bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fault distance estimation and fault type determination using least error squares method
Authors: Terzija V. V. , Djuric M. B. , Radojevic Z. M. 
Published: July 2010

AbstractIn order to avoid autoreclosure onto a permanent fault, a new numerical algorithm for fault type determination is presented. It estimates the fault distance, as well, and can be utilized in the field of distance protection. The new approach, mathematical model and the solution for the earthless faults is given. For the purpose of unknown fault distance and arc voltage amplitude estimation, the Least Error Squares Method is used. The new algorithm is tested through numerous computer simulations and in the laboratory environment.
Principal of the direct determination of the temperature‐dependant rotor and stator resistances of an induction motor
Authors: Amin B. 
Published: July 2010

AbstractIn the presented paper, a direct method for evaluating the temperature‐dependant values of the rotor and stator resistances is presented. The method is based on the evaluation of the instant powers dissipated within these two resistances using the equation of the power balance. Moreover, the way of evaluating accurately the instant values of the rotor current is indicated. Finally, the average temperature of the windings and the values of the resistances are calculated.
Calculation of current flow in grounding systems of substations and of HV line towers, in line shield wires and cable sheaths during earth faults
Authors: Gatta F. M. , Iliceto F. 
Published: July 2010

AbstractThe paper presents a method and a numerical calculation program of the repartition of the earth‐fault currents in the grounding systems of substations and of the HV line towers, as well as of the currents which flow in the shield wires of the overhead lines and/or in the sheaths and armourings of underground cables. The program may be applied also to very extendednetworks for single‐phase‐to‐ground (1‐ϕ‐to‐Gr) andphase‐to‐phase‐to‐ground (ϕ‐ϕ‐to‐Gr) faults at any point. The program is based on the simulation of the earth resistances of the HV line towers by means of a transversal conductance uniformly distributed between the shield wires and earth, and which is assumed to be variable from stretch to stretch according to soil resistivity. Models are derived which are aimed at simulating the single and double‐circuit overhead lines provided with shield wires, as well as the underground cables. These models consist in a single three‐pole or four‐pole equivalent circuit. The validity of the program is verified by comparison with the calculations carried out by the Electromagnetic Transients Program (EMTP). Mention is made of a study carried out for the Turkish 420/150‐k V network. Some measures presented are aimed at reducing the currents which flow in the shield wires of the lines outgoing from the power plants/substations following faults nearby.
Permanent‐magnet synchronous drive with wide field‐weakening range
Authors: Binder A. , Greubel K. , Piepenbreier B. , Tölle H.‐J. 
Published: July 2010

AbstractHigh‐speed small‐ to medium‐power inverter‐fed AC drives with wide field‐weakening range are realized nowadays preferably as induction motor drives. Nevertheless, in the field‐weakening range the utilization of the inverter is rather poor due to the decreasing power factor with increasing speed. In this paper it is shown both by theory and experiment that with permanent‐magnet synchronous machines ‐ in spite of the fixed rotor flux ‐field‐weakening is possible with large ratios of maximum/base speed. This is achieved by an additional negative stator current d‐component. The inverter rating for the same motor output power may be smaller by about 30 % to 40 %, as compared with the induction motor drive.
Digital simulation of reliability of contacts used in AC electromagnetic contactors
Authors: Wróblewski Z. 
Published: July 2010

AbstractIn the paper both general and simplified reliability models of contacts used in electromagnetic power contactors are presented. The models are based on digital simulation of contact‐wearing processes. The general model can be used for the estimation of influence of material and design parameters as well as operating conditions on contact durability while the simplified one is meant for forecasting new contact durability by means of simplified quality tests carried out on samples of brand new contactors.
Fast dynamic stability analysis of a power system using artificial neural networks
Authors: Kukolj D. , Popovic D. , Kulic F. , Gorecan Z. 
Published: July 2010

AbstractThis paper deals with the methodology of analysing the dynamic stability of a power system, based on the application of a variety of architecture and configurations of artificial neural networks. On the basis of the complete system state vector, which represents the input into a multi‐layered neural network, the topology detection of the transmission network is carried out. Depending on the operating regime ‐ the system topology and load level ‐ the corresponding multi‐layered neural network is activated in order to detect the stability of the system. Stability analysis is achieved by tracking changes in the dominant eigenvalues of the system which are the output of the trained neural network. Finally, the paper presents a means of analysing the dynamic stability of the power system on the basis of the reduced state vector, obtained by extraction of the characteristic state coordinates by means of self‐organizing neural network.
Fuse characteristics determined by melting or ageing?
Authors: Sloot J. G. J. , Meng X. Z. , Vermij L. 
Published: July 2010

AbstractFuses are designed to operate under fault conditions. However, because of ageing processes, fuses also operate in practice under normal load conditions. This article presents a method to determine how fuse characteristics change depending on specific load conditions. Based on metal fatigue laws, the process of ageing is described and compared with measurements. A method is proposed how to formulate general ageing behaviour from a limited number of measurements under specific conditions. The method is demonstrated for miniature fuses but also showed to be valid for fuses for the protection of motors and semiconductors.
Noise reduction in on‐site partial discharge measurement by the use of the transfer function
Authors: Weck K.‐H. , Weinel F. 
Published: July 2010

AbstractOn‐site partial discharge (PD) measurements are frequently affected by noise due to external disturbances. This, in particular, applies to PD measurements during after‐laying tests on cable systems. The paper describes a noise‐reduction method in which the PD signal is corrected corresponding to a simultaneously recorded signal from a not energized reference system using the transfer function between the two systems in the frequency domain. The number of calculation steps involved in the procedure could be minimized to an extent that solution operating in real‐time can be realized. The criteria necessary for such solutions are established.
Common and fixed‐poles resonant harmonic filters
Authors: Czarnecki L. S. 
Published: July 2010

AbstractDistribution voltage harmonics corrupt the effectiveness of resonant harmonic filters in reducing waveform distortion. The same is with load current harmonics of frequencies other than those to which the filter is tuned. Low impedance for the distribution voltage harmonics and resonances of the filter with the inductance of the distribution system are responsible for degrading filter effectiveness. A Iso, a change in the supply system structure or parameters may affect filter effectiveness. Filter effectiveness improves when the harmful resonances of the filter with the system inductance, i. e. the poles of the filter transmittance, are sufficiently far from harmonic frequencies. This paper presents a method of synthesis of resonant harmonic filters with the poles located at the designer's discretion. A line inductor with an inductance of the order of the equivalent inductance of the distribution system reduces the dependence of filter performance on changes in the distribution system parameters. Such a filter is referred to as a fixed‐poles resonant harmonic filter. Filters designed with the method described in this paper have higher effectiveness and their performance is more predictable as compared to filters designed traditionally, referred to as common filters.
About the accuracy of some proposed procedures for revenue metering under non‐sinusoidal unbalanced conditions
Authors: Sasdelli R. , Ferrero A. , Menchetti A. , Peretto L. 
Published: July 2010

AbstractIn order to discourage the insertion of polluting loads, suitable tariff policies should be adopted. A possible strategy is based on the comparison between the total active power and the active power at fundamental frequency and positive sequence. Digital Signal Processing techniques allow for the implementation of revenue meters able to measure both those quantities and any index based on them. This paper analyses the accuracy that can be expected in the measurement of both the ratio and the difference of the above powers. The results of numerical simulations confirm that the ratio measurement is suitable for revenue purposes even when the total and fundamental active powers differ for parts per thousands.
Study of commutation phenomena and faults in a system consisting of a synchronous generator and a controlled rectifier
Authors: Kappatou J. , Safacas A. 
Published: July 2010

AbstractThe effect of the system parameters on the commutation phenomena in a system consisting of a synchronous generator, a controlled rectifier and a DC load is being studied in detail. Furthermore, the behaviour of the system in cases of failure of ignition and short circuit of a controlled semiconducting element, is being investigated. The system under study was simulated by a method appropriate for the simulation of variable topology networks.
Generalized method for fault simulations in power systems
Authors: Oswald B. R. 
Published: July 2010

AbstractThis paper presents a new generalized method of modelling of any kind of shunt and series faults as single or simultaneous faults in arbitrary combination. The proposed approach can be used for conventional fault studies for the steady‐state model based on the nodal admittance representation as well as for fault simulations under transient conditions by means of the EMTP/ATP program. This method has been developed for phase coordinates but it is also suitable for any modal coordinates. The purpose of this paper is to show the incorporation of these fault conditions in the EMTP/ATP algorithm.
Load‐flow conditions for hvdc transmission in synchronous networks
Authors: Warnking J. , Balzer G. 
Published: July 2010

AbstractThe basic purpose for HVDC (high‐voltage direct current) transmission is to transmit a determined value of electrical power from one electrical node to another. If there is an AC system in parallel to an HVDC transmission, the load flow via this parallel AC system can be controlled directly. Since HVDC systems offer possibilities to perform fast load‐flow control, they can also be used for improving stability. In this paper load‐flow calculations of a simplified network are presented. First a comparison between HVDC transmission operating in asynchronous resp. synchronous networks is shown. Synchronous network means that the HVDC transmission works in parallel to an AC system at the same voltage level. It is shown how voltage at the point of installation and how the load angle are influenced due to the synchronous operation. A special regard is drawn to the losses of the transmission. Conditions for minimum total losses are presented. Informer calculations loads are involved. It is shown how they influence the minimum total losses.
Economic dispatching with prohibited zones using an extended linear hopfield model
Authors: Chiou G.‐J. , Su C.‐T. 
Published: July 2010

AbstractThis paper proposes a fast Hopfield method with a dispatching strategy to resolve the economic dispatch (ED) problems constrained by prohibited zones. The prohibited operating zones of the units cause such ED problems to become non‐convex optimization ones. The proposed method employs a linear input‐output model for neurons, enabling the development of an operational model for rapidly resolving the ED problems. Applying the strategy to the prohibited zones problem encountered in the dispatching process allows the proposed method to achieve the optimal solution for the non‐convex problems. The effectiveness of the proposed approach is demonstrated by investigating a 15‐unit system with four units possessing prohibited zones. According to the results of the example, the proposed method is more efficient and versatile than the conventional Hopfield method.
A method of gamma‐beta durability determination for reliability tests of brand‐new AC electromagnetic contactors
Authors: Wróblewski Z. 
Published: July 2010

AbstractIn the paper a method of “gamma‐beta” durability determination of AC electromagnetic contactors is presented. Based on reliability models of essential contactor sub‐assemblies, the method enables to estimate durability of the “gamma” part of the overall contactor population at the specified confidence level “beta”. The method is meant for industrial laboratories which carry out reliability tests of brand‐new AC contactors.
Excitation control of a power‐generating system based on fuzzy logic and neural networks
Authors: Karnavas Y. L. , Papadopoulos D. P. 
Published: July 2010

AbstractThis paper presents a practical design of an intelligent controller (using fuzzy logic and neural network concepts) for the excitation control of an isolated power‐generating system. The controller is suitable for realtime operation, with the aim of improving the dynamic characteristics of the generating unit by acting properly on the exciter input. At first, digital simulations of high‐ and reduced‐order models of the above system are performed using conventional control techniques on five system cases which are based on previous work. Then, a fuzzy logic proportional‐plus‐derivative controller (FPDC) is designed and the dynamic performances of the mentioned five system cases and the FPDCs are presented by comparison. Finally, an enhanced controller is designed which involves a pre‐trained neural network as a model dynamics capture. The computer simulation results obtained clearly demonstrate that the performance of the developed fuzzy logic and neural network controller offers better damping effects on the generator oscillations over a wider range of operating conditions, than the associated ones of the conventional excitation controller designs with output feedback applied to high‐ and reduced‐order system models.
Influence of cathodic protection and transmission‐line proximity on oil‐flow electrification
Authors: Metwally I. A. 
Published: July 2010

AbstractTwo reduced‐scale closed oil cycles are used to investigate the influence of both the cathodic protection of a pipeline and its proximity to AC power transmission lines on the oil‐flow electrification (OFE). For the former case, the results reveal that the OFE is highly dependent on the magnitude of the protection current. The higher the protection voltage the higher is the OFE. Also, the results show that the OFE is enhanced by oil velocity and/or temperature. For the latter case, the results indicate that conductor bundling has a monumental impact on all measured quantities: pipe floating potential, and both corona and streaming currents. In addition, oil temperature causes evident quantitative as well as qualitative changes in the measured streaming current, but no effect was found on both pipe floating potential and corona current. The results are interpreted in terms of physico‐chemical and electrochemistry point of view together with electric field computation using a program based on charge simulation method.
Wind energy converter with asynchronous machines and three‐phase ac controller in generator mode
Authors: Rösner J. , Beck H. P. , Sourkounis C. 
Published: July 2010

AbstractWind energy converters (WEC) with an asynchronous generator are usually connected to the grid during start‐up time via a softstarter, consisting of a three‐phase AC controller. In generator mode the controller is bridged and the wind turbine is connected directly to the grid. In this case changes of wind speed cause fluctuations of the electrical power. This paper shows, how the controller can be used as a power controller with the aim of reducing the grid interference and life‐time extension for the mechanical components. In simulation and on a WEC‐model 10‐kW test bed it could be shown that the power control limits the power up current to the nominal current and both power fluctuations produced by wind speed variation and tower shadow effect are reduced. The harmonics were analysed and compared to the harmonics of a six‐phase generator and a twelve‐pulse AC controller.
Tests on the vibro‐acoustic behaviour of a brushless DC‐motor
Authors: Heylen W. , Desmet W. , Belmans R. 
Published: July 2010

AbstractIn the design of rotating electrical machines, the vibro‐acoustic behaviour becomes an important criterion. In an electrical machine, electromagnetically induced forces may cause vibrations of, for instance, the stator. These vibrations may radiate annoying acoustic energy, especially at resonances of the stator assembly. This paper describes some techniques to analyse the vibro‐acoustic behaviour of a (brushless DC‐) motor. However, the technique is quite general and can be used for all types of electrical machines. The “inverse‐frequency‐response‐function” technique (I FRF) allows the identification of the actual vibration behaviour of the motor frame from the measurement of the acoustic field around the motor. Experimental modal analysis yields the resonant behaviour of the motor. A combination of both techniques indicates the critical resonances, causing the undesired acoustic emissions. This may lead to an improved, quieter design of the electrical motor.
Direct torque control of synchronous motor drives for dynamically demanding applications
Authors: Pyrhönen J. , Pyrhönen O. , Niemelä M. , Luukko J. , Kaukonen J. , Pohjalainen P. 
Published: July 2010

AbstractThis paper proposes a new concept for the Direct‐Torque‐Control (DTC)‐based synchronous machine drive. DTC technology provides a synchronous machine drive with excellent dynamic properties. The DTC principles are first briefly recalled. The study observes the problem of the flux linkage integration instability and introduces the flux linkage estimate correction method based on the current model. The field winding current control methods are analysed. It is shown that a synchronous machine drive also needs a stabilisation method when working with very high load angles especially in the field weakening range. A method to control the load angle directly is then proposed. Test results with a 14.5‐kVA laboratory prototype drive are given.
Simplified d‐q dynamic models of the slip energy recovery drive
Authors: Papathanassiou S. A. , Papadopoulos M. P. 
Published: July 2010

AbstractThe issue of the d‐q dynamic modelling of the slip energy recovery drive is addressed in this paper. Two original d‐q dynamic models are presented, in which the harmonics and commutation phenomena of the rotor converters are neglected. The performance of these models, along with another one already used in the literature, is evaluated through comparison with a detailed model of the drive, involving the valve‐by‐valve representation of the converters. One of the novel d‐q models proves to be very satisfactory, achieving good accuracy in all cases, while the other two present increased errors for certain disturbances and operating conditions.
Chromosome band 17q21 in breast cancer: Significant association between beclin 1 loss and HER2/NEU amplification
Authors: Negri Tiziana , Tarantino Eva , Orsenigo Marta , Reid James F. , Gariboldi Manuela , Zambetti Milvia , Pierotti Marco A. , Pilotti Silvana 
Published: June 2010

AbstractTreatment success of breast cancer patients with trastuzumab alone or in combination depends not only on HER2/NEU amplification but also on PTEN and PI3K status and efficient cell death programs. In this pilot study, we found a significant association between loss of beclin 1 and HER2/NEU amplification (both on 17q21) in breast cancers. This finding was confirmed in two public copy number microarray datasets. Furthermore, there is a trend associating beclin 1 loss with TP53 mutations, PI3KCA gene gain, and PTEN mutations. Finally, the observation that beclin 1 gene loss predicted a response to trastuzumab alone or in combination with other drugs is worthy of further confirmation in larger cohorts. Our results suggest that, beclin 1 loss may contribute to genome instability and to a defective autophagy that may lead to tumoral cell death in presence of competent apoptosis or senescence pathways. © 2010 Wiley‐Liss, Inc.
Assessing the value of high‐resolution isotope tracer data in the stepwise development of a lumped conceptual rainfall–runoff model
Authors: Birkel C. , Dunn S. M. , Tetzlaff D. , Soulsby C. 
Published: June 2010

AbstractA study was undertaken in a small agricultural catchment in north east Scotland with the objective of assessing the value of high‐resolution isotope data for integration within a lumped, conceptual hydrological model to improve calibration and aid evaluation. Daily samples of precipitation and stream flow, collected over a year, were analysed for deuterium using new laser spectroscopy technology. The utility of such high‐resolution isotope data was evaluated in relation to the associated uncertainty which was contextualized in relation to uncertainties over hydrometric data and the influence of different sampling resolutions. The simulations were evaluated against model and data errors using auxiliary stream deuterium time series in addition to discharge. The lumped conceptual catchment isotope model (CIM) was developed and adequately reflects flow dynamics and deuterium peaks, but a simple assumption of ‘good mixing’ is not able to fully reproduce the daily stream deuterium dynamic. Using auxiliary data for model evaluation, however, significantly constrained acceptable behavioural parameter sets and therefore reduces the model's degree of freedom. The data indicate that isotopic variability in the stream response is not adequately captured using weekly tracer data. The input resolution of precipitation deuterium concentrations, which were much more variable, proved to be crucial. This approach has provided further assessment of the value of tracers in hydrological modelling, demonstrating their usefulness in terms of model conceptualization, development and calibration, which outweighs the additional uncertainty. Copyright © 2010 John Wiley & Sons, Ltd.