检索结果-南通市图书馆

Measured Impedance and Threshold Value of Electrode Line Impedance Supervision Based Protection in HVDC Transmission System

在线全文

学校读者我要写书评

暂无评论

Journal of Modern Power Systems and Clean Energy 2023年第4期11卷 1294-1304页

作者： Qiang Sun Bin Li Jiawei He Ye Li key laboratory of Smart Grid of Ministry of Education Tianjin UniversityTianjinChina State Key Laboratory of Reliability and Intelligence of Electrical Equipment Hebei University of TechnologyTianjinChina

At present,electrode line impedance supervision(ELIS)based protection is widely used to detect faults on grounding electrode lines,which are indispensable elements of high-voltage direct current(HVDC)systems.The existing theoretical analysis of measured impedance is based on lumped line model and the threshold value is generally set according to engineering experience,which have caused the dead zone problem and even accidents.Therefore,a study on measured impedance of ELIS-based protection and its threshold value selection method is carried out to solve this problem.In this study,the expressions of measured impedance under normal operation and fault conditions are deduced based on rigorous and accurate line model.Based on the expressions,the characteristics of the measured impedance are calculated and analyzed.With the characteristics of the measured impedance,the applicability of the protection with the traditional threshold value is further discussed and the distribution of the dead zone can be located.Then,the method to calculate the threshold value of ELIS-based protection is proposed.With a proper threshold value selected by the proposed method,the dead zone of ELIS-based protection is effectively eliminated,and the protection can identify all types of faults even with large transition resistances.Case studies on PSCAD/EMTDC have been conducted to verify the conclusion.

关键词： Grounding electrode line electrode line impedance supervision(ELIS)based protection measured impedance characteristic threshold value selection

Molecular pyrolysis process and gas production characteristics of 3-element mixed insulation oil under thermal fault

在线全文

学校读者我要写书评

暂无评论

High Voltage 2022年第6期7卷 1130-1140页

作者： Dawei Feng Ge Chen Xiaoyu Yan Jian Hao Ruijin Liao state key Lab of reliability and intelligence of electrical equipment School of Electrical EngineeringHebei University of TechnologyTianjinChina Hebei International Joint Research Center for reliability and intelligence of Modern electrical equipment TianjinChina state key laboratory of Power Transmission equipment&System Security and New Technology School of Electrical EngineeringChongqing UniversityChongqingChina

Mixed insulation oil is considered as a desired substitute for traditional mineral oil.A novel 3-element mixed insulation oil has been developed in our previous works,whose parameters satisfy the mineral oil standard(IEC 60296:2012).In the application of transformer oil,dissolved gas analysis is an effective method for insulation fault diagnosis.Thermal fault is a common and typical fault in transformers;however,the pyrolysis process and gas production characteristics of mixed insulation oil under thermal fault remain unknown.In this study,the pyrolysis process and gas production characteristics of 3-element mixed insulation oil have been studied through simulation and experiments,and mineral oil is equally treated for comparison.Results show that the gas production characteristics of mixed oil are closely related to its base oils,and 3-element mixed insulation oil generates more H_(2)and C_(2)H_(6)under thermal fault,in which the percentage of H_(2)in the mixed oil is always three times that in the mineral oil.More CO_(2)is produced in mixed oil under thermal fault because of ester bonds;C_(2)H_(4)is also a main characteristic gas for mixed insulation oil under thermal fault,and its proportion increases continuously with the increase of temperature.For mineral oil,the weight loss temperature in thermogravimetric(TG)curve corresponds to evaporation rather than decomposition.Natural esters have poor thermal stability according to simulation results,but they possess high flash point and weight loss temperature in the TG curve primarily because of their large average molecular weight.

关键词： insulation fault pyrolysis

Microstructure,Properties and Crack Suppression Mechanism of High-speed Steel Fabricated by Selective Laser Melting at Different Process Parameters

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Chinese Journal of Mechanical Engineering 2023年第2期36卷 91-105页

作者： Wenbin Ji Chuncheng Liu Shijie Dai Riqing Deng State Key Laboratory of Reliability and Intelligence of Electrical Equipment Hebei University of TechnologyTianjin 300130China School of Mechanical Engineering Hebei University of TechnologyTianjin 300130China

To enrich material types applied to additive manufacturing and enlarge application scope of additive manufacturing in conformal cooling tools,M2 high-speed steel specimens were fabricated by selective laser melting(SLM).Effects of SLM parameters on the microstructure and mechanical properties of M2 high-speed steel were investigated.The results showed that substrate temperature and energy density had significant influence on the densification process of materials and defects control.Models to evaluate the effect of substrate temperature and energy density on hardness were studied.The optimized process parameters,laser power,scan speed,scan distance,and substrate temperature,for fabricated M2 are 220 W,960 mm/s,0.06 mm,and 200℃,respectively.Based on this,the hardness and tensile strength reached 60 HRC and 1000 MPa,respectively.Interlaminar crack formation and suppression mechanism and the relationship between temperature gradient and thermal stress were illustrated.The inhibition effect of substrate temperature on the cracks generated by residual stresses was also explained.AM showed great application potential in the field of special conformal cooling cutting tool preparation.

关键词： Selective laser melting High-speed steel Mechanical properties Microstructure Interlaminar cracks

A Novel On-Site-Real-Time Method for Identifying Characteristic Parameters Using Ultrasonic Echo Groups and Neural Network

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Mechanical Engineering 2024年第1期37卷 215-228页

作者： Shuyong Duan Jialin Zhang Heng Ouyang Xu Han Guirong Liu State Key Laboratory of Reliability and Intelligence of Electrical Equipment Hebei University of TechnologyTianjin 300401China Department of Aerospace Engineering and Engineering Mechanics University of CincinnatiCincinnati 45221USA

On-site and real-time non-destructive measurement of elastic constants for materials of a component in a in-service structure is a challenge due to structural complexities,such as ambiguous boundary,variable thickness,nonuniform material properties.This work develops for the first time a method that uses ultrasound echo groups and artificial neural network(ANN)for reliable on-site real-time identification of material parameters.The use of echo groups allows the use of lower frequencies,and hence more accommodative to structural complexity.To train the ANNs,a numerical model is established that is capable of computing the waveform of ultrasonic echo groups for any given set of material properties of a given structure.The waveform of an ultrasonic echo groups at an interest location on the surface the structure with material parameters varying in a predefined range are then computed using the numerical model.This results in a set of dataset for training the ANN model.Once the ANN is trained,the material parameters can be identified simultaneously using the actual measured echo waveform as input to the ANN.Intensive tests have been conducted both numerically and experimentally to evaluate the effectiveness and accuracy of the currently proposed method.The results show that the maximum identification error of numerical example is less than 2%,and the maximum identification error of experimental test is less than 7%.Compared with currently prevailing methods and equipment,the proposefy the density and thickness,in addition to the elastic constants.Moreover,the reliability and accuracy of inverse prediction is significantly improved.Thus,it has broad applications and enables real-time field measurements,which has not been fulfilled by any other available methods or equipment.

关键词： Parameter identification Ultrasonic echo group High-precision modeling Artificial neural network NDT

Cooperative effect of Cr and Al elements on passivation enhancement of eutectic high-entropy alloy AlCoCrFeNi_(2.1)with precipitates

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2023年第5期136卷 97-108页

作者： Xiaotian Duan Tiezhuang Han Xiao Guan Yuning Wang Huhu Su Kaisheng Ming Jing Wang Shijian Zheng State Key Laboratory of Reliability and Intelligence of Electrical Equipment Hebei University of TechnologyTianjin 300130China School of Material Science and Engineering Hebei University of TechnologyTianjin 300130China

In conventional corrosion-resistant alloys,precipitation usually reduces corrosion resistance severely by weakening passive films locally.In this work,we found that the aging-treated AlCoCrFeNi_(2.1)sam-ples,which have abundant nanosized L 12 and body-centered cubic(BCC)precipitates in the lamellar face-centered cubic(FCC)and B2 phases,displayed better corrosion resistance than solution-treated AlCoCrFeNi_(2.1)samples without precipitates.In the AlCoCrFeNi_(2.1)alloy,the FCC phase with L1_(2)precipi-tates and the B2 phase with BCC precipitates were protected by passive films enriched with Cr and Al elements,respectively.Moreover,the Al-rich passive film of the B2 phase was less stable than the Cr-rich passive film of the FCC phase,so B2 phase dissolved preferentially.The Cr-rich passive film of the FCC phase remained stable with the formation of Al-rich L1_(2)precipitates inside the phase because those precipitates with the size of∼5 nm were too small to affect the composition of the Cr-rich passive film.The formation of Cr-rich BCC precipitates within the B2 phase increased the content of the Al element inside the phase,improving the stability of Al-rich passive film on the B2 phase.Furthermore,BCC precip-itates with the size of∼30 nm were protected by Cr-rich passive film,which could inhibit the expansion of corrosion pits.Thus,the corrosion resistance of eutectic high-entropy alloy AlCoCrFeN 2.1 was unprece-dentedly enhanced by the precipitation of BCC precipitates.Our study could provide an attractive strategy for designing high-entropy alloys with excellent corrosion resistance and high strength.

关键词： Eutectic high-entropy alloy Passive film Corrosion resistance Precipitates TEM

Energy Management for Fuel Cell Vehicles Based on Improved MPC Considering Disturbance Variation

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Energy Management for Fuel Cell Vehicles Based on Improved M...

Improvement of the piezoelectricity of PVDF-HFP by CoFe_(2)O_(4)nanoparticles

2023中国汽车工程学会年会暨展览会

作者： Liu Caixia Gao Xiao Li Xiaoyu State Key Laboratory of Reliability and Intelligence of Electrical Equipment Hebei University of Technology

Fuel cell hybrid electric vehicles(FCHEVs) are widely considered to be an ideal substitute for the traditional vehicles.However,their high costs of operation make them uncompetitive in the current automotive market.To maximize the economy of fuel cell/battery-based hybrid electric vehicles,this paper proposes an improved model predictive control energy management strategy(IMPC) based on speed prediction with dynamic programming(DP) solver.The main principle of the proposed I-MPCis to obtain the optimal action sequence of MPC in current state through DP solver,wherein the equivalent hydrogen consumption is incorporated in the objective function.Assisted by the predictive vehicle speed obtained by BP neural network,the future demand power of the vehicle is acquired by the vehicle dynamic model.The power demands imports into the energy management system response prediction model for improving the control performance by considering more exact disturbances.Additionally,to verify the improvement of economic performance by the proposed I-MPC strategy,the normal MPC strategy and DP strategy are formulated as comparison strategies.The results indicate that I-MPC strategy can give out excellent economic performance.The proposed strategy can be effectively applied to fuel cell hybrid system.

关键词：

来源： cnki会议评论

在线全文

cnki会议

学校读者我要写书评

暂无评论

Nano Materials Science 2024年第2期6卷 201-210页

作者： Dan Lei Ning Hu Liangke Wu Alamusi Huiming Ning Yang Wang Zhaonan Jin Yaolu Liu College of Aerospace Engineering Chongqing UniversityChongqing400044China state key laboratory of reliability and intelligence electrical equipment School of Mechanical EngineeringHebei University of TechnologyTianjin300401China

High piezoelectric composite films composed of poly(vinylidene fluoride-co-hexafluoropropylene)(PVDF-HFP)and ferromagnetic cobalt ferrite(CoFe_(2)O_(4))(0.00 wt%to 0.2 wt%)are prepared by a solution casting method accompanied by uniaxial stretching and high electric field poling.The decisive effect of the poling electric field on the power generating capability was confirmed by the experiments.For pure PVDF-HFP films,when the maximum electric field Emax is 120 MV/m,the calibrated open circuit voltage reaches 2.93 V,which is much higher than those poled at lower electric fields(70 MV/m:1.41 V;90 MV/m:2.11 V).Furthermore,the addition of CoFe_(2)O_(4)also influences the piezoelectricity dramatically.In the samples containing 0.15 wt%CoFe_(2)O_(4),the calibrated open circuit voltage increases to the maximum value of 3.57 V.Meanwhile,the relative fraction of theβ-phase and the crystallinity degree are 99%and 48%,respectively.The effects of CoFe_(2)O_(4)nanoparticles on initial crystallization,uniaxial stretching and high electric field poling are investigated by XRD,FTIR and DSC.

关键词： PVDF-HFP CoFe_(2)O_(4)nanoparticles Piezoelectricity Nanocomposite

Design Optimization of a Novel Axial-radial Flux Permanent Magnet Claw Pole Machine with SMC Cores and Ferrite Magnets

同方期刊数据库博看期刊评论

在线全文

学校读者我要写书评

暂无评论

CES Transactions on electrical Machines and Systems 2023年第4期7卷 358-365页

作者： Chengcheng Liu Fan Yang Wenfeng Zhang Youhua Wang State Key Laboratory of Reliability and Intelligence of Electrical Equipment School of Electrical EngineeringHebei University of TechnologyTianjin 300401China IEEE

Soft magnetic composite(SMC)material is an ideal soft magnetic material employed for developing 3D magnetic flux electromagnetic equipment,due to its advantages of 3D magnetic isotropy characteristic,low eddy current loss,and simple manufacturing process.The permanent magnet claw pole machine(PMCPM)with SMC cores is a good case that the SMC to be adopted for developing 3D flux electrical machines.In this paper,a novel axial-radial flux permanent magnet claw pole machine(ARPMCPM)with SMC cores and ferrite magnets is proposed.Compared with the traditional PMCPM,the proposed ARPMCPM is designed with only one spoke PM rotor and its whole structure is quite compact.For the performance prediction,the 3D finite element method(FEM)is used.Meanwhile,for the performance evaluation,a previously developed axial flux claw pole permanent magnet machine(AFCPM)is employed as the benchmark machine and all these machines are optimized by using the combined multilevel robust Taguchi method.It can be seen that the proposed ARPMCPM is with higher torque/weight density and operation efficiency.

关键词： Soft magnetic composite(SMC) Permanent magnetic claw pole machine(PMCPM) Axial-radial flux

Oscillation of S5 helix under different temperatures in determination of the open probability of TRPV1 channel

在线全文

学校读者我要写书评

暂无评论

Chinese Physics B 2020年第9期29卷 574-580页

作者：李铁李军委庞春丽安海龙耿轶钊王景芹 State Key Laboratory of Reliability and Intelligence of Electrical Equipment Hebei University of TechnologyTianjin 300130China Institute of Biophysics Hebei University of TechnologyTianjin 300401China

Transient receptor potential vanilloid subtype 1 (TRPV1) is a polymodel sensory receptor and can be activated by moderate temperature (≥ 43 ℃). Though extensive researches on the heat-activation mechanism revealed some key elements that participate in the heat-sensation pathway, the detailed thermal-gating mechanism of TRPV1 is still unclear. We investigate the heat-activation process of TRPV1 channel using the molecular dynamics simulation method at different temperatures. It is found that the favored state of the supposed upper gate of TRPV1 cannot form constriction to ion permeation. Oscillation of S5 helix originated from thermal fluctuation and forming/breaking of two key hydrogen bonds can transmit to S6 helix through the hydrophobic contact between S5 and S6 helix. We propose that this is the pathway from heat sensor of TRPV1 to the opening of the lower gate. The heat-activation mechanism of TRPV1 presented in this work can help further functional study of TRPV1 channel.

关键词： TRPV1 heat-activation mechanism molecular dynamics simulation hydrogen bond gating