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Model moisture transport in oil-paper insulation of transformer:Theory and experiment

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high voltage 2024年第4期9卷 879-887页

作者： Junjie Zhou Zhicheng Wu Yiran Guo Rui Zhang Wenbing Zhu Qiaogen Zhang State Key Laboratory of Electric insulation and Power Equipment Xi'an Jiaotong UniversityXi'anChina State Grid Shandong Electric Power research institute JinanChina

The insulation performance of oil paper insulation is significantly affected by moisture such that monitoring moisture content is ***,it is difficult to obtain the moisture content accurately due to its dynamic change under multi physical *** the moisture transportation in oil paper insulation under multi physical fields becomes a vital method in solving the problem.A multi physical model describing moisture migration was proposed,which considered the effects of temperature on moisture in different existing states in oil-immersed paper(OIP).The temperature distribution formed a vapour pressure gradient to drive moisture migration and affected migration ***,experiments and simulations of moisture migration were performed,which showed that the experiments were in good agreement with *** results revealed that the temperature gradient caused uneven moisture distribution and the increased temperature reduced OIP moisture *** established model could fully characterise moisture migration under temperature gradient,which provided a theoretical reference for predicting the risk of partial dampness and evaluating insulation performance.

关键词： moisture insulation distribution

research on vibration energy harvesting technology of power equipment based on alternating magnet array

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high voltage 2024年第2期9卷 336-345页

作者： Pinlei Lv Chengyu Fan Aijun Yang Huan Yuan Jifeng Chu Mingzhe Rong Xiaohua Wang State Key Laboratory of Electrical insulation and Power Equipment Xi'an Jiaotong UniversityXi'anChina State Grid Sichuan Electric Power research institute ChengduChina

Vibration with a frequency of 100 Hz is widely distributed in the power equipment,and it can provide a new way to supply energy for sensors by vibration energy *** vibration energy harvesting method based on electromagnetic induction principle was studied through the arrayed structure of magnets and *** magnetic field models were established for four magnet array structures and it was found that the alternating magnet array has the largest magnetic flux and magnetic flux *** on the alternating magnet array,prototypes of energy harvester with vertical and parallel movement mode were *** structural parameter optimisation analysis,two different energy harvesters were fabricated and it was found that the energy harvester with a parallel movement mode has better output *** energy harvester could provide output voltage/current and power of 8.35 V/17.39 mA and 15.13 mW(matched resistance is 200Ω)at an acceleration of 5 m⋅s^(-2).The 100 mF capacitor could be charged to 2.72 V within 300 s,and the final voltage of the capacitor is greater than 3 V,which could sustainably drive commercial wireless temperature/humidity sensors.

关键词： power energy alternating

Analyses on an electronic voltage transformer's failure by its resonance with very fast transient overvoltage and suppression

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high voltage 2024年第1期9卷 150-162页

作者： Ruoyu Han Houda Zhu Qing Chen Hongbin Li Yue Tong Linshan Han Yang Jiao School of Electrical and Electronic Engineering Huazhong University of Science and TechnologyWuhanChina China Electric Power research institute WuhanChina School of Artificial Intelligence and Automation Huazhong University of Science and TechnologyWuhanChina

As voltage measuring devices are widely used in the high voltage power system with a primary-secondary-fusion structure,electronic voltage transformers are directly connected to the primary conductor and would face much more serious electromagnetic environments than general secondary *** a result,they would still experience failures even when general protection measures are adopted to suppress overvoltages'*** address this issue,an innovative method is proposed after analyses are conducted on the resonance between a transformer and an *** this method,an air-cored coil is installed in a transformer to artificially shift its natural frequency and to dodge the high-frequency dominant component of a transient overvoltage,avoiding the aforementioned resonance and suppressing the secondary *** addition,simulations and laboratory tests are conducted to prove this method's validity.

关键词： transient resonance mentioned

Permanent lining castable with low bulk density and thermal conductivity:bauxite castable for tundish obtained by adding pearlescent sand

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Journal of Iron and Steel research International 2024年第3期31卷 634-646页

作者： Yi Wang Jian Yang Bao Wang Hai-jun Zhang Juan Han Pei-yan Pei Wen-long Lv Jian-an Zhou The State Key Laboratory of Refractories and Metallurgy Wuhan University of Science and TechnologyWuhan 430081HubeiChina Key Laboratory for Ferrous Metallurgy and Resources Utilization of Ministry of Education Wuhan University of Science and TechnologyWuhan 430081HubeiChina wuhan research institute of Metallurgical Construction MCCWuhan 430081HubeiChina

The low thermal conductivity and light mass of castables for tundish permanent linings are crucial for minimizing the heat loss of molten *** consideration of the low bulk density and thermal conductivity of pearlescent sand,the thermal insulation performance of castables was attempted to be improved by adding pearlescent *** sand was modified to prevent the strength of its porous structure from *** modification mechanism of pearlescent sand and the effect of pearlescent sand on the performance of bauxite castables were *** results suggested that the addition of the modified pearlescent sand significantly raised the apparent porosity and decreased the bulk density of bauxite *** 1000℃,the bulk density of more than 60%of the modified pearlescent sand-bauxite castable was only 2.03 g/cm^(3).The mechanical properties and thermal shock resistance of the modified pearlescent sand-bauxite castable were inferior to those of conventional bauxite castable but were adequate to meet the use conditions of casta-bles for tundish permanent *** high temperatures of 200-800℃,the thermal conductivity of more than 60%of the modified pearlescent sand-bauxite castable was smaller than that of conventional bauxite *** addition of the modified pearlescent sand can greatly reduce the thermal conductivity and bulk density of bauxite castable.

关键词： Pearlescent sand-Hydrophobic modification Bauxite castable Thermal insulation performance Mechanical property

Defect recognition of oil-pressboard insulation based on frequent arc reignition phenomenon under switching impulse voltage

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high voltage 2024年第4期9卷 773-785页

作者： Simeng Li Yukun Zhang Yunfei Jia Shengchang Ji Yanhua Han Wensen Wang State Key Laboratory of Electrical insulation and Power Equipment School of Electrical EngineeringXi'an Jiaotong UniversityXi'anChina State Grid Shaanxi Electric Power research institute Xi'anChina

In the past three years,a number of oil-immersed ultra-high-voltage shunt reactors have experienced discharge defects when being put into operation,resulting in an overload of ***,detecting and identifying these discharge defects caused by switching impulse voltage is challenging under steady-state *** poses unpredictable and difficult-to-assess safety risks for the longterm operation of the equipment and subsequent transient ***,comprehending the discharge behavior of oilpressboard(PB)insulation under switching impulse voltage and devising a method to identify defects becomes *** study focuses on investigating the frequent arc reignition(FAR)pattern exhibited by typical defects under both standard and oscillation switching impulse *** objective is to uncover the mechanism behind FAR and propose a defect recognition strategy suitable for transient *** study reveals the FAR process will occur at least once during the breakdown process;the FAR phenomenon is the weakest in the surface defect with a weak vertical electric *** average recovery voltage percentage and the average discharge interval of the FAR process decrease with increasing impulse amplitude or oscillation ***,the average number of discharges decreases with higher oscillation frequency,while it initially increases and then decreases with increaseing *** on the analysis of the number of FAR processes and their variation in terms of amplitude or discharge interval,a method for recognizing oil-PB defects during switching transient processes is developed and successfully applied to a case study involving acetylene overload in a 1000 kV shunt reactor.

关键词： field. insulation oscillation

voltage-dependent P-Q Reserve Capacity Evaluation for TSO-DSO Interface Considering Uncertainties of DGs and FLs

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CSEE Journal of Power and Energy Systems 2024年第5期10卷 1935-1954页

作者： Yeyan Xu Liangzhong Yao Tianjiao Pu Siyang Liao Fan Cheng Ye Li Xinying Wang School of Electrical Engineering and Automation Wuhan UniversityWuhan 430072China China Electric Power research institute Beijing 100085China. China Electric Power research institute Beijing 100192China.

Increasing distributed generators(DGs)and flexible loads(FLs)enable distribution systems to provide both active and reactive power reserves(P-Q reserves)in supporting the frequency and voltage regulations of transmission ***,such requirements at the interface between the transmission system operator(TSO)and distribution system operator(DSO)affect the distribution system operation security,considering the uncertainties of DGs and *** exploit the reserve potential of distribution systems,this paper investigates the voltagedependent P-Q reserve capacity(V-PQRC)of such types of distribution systems.V-PQRC reflects the feasible space of PQ reserves that the DSO can provide to the TSO taking the voltage deviation limit at TSO-DSO interface into consideration,while ensuring the distribution system operation security under uncertainties of DGs and *** evaluation method for VPQRC at the TSO-DSO interface is *** improve the robust performance of the evaluation method,the DG uncertainty is captured by a generalized ambiguity set and the FL uncertainty is addressed by designing a constrained sliding mode controller(CSMC).Three objectives are considered in the evaluation,i.e.,P reserve capacity,Q reserve capacity,and the voltage deviation limit at the TSO-DSO ***,a multiobjective optimization model integrating the generalized robust chance-constrained optimization and CSMC(GRCC-CSMC)is established for V-PQRC evaluation to obtain the Pareto optimal reserve ***,a non-approximated selecting(NAS)method is proposed to build up a simplified V-PQRC linear model,which can be convenient to apply in the transmissiondistribution system *** results reveal that the V-PQRC evaluation method can achieve a good performance of accuracy and robustness against uncertainties.

关键词： Generalized robust chance-constrained optimization reserve capacity evaluation sliding mode control transmission-distribution system coordination voltage-dependent P-Q reserve capacity

Preparation and Photostriction Properties of BiFeO_(3)-BaTiO_(3)Ceramics

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Journal of wuhan university of Technology(Materials Science) 2024年第5期39卷 1079-1086页

作者： ZHENG Zewei ZHANG Liqiang CHEN Chen CAO Minghe YI Zhiguo LIU Hanxing School of Materials Science and Engineering Wuhan University of TechnologyWuhan 430070China State Key Laboratory of high Performance Ceramics and Superfine Microstructure Shanghai Institute of CeramicsChinese Academy of SciencesShanghai 200050China School of Microelectronics Shanghai UniversityShanghai 200444China International School of Materials Science and Engineering Wuhan University of TechnologyWuhan 430070China

Under illumination by 405,520 and 655 nm monochromatic visible light(light intensity of 30 kW/m^(2)),large photostriction(ΔL/L)of 0.19%,0.13%and 0.26%for 67BiFeO_(3)-33BaTiO_(3)(67BF-33BT)lead-free ferroelectric ceramics are obtained,*** studying the ferroelectric and photoelectric properties in conjunction with in situ Raman spectroscopy,it is found that the photostrictive effect of 67BF-33BT is not caused by the electrical strain induced by abnormal photovoltaic voltage,but related to the optical induced oxygen octahedral *** 67BF-33BT lead-free ferroelectric material with excellent photostrictive response in the visible light region is expected to play an important role in the field of optical drive electromechanical devices.

关键词： ferroelectric ceramics photostrictive effect visible light response

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Steady-state voltage Security-constrained Optimal Frequency Control for Weak HVDC Sending-end AC Power Systems

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Journal of Modern Power Systems and Clean Energy 2024年第2期12卷 658-669页

作者： Qiangqiang Wang Liangzhong Yao Jian Xu Yuping Zheng Wei Li Wei Wang School of Electrical Engineering and Automation Wuhan UniversityWuhan 430072China Hubei Engineering and Technology research Center for AC/DC Intelligent Distribution Network(wuhan university) Wuhan 430072China State Key Laboratory of Smart Grid Protection and Control NARI Group Corporation(State Grid Electric Power Research Institute)Nanjing 211106China

Due to the fact that a high share of renewable energy sources(RESs)are connected to high-voltage direct current(HVDC)sending-end AC power systems,the voltage and frequency regulation capabilities of HVDC sending-end AC power systems have *** has resulted in potential system operating problems such as overvoltage and overfrequency,which occur simultaneously when block faults exist in the HVDC *** this study,a steady-state voltage security-constrained optimal frequency control method for weak HVDC sending-end AC power systems is *** integrated virtual inertia control of RESs is employed for system frequency *** dynamic reactive power compensation devices are utilized to control the voltage of all nodes meet voltage security ***,an optimization model that simultaneously considers the frequency and steady-state voltage security constraints for weak HVDC sending-end AC power systems is *** optimal control scheme with the minimum total cost of generation tripping and additional dynamic reactive power compensation required is obtained through the optimization *** are conducted on a modified IEEE 9-bus test system and practical Qing-Yu line commutated converter based HVDC(LCC-HVDC)sending-end AC power system to verify the effectiveness of the proposed method.

关键词： Renewable energy source(RES) high-voltage direct current(HVDC) AC power system optimal frequency control steady-state voltage security dynamic reactive power compensation

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A Parallel-type Load Damping Factor Controller for Frequency Regulation in Power Systems with high Penetration of Renewable Energy Sources

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Journal of Modern Power Systems and Clean Energy 2024年第4期12卷 1019-1030页

作者： Zhe Zhang Siyang Liao Yuanzhang Sun Jian Xu Deping Ke Bo Wang Rui Chen Yibo Jiang Hubei Engineering and Technology research Center for AC/DC Intelligent Distribution Network School of Electrical Engineering and AutomationWuhan UniversityWuhan 430072China State Grid Hubei Electric Power Company Limited Economic research institute Wuhan 430074China State Grid(Suzhou)City&Energy research institute Company Limited Suzhou 215000China

Renewable energy sources(RESs)are rapidly devel-oping and their substitution for traditional power generation poses significant challenges to the frequency regulation in pow-er *** load damping factor D characterizes the active power of load that changes with power system frequency,which is an important factor influencing the frequency ***-ever,the value of D is small,resulting in the limitation in fre-quency regulation of the power *** paper proposes a parallel-type load damping factor controller to enhance load damping factor by utilizing static var generators(SVGs)in ***,it discusses the configuration method for the relevant parameters of the controller,evaluates its frequen-cy regulation capability,investigates the impact of large-scale application of the controller on static and dynamic loads,and conducts a comprehensive evaluation of the impact of the damp-ing factor control process on the voltage stability of the main *** large-scale application of the proposed controller can significantly improve the frequency regulation capability,and al-most have no influence on the working status of the *** can also significantly improve the dynamic performance of system *** proposed controller can provide technical sup-port for the frequency regulation of new power systems with high proportion of RESs.

关键词： Load damping factor parallel-type load damping factor controller power system frequency regulation highproportion renewable energy system

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