3,693 results
Search Results
52. Novel Analytical Solution to Fundamental Ferroresonance—Part I: Power Frequency Excitation Characteristic.
- Author
-
Yunge Li, Wei Shi, and Furong Li
- Subjects
ELECTRIC inductors ,ELECTRIC inductance ,ELECTRIC currents ,ELECTRICAL engineering ,ENGINEERING - Abstract
This paper has highlighted a major problem with the traditional excitation characteristic (TEC) of nonlinear inductors, in that the TEC contains harmonic voltages and/or currents, and has been used the way as if it were made up of pure fundamental voltage and current. In comparison to the TEC, a new concept, namely the power frequency excitation characteristic (PEC), which contains no harmonics, has been put forward. Two methods have been presented in obtaining the PEC. The first method is based on Electromagentic Transients Program simulation, resulting in discrete voltage and current pairs. This method essentially acts as a reference to validate the second one. The second method em- ploys Fourier and Maclaurin series approximation techniques, and brings forth a simple yet effective analytical expression. The expression is proven to have satisfactory precision in the saturated region of the PEC, especially in the extremely saturated region. [ABSTRACT FROM AUTHOR]
- Published
- 2006
- Full Text
- View/download PDF
53. A Novel Power Quality Monitoring Allocation Algorithm.
- Author
-
Eldery, Mohamed Amin, El-Saadany, Ehab F., Salama, Magdy M. A., and Vannelli, Anthony
- Subjects
ELECTRIC power distribution ,ELECTRICAL engineering ,ELECTRIC power systems ,ENGINEERING ,ELECTRIC circuits - Abstract
Distributed measurement architecture, due to its efficiency, is used to monitor the power quality in the electric systems. This paper introduces a novel algorithm to determine the optimum allocations of power quality monitors to reduce the cost of the distributed monitoring system taking into account the data redundancy. The optimization problem is formulated as a covering and packing one which can be manipulated by integer linear programm algorithms. The appropriate constraints are deduced by the electrical circuit topology independent of the load parameters. In addition, the problem is adopted to a general form which can be implemented by any optimization package. The proposed algorithm is applied to five different systems for validation. Then, the results are discussed in terms of the cost and data redundancy. [ABSTRACT FROM AUTHOR]
- Published
- 2006
- Full Text
- View/download PDF
54. Considerations on a Reactive Power Concept in a Multiline System.
- Author
-
Seong-Jeub Jeon
- Subjects
REACTIVE power ,ALTERNATING currents ,ELECTRIC power factor ,ELECTRICAL engineering ,ENGINEERING - Abstract
The concepts of reactive power that originate from Buchholz's theory and are present in the IEEE Standard 1459 are important in compensation theory. It is shown in this paper that some misconceptions are present in the technical literature, in particular regarding the relationship between reactive power and power oscillation. In this paper, a number of examples are given to illustrate these misconceptions. [ABSTRACT FROM AUTHOR]
- Published
- 2006
- Full Text
- View/download PDF
55. An Algorithm for Determining the Direction to a Flicker Source.
- Author
-
Axelberg, Peter G. V. and Bollen, Math H. J.
- Subjects
ELECTRIC currents ,ELECTRIC current regulators ,BANDPASS filters ,ELECTRIC filters ,ELECTRICAL engineering ,ENGINEERING - Abstract
This paper describes an algorithm for calculating the direction to a flicker source with respect to a monitoring point. The proposed algorithm is based on sampling of both the voltage and current. The low-frequency fluctuations in voltage and current are recovered from the input signals by demodulation, and passed through a bandpass filter as described in IEC 61000-4-15. A new quantity—flicker power—defined from the output signals of the two filters. The direction to a flicker source is obtained from the sign of this flicker power. The proposed algorithm has been validated by simulations and several field measurements. [ABSTRACT FROM AUTHOR]
- Published
- 2006
- Full Text
- View/download PDF
56. Voltage Regulation With STATCOMs: Modeling, Control and Results.
- Author
-
Jain, Amit, Joshi, Karan, Behal, Aman, and Mohan, Ned
- Subjects
VOLTAGE regulators ,ELECTRIC controllers ,REACTIVE power ,ENGINEERING ,ELECTRICAL engineering - Abstract
This paper presents system modeling and control design for fast load voltage regulation using static compensators (STATCOMs). The modeling strategy gives a clear representation of load voltage magnitude and STATCOM reactive current on an instantaneous basis. The particular coordinate transformation employed here also facilitates extraction of linearized system dynamics in conjunction with circuit simulators. It is rigorously shown that the control problem of load voltage regulation using reactive current is nonminimum phase. Linear and nonlinear controllers for the regulation problem are designed and compared via simulation results. Internal dynamics of the STATCOM are modeled using the same strategy. Lyapunov based adaptive controllers are designed for controlling the STATCOM reactive current while maintaining its dc bus voltage. Simulation results of the controlled STATCOM integrated with the load bus voltage controller are presented to show efficacy of the modeling and control design. [ABSTRACT FROM AUTHOR]
- Published
- 2006
- Full Text
- View/download PDF
57. Detailed Modeling of Superconducting Magnetic Energy Storage (SMES) System.
- Author
-
Chen, L., Liu, L., Arsoy, A. B., Ribeiro, P. F., Steurer, M., and Iravani, M. R.
- Subjects
MAGNETIC energy storage ,ELECTRIC power ,ENERGY storage ,ENGINEERING ,ELECTRICAL engineering - Abstract
This paper presents a detailed model for simulation of a Superconducting Magnetic Energy Storage (SMES) system. SMES technology has the potential to bring real power storage characteristic to the utility transmission and distribution systems. The principle of SMES system operation is reviewed in this paper. To understand transient and dynamic performance of a SMES system, a detailed SMES system benchmark model is given with extensive simulation results. This system is demonstrated using an electromagnetic transient program—PSCAD/EMTDC. [ABSTRACT FROM AUTHOR]
- Published
- 2006
- Full Text
- View/download PDF
58. Probabilistic Assessment of Equipment Trips due to Voltage Sags.
- Author
-
Gupta, C. P. and Milanović, Jovica V.
- Subjects
ELECTRIC power ,ELECTRIC potential ,INDUSTRIAL equipment ,ENGINEERING ,ELECTRICAL engineering - Abstract
This paper discusses the uncertainty involved in the behavior of sensitive equipment used in various industrial processes and the methodology to incorporate this effect in quantifying the equipment trips due to voltage sags over a specified time period. The exact and more precise counting of equipment trips is essential for the accurate economic assessment of power quality. Existing standards and previously published test results on the sensitivity of this equipment against voltage sags are critically reviewed and possible ranges for variation in equipment sensitivity are investigated. Four different probable behaviors within respective ranges were considered for the stochastic assessment of equipment trips due to voltage sags. This study is performed on a generic power system. [ABSTRACT FROM AUTHOR]
- Published
- 2006
- Full Text
- View/download PDF
59. Measurement of Three-Phase Transformer Derating and Reactive Power Demand under Nonlinear Loading Conditions.
- Author
-
Fuchs, Ewald F., Dingsheng Lin, and Martynaitis, Jonas
- Subjects
ELECTRIC instrument transformers ,ELECTRIC transformers ,REACTIVE power ,ENGINEERING ,ELECTRICAL engineering - Abstract
The measurement of real and apparent power derating of three-phase transformers is important for transformers feeding nonlinear loads. This paper presents a new digital data-acquisition method for measuring derating and reactive power demand of three-phase transformers under full or partial load conditions. The accuracy requirements of the instruments employed (potential, current transformers, shunts, voltage dividers, optocoupIers volt- and current meters) are addressed. Application examples demonstrate the usefulness of this new digital data-acquisition method. [ABSTRACT FROM AUTHOR]
- Published
- 2006
- Full Text
- View/download PDF
60. A DC Hybrid Circuit Breaker With Ultra-Fast Contact Opening and Integrated Gate-Commutated Thyristors (IGCTs).
- Author
-
Meyer, Jean-Marc and Rufer, Alfred
- Subjects
ELECTRIC circuits ,ENGINEERING ,ELECTRIC filters ,ELECTRICAL engineering ,THYRISTORS - Abstract
Air-magnetic circuit breakers are widely used for short-circuit protection in dc electric railways or industrial plants. The well-known drawbacks of these breakers are mainly a slow breaking action, a short lifetime, and high maintenance costs due to the destructive effects of the arc. The use of power semi-conductors in a full-static circuit breaker configuration allows the elimination of these disadvantages but is limited by excessive conduction losses. The paper will present the study of a so-called hybrid breaker, drawing its name from the combination of a high-speed mechanical switch and a bi-directional integrated gate-controlled thyristor assembly connected in parallel. The paper also includes experimental results from a prototype real scale. [ABSTRACT FROM AUTHOR]
- Published
- 2006
- Full Text
- View/download PDF
61. Application of Combined Adaptive Fourier Filtering Technique and Fault Detector to Fast Distance Protection.
- Author
-
Ching-Shan Chen, Chih-Wen Liu, and Joe-Air Jiang
- Subjects
FOURIER series ,POWER transmission ,ADAPTIVE filters ,ELECTRIC filters ,ELECTRICAL engineering ,ENGINEERING - Abstract
This paper presents the application of a combined adaptive Fourier filtering technique and fault detector to fast distance protection of transmission lines. The filtering technique is extended from the Fourier filters and can be applied under arbitrary data window length. The proposed filtering technique possesses the advantage of recursive computing, and a decaying dc offset component is removed from fault signals by using an adaptive compensation method. A variable data window scheme is embedded in the technique to adaptively speed up its transient response under various system and fault conditions. A fault detector is developed to initiate the process of the technique. For the sake of speed and security, two phasor estimation methods based on the proposed technique are designed to achieve fast distance protection. An algorithm consisting of the two methods is used to detect internal faults by "OR" logic. Extensive simulation studies show that the algorithm significantly reduces tripping time of a distance relay and provides better protection performance than that of the conventional filters with fixed data windows. [ABSTRACT FROM AUTHOR]
- Published
- 2006
- Full Text
- View/download PDF
62. Agent-Based Self-Healing Protection System.
- Author
-
Su Sheng, Li, K. K., Chan, W. L., Zeng Xiangjun, and Duan Xianzhong
- Subjects
POWER resources ,ELECTRONIC equipment ,ELECTRIC relays ,PROTECTIVE relays ,RELAY control systems ,ELECTRICAL engineering ,ENGINEERING - Abstract
This paper proposes an agent-based paradigm for self-healing protection systems. Numerical relays implemented with intelligent electronic devices are designed as a relay agent to perform a protective relaying function in cooperation with other relay agents. A graph-theory-based expert system, which can be integrated with supervisory control and a data acquisition system, has been developed to divide the power grid into primary and backup protection zones online and all relay agents are assigned to specific zones according to system topological configuration. In order to facilitate a more robust, less vulnerable protection system, predictive and corrective self-healing strategies are implemented as guideline regulations of the relay agent, and the relay agents within the same protection zone communicate and cooperate to detect, locate, and trip fault precisely with primary and backup protection. Performance of the proposed protection system has been simulated with cascading fault, failures in communication and protection units, and compared with a coordinated directional overcurrent protection system. [ABSTRACT FROM AUTHOR]
- Published
- 2006
- Full Text
- View/download PDF
63. Wide Area Protection—Technology and Infrastructures.
- Author
-
Adamiak, M. G., Apostolov, A. P., Begovic, M. M., Henville, C. F., Martin, K. E., Michel, G. L., Phadke, A. G., and Thorp, J. S.
- Subjects
ELECTRIC power ,ENERGY management ,ELECTRIC relays ,ELECTRICAL engineering ,ENGINEERING - Abstract
Wide area measurements have been widely used in the energy management systems (EMS) of power systems for monitoring, operation, and control. In recent years, the advent of synchronized phasor measurements has added another dimension to the field of wide-area measurements. At the same time, the field of protection systems has been dominated by computer based relays, which make it relatively easy to communicate with relays and thus include them in many innovative protection systems. Special Protection Systems (SPS) or Remedial Action Schemes (RAS) are one example of integration of communication and protection systems. In recent years-due to operational demands imposed on transmission networks by deregulation it has become clearer that wide-area measurements and their integration in protection and control systems is a necessity. This paper documents the state-of-the-art in modem sensor, communication, and protection technologies which show great potential for innovations in protection and control systems for the future. [ABSTRACT FROM AUTHOR]
- Published
- 2006
- Full Text
- View/download PDF
64. Selection of Station Insulators With Respect to Ice and Snow--Part II: Methods of Selection. and Options for Mitigation.
- Author
-
Farzaneh, M., Baker, T., Bernstorf, A., Burnham, J. T., Carreira, T., Cherney, E., Chisholm, W. A., Christman, R., Cole, R., Cortinas, J., de Tourreil, C., Drapeau, J. F., Farzaneh-Dehkordi, J., Fikke, S., Gorur, R., Grisham, T., Gutman, I., Kuffel, J., Phillips, A., and Powell, G.
- Subjects
RELIABILITY in engineering ,ELECTRIC fields ,ELECTROMAGNETIC fields ,ELECTROKINETICS ,ENGINEERING ,PROBABILITY theory - Abstract
In locations exposed to freezing conditions over the station service life, additional measures for selecting adequate station insulators at distribution and transmission voltage levels should be taken. This second part of the paper describes the selection process and mitigation options, based on the environmental parameters, as discussed in Part I. These include insulator size, shape, surface material, surface quality, electric field improvement, and orientation. [ABSTRACT FROM AUTHOR]
- Published
- 2005
- Full Text
- View/download PDF
65. Solution to Close-in Fault Problem in Directional Relaying.
- Author
-
Pradhan, A. K. and Jena, P.
- Subjects
ELECTRIC currents ,COMPUTER-aided design ,ELECTRIC transients ,ELECTRIC power factor ,ELECTRIC power distribution ,ELECTRIC power systems ,ELECTRIFICATION ,ELECTRICAL engineering ,ENGINEERING ,ELECTRICITY - Abstract
Directional relays use voltage as the polarizing quantity. When three-phase faults occur close to the relay bus, the available voltage becomes nearly zero and this creates a problem in estimation of the fault direction. The capacitor coupling voltage transformer subsidence transients add to this problem. The memory voltage used as the polarizing quantity at these situations is a compromise. This paper highlights these issues and proposes a simple solution using the power-flow direction in addition to other information. The performance of the technique is evaluated through simulation in Power System Computer Aided Design. [ABSTRACT FROM AUTHOR]
- Published
- 2008
- Full Text
- View/download PDF
66. Cables in Backfills and Duct Banks – Neher/McGrath Revisited
- Author
-
Leon Ramirez and George J. Anders
- Subjects
Engineering ,business.industry ,Thermal resistance ,Energy Engineering and Power Technology ,Duct (flow) ,Structural engineering ,Electrical and Electronic Engineering ,Iec standards ,business - Abstract
The Neher/McGrath paper and the IEC Standard 60287-2-1 contain the formulae for the calculation of the external thermal resistance of cables installed in backfills or duct banks. These models are based on several assumptions, which often are not valid for practical installations. This paper examines the applicability of the Neher/McGrath model and proposes a new solution for the calculation of the external thermal resistance for such installations. Numerical examples illustrate the difference between the two methods.
- Published
- 2021
67. Accuracy of Transmission Line Modeling Based on Aerial LiDAR Survey.
- Author
-
Lu, M. L. and Kieloch, Z.
- Subjects
ELECTRIC lines ,ELECTRIC power distribution ,ELECTRIC power factor ,ELECTRIC controllers ,ELECTROMAGNETIC interference ,ELECTRIC power systems ,ELECTRIFICATION ,ELECTRICAL engineering ,ENGINEERING ,ELECTRICITY - Abstract
Aerial LiDAR survey is receiving wide application in transmission-line modeling due to its efficiency. The technique is particularly useful for modeling of existing lines for the purpose of thermal rating, upgrading, or vegetation management. An accurate modeling of an existing line depends largely on proper determination of the base conductor temperature, i.e. the conductor temperature at the time of the aerial light detection and ranging (LiDAR) survey. In this paper, an acceptable accuracy for the base conductor temperature is first established. Extensive parametric studies are then conducted to reveal the effects of all the potentially major factors: ambient air temperature, electrical load, solar radiation, wind, and conductor size on the base conductor temperature. As a result, recommendations are made on the proper practice of performing an aerial LiDAR survey and determining the base conductor temperature so that the resulting transmission line modeling is within an acceptable accuracy. It is demonstrated that a wide error can easily be introduced without following a proper procedure for the LiDAR survey. [ABSTRACT FROM AUTHOR]
- Published
- 2008
- Full Text
- View/download PDF
68. Summary of Distributed Resources Impact on Power Delivery Systems.
- Author
-
Walling, R. A., Saint, Robert, Dugan, Roger C., Burke, Jim, and Kojovic, Ljubomir A.
- Subjects
ELECTRIC controllers ,ELECTROMAGNETIC compatibility ,ELECTROMAGNETIC interference ,ELECTRIC power distribution ,ELECTRIC power systems ,ELECTRIFICATION ,ELECTRICAL engineering ,ENGINEERING ,ELECTRICITY - Abstract
Because traditional electric power distribution systems have been designed assuming the primary substation is the sole source of power and short-circuit capacity, DR interconnection results in operating situations that do not occur in a conventional system. This paper discusses several system issues which may be encountered as DR penetrates into distribution systems. The voltage issues covered are the DR impact on system voltage, interaction of DR and capacitor operations, and interaction of DR and voltage regulator and LTC operations. Protection issues include fuse coordination, feeding faults after utility protection opens, impact of DR on interrupting rating of devices, faults on adjacent feeders, fault detection, ground source impacts, single phase interruption on three phase line, recloser coordination and conductor burndown. Loss of power grid is also discussed, including vulnerability and overvoltages due to islanding and coordination with reclosing. Also covered separately are system restoration and network issues. [ABSTRACT FROM AUTHOR]
- Published
- 2008
- Full Text
- View/download PDF
69. A Method for Placement of DG Units in Distribution Networks.
- Author
-
Hedayati, Hasan, Nabaviniaki, S. A., and Akbarimajd, Adel
- Subjects
ELECTRIC power transmission ,ELECTRIC network analyzers ,ELECTRIC power ,POWER transmission ,ELECTRIC power distribution ,ELECTRIC power systems ,ELECTRIFICATION ,ELECTRICAL engineering ,ENGINEERING ,ELECTRICITY - Abstract
In this paper, a method for placement of distributed generation (DG) units in distribution networks has been presented. This method is based on the analysis of power flow continuation and determination of most sensitive buses to voltage collapse. This method is executed on a typical 34-bus test system and yields efficiency in improvement of voltage profile and reduction of power losses; it also may permit an increase in power transfer capacity, maximum loading, and voltage stability margin. [ABSTRACT FROM AUTHOR]
- Published
- 2008
- Full Text
- View/download PDF
70. A Novel Control Strategy for Subsynchronous Resonance Mitigation Using SSSC.
- Author
-
Bongiorno, Massimo, Angquist, Lennart, and Svensson, Jan
- Subjects
SUBSYNCHRONOUS resonance ,ELECTRICAL engineering ,SYNCHRONOUS capacitors ,ELECTRIC currents ,TURBINE generators ,SHAFTING machinery ,TORSION ,TORQUE ,ENGINEERING - Abstract
In this paper, a novel control strategy for subsynchronous resonance (SSR) mitigation using a static synchronous series compensator will be presented. SSR mitigation is obtained by increasing the network damping only at those frequencies that are critical for the turbine-generator shaft. This is achieved by controlling the subsynchronous component of the grid current to zero. Using the IEEE First Benchmark Model, the effectiveness of the proposed control algorithm when mitigating SSR due to torsional interaction and torque amplification effect will be shown. [ABSTRACT FROM AUTHOR]
- Published
- 2008
- Full Text
- View/download PDF
71. The Design of Battery Energy Storage System in a Unified Power-Flow Control Scheme.
- Author
-
Wang, Q. and Choi, S. S.
- Subjects
STORAGE batteries ,ENERGY storage ,ELECTRIC power supplies to apparatus ,POWER transmission ,POWER (Mechanics) ,ELECTRIC discharges ,ENGINEERING - Abstract
The role of a battery energy storage system in a unified power-flow control scheme is examined. Analysis shows that the capability of the storage system to support power transmission is governed by the state of discharge (SOD) of the battery. A changeover to a standby battery is necessary once the inservice battery SOD exceeds the level determined from the analytical method described in this paper. The method also permits, the battery changeover schedule to be evaluated for a given load demand profile. Furthermore, the capacity of the battery system is determined such that the resulting system operates under an optimal economic dispatch condition, while the transfer capability of the compensated transmission is maximized. [ABSTRACT FROM AUTHOR]
- Published
- 2008
- Full Text
- View/download PDF
72. The Role Played by Current Phase Shift on Magnetic Field Established by Double-Circuit Overhead Transmission Lines—Part II: Dynamic Analysis.
- Author
-
Mazzanti, Giovanni
- Subjects
MAGNETIC fields ,POWER transmission ,ELECTRICAL engineering ,ELECTRIC power ,ENGINEERING - Abstract
The "static" analysis (relevant to fixed load conditions) of current phase-shift effects on the magnetic field from ac double-circuit overhead transmission lines (Part I of this paper) becomes "dynamic" here by considering time-varying load conditions of an existing line, derived from a database recorded from 1994 to 2001, thereby showing that current phase shift plays a major role also when load changes. Indeed, often extreme field values over a time period are not associated with extreme current values, but with current phase shifts that, for given line geometry and conductor arrangement, yield the most effective field enhancement/reduction. An estimate of the mean/median phase-shift angle over a reference period is proposed that provides a good approximation, via one single static calculation, of the mean/median magnetic-field profiles calculated over that period (e.g., one year). It is confirmed that current phase shifts are fundamental for understanding the behavior of magnetic fields from ac double-circuit overhead transmission lines. [ABSTRACT FROM AUTHOR]
- Published
- 2006
- Full Text
- View/download PDF
73. Voltage Harmonic Reduction for Randomly Time-Varying Source Characteristics and Voltage Harmonics.
- Author
-
Zobaa, Ahmed Faheem
- Subjects
ELECTRIC power systems ,ELECTRIC currents ,ELECTRIC power distribution ,ELECTRIC power ,ELECTRICAL engineering ,ENGINEERING - Abstract
Potential applications of probabilistic modeling of current and voltage harmonics concern many aspects of power system engineering as accurate prediction of power system harmonic behavior provides important information to utility companies and equipment designers. In this paper, a method of reducing the expected value of the total voltage harmonic distortion for a specified range of source impedance values at different buses by using LC compensators, where it is desired to maintain a given power factor at a specified value, is presented. The criterion is based on mean value estimation of source and load characteristics, which are enabled by sampling measurements performed on the examined electrical plant as well as statistical analysis. [ABSTRACT FROM AUTHOR]
- Published
- 2006
- Full Text
- View/download PDF
74. Analysis of Ferroresonant Overvoltages at Maanshan Nuclear Power Station in Taiwan.
- Author
-
Ta-Peng Tsao and Chia-Ching Ning
- Subjects
NUCLEAR power plants ,ELECTRICAL engineering ,ELECTRIC power ,ENGINEERING - Abstract
The "318 Blackout Incident" at the Maanshan Nuclear Power Station on March 18, 2001, is considered to be the most serious event over the 24-year history of nuclear power generation in Taiwan. This paper simulates a special overvoltage phenomenon that occurred 4 h before the blackout event, which could have caused the incident. The simulation results almost coincide closely with the actual conditions recorded. We found two major low-frequency and ferroresonant overvoltages caused by the motors which acted as generators when they lost power supply, interacting with power-line capacitance and power transformers. Since overvoltages were present for a short period, the breaker insulation did not break down immediately but the defects were accumulated. A blackout eventually occurred 4 h later, when the power supplied to the 4.16-kV essential bus A changed over from the 161-kV system to the 345-kV system, due to damage in the incoming breaker insulation. [ABSTRACT FROM AUTHOR]
- Published
- 2006
- Full Text
- View/download PDF
75. Optimal Integration of an Offshore Wind Farm to a Weak AC Grid.
- Author
-
Koutiva, X. I., Vrionis, T. D., Vovos, Nicholas A., and Giannakopoulos, Gabriel B.
- Subjects
ELECTRIC currents ,VOLTAGE to frequency converters ,WIND power ,ELECTRICAL engineering ,ENGINEERING - Abstract
This paper studies the behavior of a high-voltage direct current link based on voltage-source converters, which feeds a weak ac network with power produced from an offshore wind farm (WF) of induction generators. Its control system, which is based on adaptive fuzzy controllers, manages to offer very satisfactory performance, without the need for a detailed mathematical model, but just prior knowledge of the behavior of the electrical system. Using the simulation program PSCADIEMTDC, the study was performed under both steady-state and transient conditions. The results show that the link supplies the variable power of the WF to a weak grid, keeping the ac voltage fluctuations in the point of common coupling at an acceptable level. Moreover, due to the ability of the control system to adjust the stator frequency of the induction generators in relation to the wind velocity, maximum wind power acquisition is achieved. [ABSTRACT FROM AUTHOR]
- Published
- 2006
- Full Text
- View/download PDF
76. On the Study of Losses in Cables and Transformers in Nonsinusoidal Conditions.
- Author
-
Lessa Tofoli, Fernando, Rivera Sanhueza, Sergio Manuel, and De Oliveira, Aloísio
- Subjects
ELECTRIC transformers ,ELECTRIC currents ,ELECTRICAL engineering ,ELECTRIC power ,ENGINEERING - Abstract
This paper presents a study on losses in cables and transformers considering nonsinusoidal conditions in commercial facilities. A mathematical development based on classical definitions available in the literature supports the proposal of a factor that is suitable to indicate where losses are significant and must be compensated. A case study is also presented and meticulously analyzed in order to validate the theoretical assumptions. [ABSTRACT FROM AUTHOR]
- Published
- 2006
- Full Text
- View/download PDF
77. Compensation of Particle Accelerator Load Using Converter-Controlled Pulse Compensator.
- Author
-
Jovcic, Dragan and Kahle, Karsten
- Subjects
VOLTAGE regulators ,CASCADE converters ,REACTIVE power ,ELECTRICAL engineering ,ENGINEERING - Abstract
This paper studies the use of a voltage-source converter (VSC) with dc capacitors as an energy storage medium for the compensation of pulsating active and reactive power of the European Organization for Nuclear Research's (CERN's) proton synchrotron (PS) particle accelerator. The PS accelerator load demands periodic, active, and reactive power pulses of about 2-s duration and a magnitude of up to 45 MW and 65 Mvar. The proposed compensator is able to control both reactive and active power exchange with the network in order to eliminate network disturbances. The controllability study reveals that the best control strategy is to use a q-axis converter input for active power and a d-axis input for reactive power regulation. An analytical system model is created to study the system dynamics and to aid the controller design. The eigenvalue study with the MATLAB model reveals that with large energy storage units and small converter losses, there is only a small interaction between the control channels. The final testing is done with a detailed nonlinear model in PSCAD/EMTDC. The simulation results show that it is possible to fully compensate the active power exchange with the network during typical accelerator cycles and, at the same time, to achieve excellent ac voltage control. [ABSTRACT FROM AUTHOR]
- Published
- 2006
- Full Text
- View/download PDF
78. Power-Quality Event Analysis Using Higher Order Cumulants and Quadratic Classifiers.
- Author
-
Gerek, Ömer Nezih and Ece, Dogan Gökhan
- Subjects
ELECTRIC power systems ,ELECTRICAL engineering ,ELECTRIC power distribution ,MAXIMA & minima ,ENGINEERING - Abstract
In this paper, we present a novel power-quality (PQ) event detection and classification method using higher order cumulants as the feature parameter, and quadratic classifiers as the classification method. We have observed that local higher order statistical parameters that are estimated from short segments of 50-Hz notch-filtered voltage waveform data carry discriminative features for PQ events analyzed herein. A vector with six parameters consisting of local minimas and maximas of higher order central cumulants starting from the second (variance) up to the fourth cumulant is used as the feature vector. Local vector magnitudes and simple thresholding provide an immediate event detection criterion. After the detection of a PQ event, local maxima and minima of the cumulants around the event instant are used for the event-type classification. We have observed that the minima and maxima for each statistical order produces clusters in the feature Space. These clusters were observed to exhibit noncircular topology; hence, quadratic-type classifiers that require the Mahalanobis distance metric are proposed. The events investigated and presented are line-to-ground arcing faults and voltage sags due to the induction motor starting. Detection and classification results obtained from an experimentally staged PQ event data set are presented. [ABSTRACT FROM AUTHOR]
- Published
- 2006
- Full Text
- View/download PDF
79. Small-Signal Dynamic Model and Analysis of a Fixed-Speed Wind Farm—A Frequency Response Approach.
- Author
-
Tabesh, Ahmadreza and Iravani, Reza
- Subjects
ELECTRIC power distribution ,ELECTRICAL engineering ,ELECTRIC power systems ,ENGINEERING ,WIND power - Abstract
This paper introduces a small-signal dynamic model of a fixed-frequency (induction machine based) wind farm connected to an electrical power system. The model represents the system small-signal dynamics in the frequency range of a fraction of Hz to 50/60 Hz. The model includes the dynamics of the wind energy capturing mechanism, the rotating shaft system, the generator electrical system of each wind energy unit, the wind farm collector system, and the utility grid. Based on the proposed model, two performance indices are introduced to i) investigate sensitivity of the system modes, e.g., torsional modes, to the system parameters, and ii) evaluate the system capability to reject electrical and mechanical disturbances, e.g., a wind gust. The application of the model to the analysis of a system with two wind units is presented and the study results are validated based on comparison with the time-domain simulation results obtained in the PSCAD/EMTDC environment. [ABSTRACT FROM AUTHOR]
- Published
- 2006
- Full Text
- View/download PDF
80. Dynamic Model of a Matrix Converter for Controller Design and System Studies.
- Author
-
Nikkhajoei, Hassan, Tabesh, Ahmadreza, and Iravani, Reza
- Subjects
ELECTRIC power distribution ,ELECTRICAL engineering ,ELECTRIC power systems ,CASCADE converters ,ENGINEERING - Abstract
This paper presents a systematic approach to develop a dynamic model for a matrix converter. The matrix converter interfaces two three-phase ac systems that can be at different voltages and/or frequencies, e.g., a high-speed micro-turbine generator and a utility distribution system. The model is developed by (i) transferring the abc frame equations to a newly defined switching reference frame and then (ii) transferring the resultant equations to a rotating dqo frame. The model is then linearized and the concept of "sequential loop closing" is used to design a controller for the matrix converter as a multi-input multi-output system. The accuracy of the developed model and performance of the controller are evaluated based on comparing the study results with those obtained from digital time-domain simulations in the PSCAD/EMTDC software environment. [ABSTRACT FROM AUTHOR]
- Published
- 2006
- Full Text
- View/download PDF
81. A Hybrid Tool for Detection of Incipient Faults in Transformers Based on the Dissolved Gas Analysis of Insulating Oil.
- Author
-
Morais, Diego Roberto and Rolim, Jacqueline Gisèle
- Subjects
ELECTRIC instrument transformers ,ELECTRIC transformers ,ENGINEERING ,ELECTRICAL engineering ,ARTIFICIAL neural networks - Abstract
This paper describes the development and implementation of a tool for the diagnosis of faults in power transformers through the analysis of dissolved gases in oil. The computational system approach is based on the combined use of some traditional criteria of the dissolved gas analysis published in standards, an artificial neural network, and a fuzzy logic system. The objective of the tool is to provide the user with an answer obtained from analysis not only of the traditional methods already consolidated in the technical literature, but also via artificial-intelligence techniques, reaching a higher degree of reliability with respect to each technique individually. The results obtained with this tool are promising in the diagnosis of incipient faults in transformers, reaching success levels of more than 80%. [ABSTRACT FROM AUTHOR]
- Published
- 2006
- Full Text
- View/download PDF
82. Historical Review of High Voltage Switchgear Developments in the 20th Century for Power Transmission and Distribution System in Japan.
- Author
-
Yanabu, S., Zaima, Eiichi, and Hasegawa, Taizo
- Subjects
POWER transmission ,ELECTRONIC equipment ,ELECTRIC circuits ,ENGINEERING ,ELECTRICAL engineering - Abstract
In Japan during the 20th century, developments of high voltage transmission and distribution apparatus advanced tremendously and circuit breakers were the center of these developments. And as a result, 1100 kV SF6 gas insulated switchgear (GIS) for ac transmission systems and also 500 kV dc GIS for dc transmission systems have become available. Vacuum circuit breakers (VCBs) have also been actively developed and a 168 kV two break VCB and 100 kA VCB are already available. This paper describes these developments and future trends in technology. [ABSTRACT FROM AUTHOR]
- Published
- 2006
- Full Text
- View/download PDF
83. A Hybrid Drive Merging a Servo-Controlled Motor and a Spring Mechanism.
- Author
-
Dupraz, Jean Pierre, Lüescher, Robert, and Montillet, Georges F.
- Subjects
ELECTRIC circuits ,ENGINEERING ,ELECTRIC power failures ,ELECTRIC filters ,ELECTRICAL engineering - Abstract
Spring mechanisms have demonstrated their high reliable performance by operating thousands of circuit breakers (CBs) safely all over the world for decades under the most severe conditions. This well-known technology could be improved, when merged with a servo motor system. The result is a hybrid drive, which offers the accuracy and flexibility of servomechanisms and the reliability of spring operating mechanisms. The paper starts with a reminder of the state of the art of operating mechanisms, followed by an overview of spring mechanisms with the aim of identifying potential improvements. The remaining part is dedicated to the first evolution of the hybrid drive. The architectural description emphasizes the reliability aspects, especially due to the application of redundant tripping circuits, allowing the tripping operation without either an auxiliary power supply or electronic support. Test results are discussed. The conclusion illustrates that if technical benefits are obtained, the cost of some critical components still remains high. The applications of such a hybrid technology are restricted today to specific applications. As the prices of electronic systems decrease with time and, hopefully, the cost of low inertia motors, the architecture of operating mechanisms could be dramatically modified and tightly merged with the CB. The advantages of hybrid drives could be decisive for the long-term future. [ABSTRACT FROM AUTHOR]
- Published
- 2006
- Full Text
- View/download PDF
84. Bayesian Networks-Based Approach for Power Systems Fault Diagnosis.
- Author
-
Zhu Yongli, Huo Limin, and Lu Jinling
- Subjects
POWER transmission ,ELECTRIC fault location ,ELECTRICAL engineering ,ENGINEERING ,ELECTRIC power failures - Abstract
In this paper, three element-oriented models based on simplified Bayesian networks with Noisy-Or and Noisy-And nodes are proposed to estimate the faulty section of a transmission power system. The three models are used to test if any transmission line, transformer, or busbar within a blackout area is faulty. They can deal with uncertain or incomplete data and knowledge relating to power system diagnosis, so they are flexible. The structures and initial parameters of the Bayesian networks depend on the prior knowledge of the domain experts. The parameters can be revised by using an error back propagation algorithm similar to the back- propagation algorithm for artificial neural networks. The fault diagnosis models do not vary with the change of the network structure, so they can be applied to any transmission power system. Furthermore, they have clear semantics, rapid reasoning, powerful error tolerance ability, and no convergence problem during the diagnosing procedure. Experimental tests show that the approach is feasible and efficient, so the prototype program based on the approach is promising to be used in a large transmission power system for online fault diagnosis. [ABSTRACT FROM AUTHOR]
- Published
- 2006
- Full Text
- View/download PDF
85. Accurate Location of Faults on Power Transmission Lines With Use of Two-End Unsynchronized Measurements.
- Author
-
Izykowski, Jan, Molag, Rafal, Rosolowski, Eugeniusz, and Saha, Murari Mohan
- Subjects
POWER transmission ,ELECTRIC fault location ,ELECTRIC circuits ,ELECTRICAL engineering ,ENGINEERING - Abstract
This paper presents a new algorithm for locating faults on two-terminal power transmission lines. Unsynchronized two-end voltages and currents are processed for determining the sought distance to fault and the synchronization angle. The calculations are performed initially for the lumped model of a transmission line. Then, these results are used as the initial data for the Newton-Raphson method-based iterative calculations, in which the distributed parameter line model is utilized. The delivered fault location algorithm has been tested and evaluated with the fault data obtained from versatile ATP-EMTP simulations. The sample results of the evaluation are reported and discussed. [ABSTRACT FROM AUTHOR]
- Published
- 2006
- Full Text
- View/download PDF
86. Voltage Distribution Analysis of 500-kV DC Transmission-Line Voltage Divider Under Impulse Voltages: Stray Parameter Extraction.
- Author
-
Jinliang He, Shanqiang Gu, Shejiao Han, Shuiming Chen, and Guozheng Xu
- Subjects
ELECTRIC equipment ,ELECTRIC inductance ,ELECTRIC inductors ,ELECTRICAL engineering ,ENGINEERING - Abstract
It is essential to extract the stray parameters accurately and efficiently in analyzing impulse responses of a power apparatus. In this paper the stray capacitances and stray inductances of a 500-kV dc transmission-line voltage divider are extracted by the hybrid finite element-analytical approach, and the corresponding equivalent circuit for analyzing the impulse voltage response of the voltage divider is established. According to the discussion of the results of the extracted stray parameters of the voltage divider, reasonable simplification of the equivalent circuit of the voltage divider is made. In addition, the influence of the insulating housing and the electrical insulation oil on the stray capacitances of the voltage divider is discussed. [ABSTRACT FROM AUTHOR]
- Published
- 2006
- Full Text
- View/download PDF
87. Extension of Dynamic Model of Impulse Behavior of Concentrated Grounds at High Currents.
- Author
-
Wang, Junping, Liew, Ah Choy, and Darveniza, Mat
- Subjects
ELECTRIC currents ,SOIL science ,CRITICAL currents ,STRAY currents ,EARTH sciences ,ENGINEERING - Abstract
A dynamic model which describes the impulse behavior of concentrated grounds at high currents is described in this paper. This model is an extension of previous models in that it can successfully account for the surge behavior of concentrated grounds over a much wider range of current densities. It is able to describe the well known effect of ionization of soil as well as the observed effect of discrete breakdowns and filamentary arc paths at much higher currents. Results of verification against experimental results are also presented. [ABSTRACT FROM AUTHOR]
- Published
- 2005
- Full Text
- View/download PDF
88. Modulated Model Predictive Control of Modular Multilevel Converters in VSC-HVDC Systems
- Author
-
Reza Ahmadi, Hamid Mahmoudi, and Mohsen Aleenejad
- Subjects
Engineering ,business.industry ,020209 energy ,020208 electrical & electronic engineering ,Energy Engineering and Power Technology ,02 engineering and technology ,Converters ,Modular design ,Grid ,law.invention ,Nonlinear system ,Capacitor ,Model predictive control ,Control theory ,law ,0202 electrical engineering, electronic engineering, information engineering ,Electronic engineering ,Voltage source ,Electrical and Electronic Engineering ,business ,Voltage - Abstract
This paper proposes a new modulated model predictive control method for the control of modular multilevel converters (MMCs) in voltage source converter-high voltage dc systems. The proposed method retains the advantages of the conventional finite control set-model predictive control methods by programing the nonlinear properties of the MMC into the design calculations while minimizing the ac line and circulating current ripples and steady-state error by generating modulated switching signals with a fixed switching frequency. In this paper, first, the predictive modeling of the MMC is provided. Next, the proposed control method is described. Then, the application of the proposed method to an MMC system is detailed. Finally, experimental results from an MMC system connected to a three-phase grid are provided to validate the theoretical outcomes.
- Published
- 2018
89. Modeling of Reaction Forces in High-Voltage Substation Structures
- Author
-
Ian C. Hodgson, Lukas Graber, E. Tahmasebi, S. Sagareli, Richard Sause, L. Villani, Michael Steurer, D. Birrell, M. Bosworth, A. Zorn, and M. Hughes
- Subjects
Engineering ,business.industry ,020209 energy ,Energy Engineering and Power Technology ,Mechanical engineering ,High voltage ,Control engineering ,02 engineering and technology ,Calculation technique ,Fault (power engineering) ,Finite element method ,Time history ,0202 electrical engineering, electronic engineering, information engineering ,Electrical and Electronic Engineering ,business ,Electrical conductor ,Open air - Abstract
When designing utility substations, it is necessary to consider all directional components of the electromagnetic reaction forces during short-circuit faults to properly account for their effects on substation equipment. IEEE 605 assumes straight long parallel conductors in its two-dimensional (2-D) force calculations while ignoring any bends and 3-D placement of conductors. CIGRE's Brochure 105 provides practical information on the mechanical effects of short-circuit currents in HV and EHV open air, conventional substations. Although these computational methods are easy to implement, they have several limitations and are sometimes too conservative. Previously published papers address such conservatism using dynamic analysis approaches that provide more accurate results when compared to experimental data. This paper provides two extensions to IEEE 605 and CIGRE 105 for calculating fault current reaction forces. A closed-form equation defining the simplified 2-D short-circuit force time history during a fault based on CIGRE 105 and a computationally inexpensive numerical 3-D force calculation technique are presented.
- Published
- 2018
90. On Savitzky–Golay Filtering for Online Condition Monitoring of Transformer On-Load Tap Changer
- Author
-
Tapan Kumar Saha, Hui Ma, and Junhyuck Seo
- Subjects
Engineering ,business.industry ,020209 energy ,System of measurement ,Energy Engineering and Power Technology ,Condition monitoring ,Control engineering ,02 engineering and technology ,Filter (signal processing) ,Tap changer ,law.invention ,Binary Golay code ,law ,0202 electrical engineering, electronic engineering, information engineering ,Electronic engineering ,Electrical and Electronic Engineering ,Transformer ,business ,Voltage - Abstract
Vibro-acoustic measurement on a transformer's on-load tap changer (OLTC) can provide indications on its mechanical condition. Recently, a joint vibro-acoustic and arcing measurement system has been proposed, which can correlate the vibro-acoustic signal to mechanical events of OLTC's operation. However, there are still considerable difficulties in extracting useful information from both vibro-acoustic signal and arcing signal in a synchronized manner without any distortions in the extracted signals. In this paper, Savitzky–Golay filter is introduced to process the signals acquired from a joint vibro-acoustic and arcing measurement system installed on in-service OLTCs. It proves that the Savitzky–Golay filter can process both vibro-acoustic and arcing signals induced by OLTC, extract essential information without any time delay from both types of signals, and retrieve voltage phase information from the arcing signal. The methodologies developed in this paper can improve the visibility of OLTC's mechanical operation for an effective online condition monitoring.
- Published
- 2018
91. Fault Analysis of Inverter-Interfaced Distributed Generators With Different Control Schemes
- Author
-
Z. John Shen, Xin Yin, Zhikang Shuai, Xuan Liu, and Chao Shen
- Subjects
Engineering ,business.industry ,020209 energy ,020208 electrical & electronic engineering ,Energy Engineering and Power Technology ,Control engineering ,Hardware_PERFORMANCEANDRELIABILITY ,02 engineering and technology ,Fault (power engineering) ,Power (physics) ,Fault indicator ,Control theory ,Control system ,0202 electrical engineering, electronic engineering, information engineering ,Inverter ,Constant current ,Voltage droop ,Microgrid ,Electrical and Electronic Engineering ,business - Abstract
Diversification of control schemes adopted by inverter-interfaced distributed generators (IIDGs) leads to difficulties in fault current estimation in a microgrid, which might make preexisting protection systems invalid and threaten the safety of power electronic devices. It is therefore important to study fault characteristics of IIDGs. This paper investigates characteristics of fault current of IIDGs caused by both symmetrical and asymmetrical faults. Two kinds of widely used control modes, current control (constant current control and PQ control) and voltage control (V/F control and droop control), are under investigation to provide an intuitive comparison on fault current. In particular, a novel algorithm is proposed to calculate fault current of droop-controlled IIDGs. It is found that different limiters have great impacts on fault response of IIDGs and detailed research works are carried out to identify the effects in this paper. Simulation results based on PSCAD/EMTDC and calculation results based on MATLAB/Simulink verify the correctness of the proposed fault models.
- Published
- 2018
92. Evaluation of Low-Power Instrument Transformers for Generator Differential Protection
- Author
-
Jean Mahseredjian and Michel Normandeau
- Subjects
Engineering ,Test bench ,Computer science ,business.industry ,020209 energy ,Energy Engineering and Power Technology ,02 engineering and technology ,Automotive engineering ,Current transformer ,Power (physics) ,Generator (circuit theory) ,Electricity generation ,Hydroelectricity ,0202 electrical engineering, electronic engineering, information engineering ,Electronic engineering ,Measurement uncertainty ,Metering mode ,Electrical and Electronic Engineering ,Current (fluid) ,business ,Accuracy class - Abstract
In hydroelectric power plants, which are characterized by particularly high short-circuit current levels and high time constants, conventional current transformer (CT) specifications can result in increased equipment dimensions, thus complicating their installation, especially during refurbishment projects. This paper presents a study to assess the potential of various low power instrument transformers (LPITs) for generator protection applications. Two types of LPITs were evaluated: the optical current transformer (OCT) and the stand alone merging unit (SAMU). To test the OCT, a 65-kA-peak test source was developed using a real-time simulator. This source was used to inject symmetrical and asymmetrical currents into LPITs for the assessment of protection accuracy class. Low-current tests were also performed to assess their metering classes. This paper presents the design of a high-current test bench, measurement uncertainty analysis and analysis algorithms used for device evaluation. Analysis results are then presented and discussed in terms of their applicability to generator differential protection using SAMUs and OCTs.
- Published
- 2018
93. Calculation of the Three-Phase Internal Fault Currents in Medium-Voltage Electrical Installations.
- Author
-
Xiang Zhang, Jiaosuo Zhang, and Pietsch, Gerhard
- Subjects
ELECTRIC resistors ,ELECTRIC power factor ,ELECTRIC power distribution ,ELECTRIC controllers ,ELECTRIC power systems ,ELECTRIFICATION ,ELECTRICAL engineering ,ENGINEERING ,ELECTRICITY - Abstract
Fault arc tests showed that the three-phase fault arc currents depend on the arrangement of electrodes at the fault site and vary stochastically. Up to now, experimental investigations have mainly been carried out for the medium-voltage switchgears, and the fault arc currents are either recognized by the experimental results or derived by the probability method. A calculation method used for the determination of the three-phase fault arc currents is introduced in this paper, which can be expressed accurately by mathematics according to the characteristics of the three-phase internal faults. [ABSTRACT FROM AUTHOR]
- Published
- 2008
- Full Text
- View/download PDF
94. Harmonic Resonance Characteristic of Large-Scale PV Plant: Modelling, Analysis, and Engineering Case.
- Author
-
Liu, Qianyi, Liu, Fang, Zou, Runmin, and Li, Yong
- Subjects
RESONANCE ,ENGINEERING ,HARMONIC suppression filters ,ELECTRIC power filters - Abstract
Harmonic amplification and interaction of the PV plant which contains multiple parallel inverters influence the renewable power generation and operation seriously. In this article, the resonance mechanism and characteristics of a real large-scale PV plant are explored based on its plant-level circuit model. The component and system models are established first. The distribution rules of wideband resonance frequency from the perspective of the point of common coupling (PCC) and the inverter are respectively determined. Two different resonance bands excited by LCL filter and underground cable are further identified. At last, the practical case of harmonic resonance in the studied PV plant is investigated. Both the measured data and the simulation results support the analytical conclusions. This article combines the theoretical study with the engineering practice, which provides beneficial guidance on the resonance prevention. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
95. A Loss-of-Field Detection Relay Based on Rotor Signals Estimation
- Author
-
Moein Abedini, Majid Sanaye-Pasand, Mahdi Davarpanah, and Reza Iravani
- Subjects
Engineering ,Rotor (electric) ,business.industry ,020209 energy ,Energy Engineering and Power Technology ,02 engineering and technology ,law.invention ,Field detection ,Shock absorber ,law ,Relay ,Digital algorithm ,0202 electrical engineering, electronic engineering, information engineering ,Electronic engineering ,Dependability ,Electrical and Electronic Engineering ,business ,Electrical impedance - Abstract
This paper 1) introduces a new approach for dependable and secure detection of loss-of-field (LOF) events based on estimating rotor signals, 2) implements digital algorithm of the corresponding LOF relay in an industrial hardware platform, and 3) evaluates performance of the LOF relay in a real-time-digital-simulator (RTDS) based control-hardware-in-the-loop (CHIL) environment. The main features of the proposed relay as compared with the conventional approaches include 1) capability to discriminate between system disturbances and LOF events, and 2) dependability and higher speed of the LOF detection mechanism. To evaluate the proposed approach performance for various types of LOF events, a detailed excitation system is modeled and implemented in the RTDS-based CHIL environment. This paper also verifies superior performance of the proposed LOF relay as compared with that of a conventional impedance-based LOF relay, using the RTDS-based CHIL platform.
- Published
- 2018
96. Probabilistic Voltage Management Using OLTC and dSTATCOM in Distribution Networks
- Author
-
Ali Arefi, Peter Wolfs, Gerard Ledwich, and Houman Pezeshki
- Subjects
Engineering ,business.industry ,020209 energy ,Photovoltaic system ,Probabilistic logic ,Energy Engineering and Power Technology ,Particle swarm optimization ,02 engineering and technology ,AC power ,Probabilistic method ,Control theory ,0202 electrical engineering, electronic engineering, information engineering ,Electronic engineering ,Voltage regulation ,Electrical and Electronic Engineering ,business ,Cluster analysis ,Voltage - Abstract
Low-voltage (LV) feeder voltage magnitude and unbalance are often the constraining factors on a feeder's capacity to absorb rooftop photovoltaic (PV) generation. This paper presents a new probabilistic method for voltage management in distribution networks through the placement of distribution static compensators (dSTATCOMs) and on-load tap changers (OLTCs) considering the reactive capability of PV inverters in multiple LV and medium-voltage distribution networks. The method uses a modified particle swarm optimization. In this paper, several scenarios for the placements of multiple dSTATCOMs with and without embedded energy storage systems using both reactive and real power compensation are investigated in combination with an OLTC equipped with independent per-phase tap-changing control. The voltage constraints in the proposed method are statistically defined using three duration curves. These are the voltage unbalance, maximum voltage, and minimum voltage duration curves. The method is comprehensively tested for varying load and PV generation based on data from a real Australian distribution network with considerable unbalance and distributed PV generation. The results show that PV hosting capacity increases where the proposed approach is applied.
- Published
- 2018
97. Safe Operation of DFIG-Based Wind Parks in Series-Compensated Systems
- Author
-
Richard Gagnon, Ilhan Kocar, Jean Mahseredjian, Simon Jensen, Ulas Karaagac, and Martin Fecteau
- Subjects
Engineering ,Series (mathematics) ,business.industry ,020209 energy ,Induction generator ,Energy Engineering and Power Technology ,Control engineering ,02 engineering and technology ,Transmission system ,AC power ,Control theory ,Transmission line ,Control system ,0202 electrical engineering, electronic engineering, information engineering ,Transient (oscillation) ,Electrical and Electronic Engineering ,business ,Active filter - Abstract
Subsynchronous control interaction (SSCI) is the interaction between the power-electronics control and the series-compensated transmission system that occurs at frequencies below the system nominal frequency. SSCI may occur between the doubly-fed induction generator (DFIG) control system and the series-compensated transmission line, to which the wind park (WP) is connected. Not only do the DFIG control system parameters, but also the WP operating conditions have a significant impact on SSCI. In this paper, the impact of WP operating conditions and DFIG control system parameters on SSCI is analyzed in detail. Guidelines are presented for modifying the DFIG control system parameters to ensure safe operation and acceptable transient responses due to faults. This paper also examines the accuracies of various analytical tools used for SSCI problem identification and proposes a new frequency scan analysis approach for accurate prediction of potential SSCI problems.
- Published
- 2018
98. Nelson River Pole 1 Thyristor Leakage Problem
- Author
-
Luis Sintra, Xin Li, and Narinder S. Dhaliwal
- Subjects
Gate turn-off thyristor ,Engineering ,business.industry ,020209 energy ,Electrical engineering ,Energy Engineering and Power Technology ,Thyristor ,Failure mechanism ,02 engineering and technology ,MOS-controlled thyristor ,law.invention ,Integrated gate-commutated thyristor ,Static induction thyristor ,law ,0202 electrical engineering, electronic engineering, information engineering ,Electrical and Electronic Engineering ,business ,Leakage (electronics) ,Voltage - Abstract
The Nelson River HVDC system currently consists of two thyristor-based bipole schemes: Bipoles I and II. Pole 1 in Bipole I was found to have suffered from a serious thyristor leakage problem (TLP) after 20 years in service. In order to understand, evaluate, and resolve this problem, a comprehensive study was conducted in 2013 at Manitoba Hydro, which involved thyristor voltage monitoring, leakage current measurements, and simulations. The study revealed that the majority of thyristors in two of the three valve groups at both ends were leaky (i.e., exhibiting increased leakage currents) to various degrees. This paper provides an overview of the TLP and related investigation. The effects and symptoms/behaviors of the leaky thyristors are illustrated with the study results for one of the worst valves at each end. The failure mechanism of the leaky thyristors is also discussed. This paper should provide a clear understanding of the TLP from the user's perspective. A question, however, remains with regard to the root-cause of the TLP. Further research is required to answer this question.
- Published
- 2018
99. A Novel Reclosing Scheme for Mitigation of Distributed Generation Effects on Overcurrent Protection
- Author
-
Sherif O. Faried, Keaton A. Wheeler, and Mohamed Elsamahy
- Subjects
Engineering ,business.industry ,020209 energy ,Frame (networking) ,Control unit ,Energy Engineering and Power Technology ,Context (language use) ,02 engineering and technology ,Fault (power engineering) ,Fault detection and isolation ,Overcurrent ,Recloser ,Distributed generation ,0202 electrical engineering, electronic engineering, information engineering ,Electronic engineering ,Electrical and Electronic Engineering ,business - Abstract
This paper proposes a novel scheme to mitigate distributed generation (DG) effects on existing fuse-recloser protection infrastructure in radial distribution networks. The proposed scheme employs a control unit, variable load bank, and dedicated recloser at the point of common coupling (PCC). It detects the increase in the DG terminal current producing a tipping signal when it exceeds a preset value. The proposed scheme also receives a fault detection signal from the head-end recloser via a fast communication channel. Upon verifying both signals, the scheme disconnects the DG unit from the system. Simultaneously, it connects a transfer impedance at the PCC to operate the DG unit at its prefault load-sharing condition. This allows the DG unit to continue supply to the transfer impedance at the prefault load-sharing condition, that is, maintain operation at the prefault level with no need for immediate shut down. Furthermore, it also allows the DG to maintain its speed and frequency at the prefault levels which, in turn, allows faster reconnection of the DG unit to the system after successful reclosing. For the case of unsuccessful reclosing or the case where the fault is not cleared within the set utility time set frame, the proposed scheme shuts the DG source down. The transfer impedance is selected from a variable load bank and is a function of the prefault load-sharing condition; therefore, a sensitivity survey was performed during the investigations of this paper to cover all possible system operating conditions and its corresponding transfer impedances. In the context of this paper, multiple in-depth time-domain simulations are conducted to ascertain the efficiency of the proposed scheme in mitigating the impact of DG sources on existing overcurrent protection infrastructure. Time-domain simulations have been conducted using a typical distribution network in the EMTP-RV software environment for validation purposes.
- Published
- 2018
100. Transient-Based Fault Location on Three-Terminal and Tapped Transmission Lines Not Requiring Line Parameters
- Author
-
Masoud Davoudi, Ebadollah Kamyab, and Javad Sadeh
- Subjects
Engineering ,Optimization problem ,Emtp ,business.industry ,020209 energy ,Energy Engineering and Power Technology ,02 engineering and technology ,Fault (power engineering) ,Stuck-at fault ,Synchronization (alternating current) ,Electric power transmission ,Line (geometry) ,0202 electrical engineering, electronic engineering, information engineering ,Electronic engineering ,Transient (oscillation) ,Electrical and Electronic Engineering ,business - Abstract
In this paper, fault location on three-terminal and tapped transmission lines without requiring line parameters is presented, which mitigates the effect of line parameter variations due to weather and loading conditions on fault-location accuracy. For three-terminal lines, a fault-location method is presented, which utilizes postfault measurements of all three terminals. For tapped lines, two methods are presented. The first one uses postfault measurements of the main two terminals. The second one needs one cycle of prefault measurements at the main terminals as well. Synchronized transient-based measurements are used in methods proposed in this paper. In all of the presented methods, the fault-location problem is converted to an optimization problem and then solved to find the line parameters and the accurate location of the fault. The simulations are carried out by alternative transients program/electromagnetic transients program (ATP/EMTP) software, and the presented algorithms are executed by MATLAB. Simulation results assess the effects of fault resistance, type, and inception angle on the accuracy of the presented methods. Further discussion is also provided on the impacts of synchronization errors, noisy measurements, and nonresistive faults.
- Published
- 2018
Discovery Service for Jio Institute Digital Library
For full access to our library's resources, please sign in.