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Research on the performance of wavelet packet transform based non-unit transient current protection

Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering 2005年第SUPPL.期25卷 151-156页

作者： Wang, Zeng-Ping Liu, Hao-Fang Laboratory of Power System Protection and Dynamic Security Monitoring and Control North China Electric Power University Baoding 071003 China

The reflection and refraction of fault-generated wave on EHV lines were investigated and the equations of transient current detected by relay were deduced. Theoretical analysis shows that the protection based on the energy ratio of higher frequency components is more adaptive to various faults and can distinguish between the internal and external faults near the remote busbar more effectively. Such protection also has similar performance when used on EHV lines and series compensated EHV lines. The wavelet packet transform technique was employed to determine the energy ratio. Simulation results show that the proposed conclusions are correct.

关键词： Electric lines

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New algorithm based on the mathematical morphology for avoiding mal-operation of transformer differential protection

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Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering 2005年第20期25卷 6-11页

作者： Zheng, Tao Liu, Wan-Shun Liu, Jian-Fei Xiao, Shi-Wu Laboratory of Power System Protection and Dynamic Security Monitoring and Control North China Electric Power University Beijing 102206 China

To avoid the mal-operation of transformer differential protection when out-zone fault occurs under current transformer (CT) saturation, a new algorithm based on the mathematical morphology is put forward in this paper. Unlike the traditional time-differential method, which is based on the time difference between fault occurrence and the differential current increase, this algorithm only needs detecting the time of fault occurring, while the time of differential current increasing is no more needed. A new current waveform is obtained by a symmetrical transformation of the initial part of differential current after fault occurred, and then its characteristic is extracted by morphological gradient. In the case of CT's serious saturation, a discrimination of out-zone fault and inner-zone fault can be clearly made by this algorithm, which needs a little calculation and a short data window. Simulation results of EMTP validate its feasibility and reliability.

关键词： Transformer protection

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power system cascading outages assessment based on support vector machine

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Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering 2005年第SUPPL.期25卷 178-183页

作者： Deng, Hui-Qiong Ai, Xin Liu, Hao Laboratory of Power System Protection and Dynamic Security Monitoring and Control North China Electric Power University Beijing 102206 China

A method of power system cascading outages assessment based on support vector machine (SVM) was provided in this paper. Taking full advantages of the ability of SVM to solve the problem with small sample, nonlinear and high dimension, this method constructs an assessment mode which uses resampling classification technique based on boosting method, pretreatment technique based on distance criterion and information fusion technique. This mode can help to improve the precision and stability of assessment, hence better generalization ability of assessment is guaranteed. At the end of this paper, an example is provided to demonstrate the validity of the proposed approach.

关键词： Electric power system protection

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Applied clusters and entropy in discreting attributes of load forecasting

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Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering 2005年第SUPPL.期25卷 65-70页

作者： Li, Jing-Hua Li, Ran Li, He-Ming Gu, Xue-Ping Laboratory of Power System Protection and Dynamic Security Monitoring and Control North China Electric Power University Baoding 071003 China

Attributes are require to be discrete when using data mining methods to establish forecasting model, for example, rough set, ANN and decision tree. But most discrete methods used before can't consider the relationship of conditional and decision attributes well, so the discrete results are not very satisfaction. This paper presents a new discrete method which combines clusters and entropy. First, cluster is adopted to get the waiting breakpoints. Then finally results are decided by their rate of entropy. According to clustering, the boundary value is greatly reduced. Meanwhile, through entropy which considers the condition attributes and decision attributes, attributes can be discreted more exactly. At last, the discrete results compared with the method based on the importance of breakpoints show that the proposed method assurance the quality of classing. The space of sample can be compressed effectively, which lightens the training load of model and the gotten rules are with good adaptability and useful value. The correctness and effectiveness are validated by the practical application and the accuracy of forecasting will be increased.

关键词： Electric load forecasting

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New algorithm based on the distribution of the normalized equivalent instantaneous inductance for the discrimination of inrush

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Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering 2005年第23期25卷 47-53页

作者： Zheng, Tao Liu, Wan-Shun Zhuang, Heng-Jian Li, Xiao-Bo Laboratory of Power System Protection and Dynamic Security Monitoring and Control North China Electric Power University Beijing 102206 China SP Longyuan Environment Engineering Beijing 100761 China

Oriented to wye-delta connected three phase transformer, a new configuration of current transformer (CT) in transformer differential protection is proposed. In this configuration, only one single phase CT connected in any phase of the delta side is more needed than the traditional scheme. Worked with line currents measured by other current transformers connected in both sides of the transformer, any phase current in the delta side can be calculated based on the Kirchhoff's Current Law. This new scheme ensures the accurate calculation of the equivalent instantaneous inductance, which is immune to the loop current existed in the delta side of transformer, as well as no dead zone in transformer differential protection. A new algorithm based on the distribution of the normalized equivalent instantaneous inductance for the discrimination between inrush current and fault current is proposed. The normalization of equivalent instantaneous inductance makes the setting-value have little relation with the parameter of transformers, which has more universal meaning in the determination of setting values. Utilizing the distributive characteristic of the normalized equivalent instantaneous inductance, the variety of the normalized equivalent instantaneous inductance is effectively revealed. At last, experiment data obtained from HYBRISIM (Hybrid Simulator) validates the reliability and sensitivity of this algorithm. This algorithm has good prospect of engineering application in the EHV transformer protection.

关键词： Transformer protection

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Residual voltage transformation method for short-circuit current calculation with matrix transformation

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Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering 2005年第23期25卷 61-65页

作者： Jiang, Tong Bai, Xue-Feng Guo, Zhi-Zhong Lu, Ying Laboratory of Power System Protection and Dynamic Security Monitoring and Control North China Electric Power University Beijing 102206 China School of Electrical Engineering and Automation Harbin Institute of Technology Harbin 150001 China Dept. of Electrical Engineering Tsinghua University Beijing 100084 China

Unbalanced element brings a big problem to fault analysis of symmetrical components method. According with fault analysis of phase components, a residual voltage transformation method for short-circuit current calculation is presented with matrix translation in the place of classical sequence networks connection, which is suitable for both phase coordinates and symmetrical components coordinates. Calculation formulas are proposed with matrices calculation to deal with unsymmetrical faults and parameter matrices for various faults are listed. Analysis of simultaneous faults with unbalanced parameter element is done without calculation qualities increased. Simple examples have shown that the method is practical and suitable for programming.

关键词： Short circuit currents

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Numerical prediction of EMI on the secondary DC cable in cable tunnel due to a direct lightning strike in substation

Numerical prediction of EMI on the secondary DC cable in cab...

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作者： Qi, Lei Cui, Xiang Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control Ministry of Education North China Electric Power University Hebei 071003 China

Electromagnetic interference (EMI) on secondary dc cable in cable tunnel due to a direct lightning strike in substation threatens the safe operation of electronic equipment and system connected to the cable. In order to reduce EMI, the cable shield is generally connected to the grounding grid at both ends. Ground potential difference between two grounding points of the cable shield can be high due to high impedance of the grounding grid at high frequencies. In this paper, we present a hybrid method to analyze this complex system. As a result, both the current flowing in the cable shield and the transverse voltage between the cable core and shield are calculated. Compared with the measured results, the proposed method is demonstrated to be correct and effective. © 2006 IEEE.

关键词： Signal interference

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Subcell FDTD analysis of shielding effectiveness of a thin-walled enclosure with an aperture

Subcell FDTD analysis of shielding effectiveness of a thin-w...

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作者： Jiao, Chaoqun Li, Lin Cui, Xiang Li, Huiqi Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control Ministry of Education North China Electric Power University Hebei 071003 China

An improved subcell model is presented for including thin material sheets method in the finite-difference time-domain (FDTD) method. This improved subcell can be used to simulate a thin magnetic (μs ≠ μo) sheet. Then, the improved subcell model is applied to the analysis of the shielding effectiveness (SE) of the electromagnetic wave propagating through a thin infinite material sheet, which is verified by comparison with the analytical results. Updated equations for components of the field on special spatial grids which are on edges and corners of the enclosure are presented, and the subcell model is used for the analysis of a thin-walled enclosure with an aperture. The FDTD results are in very good agreement with the test results. © 2006 IEEE.

关键词： Thin walled structures

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Improved subcell model of thin multilayer material sheet in FDTD method

Improved subcell model of thin multilayer material sheet in ...

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作者： Jiao, Chaoqun Cui, Xiang Li, Lin Li, Huiqi Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control Ministry of Education North China Electric Power University Hebei 071003 China

An improved subcell model is presented for including thin sheets in the finite-difference time-domain (FDTD) method. This improved subcell model can simulate thin multilayer material sheets and was verified by comparison with the analytical results for the analysis of shielding effectiveness (SE) of the electromagnetic wave through a thin multilayer sheet. Then, the subcell model was used for the analysis of SE of a multilayer thin-walled enclosure with an aperture. The FDTD results were in very good agreement with the test results. Finally, the electromagnetic wave penetration through a wall of an enclosure and the electromagnetic wave coupling through an aperture of enclosure were compared. © 2006 IEEE.

关键词： Mathematical models

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Information Retrieval Technology 1

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丛书名： Lecture Notes in Computer Science

1000年

作者： Sung Hyon Myaeng Ming Zhou Kam-Fai Wong Hong-Jiang Zhang

ISBN: (数字)9783540318712

ISBN: (纸本)9783540250654

TheAsiaInformationRetrievalSymposium(AIRS)wasestablishedbytheAsian information retrieval community after the successful series of Information - trieval with Asian Languages (IRAL) workshops held in six di?erent locations in Asia, starting from 1996. While the IRAL workshops had their focus on inf- mation retrieval problems involving Asian languages, AIRS covers a wider scope of applications, systems, technologies and theory aspects of information retrieval in text, audio, image, video and multimedia data. This extension of the scope re?ects and fosters increasing research activities in information retrieval in this region and the growing need for collaborations across subdisciplines. We are very pleased to report that we saw a sharp increase in the number of submissions and their quality, compared to the IRAL workshops. We received 106papersfromninecountriesinAsiaandNorthAmerica,fromwhich28papers (26%) were presented in oral sessions and 38 papers in poster sessions (36%). It was a great challenge for the Program Committee to select the best among the excellent papers. The low acceptance rates witness the success of this year’s conference. After a long discussion between the AIRS 2004 Steering Committee and Springer, the publisher agreed to publish our proceedings in the Lecture Notes in Computer Science (LNCS) series, which is SCI-indexed. We feel that this strongly attests to the excellent quality of the papers.

关键词： Information Storage and Retrieval Information systems Applications (incl. Internet) Algorithm Analysis and Problem Complexity Data Structures Data Storage Representation Discrete Mathematics in Computer Science

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