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IEEE General Meeting power& Energy Society

作者： Shaofeng Huang Qiankuan Liu Huanzhang Liu Qixun Yang Laboratory of Power System Protection and Dynamic Security Monitoring and Control under Ministry of Education North China Electric Power University Beijing China

Although the fault component impedance relay has many perfect performances, it is still restricted by high fault resistance. In order to improve its resistive tolerance and overcome unreliable operation, a new type relay with double circular characteristic is put forward, as well as its operating boundary and general operating equation are researched in this paper. The relay is comprised of two groups operation equations, one of them is calculated by sampling integral arithmetic to achieve its ultra-high speed while the other by Fourier arithmetic to enhance the relay capability against high resistance. dynamic simulation test has been made with a typical two sources system operating at 750 kV to verify the relay performance. Theoretical analyses and test results show that the fault component impedance relay with double circular characteristic is simple, reliable and secure with ultra-high speed and great capability against fault resistance.

关键词： Impedance Relays Protective relaying power system relaying Arithmetic power system reliability power system stability power system protection power system faults Integral equations

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Study of UHV DC corona performance in a mini corona cage

Study of UHV DC corona performance in a mini corona cage

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Electrical Insulation Conference and Electrical Manufacturing & Coil Winding Conference

作者： Wei Wang Chengrong Li Jianbin Fan Chen Gu Yitao Jiang Guohua Cui Beijing Key Laboratory ofHigh Voltage & EMC Key Laboratory ofPower System Protection and Dynamic Security Monitoring and Control Ministry of Education North China Electric Power University Beijing China China EPRI Beijing China

To research the effect of high altitude on corona performance of UHV DC transmission line, the corona inception voltage gradient of a copper line at different air pressure level from 101 kPa to 61 kPa was measured in a mini corona cage. The results have been compared with calculated results of Peek law and the corona inception voltage gradient correction factor of air pressure was presented.

关键词： Corona Voltage Humidity system testing Laboratories Copper Pressure measurement Oscilloscopes power transmission lines Acoustic measurements

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An Integrated Approach on Allocating the Fixed Wheeling Cost of Large Consumers Considering Time-of-Use Pricing and power Quality

An Integrated Approach on Allocating the Fixed Wheeling Cost...

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power Tech Conference

作者： Ming Zhou Gengyin Li Yanan Zheng Jin Yang Jianxun Qi School of Business Management North China Electric Power University Beijing China Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control under Ministry of Education North China Electric Power University Beijing China

With start of trial operation of direct purchasing electricity for large consumers in China, the method on how to allocate wheeling costs among large consumers is of vital theoretical and practical significance. An integrated method for allocating fixed wheeling cost among larger consumers is presented taking time-of-use (TOU) feature, power quality demand and electricity quantity of direct purchase into account. TOU index modeling and power quality index modeling is proposed. The weights of three indices are determined by interacting between the transmission service provider (TSP) and large consumers based on multilevel models to get comprehensive evaluation indices for all consumers. The postage stamp method is modified to allocate the cost using the integrated indices instead of electric energy. Numerical example shows that the proposed approach can allocate fixed cost more reasonable and fair.

关键词： Costs Pricing power quality Energy consumption power generation Load flow IEEE members power industry Energy management power system management

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Combined Use of Fuzzy Set-Covering Theory and Mode Identification Technique for Fault Diagnosis in power systems

Combined Use of Fuzzy Set-Covering Theory and Mode Identific...

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2007 IEEE power Engineering Society General Meeting (PES 2007), vol.6

作者： Jian Xiao Fushuan Wen Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control (North China Electric Power University) Ministry of Education Beijing China Department of Electrical Engineering South China University of Technology Guangzhou China

After a fault occurs in a power system, generally some operating information of protective relays and circuit breakers could be obtained. Because protective relays and circuit breakers might improperly operate or fail to operate, and some errors and distortion may exist in data acquisition and communication, as a result uncertainties could be involved in the received information. A fault diagnosis model based on fuzzy set-covering theory and mode identification technique is proposed in this paper. With the fuzzy technology, the above mentioned uncertainties could be dealt with very well. Meanwhile, as the protective relays and circuit breakers may fail to operate in some cases, there are several different operating modes in protective relays and circuit breakers even for a same electrical device failure. Based on the received information, the proposed model could identify the most possible operating mode, and then the information corresponding to a fault hypothesis could be obtained. In the proposed model, the proposed fault diagnosis problem is described as a 0-1 integer programming one, and thus could be solved by the widely employed search technology, i.e., the well-known Tabu search method. The feasibility and efficiency of the proposed model is demonstrated by a sample power system.

关键词： Fault Diagnosis Fuzzy Sets Set-Covering Theory Mode Identification Technique

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power system Restoration in Restructured power Industry

Power System Restoration in Restructured Power Industry

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2007 IEEE power Engineering Society General Meeting (PES 2007), vol.6

作者： Zhenzhi Lin Fushuan Wen Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control under Ministry of Education North China Electric Power University Beijing China Department of Electrical Engineering South China University of Technology Guangzhou China

power system restoration decision-making is one of the most important and indispensable issues for ensuring fast power supply restoration to end users. In recent years, the power industry around the globe has been undertaking an in-depth restructuring, and this has led to some new challenges to the problem of power system restoration. In this paper, several important issues related to power system restoration in the traditional power industry and in the electricity market environment are analyzed and compared, and then the impacts of the restructuring efforts on the power system restoration are identified and clarified from several aspects including black-start, restoration tests, dispatching and distribution system service restoration. Up to now, in most of the practically operating electricity markets around the globe power system restoration ancillary service is still based on cost compensation rather than market mechanism.

关键词： Electricity market power system restoration Black-start Distribution system service restoration

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Economic Assessment of Voltage Sags Based on Quality Engineering Theory

Economic Assessment of Voltage Sags Based on Quality Enginee...

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power Tech Conference

作者： Gengyin Li Ming Zhou Biao Zhang Jin Yang Key Laboratory of Power System Protection Dynamic Security Monitoring and Control under Ministry of Education North China Electric Power University Beijing China School of Electrical and Electronic Engineering China Electric Power University Baoding Hebei China

Voltage sag, one of the modern power quality problems, may cause tremendous economic loss, which needs scientific method to evaluate. This paper proposes an approach using quality loss function and signal-to-noise ratio (SNR) in quality engineering theory to make economic assessment to voltage sag. The inverted normal probability loss function is used to describe losses of single-type sags, where SNR method is applied to integrate different types together. The index of sag-caused loss is proposed, which is an important parameter for PQ evaluation. A five-node 35 kV distribution system is used to verify the proposed approach. The result shows that the proposed method could effectively assess financial losses caused by sags and be a reasonable instruction for PQ evaluation, improvement and pricing.

关键词： power quality Voltage fluctuations power generation economics power engineering and energy IEEE members power markets Pricing Signal to noise ratio power system economics Electric variables measurement

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High frequency two-port circuit model for potential transformer based on the scattering parameter

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Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering 2007年第27期27卷 39-43页

作者： Zhang, Zhong-Yuan Lu, Fang-Cheng Liang, Gui-Shu Chen, Yu-Tong Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control North China Electric Power University Baoding 071003 China

For accurate simulation of voltage stress on secondary circuits caused by very fast transient over-voltage in gas insulated substation (GIS), a sophisticated modeling of potential and current transformers (PT/CT) is of vital importance. A new method is proposed to setup high frequency two-port circuit model of PT based on scattering parameters. First, the scattering parameters of PT are transformed in to Y-parameters and equivalent 'π' circuit model could be established. Second, vector fitting method is used to approximate admittances of equivalent 'π' circuit model by rational functions. At last, a circuit synthesis method for rational functions is applied to build circuit model. The simulation and measurement results are presented, which confirmed validity of the proposed model. The proposed method is effective and general, and overcomes the limitation of former methods. The model setup by this method can make simulation more accurate of conductive coupling through PT/CT in GIS.

关键词： Electric substations

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New algorithm based on time differential method to identify sympathetic inrush of transformers connected in wye-delta mode

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Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering 2007年第13期27卷 6-11页

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

In recent years, several cases of mal-operation of transformer differential protection due to sympathetic inrush appeared, but the problem how to distinguish the sympathetic inrush has not been resolved yet. Based on the synchronization measurement of the change of line current and differential current, an algorithm of distinguishing the sympathetic inrush and blocking the differential protection was put forward, which is applicable to two paralleled wye-delta connected transformers. Under the condition that the current transformer saturated, a method based on the mathematical morphology to identify the synchronization of the change of line current and differential current was proposed. Adopting the abrupt change of line current in the other side as auxiliary criterion, this algorithm could distinguish the sympathetic inrush, and internal, external fault during sympathetic inrush occurring. Simulation results validate its feasibility and reliability.

关键词： Transformer protection

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Improved multilevel SVPWM and its generalized algorithm

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Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering 2007年第4期27卷 90-95页

作者： Jiang, Xu Xiao, Xiang-Ning Zhao, Yang Ren, Ai-Ping Wang, Quan-Tao Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control North China Electric Power University Beijing 102206 China

The modulation is the key technique for multilevel inverter, an improved line voltage modulation strategy is proposed, which is based on the nonorthogonal AX coordinates SVPWM and makes some further comprehensive analysis on the original conclusions. The advantage of the strategy is that it has clearer physical meaning and more simple form. One improved three phases balance modulation algorithm for the single phase is got by the proper arrangement of output vectors taking advantage of the basic circuit theory;and then the generalized modulation strategy is deduced, which is suitable for three phases unbalance situation by the consideration of pulse area equal principle. This proposed modulation algorithm has simple format and clear physical concept, in addition, it's easy for the digital implementation. The digital simulations and experiments are presented to verify the conclusions.

关键词： Pulse width modulation

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Novel principle of transformer protection based on equivalent instantaneous leakage inductance and loop equation

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Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering 2007年第19期27卷 39-44页

作者： Wang, Zeng-Ping Ma, Jing Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control North China Electric Power University Baoding 071003 China

On basis of transformer loop equation, a novel principle of transformer protection using equivalent instantaneous leakage inductance is presented. The principle is independent of short-circuit reactance and leakage inductance of each side can be effectively monitored in real time. Therefore, sensitivity and reliability of transformer protection can both be improved by calculating equivalent instantaneous leakage inductance. The principle is also applicable for three-winding transformer. dynamic testing results verify this scheme that has been stable during inrush current and is able to reliably and quickly clear internal fault even fault is light.

关键词： Transformer protection

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