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Influence characteristics of water penetration on fibre-reinforced polymer/rigid polyurethane foam interface of the composite cross-arm considering natural ageing

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High Voltage 2024年第1期9卷 81-93页

作者： Jun Xie Zhe Zhou Ziqian Liu Haonan Tian Sigang Zhang Qing Xie Hebei Provincial Key Laboratory of power Transmission equipment Security Defense North China Electric Power UniversityBaodingChina State Grid Gansu Electric power Company LanzhouChina

Fibre-reinforced polymer(FRP)/rigid polyurethane foam(RPUF)interface is susceptible to moisture intrusion in addition to natural ageing during *** study investigated the influence of moisture intrusion on the FRP/RPUF interface under natural ageing using experiments and molecular dynamics(MD)*** absorption,shear strength,and leakage current tests were used to clarify the changes in the interface *** degradation mechanism of moisture intrusion at the interface under natural ageing was revealed by MD simulation and *** results show that the natural ageing of interfacial materials will slightly reduce the quality of the interface but will reduce the water resistance of the material and promote the process of water intrusion into the *** addition,water mainly invades the interface through *** water penetration,the interfacial bonding strength and insulation performance significantly *** and hydrolysis of interfacial materials are the main reasons for decreased interfacial *** can cause irreversible damage to the interface,increasing interface defects and water *** vicious cycle of material hydrolysis is the ultimate cause of interfacial *** polar molecules produced by this process and the water absorbed by the interface caused the degradation of the interface insulation performance.

关键词： interface polyurethane interfacial

Simulation of gas-solid flow characteristics of the circulating fluidized bed boiler under pure-oxygen combustion conditions

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Chinese Journal of Chemical Engineering 2024年第6期70卷 9-19页

作者： Kaixuan Gao Xiwei Ke Bingjun Du Zhenchuan Wang Yan Jin Zhong Huang Yanhong Li Xuemin Liu Key Laboratory of Special equipment Safety and Energy-Saving for State Market Regulation China Special Equipment Inspection&Research InstituteBeijing 100029China department of Energy and power Engineering Tsinghua UniversityBeijing 100084China School of Electrical and power Engineering Taiyuan University of TechnologyTaiyuan 030024China

Under the pressure of carbon neutrality,many carbon capture,utilization and storage technologies have witnessed rapid development in the recent years,including oxy-fuel combustion(OFC)***,the conventional OFC technology usually depends on the flue gas recirculation system,which faces significant investment,high energy consumption,and potential low-temperature corrosion *** these deficiencies,the direct utilization of pure oxygen to achieve particle fluidization and fuel combustion may reduce the overall energy consumption and CO_(2)-capture *** this paper,the fundamental structure of a self-designed 130 t·h^(-1) pure-oxygen combustion circulating fluidized bed(CFB)boiler was provided,and the computational particle fluid dynamics method was used to analyze the gas-solid flow characteristics of this new-concept boiler under different working *** results indicate that through the careful selection of design or operational parameters,such as average bed-material size and fluidization velocity,the pure-oxygen combustion CFB system can maintain the ideal fluidization state,namely significant internal and external particle ***,the contraction section of the boiler leads to the particle backflow in the lower furnace,resulting in the particle suspension concentration near the wall region being higher than that in the center ***,the upper furnace still retains the classic core-annulus flow *** addition to increasing solid circulation rate by reducing the average bed-material size,altering primary gas ratio and bed inventory can also exert varying degrees of influence on the gas-solid flow characteristics of the pure-oxygen combustion CFB boiler.

关键词： Circulating fluidized bed Pure-oxygen combustion Gas-solid flow characteristics Simulation CO_(2)capture

Study on moisture absorption characteristics of glass fibrereinforced epoxy resin material for composite insulators based on the 3D-Fick model

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High Voltage 2024年第4期9卷 888-901页

作者： Yuming Zhang Yunpeng Liu Sizu Hou Jianghai Geng Ping Wang Hebei Provincial Key Laboratory of power Transmission equipment Security Defense North China Electric Power UniversityBaodingChina Hebei Key Laboratory of power Internet of Things Technology BaodingChina

Long-term exposure to moisture leads to a gradual deterioration of performance and reduced service life of glass fibre-reinforced epoxy resin(GFRP)material in composite ***,it is necessary to analyse the moisture absorption characteristics of GFRP material and the evolution of damage to their internal interface *** absorption tests on GFRP rod material used in composite insulators to obtain their three-dimensional diffusion coefficients are *** force microscopy was then employed to obtain the composite material system's fibre/matrix interfacial phase ***,a finite element model incorporating representative volume elements with interfacial phases and a mesoscale transient moisture absorption finite element model for the composite material was ***,the moisture absorption characteristics of GFRP material and the evolution of damage to the interfacial phase under thermal-humidity cycling conditions were *** results showed that the diffusion coefficient along the fibre direction in GFRP material was higher than that in the perpendicular *** moisture diffusion finite element model,incorporating an anisotropic interfacial phase,fitted the anisotropic diffusion coefficients of GFRP material more *** moisture invaded the GFRP material,the mismatch stresses continuously increased during the moisture ***,the non-uniform arrangement of fibres resulted in uneven distribution of moistureinduced stresses inside the material,leading to higher mismatch stresses in areas with dense fibre arrangements in the *** high and low humidity cycles led to the development of micro-cracks,micro-porosity,and interface debonding along the fibre direction at the GFRP material interfaces,thereby affecting the anisotropic moisture absorption characteristics of the *** findings of this study provide valuable insights into the mechanisms underlying the

关键词： composite fibre moisture

Study on the dynamic mechanical properties of winding-block axial structure considering short circuit strain rate effect

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High Voltage 2024年第2期9卷 380-390页

作者： Xinyu Wang Ping Wang Jianghai Geng Zikang Zhang Fangcheng Lü Shuguo Gao Hebei Provincial Key Laboratory of power Transmission equipment Security Defense North China Electric Power UniversityBaodingChina State Grid Hebei Electric power Research Institute ShijiazhuangChina

Transformers may suffer multiple short-circuit impacts during long-term operation,and axial instability is one of the typical types of serious accidents caused by short-circuit *** axial instability form of the winding-block structure is analysed,and the dynamic solution of the winding short-circuit electromagnetic force is obtained by estab-lishing the three-dimensional magnetic-circuit-force multi-physical field coupling simulation *** influence of strain rate on the cushion block constitutive equation is corrected,and the modified model is verified by short-circuit impact test and quasi-static *** research results show that for 110 kV 31.5 MVA transformers,the maximum electromagnetic axial resultant force of winding is 363.16 kN,and the ultimate tilt force is 1214.2 *** pre-tightening force configuration is accordingly recom-mended to range from 363.16 to 608.28 kN,which is narrowed by 18.49%compared with the static calculation method;Meanwhile,adding a logarithmic strain rate correction term to the classical constitutive equation of the cushion block can achieve a good correction of the stress-strain relationship with the coefficient of determination above 0.99,and the cushion block has a larger elastic modulus under high strain rate *** research results provide an important theoretical reference for the axial stability structure of transformers.

关键词： axial correction structure

Effect of operational and geometric parameters on the hydrodynamics of a Wurster coater:A CFD-DEM study

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Particuology 2024年第2期85卷 62-76页

作者： Yinqiang Song Tuo Zhou Ruiqi Bai Man Zhang Hairui Yang department of Energy and power Engineering Tsinghua UniversityBeijing100084China Key Laboratory for Thermal Science and power Engineering of Ministry of Education Tsinghua UniversityBeijing100084China State Key Laboratory of power System and Generation equipment Tsinghua UniversityBeijing100084China

A coupled CFD-DEM method was used to study the hydrodynamics of a Wurster ***,the CFD part of the model was validated by the accurate prediction of the pressure drops over a pseudo-2D fluidized bed under various gas *** effect of gas velocity,gap height,tube length and batch volume of the particles on the cycle time and the residence time of the particles was thoroughly *** central jet gas velocity ui was found to speed up the particle cycle but undermine the coating *** gas velocity at the horizontal transport zone u2 was able to promote the horizontal transport of the particles but should not be too high,otherwise,it would obstruct the normal falling back of the particles in the downward *** gap heights would decrease the coating efficiency but tube length had little impact on *** increment of batch volume would commonly abase the cycle time and the working efficiency under a given *** de-fluidization problem arose when the batch volume increased to 550 ***,this problem could be swept out by the optimization of u1 and *** a mixture of different sizes,the coarse particles enjoyed higher coating efficiency and could travel closer to the *** may shield the fine particles from getting enough coating liquids,and thus coarse particles and fine particles were not recommended to get coated in the same batch.

关键词： Numerical simulation CFD-DEM Wurster coater Hydrodynamics Cycle time Residence time

Analysis of multi-objective optimisation method for main insulation structure configuration scheme of valve-side winding of ultra-high voltage converter transformer considering multi-field coupling

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High Voltage 2024年第2期9卷 296-308页

作者： Lijun Yang Zhidong Cheng Li Cheng Ruijin Liao State Key Laboratory of power Transmission equipment Technology School of Electrical EngineeringChongqing UniversityChongqingChina

Because DC conductivities of oil-paper materials can be easily affected by electric field and temperature,the electrical properties under electro-thermal coupling of oil-paper materials should be considered when optimising the insulation structure of valve-side winding of the converter *** on the finite element multi-physical field coupling simulation,the multi-objective optimisation of main insulation structure of valve-side winding is carried *** view of the high time consuming of multi-physical field calculation and the actual needs of an insulation structure optimisation,the Kriging method and technique for order preference by similarity to the ideal solution(TOPSIS)method are introduced,and combines them with NSGA-II to obtain a joint algorithm that can be used for the optimisation of insulation structure of the converter *** using the joint algorithm of multi-objective optimisation,the insulation structure configuration scheme of valve-side winding is *** can be seen from the experiment result that,on the one hand,the joint algorithm adopted can obtain the insulation structure configuration scheme that meets the design *** the other hand,when facing the configuration scheme optimisation under multi-field coupling,the computational time required by this method is only 0.15%of that required by original genetic algorithm.

关键词： converter insulation coupling

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

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

Microstructure-ionisation potential relationship analysis for understanding the molecular ionisation difference of natural esters during the impulse discharge via DFT calculation

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High Voltage 2024年第4期9卷 920-929页

作者： Jingwen Zhang Jian Hao Wenyu Ye Junyi Zhang Ruijin Liao State Key Laboratory of power Transmission equipment Technology School of Electrical/EngineeringChongqing UniversityChongqingChina

Understanding the impulse discharge behaviour of natural ester(NE)is crucial for its safe application in high-voltage *** ionisation potential(IP)of triglycerides plays a significant role in the process of molecular ionisation during impulse discharge for *** correlation coefficients between molecular size,frontier orbital,electrostatic potential,polarity,and IP were *** the quantitative microstructure-IP model for triglycerides were built,which revealed that IP is strongly related to the highest occupied molecular orbital(HOMO)energy EHM,as well as the average value of positive electrostatic potential V_(p)(t),the average value of negative electrostatic potential V_(p)(-),and the surface area of negative electrostatic potential S(-).The HOMO and negative electrostatic potentials of saturated triglycerides are predominantly linked to the carbonyl O ***,in unsaturated triglycerides,the influence of C=C double bonds on HOMO and negative electrostatic potentials is more ***,the IP of unsaturated NE with C=C bonds is lower than that of saturated NE,rendering it more susceptible to ionisation under a strong electric field which is unfavourable for impulse breakdown *** structure-property correlation analysis is valuable for understanding ionisation mechanism during the impulse discharge breakdown of NE at the microscopic level.

关键词： electrostatic potential bonds