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Assessment on gas-polyethylene terephthalate solid interface partial discharge properties of C4F7N/CO_(2)gas mixture for eco-friendly gas insulating transformer

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High Voltage 2024年第1期9卷 35-45页

作者： Song Xiao Yifan Wang Chenhua Ren Haoran Xia Yue Zhao Jingzi Qin Xiaoxing Zhang Yi Luo Yi Li state key laboratory of Power Grid Environmental Protection School of Electrical Engineering and AutomationWuhan UniversityWuhanHubeiChina Beijing International S&T Cooperation Base for Plasma Science and Energy Conversion Institute of Electrical EngineeringChinese Academy of SciencesBeijingChina state Grid Anhui Electric Power Company Anhui Electric Power Research Institute HefeiAnhuiChina Hubei Engineering Research Center for Safety Monitoring of New Energy and Power Grid equipment School of Electrical and Electronic EngineeringHubei University of TechnologyWuhanHubeiChina

The eco-friendly insulating gas perfluoroisobutyronitrile(C_(4)F_(7)N)is potentially used in gas-insulated transformers(GIT)to replace sulphur hexafluoride(SF_(6)).However,evaluation of the long-term insulation reliability and gas–solid interface discharge decomposition characteristics of the gas–solid film insulation structure in GIT is indispensable.The authors simulated the gas–solid film insulation structure in GIT and explored the interface partial discharge(PD)characteristics of C4F7N/CO_(2)gas mixture with polyethylene terephthalate(PET).The effect of gas pressure,mixing ratio on gas–solid interface gas decomposition,PET degradation was investigated,and the interaction mechanism was analysed.It is found that the interface PD generated three degradation regions on a PET film.The gas–solid interface reaction in the electrode contact region and the discharge development trace was significantly higher than that of halation region.The content of gas decomposition products decreases with the increase of gas pressure and the PD intensity of SF6-PET is inferior to that of C_(4)F_(7)N/CO_(2)under the same condition.Relevant results provide reference for the development and application of C_(4)F_(7)N/CO_(2)based GIT.

关键词： interface solid insulation

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

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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

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

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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

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Design and Performance Analysis of Permanent Magnet Claw Pole Machine with Hybrid Cores

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中国电工技术学会电机与系统学报(英文) 2023年第3期7卷 275-283页

作者： Chengcheng Liu Zheng Chao Shaopeng Wang Youhua Wang IEEE state key laboratory of reliability and intelligence of electrical equipment Hebei University of Technology and Key Laboratory of Electromagnetic Field and Electrical Apparatus Reliability of Hebei ProvinceHebei University of TechnologyTianjin 300130China

Permanent magnet claw pole machine(PMCPM) is a special kind of transverse flux permanent magnet machine. Compared with other electrical machines, it has the advantages of high torque density and high efficiency for high speed operation. However, because of its complex irregular structure, the manufacturing process using silicon sheets is complicated. Soft magnetic composite material(SMC) is manufactured by powder metallurgy technology, which can produce various shapes of stator core structures, so it is easier to produce various irregular shapes of the stator core. However, the raw SMC material is relatively expensive, and the mechanical strength of SMC is weak. In this paper, a PMCPM with hybrid cores is proposed. With the adoption of hybrid silicon sheet-SMC cores and amorphous alloy-SMC cores, the torque ability of PMCPM can be improved greatly and it can have higher efficiency for more wide operation frequency. Meanwhile, its mechanical strength has been improved and it can be designed for high torque direct drive applications as it is a modular machine. Furthermore, three methods are proposed to reduce the additional eddy current loss which resulted from the employment of hybrid cores in PMCPM.

关键词： Permanent magnet claw pole machine(PMCPM) Soft magnetic materials(SMC) Hybrid cores Eddy current loss

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

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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

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

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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

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

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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

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A method of phase demodulation of OFDR based on ARC-DSM algorithm

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Optoelectronics Letters 2022年第1期18卷 13-17页

作者： LIU Jianfei LI Chao FAN Xujun LUO Mingming LUAN Nannan YANG Wenrong School of Electronic Information Engineering Hebei University of TechnologyTianjin 300401China state key laboratory of reliability and intelligence of electrical equipment Hebei University of TechnologyTianjin 300130China

Aiming at low stability and high harmonic distortion of the traditional phase-generated carrier(PGC)demodulation algorithm,we propose a modified demodulation algorithm for distributed strain sensing in phase-sensitive optical frequency domain reflectometry(OFDR).The proposed algorithm combines the arctangent function and differential-self-multiplying(ARC-DSM),which eliminates the effect of modulation depth and realizes the high precision strain variation measurements.Simulation results show that distortion and harmonic distortion are effectively suppressed by the ARC-DSM algorithm.The minimum variation of the measurable static strain is about 0.3μεand the spatial resolution can reach 0.2 m within 270 m range.

关键词： algorithm distortion phase

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Impact of p-AlGaN/GaN hole injection layer on GaN-based vertical cavity surface emitting laser diodes[Invited]

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Chinese Optics Letters 2022年第3期20卷 35-40页

作者：韩磊高元斌杭升楚春双张勇辉郑权李青张紫辉 state key laboratory of reliability and intelligence of electrical equipment Hebei University of TechnologyTianjin 300401China key laboratory of Electronic Materials and Devices of Tianjin School of Electronics and Information EngineeringHebei University of TechnologyTianjin 300401China Hebei key laboratory of Advanced Laser Technology and equipment Tianjin 300401China key Engineering Center of Flat-Panel-Display Glass and equipment Shijiazhuang 050035China

The hole injection capability is essentially important for GaN-based vertical cavity surface emitting lasers[VCSELs]to enhance the laser power.In this work,we propose GaN-based VCSELs with the p-AlGaN/p-GaN structure as the p-type hole supplier to facilitate the hole injection.The p-AlGaN/p-GaN heterojunction is able to store the electric field and thus can moderately adjust the drift velocity and the kinetic energy for holes,which can improve the thermionic emission proc-ess for holes to travel across the p-type electron blocking layer[p-EBL].Besides,the valence band barrier height in the p-EBL can be reduced as a result of usage of the p-AlGaN layer.Therefore,the better stimulated radiative recombination rate and the increased laser power are obtained,thus enhancing the 3 dB frequency bandwidth.Moreover,we also inves-tigate the impact of the p-AlGaN/p-GaN structure with various AIN compositions in the p-AlGaN layer on the hole injection capabilit,the laser power,and the了dB frequency bandwidth.

关键词： GaN-based VCSEL hole injection laser power modulation response

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Dependence of Plastic Stability on 3D Interface Layer in Nanolaminated Materials

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Acta Metallurgica Sinica(English Letters) 2022年第11期35卷 1759-1764页

作者： Shuimiao Jiang Lichen Bai Qi An Zhe Yan Weiming Li Kaisheng Ming Shijian Zheng Tianjin key laboratory of Materials Laminating Fabrication and Interface Control Technology School of Materials Science and EngineeringHebei Universityof TechnologyTianjin 300130China state key laboratory of reliability and intelligence of electrical equipment Hebei University of TechnologyTianjin 300130China

The nanolaminated materials generally exhibit poor plasticity due to the fast onset of shear instability.Engineering interface structure is an eff ective approach for enhancing plasticity via postponing or suppressing the shear instability.Here,we introduce 4 nm thick CuNb 3D amorphous interface layers and Nb 3D crystalline interface layers in Cu nanolaminated materials,respectively.In situ micro-pillar compression tests show that samples with crystalline interface layers exhibit shear instability,while the samples with amorphous interface layers display uniform deformation.Since the plastic deformation of the singlecrystal crystalline interface layer is anisotropic,except for well-aligned slip systems,dislocations on other slip systems have a poor ability to transmit the 3D crystalline interface layer,leading to localized dislocations pileups and shear instability.In contrast,the amorphous interface layer which is plastically isotropic accommodates dislocations from arbitrary slip systems of the matrix,which can alleviate the stress concentrations at the interface,and thus suppresses the shear instability.

关键词： Multilayers Interface Plastic deformation Dislocation Amorphous interface

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