. Unfortunately, non‐periodic variation of load parameters or their periodic variation but with a frequency different than the frequency of the voltage produced by power generators, causes non‐periodic currents. Such non‐periodic currents, however, are often much lower than periodic components and consequently, the entire current can be considered as semi‐periodic. The notion of semi‐periodic voltage has similar meaning. This paper discusses the main properties of semi‐periodic currents, it provides their classification and introduces a concept of primary, secondary, coperiodic, non‐coperiodic components as well as the concept of interharmonic noise and quasi‐harmonics. The paper investigates how circuits with semi‐periodic voltages and currents could be described in power terms.
The contribution of oil‐flow electrification to the leakage current of multi‐point gaps under direct and alternating voltages
Authors: Metwally I. A.
Published: July 2007

This paper demonstrates the effect of oil‐flow electrification (OFE) on the leakage current in oil‐cooled electric power apparatus using a closed cycle model. The current in multi‐point gaps is measured as a function of oil‐flow velocity and temperature, type and polarity of the applied voltage, number of points and their interspacing, and type of the solid insulating material used in such composite insulation system. The results reveal that OFE phenomenon exists for both energized and unenergized cases. It causes a polarity reversal for the current under positive direct voltage, while it augments that current for negative voltage case. The measured current increases exponentially with temperature and/or voltage. Higher number of points or interspacing between points leads to higher current under both direct (both polarities) and alternating voltages for both stationary and flowing conditions. Also, the experimental results are interpreted and discussed in the light of electric field computation using a package based on the charge simulation method. The electric field profiles, corona inception voltage and number of streamers are invoked to explain the trend of the experimental results.
Application of a self‐tuning to automatic generation control in power system including smes units
Authors: Demirören A.
Published: July 2007

In this study, a self‐tuning control scheme is proposed and applied to automatic generation control (AGC) in power system with superconducting magnetic energy storage (SMES). The system is assumed consisting of two areas. The proposed self‐tuning control scheme is used to implement the automatic generation control adding to conventional control configuration. The performance of the system for load changes in the areas in the interconnected power system is studied. A comprehensive performance evaluation of the system is presented. The computer simulation of the interconnected power system with two areas shows that the proposed self‐tuning control scheme is very effective in damp out of oscillations caused by load disturbances.
Sensorless MRAS‐based induction motor control with parallel speed and stator resistance estimation
Authors: Vasić V. V. , Vukosavić S. N.
Published: July 2007

This paper proposes a novel MRAS‐based speed controller for the induction motor drive without shaft sensor, with the integral adaptation mechanism for on‐line tuning of the stator resistance (Rs). For an accurate estimate of the shaft speed (ω) even at near zero speeds, proposed Rsestimator running parallel in order to compensate for the RS thermal variation. In an intent to accurately estimate the ω at low speeds, without deterioration the drive performance, parallel with the ω estimation the Rsis also estimated to compensate Rsthermal variation. The reference and adjustable models of MRAS‐based ω estimator change their roles in the Rsestimator context. The dynamics of the ω derivation and the Rsestimation are investigated for a wide range of operating conditions and straightforward design procedure is proposed, derived from the hyperstability theory. Extensive computer simulations prove the effectiveness of the proposed solution.
Power system load‐model identification through simulation of field measurements
Authors: Milanovic J. V. , Halley A. J. , Piekutowski M.
Published: July 2007

The paper describes some of the simulations of measurements taken using EMTDC to estimate power system load models. It shows how different load structure and non‐ideal conditions in power systems influence results of the measurements. On the basis of simulations performed different load models are proposed for various classes of load compositions. An example of load parameter estimation from measured results is given.
Digital algorithm for distance relay including grounding impedance at fault place
Authors: Radojević Z. M. , Popović Lj. M.
Published: July 2007

The influence of the fault place grounding impedance in algorithms for ground faults distance relay is not usually taken into account. The fault place grounding impedance depends on design characteristics of the ground wire and towers footing resistance. This paper shows a possibility of taking into account the fault place grounding impedance in the algorithm for the ground fault distance relay. The algorithm taking into consideration the fault place grounding impedance has better accuracy and only slightly greater complexity.
Influence of conductor coating and bundling on corona phenomenon of hybrid AC/DC transmission lines
Authors: Metwally I. A.
Published: July 2007

This paper presents theoretical and experimental investigations of the factors affecting corona phenomenon on hybrid AC/DC transmission lines using a single‐phase AC (50 Hz)/single‐pole DC reduced‐scale model. A field computation program is used to model both an AC 132‐kV double‐circuit transmission line and an analog hybrid line. The results reveal that the corona inception voltage of DC conductors is much higher than that of AC conductors, where it augments with increasing number of bundles, coating thickness and/or permittivity. Conductor coating and/or bundling causes a drastic reduction in both audible‐ and radio‐noise profiles, but there is no effect of bundle orientation. The trends of the experimental results are in agreement with the computed corona inception voltage, number of streamers and electric field. Increasing the number of bundles and/or DC voltage reduces the AC corona current, and so does the number of streamers. Both the interspacing between AC and DC conductors, and the relative amplitude of applied voltages determine the variation of AC corona current. Conductor coating gives an economical solution to increase the corona inception voltage, and reduces the number of streamers at the conductor surface. For thinner coatings, the AC corona current is unchanged while the DC corona current increases.
On the segmentation method used for analyzing nonuniform transmission lines: Application to the exponential line
Authors: Brand Faria J. A. ão
Published: July 2007

This paper addresses the topic of nonuniform transmission line modeling with emphasis on the determination of the high‐frequency propagation parameters. A well‐known tool for analyzing nonuniform line structures, the segmentation method is characterized by modeling the line by a cascade of uniform segments. However, such an approach seems to have a flaw, as it apparently does not include the series‐impedance and shunt‐admittance space‐derivative terms appearing in the wave equations. The importance of that problem is investigated here. A double‐section exponential single‐phase line structure, for which exact closed‐form results are derived, is analyzed using the segmentation method. The approximate results obtained are compared with exact ones. Comparison shows that for typical line geometrical dimensions the segmentation method performs excellently. Further, it is shown that besides the limitations inherent to the line discretization process no other formal limitations to the segmentation method do really exist.
Modelling of permanent magnet synchronous motors with spatial harmonics
Authors: Bonet‐Madurga J. , Díez‐González A.
Published: July 2007

A mathematical model of the permanent magnet synchronous motor with spatial harmonics is presented. The model equations are expressed in a stator reference frame and in a field‐oriented d‐q reference frame. They have been derived applying the space‐phasor theory, which allows the analysis of transients and of spatial harmonics. The spatial distribution of the stator windings, the square‐type induction wave of the magnets and an airgap of variable length have been considered. Expressions for the airgap permeance, inductances, flux linkages, electromagnetic torque and the voltage equations have been obtained. The validity of the model is confirmed by previous experimental works.
Determinination of the ARC extinction time on power lines using voltage signals
Authors: Djurić M. , Radojević Z. , Zorić K.
Published: July 2007

This paper presents a simple algorithm for the overhead lines secondary arcing fault detection and determination of the exact arc extinction time. The algorithm is based on the bus voltage signals only. It uses the method of Least Error Square Technique based on the calculation of the relative error between the modelled voltage sine signal and the measured bus voltage signal. The algorithm was successfully tested with the signals recorded on the real power system and signals obtained through laboratory tests. The test results demonstrate the ability of this algorithm to detect reliably secondary arcing faults and the ability to determine the exact arc extinction time. The algorithm can be used for defining the reclosing dead time and blocking automatic reclosing of overhead lines with permanent faults.
Long arc in free air elongation effects modeling and simulation
Authors: Terzija V. V. , Koglin H.‐J.
Published: July 2007

In the paper the elongation effects on the long arc in still air are investigated and modelled. Arc is initiated under laboratory conditions in the high power test laboratory FGH‐Mannheim (Germany). Based on the analysis of laboratory arc voltage and current wave forms, the new dynamic arc model, taking into account the arc length variation, is derived. An example of arc computer simulation using the new model is given. The main features of the simulated arc are presented. The main features of both the real and the simulated arc are given in the time and the spectral domains.
Steady state of the cascaded doubly‐fed induction machine
Authors: Hopfensperger B. , Atkinson D. J. , Lakin R. A.
Published: July 2007

A cascaded doubly‐fed induction machine (CDFM) is a connection of two wound rotor induction machines. The rotors of the two individual machines are electrically and mechanically coupled so that brushes for the rotor sliprings are no longer required.

This paper describes the steady state behaviour of such a cascaded machine arrangement. Frequency and slip values are defined. A per‐phase equivalent circuit, based on the common induction machine equivalent circuit, helps to gain understanding of the machine quantities. Measurements on a CDFM confirm simulations with the equivalent circuit experimentally. Saturation effects are discussed to show the limitation of the simple equivalent circuit model. By studying the power flow within the CDFM and taking machine utilisation into consideration allows to suggest that a CDFM has to consist of two identical machines.
Cable model with frequency dependent parameters calculated by using subconductors
Authors: Hofmann L.
Published: July 2007

A cable model with frequency dependent parameters in the time domain for the simulation of transients in the short time range is presented. The model is based on the division of the transmission line into m short lossless delay line segments of length Δxk = l/m, which are connected to each other by damping‐networks consisting of constant ohmic resistances and by distortion‐networks simulating the frequency dependence of the series impedance per unit length. The damping‐networks consider ohmic line losses as well as leakage losses by shunt conductances. The distortion‐networks are represented by state space equations in the time domain. One advantage of the model in comparison to generally used models is the direct determination of the model parameters from the geometrical dimensions of the line‐ground configuration. This model also provides a fast and accurate algorithm.
DSTRP: A new algorithm for high impedance fault detection in compensated neutral grounded M.V. power systems
Authors: Ruz F. , Quijano A. , Gómez E.
Published: July 2007

The detection algorithms depend on the network topology, the neutral grounding of the secondary winding in H.V./M.V. transformers being one of the main factors to consider. In compensated distribution systems, we need complex detection algorithms based on network parameters estimation. The neutral voltage is the most sensitive magnitude to detect an unusual situation but it is not a selective parameter. In this paper we present the new DSTRP that calculates the influence of each feeder asymmetry in neutral voltage. We also analyze the measurement errors influence that limits the sensitivity threshold of this algorithm.
Nonlinear disturbance attenuation control of static phase shifter in sense of L2‐gain
Authors: Mei S. , Guan T. , Lu Q. , Song Y. H. , Goto M.
Published: July 2007

Static phase shifters (SPS) have the abilities to optimize power flow and to improve transient stability of power systems. In this paper, improving transient stability of the power system using the static phase shifter is considered. First, a nonlinear robust model of the power system including SPS is established. Then a Backstepping method is used to construct the storage function, and a disturbance attenuation controller in the sense of L2‐gain is achieved consequently. The controller reflects the nonlinearity of the system and attenuates disturbances explicitly. Simulations have proved the effectiveness of the nonlinear disturbance attenuation controller.
A new probabilistic load‐flow method for radial distribution networks
Authors: Golkar M. A.
Published: July 2007

Probabilistic load flow is a technique which recognizes the probabilistic nature of the input parameters and takes account of the uncertainties and random variations of generation and load within one computer run. Many formulations have been presented to implement this technique. The majority have assumed either a linear model to represent the load flow equations, or the output random variables to be normally distributed. In this paper, a new probabilistic method for the load flow study of radial distribution system is presented. To increase the accuracy of the method, a new linearization method specific for radial distribution feeders has been developed. As the manipulations required in this method are much less than conventional methods, it is very fast. The method has been used for analyzing some practical networks and the result shows the superiority of the method to conventional ones.
Probabilistic approach of description of thyristor converter faults due to parasitic impulses
Authors: Masmoudi N. , Sellami F.
Published: July 2007

This paper presents a study method of faults linked to parasitic impulses in thyristor converters. In the proposed method control signals are presented in vector form allowing the generalization of parasitic signals. An evaluation of probability of correct operation becomes systematic both in the study of evolution of the system and in the detection of malfunction. An example is given to illustrate the implementation of the method.
Review of the basic insulation level for 400 kV oil‐filled cable systems: Switching and temporary overvoltages (TOV)
Authors: Probert S. A. , Song Y. H. , Basak P. K. , Ferguson C. P.
Published: July 2007

This paper investigates the switching impulse and temporary overvoltage (TOV) duty for 400 kV underground power cables using ATP. This work together with the work reported in [1], investigates the full range of transient overvoltages due to lightning, switching and other temporary overvoltages (TOVs) using ATP. [1] re‐assesses the basic insulation level (BIL) for 400 kV oil‐filled cables. The objective of this work was to check the impact of switching surges on the choice of BIL and to re‐assess the switching impulse insulation level (SIL) and TOV withstand level for 400 kV cables. A comprehensive study of the transient overvoltages experienced by cables within National Grid's transmission system has been performed. This paper provides an argument, for reducing the BIL and SIL for 400 kV cables.
Evaluation of electromagnetic interference on telecommunication cables from an AC railway line: Measurements and calculations
Authors: Lucca G. , Moro M. , Ferrero C. , Giunta M.
Published: July 2007

The paper describes the main results of a field measurement campaign of the electromagnetic interference produced by a 25 kV ‐ 50 Hz railway line on nearby telecommunication cables; the results of the measurements were compared with the results of calculations based on suitable circuit models for studying the inducing and induced systems. The results of the comparison were deemed satisfactory.