11 results
Search Results
2. Lightning Performance of 500-kV Double-Circuit Line Schemes for the Three-Gorge Project.
- Author
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Huang Wei-Gang
- Subjects
ELECTRIC circuit analysis ,ELECTRIC circuit breakers ,ELECTRIC circuits ,ENGINEERING ,ELECTRICAL engineering - Abstract
A few problems in the present calculation methods in the aspects of insulation flashover criteria, influence of operating voltages, induced overvoltage component, and shielding failure in China are briefly analyzed and discussed. Lightning performance of 500-ky double-circuit line schemes (nine tower types and thirteen schemes of insulation disposition) for the Three-Gorge Project is computed and compared with the existing operation experience of double-circuit lines. Different schemes are compared with each other. The cause of the remarkable increase of the total lightning outage rate of the usual unbalanced double-circuit lines, with one circuit insulation reduced, in the operation is analyzed. Different from the usual unbalanced insulation lines, a one-circuit insulation enhanced scheme is proposed in this paper. It is emphasized in the paper that the key of the lightning protection of double-circuit transmission lines is to reduce the double-circuit simultaneous trip-out rate and to keep a reasonable total trip-out rate at the same time. It can be achieved by choosing the proper insulation disposition scheme referring to the order of the weighted trip-out rate values. The viewpoints and methods in the paper would be useful to others working in this field. [ABSTRACT FROM AUTHOR]
- Published
- 2006
- Full Text
- View/download PDF
3. Analysis of Fast Onload Multitap-Changing Clamped-Hard-Switching AC Stabilizers.
- Author
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Vaquero López, Joaquín, Campo Rodréguez, Juan Carlos, Monteso Fernández, Santiago, Martínez García, Salvador, and Pérez García, Miguel Angel
- Subjects
THYRISTORS ,THYRISTOR control ,ENGINEERING ,ELECTRIC power distribution ,ELECTRIC circuits - Abstract
The rate of change in classic thyristor-based onload tap-changing ac stabilizers is limited to that of the load current zero crossing (once per half cycle) due to the natural turnoff method involved. The growth of the power rate of insulated-gate bipolar transistor and other gate turnoff switches allows exploring of stabilizers that are able to change taps several times in a half cycle of the mains wave (subcyclic commutation). This paper analyzes the best four solutions for the power circuit of this new class of tap-changers in the multitap version, developed through an iterative analysis and synthesis cost comparative method that moves the tap-changing stabilizers over to the world of low-frequency voltage harmonics, oscillations, flicker, and instability phenomena attenuators. These topologies allow changing times as low as 150 μs by using a multicoil inductance to perform current limitation and voltage clamping tasks during the switching operation, as it shall be shown in a second paper dedicated to the synthesis and experimental aspects. [ABSTRACT FROM AUTHOR]
- Published
- 2006
- Full Text
- View/download PDF
4. Ground Method Analysis of Maintained Distribution Transformers Considering Reverse Energy From End Users.
- Author
-
Chien-Hsing Lee and Teng-Chin Hsu
- Subjects
ELECTRIC transformers ,ELECTRICAL engineering ,ENGINEERING ,ELECTRIC current grounding ,ELECTRIC circuits - Abstract
This paper analyzes four basic ground methods for personal protection during maintained distribution transformers considering reverse energy from end users. The test in this paper considers that no loads are connected at both the primary and secondary of the distribution transformer. The results are summarized to determine the effective grounding method of protecting distribution line workers on de-energized lines during accidental-line energization from the end users. The secondary voltage at the transformer was recorded with various configurations of temporary grounds, and the primary voltage is then computed by using the transformer turn ratio. As a result, the case of installing no temporary ground is considered lethal. Moreover, the cases of installing temporary ground with a short circuit at either the primary or secondary of the transformer are considered to be the effective means of protecting distribution line workers. [ABSTRACT FROM AUTHOR]
- Published
- 2006
- Full Text
- View/download PDF
5. Novel Analytical Solution to Fundamental Ferroresonance Part II: Criterion and Elimination.
- Author
-
Yunge Li, Wei Shi, and Furong Li
- Subjects
ELECTRIC circuits ,ELECTRIC currents ,ELECTRICAL engineering ,ENGINEERING ,VOLTAGE regulators - Abstract
For ferroresonant circuits, the sufficient condition for preventing fundamental ferroresonance (FF) from occuring is that there is no intersection between the voltage-current characteristic of the linear part of the circuit, and the saturated power frequency excitation characteristic of the nonlinear part. Based on this understanding, part II of this paper has presented a criterion for the possibility of FF in the form of an analytical expression which is composed of the essential parameters of the circuit. By giving the critical resistance value for damping FF, the expression clearly indicates not only the possibility of FF but also the methods for eliminating the FE The possibility of FF is judged by comparing the critical resistance value with the real value. In the meantime, the expression suggests how to adjust the essential parameters to suppress FE The criterion has been proven by both simulation results and field tests. With this criterion, the possibility and elimination of FF can be studied for the first time by a simple yet effective analytical method. [ABSTRACT FROM AUTHOR]
- Published
- 2006
- Full Text
- View/download PDF
6. A Novel Power Quality Monitoring Allocation Algorithm.
- Author
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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
7. A DC Hybrid Circuit Breaker With Ultra-Fast Contact Opening and Integrated Gate-Commutated Thyristors (IGCTs).
- Author
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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
8. Historical Review of High Voltage Switchgear Developments in the 20th Century for Power Transmission and Distribution System in Japan.
- Author
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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
9. 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
10. Accurate Location of Faults on Power Transmission Lines With Use of Two-End Unsynchronized Measurements.
- Author
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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
11. The Detection of the Closing Moments of a Vacuum Circuit Breaker by Vibration Analysis.
- Author
-
Yongpeng Meng, Shenli Jia, Zongqian Shi, and Mingzhe Rong
- Subjects
ELECTRIC circuits ,ENGINEERING ,ELECTRIC filters ,ELECTRICAL engineering ,VIBRATION measurements - Abstract
The vibration signals during the closing operation of three-phase vacuum circuit breakers (VCB5) were recorded for detecting the closing moment of each pole. The short-time energy (STE) analysis of the vibration signals with a moving Hamming window is used to derive the closing moments both under no-load conditions and load conditions. By determining a proper length for the moving window, the improved signal-to-noise ratio by the STE analysis greatly facilitates the identification of the closing moments. Under no-load condition, the results obtained from the vibration signals are in good agreement with those measured by the contact timing signals. Under load conditions, it is found that the effect of the making current on the detection results is too tenuous to be neglected. This makes it possible to apply this method to online detection of the closing moments of VCBs. [ABSTRACT FROM AUTHOR]
- Published
- 2006
- Full Text
- View/download PDF
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