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2016 IEEE Conference on Electrical Insulation and Dielectric Phenomena, CEIDP 2016

作者： Zhang, Yunxiao Zhou, Yuanxiang Zhang, Ling Ming, Chen Zhang, Xu Yanchao, Sha State Key Lab of Control and Simulation of Power Systems and Generation Equipments Department of Electrical Engineering Tsinghua University Beijing100084 China North China Electric Power Research Institute Co Ltd. Beijing100045 China

ISBN: (纸本)9781509046546

Electrical tree break-down is the major failure problem in cable accessories, however, mechanisms of the electrical tree initiation and propagation are still lack of deeply research, especially in silicone rubber (SIR) which is widely used as insulation material for cable accessories. Long-term aging (0- 1000 h) experiments under the different voltages were conducted to observe electrical tree initiation and propagation processes. In trees initiation stage, with increasing of applied voltage, electrical tree initiation probability becomes larger, while tree initiation time dramatically decreases. The experiment observations demonstrated four shapes of trees which are dominated. As applied voltage increasing, the numbers of electrical trees life-cycles increased and exponential relationship was found between tree length and magnitude of applied voltage. It is noted that charges, whose energy exceeding a certain critical value, destroy microstructure of dielectric accumulatively via injection and extraction, and cause electrical trees initiate when it accumulates to a visible extent. © 2016 IEEE.

关键词： Life cycle

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Failure analysis of fan mill in thermal power plant 68

Failure analysis of fan mill in thermal power plant

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68th Society for Machinery Failure Prevention Technology Conference: Technology Solutions for Affordable Sustainment, MFPT 2014

作者： Liu, Chao Jiang, Dongxiang Chu, Fulei Department of Mechanical Engineering Tsinghua University Beijing100084 China State Key Laboratory of Control and Simulation of Power System and Generation Equipments Department of Thermal Engineering Tsinghua University Beijing100084 China

Fan mill is an important device in thermal plants, which supply coal power to boiler. Crack failures recently occurred in pulverizing wheels of fan mills in a power plant in China. The cracks happens in quite a few pulverizing wheels and they affect the normal operation. To find out the root cause of the cracks, Finite Element Analysis (FEA) of the pulverizing wheel is carried out in this work. The assembly with real dimensions is modelled to calculate the concentrated stress and strain with centrifugal load, driving load, and operational temperature taken into account. Contact effects are included in the finite element model as well as nonlinear material property. Based on the analysis, the crack causes are determined: (i) the initial stress exceeds the yield limit in normal operational condition, resulting low safety coefficient;(ii) the stress increases significantly in the worn pulverizing wheel, where the risk of failure is greatly increased.

关键词： Cracks

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Unit commitment considering demand response behavior based on utility maximization

Unit commitment considering demand response behavior based o...

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2017 IEEE Conference on Energy Internet and Energy System Integration, EI2 2017

作者： Zhang, Yumin Han, Xueshan Xu, Bo Zhang, Li Sun, Donglei Miao, Xiaofeng Jiang, Jiayin Key Laboratory of Power System Intelligent Dispatch and Control of Ministry of Education Shandong University Jinan China State Key Laboratory of Control and Simulation of Power Systems and Generation Equipment Department of Electrical Engineering Tsinghua University Haidian District Beijing100084 China Economic and Technology Research Institute of State Grid Shandong Electric Power Company Jinan China State Grid Shandong Electric Power Company Yantai Electric Power Company Yantai264001 China

ISBN: (纸本)9781538614273

The active participation of demand side resources in power grid operation not only benefits the individual participant but also benefits the whole system. The optimal goal can promote by excavating the active behaviors of demand side. The welfare maximization of market participant is the driving force of such active behaviors. Considering the independence of each user's behavior, the consumer's utility function is selected to depict consumer's preference and demand response behavior. In order to coordinate the consumers' maximum welfare with social welfare maximization, consumers' utility function and units' operation cost are integrated into Unit Commitment (UC) model. The objective function is to maximize social welfare, by subtracting units' operation cost from consumers' total utility, and this objective can be acquired. Considering the proposed model should be solved in a distributed manner, the idea of the centralized coordination and the decentralized decision-making is proposed. Based on the Lagrangian relaxation (LR) principle and distributed real-time pricing scheme, a closed-loop feedback mechanism is constructed to reflect the relationship among generator output, price level, and load demand. The ten generating units example can illustrate the effectiveness of the proposed method. © 2017 IEEE.

关键词： power markets

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Research on impulse discharge characteristics of parallel gap

Research on impulse discharge characteristics of parallel ga...

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2011 7th Asia-Pacific International Conference on Lightning, APL2011

作者： Chen, He Peng, Xiang Yu, Zhanqing Yu, Junjie Zeng, Rong Maintenance and Test Center of EHV Power Transmission Company China Southern Power Grid Co. Ltd. Guangzhou 510663 China State Key Laboratory of Control and Simulation of Power Systems and Generation Equipments Dept. of Electrical Engineering Tsinghua University Beijing 100084 China

ISBN: (纸本)9781457714665

With parallel gap, by controlling the motion path of the electric arc, effectively avoid burning and damaging the insulator during lightning strike so that its importance in measures of lightning protection for transmitting line is continually improved. Initial discharge position is key consideration during design of parallel gap and depends on discharge characteristics of parallel gap under the action of lightning surge when the lightning strikes the tower or line. This paper gives three types of parallel gap used to protect the composite insulator, sets up the impulse discharge test and observation platform including high-speed camera, studies the impulse discharge characteristics of parallel gap and analyzes the influence of structural parameters on the discharge characteristics. This study showed that there is randomness for discharge path of parallel gap;three types of parallel gap given in this paper can achieve 100% discharge rate of parallel gap;the determinant of discharge rate in the presupposition discharge area (PDA) is the distance that the presupposition discharge area stands out of the whole electrode plane. When this distance exceeds 20mm or more, it can ensure that most of the discharge occurs in the PDA;the parallel gap can reduce the insulation distance of 4000mm insulator about 40mm, U50 about 1%, which may approximately consider that the parallel gap has no influence on the insulating property of the insulator. © 2011 IEEE.

关键词： Electric arcs

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Influences of temperature on Space Charge in Gas-to-Liquid Oil-Impregnated Paper

Influences of temperature on Space Charge in Gas-to-Liquid O...

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International Conference on High Voltage Engineering and Application, ICHVE

作者： Yuanxiang Zhou Xin Huang Ling Zhang Yunxiao Zhang Zhongliu Zhou Chenyuan Teng China State Key Laboratory of Control and Simulation of Power Systems and Generation Equipment Tsinghua University Beijing China

ISBN: (数字)9781728155111

ISBN: (纸本)9781728155128

Gas-to-liquid (GTL) transformer oil has been on trial in converter transformers. However, its influence on the space charge characteristic is not clear. This work aims at exploring space charge characteristics of GTL oil at different temperatures as well as comparing with commercial naphthenic oil (KI50X). Space charge distribution during the polarization and the dissipation process in the GTL oil-impregnated paper at different temperature was measured by the pulse electroacoustic method (PEA), which were contrasted with those of the KI50X oil-impregnated paper. Results illustrated that high temperature accelerated the injection and migration of charge carriers in the oil-impregnated paper. And the polarity of the accumulated charge in the vicinity of anode changed from positive to negative with the increase of temperature. It was perceived that oil-paper conductivity and carrier mobility grew with the increase of temperature, resulting in the easier migration of injected charge to another electrode. Furthermore, the space charge dissipation rate in the GTL oil-impregnated paper is lower than that in the naphthenic oil-impregnated paper at the same temperature. Thus, a longer time interval of tests or switch operation in the factory test and operation process may need if GTL oil is used rather than naphthenic oil.

关键词： Oils Space charge power transformer insulation Oil insulation Electric fields Distortion Temperature measurement

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Multi-source information based current matching state estimation for distribution network

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Dianli Xitong Zidonghua/Automation of Electric power systems 2012年第16期36卷 53-57页

作者： Ju, Yuntao Wu, Wenchuan Cheng, Xueqi Zhang, Boming Sun, Hongbin State Key Laboratory of Control and Simulation of Power Systems and Generation Equipments Tsinghua University Beijing 100084 China Weifang Power Supply Bureau Shandong Provincial Power Corporation Weifang 261000 China

By taking into account the real-time measurement with low redundancy and of only partial current in distribution systems and referring to the quasi-real-time current measuring data of the metering system, the current matching technique is proposed to solve the distribution network state estimation. The matching current equations in the sense of optimal estimation and its systematic solution are deduced. Based on the assumption that the load power factor is stable, a quasi-real-time measurement generating method is proposed for loads. With boundaries demarcated by real-time current measurement, the distributed network is divided into several measured areas and current matching state estimation is made for each area. Numerical tests and results of an actual system show that the method proposed can satisfy the real-time application demand of the distribution system. ©2012 state Grid Electric power Research Institute Press.

关键词： state estimation

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Planning of active power distribution network based on source-network-load collaborative optimization 16

Planning of active power distribution network based on sourc...

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16th IET International Conference on AC and DC power Transmission, ACDC 2020

作者： Jiang, Zhicheng Yu, Qingguang Li, Ang Xiong, Yufeng Long, Gaoxiang Liu, Yuming Key Laboratory of Modern Power System Simulation and Control and Renewable Energy Technology Ministry of Education Northeast Electric Power University Jilin132012 China State Key Laboratory of Power Systems Department of Electrical Engineering Tsinghua University Beijing China

ISBN: (纸本)9781839533914

With the fast development of renewable energy generation, the randomness and volatility seriously threaten the stability of the power system. In order to improve the consumption rate of renewable energy and the economic benefit, the source-network-load collaborative optimization is put forward and widely used in the power system. And the active power distribution network which consists of the energy storage devices and flexible load is the best carrier to realize it. Based on the active power distribution network planning, this paper firstly designs an economic index covering construction cost and operation cost as the optimization objective. Then with the physical constraints consisting of the physical features of generation units, energy storage devices and flexible load, the source-network-load collaborative optimization model of active power distribution network is established. Finally, a case of city distribution network is presented to verify the effect of source-network-load collaborative optimization and the efficiency of the optimization model. © 2020 Institution of Engineering and Technology. All rights reserved.

关键词： Optimization

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Medium and long-term wind energy forecasting method considering multi-scale periodic pattern 10

Medium and long-term wind energy forecasting method consider...

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2020 10th International Conference on power, Energy and Electrical Engineering, CPEEE 2020

作者： Lin, Yisha Lu, Zongxiang Qiao, Ying Li, Mingjie Liang, Zhifeng State Key Lab of Control and Simulation of Power Systems and Generation Equipment Department of Electrical Engineering Tsinghua University Haidian District Beijing100084 China State Grid Corporation of China Haidian District Beijing100031 China

Medium and long-term weather sequence forecast becomes unreliable beyond two weeks since the weather is a chaotic system. Using values of same months for electricity prediction of wind power is the usual method. This approach defaults wind power output with annual cycle law. However, the periodic pattern can be very complicated in fact with multiple time scales. This paper proposes an approach with multi-scale periodic pattern considered. The application of parametric estimation on cumulative distribution function avoids the difficulty of predicting the power curve. Meteorological condition is considered to some extent via multi-scale periodic pattern explored basing on historical energy data. This work is an exploration for medium and long-term wind power forecasting that can well adapt to existing conditions. It has better prediction accuracy than the method without multi-scale periodicity considered. © 2020 The Authors, published by EDP Sciences.

关键词： Wind power

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Design Optimization of Ferrite Rings for VFTO Mitigation

Design Optimization of Ferrite Rings for VFTO Mitigation

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作者： He, Jiaxi Guan, Yonggang Liu, Weidong Chen, Weijiang Li, Zhibing The Department of Electrical Engineering State Key Lab of Control and Simulation of Power Systems and Generation Equipment Tsinghua University Beijing100084 China State Grid Corporation of China Beijing100031 China China Electric Power Research Institute Beijing100192 China

very-fast transient overvoltage (VFTO)-related problems are raising growing concerns in China with the development of ultra-high voltage. The practice of fitting ferrite rings on gas-insulated switchgear busbars for VFTO mitigation has long been proposed but few investigations on its design optimization were conducted. Based on theoretical analysis of the simplified model, the optimal damping condition of ferrite rings is proposed, which is conducive to the type selection. The number of rings to be employed to ensure visible suppressing effects is given through simulations and the influence of the saturation is discussed. Impact on the power frequency is analyzed to be negligible. Finally, comparisons are made between the theoretical conclusions and existing experiment results, which approve the optimal damping condition and agree with the number of rings to be employed. © 2014 IEEE.

关键词： Damping

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Phase Segmentation of Ni/YSZ Anode for Solid Oxide Fuel Cells by Deep Learning

Phase Segmentation of Ni/YSZ Anode for Solid Oxide Fuel Cell...

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243rd ECS Meeting

作者： Wang, Y. Matsui, Y. Hosomizo, A. Kishimoto, M. Han, M. Iwai, H. Department of Mechanical Engineering and Science Kyoto University Nishikyo-ku Kyoto615-8540 Japan State Key Laboratory of Control and Simulation of Power Systems and Generation Equipment Department of Energy and Power Engineering Tsinghua University Beijing100084 China

ISBN: (纸本)9781607685395

A deep learning network is implemented for the phase segmentation of Ni/YSZ anode of solid oxide fuel cells (SOFCs), as manual segmentation of focused ion beam-scanning electron microscopy (FIB-SEM) images is time-consuming. Segmentation is performed on two samples with different volume ratios of Ni to YSZ. The mean intersection over union (mIoU) reaches 0.9363, indicating good agreement between the predicted images and the manually segmented images. Furthermore, the impact of image augmentation on segmentation accuracy is investigated, and it is found that augmentation is necessary when the number of images in the training set is small or the training and testing sets come from different samples. Furthermore, mixing a sixth of manually segmented images from a new sample into the training set can significantly improve the accuracy of automated segmentation for the new sample. This strategy reduces the number of images requiring manual segmentation and improves processing efficiency. © The Electrochemical Society.

关键词： Solid oxide fuel cells (SOFC)

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