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International Conference on Electrical Machines and systems (ICEMS)

作者： H.Y. Wang P.S. Su X.H. Wang Department of Electrical Engineering State Key Laboratory of Control and Simulation of Power Systems and Generation Equipment Tsinghua University Beijing China

To simplify the calculation of winding bar temperature for the condition monitoring of the water cooling stator of Three-Gorge hydro-generator, this paper calculates three of two-dimension thermal fields. Using the three fields simulates the different section along the axial direction of the generator. The total amount of heat taken away by water can be calculated by weighting the result of three fields on the total axial length of them. Four groups of thermal-fields with different outlet-water temperature are calculated by using ANSYS multi-physical software. The calculation results of temperature of measurement-point between up-layer and down-layer bars in stator are partly supported by the measurement data. And the relatively error between the heat taken by cooling-water and the heat generated by the stator bar is always less than 5%

关键词： Cooling Stator cores Stator windings Solids Bars Heat transfer power system simulation Temperature Thermal engineering Condition monitoring

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Optimized design of main protection configuration scheme for internal faults of Shawan generator

Optimized design of main protection configuration scheme for...

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International Conference on Electrical Machines and systems (ICEMS)

作者： Yuguang Sun Xiangheng Wang Lin Gui Weijian Wang Department of Electrical Engineering State Key Laboratory of Control and Simulation of Power Systems and Generation Equipment Tsinghua University Beijing China

ISBN: (纸本)7506274078

In order to provide high-quality protection for large- and medium-sized generators, a new feasible method of designing main protection configuration scheme for internal faults of generators is desirable. Based on calculation of all the possible internal faults with the multi-loop method, the optimized design method is illustrated through Shawan generator in this paper. With this method, the optimal protection configuration scheme, composed of the split-phase transverse differential protection, two sets of incomplete longitudinal differential protection as well as one set of single element transverse differential protection, is determined for the internal faults of Shawan generator, which has two branches in each phase. The rate of operation and double-protection of the optimal scheme both reach the maximum. In addition to that, on all the possible phase-to-phase faults, at least two kinds of protection of the optimal scheme are sure to operate correctly. The optimized scheme excels the conventional one in protection performance index, which verifies the validity of the optimized method of designing main protection configuration scheme for generators.

关键词： Design optimization Circuit faults Design methodology power generation power system protection Character generation power system simulation Performance analysis Stators Sun

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Parameter calculation for induction machine rotor bar with non-sinusoidal current

Parameter calculation for induction machine rotor bar with n...

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International Conference on Electrical Machines and systems (ICEMS)

作者： Xinzhen Wu Xiangheng Wang Department of Electrical Engineering State Key Laboratory of Control and Simulation of Power Systems and Generation Equipment Tsinghua University Beijing China

ISBN: (纸本)7506274078

To evaluate the rotor bar parameters of an induction machine with the non-sinusoidal current, a new analysis approach, which employs the circuit analysis theory instead of electromagnetic field theory to count the skin effect, is proposed. In the presented method, a rotor bar is divided into many thin-layers with their own parameters derived. The superposition principle is proven for the calculation of total bar losses and slot magnetic energy due to the non-sinusoidal current composed of sinusoidal components with different frequencies, which shows the parameters of the bar can be expressed with the parameters at respective frequencies. For given examples, the parameters at different frequencies are calculated, and the results are verified by the analytical method or the finite element method.

关键词： Induction machines Skin effect Frequency Rotors Electromagnetic analysis Circuit analysis Magnetic losses Magnetic analysis Finite element methods power system simulation

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A ratio variation of equivalent instantaneous inductance based method to identify magnetizing inrush in transformers

A ratio variation of equivalent instantaneous inductance bas...

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International Conference on Electrical Machines and systems (ICEMS)

作者： D.Q. Bi X.H. Wang W.X. Liang W.J. Wang State Key Laboratory of Control and Simulation of Power System Tsinghua University Beijing China

In terms of the characteristic of instantaneous magnetizing inductance reflecting the saturation stage in transformer, an improved method is proposed to distinguish between the magnetizing inrush current and short-circuit fault based on the ratio of average equivalent instantaneous inductances between the non-saturation and the saturation zone, which are divided according to a threshold of differential current. During the inrush, the value of equivalent instantaneous inductance varies severely from small to large as the transformer entering into the saturation and withdrawing from it, so the ratio of average equivalent instantaneous inductances between the non-saturation and the saturation zone is very large in one cycle. However, for the short-circuit fault in transformer, the equivalent instantaneous inductance is very small, and keeps little variation, so the ratio is approximately equal to one. The principle and setting of this method is simple and easy, and its identification time is short. The experimental results verify that the method is correct and effective

关键词： Inductance Surge protection Saturation magnetization Circuit faults Transformer cores Magnetic cores Magnetic circuits Capacitance Fault diagnosis Bismuth

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Application of direct torque control in multi-level high power adjustable speed drive systems

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Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering 2005年第SUPPL.期25卷 241-247页

作者： Zhao, Zheng-Ming Bai, Hua Zhang, Hai-Tao Yuan, Li-Qiang Laboratory of Control and Simulation of Power System and Generation Equipment Tsinghua University Beijing 100084 China

As a high-performance control algorithm, the Direct Torque control has been applied in multi-level high power adjustable speed drive systems. However, the high voltage and high power system based on DTC is still not in wide applications. This paper analyzed and summarized these applications which are mainly in allusion to three-level NPC inverter. Meanwhile, combined with the relevant engineering practice, some special issues in the application of DTC in the three-level neutral point clamped inverter based on IGCT have been presented, such as keeping the neutral point balance, investigating the relationship of switching frequency and operational frequency, reducing the large starting current and observing the flux linkage with LC filter and induction motor. These are all the fatal issues in the DTC applications. This paper proposes some feasible strategies through investigation and experiments in the real applications.

关键词： Torque control

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Aging effect of UV radiation on SIR insulators' hydrophobicity property

Aging effect of UV radiation on SIR insulators' hydrophobici...

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Conference on Electrical Insulation and Dielectric Phenomena, (CEIDP)

作者： Xun Wang Xidong Liang Yuanxiang Zhou State Key Laboratory of Control and Simulation of Power System and Generation Equipment Department of Electrical Engineering Tsinghua University Beijing China

ISBN: (纸本)0780385845

Based on the simulation of ultraviolet (UV) radiation in the Sun's rays and in corona, the aging effect of UV radiation on composite insulators was studied in this paper, especially the effect on hydrophobicity properties. It is found that after irradiation with UV, no matter whether a short time of less than 24 hours or a long time of 2000 hours, the hydrophobicity and the hydrophobicity transfer properties of silicone rubber (SIR), which are described by contact angle, slowly turns better. Four different kinds of samples with different prescriptions were used in the test. As UV sources, a special setup to simulate the UV rays of corona and a xenon light to simulate the sunlight were both used. The change of rigidity of silicone rubber was also measured. Infrared spectra of the silicone rubber surface, irradiated by UV for various times, show that the content of the low molecule weight on the surface is different, and this can be due to the discrepancy of hydrophobicity properties of the samples.

关键词： Aging Testing Slabs Xenon Corona Rubber power system simulation Surface cleaning Dielectrics and electrical insulation Stress

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Influence of annealing method on the space charge properties in polyethylene

Influence of annealing method on the space charge properties...

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Conference on Electrical Insulation and Dielectric Phenomena, (CEIDP)

作者： Ninghua Wang Yuanxiang Zhou Hongbin Liu Bin Gao Xidong Liang Zhicheng Guan T. Takada State Key Laboratory of Control and Simulation of Power System and Generation Equipment Tsinghua University Beijing China Electronic Measurement Laboratory Musashi Institute of Technology Tokyo Japan

In this paper, high-density polyethylene (HDPE) films were prepared by three kinds of annealing methods which were different in cooling speed. The crystallinity of those HDPE samples were measured and compared. A high DC voltage was applied to the samples and the space charge formed was measured. Homo-charges were found in samples that were applied with a negative high voltage. The space charge properties were discussed, based on crystallinity. From these results, it is found that the space charge formed in samples cooled at high speed is more than that of the samples cooled at normal and low speed.

关键词： Annealing Space charge Polyethylene Voltage Current measurement Charge measurement Conducting materials Crystallization Morphology Laboratories

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Extended load-flow arithmetic for voltage stability analysis

Extended load-flow arithmetic for voltage stability analysis

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International Conference on power system Technology (powerCON)

作者： L. Zhu S. Zhou Y. Zhang State Key Laboratory of Control and Simulation of Power Systems and Generation Equipment Tsinghua University Beijing China

ISBN: (纸本)0780363388

In this paper, a novel load-flow arithmetic for voltage stability analysis is studied where models of various dynamic elements in power systems are taken into account. It simultaneously solves the load flow equation and the state equation of dynamic elements and gets both the voltage amplitude, phase of all buses and the inner state variables of the dynamic elements. In this arithmetic different limits are considered and the assumption of PV bus, PQ bus and slack bus are eliminated, so the result is closer to the real operation condition. Using a flow arithmetic based on continuation-power-flow (CPF) method, the critical point of voltage stability of the system can be computed. The proposed method is demonstrated on a test system and the results are compared with the conventional power flow method.

关键词： Arithmetic Voltage Stability analysis power system dynamics power system modeling Load flow Equations power system analysis computing power system stability system testing

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Digital power system

Digital power system

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World Congress on Intelligent control and Automation (WCICA)

作者： Lu Qiang State Key Laboratory of Control and Simulation of Power Systems and Generation Equipments China

The concept of a digital power system (DPS) is set forth in the paper. The definition, the contents, the function, the hardware and the software conditions for implementing it are discussed. Moreover, the necessary basic research work for implementing a DPS is also discussed. The DPS may be defined like this: the digital power system is the digital, figuration and real time description and reappearance of physical structure, technical characteristic, management system as well as personal information system of a real power system which is in operation. The DPS will be able to make a significant contribution to administrating and decision-making more scientifically, improving security and stability online, online making and implementing economical operation strategy and carrying out emergency and anti-fault control, etc.

关键词： power system control

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Movement simulation of long electric arc along the surface of insulator string in free air

Movement simulation of long electric arc along the surface o...

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作者： Gu, Shanqiang He, Jinliang Zhang, Bo Xu, Guozheng Han, Shejiao State Key Lab of Control and Simulation of Power Systems and Generation Equipment Department of Electrical Engineering Tsinghua University Beijing 100084 China

This paper presents the study of a long electric arc in free air due to lightning stroke on the parallel gap lightning protection device (PGLPD) on high-voltage overhead transmission lines. Based on the latest electric arc model, the analysis method of the magnetic field generated by the current flowing through the PGLPD, electric arc, transmission lines, steel tower, and ground wires is developed, and the movement process of the long arc along the surface of the insulator strings is simulated. The simulation results are in agreement with the experimental results. The study is very helpful for the optimal design and suitable assemblage of the PGLPD. © 2006 IEEE.

关键词： Electric arcs

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