bluuebunny/crossref_metadata_2025_split huggingface dataset:
Use of similarity relations in the analysis of lightning‐induced transient phenomena
Authors: Frentzel R. 
Published: July 2010

AbstractThe Similarity Theory is an applied scientific method employed in experimental analysis. Also in the analysis of lightning protection, the Similarity Theory can be an aid, e. g. in the conversion of test results from models to full scale. Some fundamentals of the Similarity Theory were, therefore, explained in this treatise and scale laws for transient phenomena during lightning developed. These laws allow, with proper application, the construction of experimental models in which phenomena similar to those occurring in the original are reproduced. The results can then be recalculated, using the scale factor for the physical quantity, into the original configuration.
Modular secondary voltage control based on local information
Authors: Gubina F. , Curk J. 
Published: July 2010

AbstractA new concept of highly decentralized secondary voltage control is presented. The concept is based on secondary voltage controllers attached to each reactive power source. The secondary controllers utilize only local information available from measurements at the generating bus and they act completely autonomously. To successfully attain information on the electrically close load bus behaviour describing their voltage profile, a group of fuzzy sets is derived based on intrinsic load node properties and statistics of their voltage deviations. They are used in the fuzzy decision process to yield new reference setting for primary voltage controllers. The tests results of proposed modular secondary control are presented for standard and non‐standard networks. The efficacy of the new concept is demonstrated.
An interactive procedure for the coordination of decoupled var/volt control in radial distribution systems
Authors: Calovic M. S. , Saric A. T. 
Published: July 2010

AbstractThis paper deals with mutually connected problems of reactive power compensation and voltage control in radial distribution systems. The paper presents a simple iterative procedure for optimal coordination of actions of main means for reactive compensation (shunt capacitors) and voltage control (variable turn ratio transformers), within the decoupled solution of these two subproblems. The procedure is based on the static optimization, specified as a non‐linear programming‐type problem. The paper presents the derivation of a method for the solution of specified control problems and gives an illustrative application of this method on the test example of a one‐source radial distribution system, consisting of 53 nodes and 52 branches.
Flexible approach to dynamic simulation of voltage collapse phenomenon
Authors: Rajakovic N. , Tasic D. 
Published: July 2010

AbstractThis paper presents the dynamic simulation of voltage collapse phenomenon in a flexible manner concerning modelling complexity. In that respect a special attention has been paid to modelling aspects of induction motor as a representative of variety of loads. A complete mathematical model used in this paper for the study of dynamic behaviour of an induction motor consists of five differential equations. This set of equations is solved by using the Runge‐Kutta method. As a parallel model a simplified approach is considered (without differential equations) reduced to algebraic network equations and the equation of motion. The effect of transformers equipped with automatic under load tap changers is also simulated. The complete model is rigorous enough in order to calculate the precise voltage‐time and P‐U curves during the induction motor start‐up procedure, while the simplified model can be used for calculation of P‐U curves only. Results from this study can be used for real‐time system control actions and for induction motor relay settings.
Extended algorithm of a fuzzy‐set based power‐system stabilizer with genetic algorithm timing
Authors: Pedram M. M. , Seifi H. 
Published: July 2010

AbstractThe application of fuzzy logic controllers to improve power‐system damping behaviour has received some attention in the literature during the last few years. The paper presents an approach in which besides speed and its first derivative, the second derivative is applied to the Fuzzy‐set based power‐system stabilizer (PSS), so that a three‐dimensional space with improved behaviour is formed. The parameters are then optimized by the new searching technique, the genetic algorithm. Excellent digital simulation results are demonstrated for a single machine infinite bus‐bar system.
Experimental comparison of digital control strategies in a DC servo‐drive
Authors: Dallago E. , Sassone G. 
Published: July 2010

AbstractIn this paper, three fixed‐parameter algorithms are studied and applied to the speed control of a DC servo‐drive. They are Proportional Integrative (PI), Pole Placement (PP), and Generalized Minimum Variance (GMV). A comparison between these algorithms is made for small‐signal step response by simulation and by obtaining experimental results. The comparison, which involves changing of some of the most important system parameters, brings out advantages and drawbacks of each algorithm when it is applied to a non‐ideal system such as the servo‐drive considered.
Stator current control for high‐speed induction machines operated from inverters with lc‐output‐filter
Authors: Rapp H. , Haag J. 
Published: July 2010

AbstractOperating modern high‐speed spindles directly from an inverter often leads to intolerable disadvantages. Equipping the inverter with an LC‐outputfilter avoids these disadvantages but, on the other hand, drastically increases the system's complexity. Particularly there is no method known yet that combines an operation of high‐speed spindles via LC‐filter with high‐quality motion control. In this paper a new robust method for stator current control is introduced, which makes field‐oriented motion control easily applicable to such a system.
Suppression of torsional oscillations using thyristor‐controlled conductance in parallel to series‐capacitor segment
Authors: Wang L. 
Published: July 2010

AbstractThis paper presents the analyzed results of a study on the application ofthyristor‐controlled conductance in parallel to one series‐capacitor segment for suppressing sub synchronous resonance (SSR) that occurs in a series‐compensated power system. The IEEE Second Benchmark Model, systems, which has one turbine‐generator set, is taken as a standard model for this study. In order to stabilize all SSR modes in the studied system, a unified approach based on modal control theory is proposed to design a damping controller which is a dynamic output feedback compensator using shaft speed deviation of the studied generator as a feedback signal. To demonstrate the effectiveness of the proposed control scheme, frequency‐domain approach based on eigenvalue analyses and time‐domain approach based on non‐linear model simulations are performed. The simulated results show that the proposed SSR damping scheme can effectively suppress torsional oscillations of the studied system.
A diagnostic system for live electrical joints in power transmission systems
Authors: Rogler R.‐D. , Löbl H. , Schmidt J. 
Published: July 2010

AbstractThe resistance of an electrical joint increases depending on load current and environment until the temperature of the joint reaches a critical level, i. e. hot spots occur. To avoid such failures the joints have to be diagnosed and, if necessary, maintained. A widely applied method to inspect electrical joints is to measure the temperature rise and to compare it with empirical limit temperature rises that are assigned to several decisions. Due to unconsidered parameters this method is not sensitive enough to allow a long‐term maintenance concept. To overcome this shortcoming, the resistance of the joint has to be determined from the measured temperature. All the processes of producing, transmitting and storing power are modelled by a thermal network in which the resistance is the only unknown quantity. It can be ascertained by comparing measured and calculated temperatures. The resistance is used to determine the residual life time which depends strongly on this momentary resistance of the joint and the further load current of the line. This method will be described in a following paper.
Fault‐current limiter as an effective mean to compensate voltage dips in distribution utilities
Authors: Quaia S. , Tosato F. 
Published: July 2010

AbstractThe paper deals with the topic of utility power quality improvement by short‐circuit current limitation. A novel double‐tuned medium‐voltage (MV) fault‐current limiter (FCL), whose operation shows several interesting characteristics, is analyzed and discussed in the paper. A special property of this kind of FCL is the capability to quickly change its configuration in case of short circuit by either a back‐to‐back thyristor switch or a ZnO varistor. The latter solution is very attractive since it allows a significant simplification in the limiter hardware, that, in such a case, does not require any power electronic component. The above solutions are studied and compared, also through relevant computer simulation.
Application of static phase shifters on the damping of common‐mode torsional oscillations
Authors: Wang L. 
Published: July 2010

AbstractA study on the application of thyristor‐controlled static phase shifters (SPS) to stabilize the common‐mode torsional oscillations occurring in a series‐capacitor compensated power system is presented in this paper. The IEEE Second Benchmark Model, system‐2, which has two non‐identical turbine‐generator sets connected to an infinite bus through a series‐capacitor compensated transmission line, is employed to investigate whether the possible unstable subsynchronous resonance (SSR) modal interactions can be suppressed by the proposed damping scheme. The torsional interactions due to one of the torsional oscillating frequencies in one machine is nearly the same as the one in another machine. In order to effectively suppress the unstable torsional modes in the studied system, a systematic approach based on modal control theory is proposed and a set of static phase‐shifter controllers (SPSC) is designed. The effectiveness of the proposed damping scheme is demonstrated by means of frequency‐domain approach based on eigenvalue analyses and time‐domain approach based on non‐linear model simulations. The simulations results show that the static phase shifters and the designed controllers can be applied to suppress common‐mode torsional interactions.
Calculation of the lifetime of electrical busbar joints
Authors: Bergmann R. , Löbl H. , Bohme H. , Großmann S. 
Published: July 2010

AbstractElectrical joints can be a weak points and with it endanger the reliability of electrical power‐transmission systems. On the example of Aluminium‐to‐Aluminium and Aluminium‐to‐Copper busbar joints is shown how one can get information about the principle ageing behaviour from long‐term test. Furthermore a possibility is presented to determine limiting values for the joint resistance and to calculate the lifetime of a joint depending on the construction, conductor material and loading.
Transient behaviour of optimum‐designed three‐phase squirrel‐cage induction motors
Authors: Faiz J. , Sharifian M. B. B. 
Published: July 2010

AbstractThis paper describes the transient behaviour of optimum‐designed three‐phase squirrel‐cage induction motors. These motors have been designed based upon three different objective functions. They are cost, efficiency and combination of efficiency‐cost functions. Transient performance of these optimum designs and an industrial motor are compared and a suitable design for a particular fault is then introduced. A symmetrical voltage disturbance, startup and a symmetrical three‐phase short circuit are three cases considered in this investigation.
Development of power‐factor correction circuit using zero‐current switching cuk converter
Authors: Lin B.‐R. , Huang T.‐S. 
Published: July 2010

AbstractA new Cuk resonant high power‐factor single‐phase AC‐to‐DC converter for the power‐factor correction is proposed in this paper, which employs zero‐current switching (ZCS) technique. Merits of the proposed converter include unity power factor, less harmonic control content, zero switching loss, simpler control stage, higher power density and unidirectional power flow. Operation principle, design analysis, small‐signal models and conditions achieving zero switching loss for the proposed converter are described. Finally, some simulation and experimental results are discussed.
The behaviour of damper cages
Authors: Fritz W. , Hyrenbach M. , Schneckmann H.‐W. 
Published: July 2010

AbstractThe central point of the following treatise is the investigation of the reaction mechanism of the single bars and rings of a damper cage when it is hit by the normal component of an alternating field. The reacting field of the cage is calculated by Ampere's law. The bars and rings generate positive and negative field components which are superimposed to the total reacting field. The resulting flux in a mesh is an indicator for the damping effect. The validity of the theory will be proved by measurements at a damper model in a room with constant permeability.
Algorithms of phase and current comparison protection for transmission lines
Authors: Witek B. 
Published: July 2010

AbstractThe paper presents a concept of a high‐speed phase/current comparison protection (PCCP) based on the digital evaluation of the differences both in phase angle and instant values of the current waveforms measured at the protected line terminals. Signal processing algorithms immune to direct current and high‐frequency components, harmonics and current transformer saturation are described. The results of faults off‐line simulations for transmission system model with frequency‐dependent parameters estimated in time domain are used for the analysis of the PCCP schemes performance during in‐zone and out‐zone faults.
Thermal stressing of power semiconductors in pulse‐controlled inverters by output currents of low fundamental frequency
Authors: Gambach H. 
Published: July 2010

AbstractThe range of fluctuation of the junction temperature of power semiconductors in pulse‐controlled inverters rises constantly as the fundamental frequency of the inverter output current falls. As a result, the maximum value of the junction temperature lies with low fundamental frequencies considerably above the mean value that is decisive for high fundamental frequencies. This paper takes the example of a GTO (gate‐turn‐off) pulse‐controlled inverter to explain two processes for reducing the thermal stressing of the power semiconductors at low fundamental frequencies.
Steady‐state security prediction in presence of load uncertainty
Authors: Testa A. , Menniti D. , Picardi C. , Sorrentino N. 
Published: July 2010

AbstractAn important problem in the Electrical Power System operation is the steady‐state security prediction. In order to take into account the load uncertainty, in this paper the authors apply a Monte‐Carlo method together with an opportune Security Index to evaluate in a preventive manner the probability to fall in insecure operating state, by determining the security index probability density function. For this aim, in a previous paper proposed by the authors, it has been possible to take advantage of an Artificial Neural Network, trained to evaluate the Security Index probability density function in presence of the optimal economical dispatching of the generation powers for the load forecast. In the present paper, a more complex scenario is considered where the security analysis can suggest to the dispatcher to determine also non‐optimal economical operating conditions to improve security. So a new, more complex, organization of the Artificial Neural Network training stage, necessary in order to obtain increased generalization capacity in the production stage, has been considered. In the first part of the paper the used security index, the Monte‐Carlo simulation and the neural network structure with its learning algorithm utilized by the authors for the particular problem are briefly recalled. Finally, a numerical application on a simple electrical test system is shown pointing out very encouraging results.
About the concept of consumed life of electrical machine windings and its application
Authors: Busch R. 
Published: July 2010

AbstractIn order to economize on electrical energy and materials a higher load of electrical motors is necessary. In this way it is possible that the motors operate above their rated power. Consequently, the rated temperature of the winding is exceeded and, therefore, its lifetime is shortened. For the description of the winding aging process the consumed life is an appropriate quantity. The meaning of this quantity is explained and its application is demonstrated.
On the order reduction and stability analysis of large electric machines
Authors: Toumi A. , Kamoun M. B. A. 
Published: July 2010

AbstractThis paper deals with the model reduction of electric machines, in order to study their steady‐state stability. The modelling of these machines is described on the base of the state‐space representation. A state‐equation form has been established, which is valid for different kinds of electric machines. The reduction condition is formulated as a non‐linear Riccati equation. In a first step, this equation is resolved under the assumption of an infinite inertia. Under such condition, the popular damping and synchronizing torque approach has been expressed in terms of the reduced model parameters. In a second step, this study is generalized taking into account the inertia, by resolving iteratively the Riccati equation. Thus, the damping and synchronizing torques in terms of inertia have been established for the first time. In order to illustrate the above results, two examples concerning the synchronous and the doubly‐fed machines are treated.
An expert‐system based power‐system restoration procedure
Authors: Seifi H. , Sedighi A. 
Published: July 2010

AbstractThe expert‐system restoration procedure developed in this paper employs an algorithm in which by line switchings, the downloads are restored with regard to their priorities, while any line overloads and out‐of‐limit voltages are avoided. The solutions are presented to the user in an understandable way. Computer results on the IEEE‐14‐bus system are presented.
New approach to the calculation of electrical transients, part II: Applications
Authors: Bijl N. , Van Sluis L. Der 
Published: July 2010

AbstractThe calculation of electrical transients in power systems is important for insulation coordination. Most of the computer programs in current use are based on the nodal admittance method. This paper describes a computer program for the calculation of electrical transients based on a new approach which enables the use of more sophisticated numerical integration routines. The program can cope with linear network elements like resistors, capacitors, reactors, voltage and current sources and with non‐linear network elements like surge arresters and arc models. The descriptions of the models and their parameters are stored in libraries separate from the main program. The user can define his own models.
Electromagnetic transient simulation studies of sinusoidal PWM unified power‐flow controllers
Authors: Song Y. H. , Liu J. Y. 
Published: July 2010

AbstractThis paper is concerned with the digital studies of the sinusoidal pulse‐width modulation (SPWM) unified power‐flow controller (UPFC). At first the SPWM scheme generation and the main factors affecting the functions and the control of the UPFC are discussed. Secondly, how the series part and shunt part of the SPWM UPFC are controlled and coordinated is analyzed. The paper then places the emphasis on the detailed electromagnetic transient program (EMTP) simulation of SPWM UPFC. Simulation results of SPWM UPFC regulation performance and open‐loop control are presented. The simulator is further used to investigate the operating envelope and closed‐loop control. The digital EMTP‐based simulator of SPWM UPFC implemented in this paper provides a useful tool for further research. The information presented gives a deep insight into UPFC performance.
Currents and voltages induced during earth faults in a system consisting of a transmission line and a parellel pipeline
Authors: Satsios K. J. , Labridis D. P. , Dokopoulos P. S. 
Published: July 2010

AbstractA numerical procedure employing thefinite‐element method (FEM) is used in conjunction with Faraday's law, in order to predict the current in a faulted transmission line as well as the induced voltages across points on a pipeline running parallel to the faulted line and remote earth. The problem is a two‐dimensional one, be‐ cause the phase‐to‐ground fault is assumed to be outside of the parallel exposure so that the conductive in‐ terference is negligible. Therefore a two‐dimensional finite‐element mesh has been solved, that leads to the field distribution andfinally to the induced voltages. The effectof the problem “operational parameters” (mitigation wires numbec earth resistivity and overhead transmission line geometrical configuration) has been taken into account. The results lead to conclusions that may be useful to power‐system engineers.
Transient temperature rise of cable crossings
Authors: Brakelmann H. , Sahin M. 
Published: July 2010

AbstractThis article presents a calculation method for the transient heating of power cables in crossing configuration. By the aid of this method the current ratings can be determined taking into account the longitudinal heat flux through the metallic construction elements of the cables as well as the transient conductor temperatures for different load situations. An example will elucidate the calculation method.
Critical analysis of the concepts of instantaneous power current and of active current
Authors: Willems J. L. 
Published: July 2010

AbstractThis note deals with the relationship between various definitions of instantaneous power currents. From a general framework the m‐phase and the (m + l)‐conductor approaches are derived, as well as the case of unequal conductor resistances. The relationship between instantaneous, sinusoidal and time‐varying situations is also discussed.
Formal approach to multi‐phase systems
Authors: Furga G. Superti 
Published: July 2010

AbstractSome formal definitions and statements about multi‐phase systems, which the three‐phase systems are particular cases of, are discussed, n‐phase elements must have one or more ordered sets ofn electrical ports. Star connection and polygonal connection are special elements. General properties of decoupling linear transformations are discussed, to fully exploit the symmetrical structure of such systems.
Separate control of power‐factor components based on phase‐locked loop
Authors: Balcells J. , González D. , Lamich M. , Aldabas E. 
Published: July 2010

AbstractThe power factor (PF) of a supply system can be split up in two parts: The displacement factor, due to the quadrature component of the fundamental current and the distortion factor, mainly due to harmonics in the current wave. The separate compensation of both terms has important advantages, but the controller for such separate compensation needs powerful resources to get a suitable dynamic behaviour if a frequency‐domain approach is used. This paper describes a controller based on a new method for splitting up the current wave into its fundamental component and its harmonic residue. The method uses a time‐domain approach and simplifies the closed‐loop control of power factor while giving a suitable dynamic response.