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Effect of temperature on electric-thermal properties of semiconductive shielding layer and insulation layer for high-voltage cable

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High Voltage 2021年第5期6卷 805-812页

作者： Yanhui Wei Mingyue Liu Xuejing Li Guochang Li Naiyi Li Chuncheng Hao Qingquan Lei Institute of Advanced Electrical Materials Qingdao University of Science and TechnologyQingdaoChina State Grid Zhejiang Electric Power Co. LtdResearch InstituteHangzhouChina

A semi‐conductive shielding layer plays an important role in the uniform electric field for a high‐voltage *** electric‐thermal properties of the semi‐conductive layer and insulation layer directly affect the overall insulation performance of the *** physicochemical performances of semi‐conductive composites are firstly analysed ***,electric‐thermal properties of the semi‐conductive layer and insulation layer are *** experimental results show that the thermal conductivity of the commercial semi‐conductive layer is about twice that of the insulation layer,owing to the effect of carbon *** thermal expansion coefficient of the insulation layer rises from 1.86×10^(−4)/K at 25℃ to 3.20×10^(−4)/K at 90℃.By contrast,the semi‐conductive layer begins to slowly decline at a certain temperature,and decreases signif-icantly to 2.25×10^(−4)/K at 80℃,owing to the effect of ethylene‐vinyl acetate copolymer(EVA).The electrical experiments show that the resistivity of semi‐conductive composite gradually rises with an increase in temperature,and gradually declines with an increase in the carbon black *** dc breakdown strength of the composite structure of the semi‐conductive layer/insulation layer decreases significantly with an increase in tem-perature,decreasing from 307 kV/mm at 25℃ to 203 kV/mm at 90℃.At four typical temperatures,the breakdown strength reaches the maximum value when the carbon black content is 25 *** is about 15%and 19%higher than carbon black contents of 20 and 30 *** findings have reference significance for high‐voltage cable breakdown fault analysis and material selection in cable design.

关键词： composite insulation composites

Analysis of low‐frequency polarisation behaviour for oil‐paper insulation using logarithmic‐derivative spectroscopy

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High Voltage 2021年第3期6卷 460-469页

作者： Jiefeng Liu Xianhao Fan Yiyi Zhang Benhui Lai Jian Jiao School of Electrical Engineering Guangxi UniversityNanningGuangxiChina Electric Power Research Institute Guangxi Power Grid CorporationNanningGuangxiChina

The low‐frequency polarisation information of oil‐paper insulation could be easily obscured by the conductance effect,and the contained polarisation information thus can not be readily extracted from the frequency domain spectroscopy(FDS).Given this issue,an alternative idea is reported to extract the low‐frequency polarisation infor-mation by using logarithmic‐derivative spectroscopy(LDS).The present findings proved that the parameters extracted by using the LDS can be applied for studying the low‐frequency polarisation behaviour under the moisture *** that respect,the novelty of this work is in the exploration of the LDS as a potential tool to extract feature parameters for analyzing the low‐frequency polarisation information of trans-former oil‐paper insulation.

关键词： effect insulation behaviour

Method for identifying ageing in epoxy-mica composite insulation used in rotational machines through modelling of dielectric relaxation

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High Voltage 2020年第2期5卷 184-190页

作者： Nikhil Mondal Nasirul Haque Sovan Dalai Sivaji Chakravorti Biswendu Chatterjee Department of Electrical Engineering Jadavpur UniversityKolkataIndia NIT Calicut CalicutIndia

Dielectric response analysis,performed in time domain and frequency domain is one of the interesting methods used for condition assessment of high voltage *** this article,the degradation of epoxy-mica composite insulation which is widely used in rotating machines has been investigated through frequency domain spectroscopy *** ageing of the carefully prepared stator bar insulation sample was performed through simultaneous application of high temperature and electric field in a designated environmental chamber for specific *** study the effect of temperature,the measurements were performed at temperatures ranging from 20 to 60°C at different ageing *** experimental work,the measurement results were modelled using Havriliak–Negami model and ageing sensitive parameters were *** study the effect of temperature,the measurements were performed at temperatures ranging from 20 to 60°*** modelled results matched well with the experimental measurements and certain model parameters sensitive to the ageing condition were *** numerical relationships between the insulation status of the stator bar and the aforementioned parameters were *** was observed that the nature of the numerical relationship remains identical in the investigated temperature range,although the coefficients vary to some extent.

关键词： insulation composite relaxation

Description of space charge transport in oil‐paper insulation using adaptive time‐stepping transient upstream finite element method

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High Voltage 2022年第1期7卷 75-85页

作者： Jiefeng Liu Mingchen Shi Yiyi Zhang Bing Gao Wei Zhang Shuo Liang School of Electrical Engineering Guangxi UniversityNanningChina College of Electrical and information Hunan UniversityChangshaChina Electric Power Research Institute of Guangxi Power Grid Co LtdNanningChina

The charge transport and accumulation in oil-paper can cause the insulation *** far,the most widely used model to simulate space charge transport and accumulation is the bipolar charge transport(BCT)model,which can well simulate the space charge ***,there are two shortcomings in the algorithms for solving the BCT *** is that there is almost no use of vectorisation technology,which may increase the complexity of the algorithm,the other is the usage of fixed step size which might bring extra computation *** view of this,an adaptive time‐stepping transient up-stream finite element method(FEM)is developed to solve the BCT model considering trapping/detrapping,as well as the recombination phenomenon under DC condition in this ***,a vectorisation technology is used in the method to optimise the ***,the adaptive time‐stepping method is introduced in simulation to reduce computation time and calculation *** results are obtained by programing and later presented,which are basically consistent with the corresponding experimental ***,the proposed method is expected to promote the opti-mization design of the oil-paper insulation system.

关键词： charge insulation transport

Electrical tree degradation in high-voltage cable insulation:progress and challenges

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High Voltage 2020年第4期5卷 353-364页

作者： Jingang Su Boxue Du Jin Li Zhonglei Li Electric Power Research Institute of State Grid Hebei Electric Power Supply Co.Ltd. Shijiazhuang 050021People's Republic of China School of Electrical and Information Engineering Tianjin UniversityWeijin Road 92Tianjin 300072People's Republic of China

High-voltage direct current(HVDC)and high-voltage alternating current(HVAC)cables are the most important equipment for high-voltage,large-capacity and long-distance power *** tree is a pre-breakdown phenomenon leading to failure of insulation materials,and it is the major issue that threatens the safe and stable operation of HVDC and HVAC cable *** study summarises and analyses the achievements in the research of electrical tree for HVDC and HVAC *** initiation mechanisms of the electrical tree,including Maxwell electro-mechanical stress,charge injection-extraction,charge trapping and electroluminescence theories,are elaborated for fully understanding the electrical degradation process in insulation ***,the influences of the high electric field,high temperature and mechanical stress on electrical tree behaviours are discussed,and the relationship between charge transport and the electrical tree is analysed and *** suppression methods of the electrical tree are put forward by introducing inorganic and organic additives into insulation materials,and the suppression mechanisms are presented from the viewpoints of the structure-property and microscale-macroscale ***,the electrical tree research studies are focused on the high-precision of initiation models,high-dependence of multi-physical fields and high-efficiency of suppression *** achievements provide theoretical support for improving the electrical performance of insulation materials,while it is a practical problem to explore their application feasibility in HVDC and HVAC cable.

关键词： insulation Electrical tree

ShuffleNet-based comprehensive diagnosis for insulation and mechanical faults of power equipment

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High Voltage 2021年第5期6卷 861-872页

作者： Yanxin Wang Jing Yan Qifeng Sun Yiming Zhao Tingliang Liu State Key Laboratory of Electrical insulation and Power Equipment Xi'an Jiaotong UniversityXi'anShaanxi ProvinceChina School of Foreign Studies Xi'an Jiaotong UniversityXi'anShaanxi ProvinceChina

Despite the complicated fault mechanism of power equipment,with the increasing promotion and development of the Ubiquitous Power Internet of Things(UPIoT),the fault information of power equipment can be instantly saved,which makes possible intelligent diagnosis via fault *** study proposes a new method to implement comprehensive intelligent diagnosis by adopting the ShuffleNet light-weight convolution neural network(SLCNN).Considering the requirements of the UPIoT intelligent terminal,this study constructs six models,which are measured in terms of recognition accuracy,model storage,and calculation cost when applied to insulation and mechanical *** with the existing models,the SLCNN outperforms them significantly in terms of recognition accuracy,with an accuracy of 95.77%and 99.9%in insulation and mechanical fault diagnoses,*** SLCNN also demonstrates obvious advantages in other performance indicators,all of which contribute to its use in the accurate and reliable fault diagnosis of power equipment in the UPIoT ***,through comparing feature maps,it is discovered that the aliasing degree and boundary of insulation defects are not as obvious as those of mechanical faults,which means that insulation fault diagnosis is much more difficult than mechanical fault diagnosis.

关键词： fault diagnosis insulation

Experimental and molecular level analysis of natural ester delaying degradation of cellulose insulation polymer

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High Voltage 2022年第5期7卷 1001-1015页

作者： Jian Hao Wenyu Ye Chenyu Gao Mengzhao Zhu Lijun Yang Ruijin Liao State Key Laboratory of Power Transmission Equipment&System Security and New Technology Chongqing UniversityChongqingChina State Grid Shandong Electric Power Co. Shandong Electric Power Research InstituteJinanChina

Developing green insulation materials has become an important direction for future *** a new environmental insulation liquid,natural ester can effectively delay cellulose insulation polymer *** the mechanism of natural ester delaying the cellulose ageing could promote its application in power *** this study,based on the accelerated thermal ageing of pressboard immersed in natural ester and 25#mineral oil at 120°C for 221 days,the thermal ageing rate and the levelling off degree of polymerisation(LODP)for two kinds of oil-impregnated pressboards were *** molecular level mechanism of natural ester delaying cellulose degradation and keeping higher LODP value was proposed using molecular dynamics *** the early stage of thermal ageing,cellulose with a higher degree of polymerisation(DP)can form many hydrogen bonds with hydronium ions,and their binding energy is stronger,which can accelerate the acid hydrolysis of cellulose,causing the DP of pressboard immersed in natural ester and mineral oil to decrease *** the breaking of the cellulose molecular chain,the number of hydrogen bonds and binding energy between cellulose and hydronium ions becomes smaller and the thermal ageing rate decreases *** the end stage of ageing,it is difficult for the hydronium ions to enter the crystalline cellulose,acid hydrolysis of crystalline cellulose is hard to conduct,leading to the occurrence of the LODP *** degradation rate of cellulose in natural ester is only 50%of that in mineral *** cellulose LODP value in natural ester is over 200 larger than that in mineral *** with the mineral oil-cellulose system,natural ester can form hydrogen bonds with hydronium ions and lead to fewer hydronium ions in cellulose,fewer hydrogen bonds and smaller binding energy between cellulose and hydronium ions,which can reduce the acid hydrolysis reaction of *** study provides a theoretical explanation for

关键词： insulation delay cellulose

Review of accumulative failure of winding insulation subjected to repetitive impulse voltages

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High Voltage 2019年第1期4卷 1-11页

作者： Potao Sun Wenxia Sima Xiongwei Jiang Dingfei Zhang Jiahui He Lian Ye State Key Laboratory of Power Transmission Equipment&System Security and New Technology Chongqing UniversityChongqing 400030People's Republic of China Department of Materials Science College of Engineering MaterialsChongqing UniversityChongqing 400030People's Republic of China Department of Electrical and Computer Engineering University of FloridaGainesvilleFL 32611USA

The premature failure phenomenon that occurs in solid insulation under the application of repetitive impulse voltages is known as the accumulative effect of impulse voltages on a solid *** accumulative failure of winding insulation is considered to be a core problem resulting from this *** main problems include the accumulative failure of motor winding insulation under pulse-width modulation impulses and the accumulative failure of transformer winding insulation under the application of overvoltages,and these problems represent new challenges in the safe and stable operation of power *** regards to the above problems,this study reviews the results of recent research on the accumulative failure characteristics and mechanisms of winding insulation when subjected to repetitive impulse *** challenges faced are discussed at the end of this study.

关键词： insulation winding dielectric

Epoxy/α-alumina nanocomposite with high electrical insulation performance

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Progress in Natural Science:Materials International 2017年第5期27卷 574-581页

作者： Yun Chen Donghai Zhang Xiaofeng Wu Haosheng Wang Chong Zhang Wei Yang Yunfa Chen State Key Laboratory of Multi-phase Complex Systems Institute of Process EngineeringChinese Academy of Sciences State Key Laboratory of Advanced Transmission Technology Global Energy Interconnection Research Institute

An experimental study was conducted to improve the electrical insulation of epoxy resin. The effects of boehmite, γ-alumina and α-alumina nanoparticles on the volume resistivity, dielectric strength and glass transition temperature of epoxy nanocomposites were investigated. The results showed that α-alumina nanoparticles displayed obvious advantages in enhancing electrical insulation performance of epoxy nanocomposites, compared to boehmite and γ-alumina nanoparticles. The direct current volume resistivity and breakdown strength of epoxy nanocomposite with 2.0 wt% α-alumina nanoparticles was improved to 2.2 × 10;Ω cm and76.1 kV mm;respectively. And these improved values of electrical insulation properties are much higher than these of epoxy nanocomposites reported in previous studies. The main reason of these improvements may be that the epoxy/α-alumina interaction zone was enhanced by crosslink.

关键词： Nanocomposite Epoxy resin insulation α-alumina