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Dielectric response--A nondestructive approach to probing the micro‐interface of aluminium hydroxide filled silicone rubber composites for outdoor insulation

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High Voltage 2023年第4期8卷 810-818页

作者： Chao Wu Leonard Alexander Dissado Yanfeng Gao Qian Wang Yingyan Liu Yang Cao xidong liang Department of Electrical Engineering Tsinghua UniversityBeijingChina Department of Engineering University of LeicesterLeicesterUK State Grid Jibei Electric Power Co.Ltd.Research Institute BeijingChina Electrical Insulation Research Center Institute of Materials ScienceUniversity of ConnecticutStorrsConnecticutUSA

Composite polymer dielectrics have strong electrical,mechanical,thermal and environmental properties but experience both high electric fields and harsh environmental conditions as outdoor insulation.The present investigation of the stress-strain characteristics and morphology of the fracture cross-section reveal the risk of a weakly bonded interface between the aluminium hydroxide(ATH)filler and silicone rubber used for insulators in transmission lines and substations.Dielectric response measurements are proposed as a non-destructive probe of the interface quality.An analysis,based on the Dissado–Hill model,indicated that the introduction of ATH interfaces gave rise to a quasi-DC process,in which charge transport is in the form of hopping along the weakly bonded interfaces.A schematic plan is proposed that would allow such an analysis to be used to obtain quantitative information correlated to the status of the weakly bonded interface for the diagnosis of micro-interface quality in ATH-filled silicone rubber and dielectric composites in general.

关键词： composites interface rubber

Non-destructive thermal ageing evaluation of P(VDF-HFP)film based on broadband dielectric response

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High Voltage 2022年第6期7卷 1123-1129页

作者： Qian Wang Chao Wu Yanfeng Gao Shuming Liu Shuqi Liu Zhou Zuo xidong liang Department of Electrical Engineering State Key Lab of Power SystemTsinghua UniversityBeijingChina Electrical Insulation Research Center Institute of Materials ScienceUniversity of ConnecticutStorrsConnecticutUSA State Grid Jibei Electric Power Co.Ltd.Research Institute North China Electric Power Research Institute Co.Ltd.BeijingChina

Capacitors and sensors based on polymer dielectric materials are key components in electrical systems and electronic devices.Considering the temperature rise during operation,an effective evaluation method for the thermal ageing of polymer matrix is urgently needed.P(VDF-HFP)film with a thickness of 20μm is manufactured by solution casting and a thermal ageing experiment up to 1000 h is conducted.Dielectric responses of wide ranges of temperatures and frequencies are measured for samples with different ageing durations.The universal relaxation law and Dissado–Hill dielectric response model are applied to further investigate the results.The characteristics of individual processes are obtained,which demonstrate that the main chain relaxation following the Vogel−Fulcher−Tammann equation and side chain relaxation following the Arrhenius equation both remain unchanged after thermal ageing.However,the activation energies of those two processes change significantly during the process and show different variation trends.The activation energy of the side chain relaxation gets larger monotonically due to the influence of annealing and the breaking of crystalline region.As a result,a non-destructive evaluation method for the thermal ageing of P(VDF-HFP)is proposed accordingly.

关键词： casting thermal relaxation

Puncture Phenomena and Mechanism Analysis of a RTV Coated Cap and Pin Insulators in a Steep-front Impulse Voltage Test

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CSEE Journal of Power and Energy Systems 2021年第4期7卷 832-839页

作者： Tao Deng xidong liang Zhiyi Su Jun Zhou Electrical Engineering Department Tsinghua UniversityBeijing 100084Chinaand also with Department of High VoltageChina Electric Power Research Institute Co.LtdBeijing 100192China Department Tsinghua UniversityBeijing 100084China Department of High Voltage China Electric Power Research Institute Co.LtdBeijing 100192China

In recent years,more than 6 million room temperature vulcanized(RTV)silicone rubber coated cap and pin insulators with high mechanical ratings were used in ultra-high voltage transmission lines in China to improve pollution performance.However,the unexpected puncture phenomena of RTV coated insulators were exposed during steep-front impulse voltage tests;for instance,the steep-front impulse voltage test pass rate decreased to less than 50% for 550 kN glass insulators with RTV coatings.The steep-front impulse voltage test is the most effective method used to check the insulation quality of cap and pin insulators・This unexpected phenomenon once caused serious concerns to power utilities.In this paper,several possible factors that affect the puncture of insulators were analyzed.Then,the extent of the decline in the breakdown of the 550 kN glass cap and pin insulators with and without RTV coatings were studied.The initial puncture location was then found,and the developmental process of the arc on the insulator surface in steep-front impulse voltage tests was observed with an ultra-high-speed intensified charge coupled device camera.Lastly,a breakdown mechanism is proposed.The puncture phenomena of a RTV coated insulator in a steep-front impulse voltage test is essentially an electrical breakdown of the internal insulation・The RTV coating induces the close adherence of the arc to the surface of the insulator.Such closeness changes the arc development path on the insulator surface and facilitates easy breakdown in the shed weak part.All these factors result in a significant increase in the breakdown probability of RTV coated insulators in steepfront impulse voltage tests.

关键词： Cap and pin insulator puncture RTV coating steep-front impulse voltage test

Failure analysis of a field brittle fracture composite insulator:characterisation by Xray photoelectron spectroscopy analysis

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High Voltage 2019年第2期4卷 89-96页

作者： Yanfeng Gao xidong liang Weining Bao Chao Wu Shaohua Li State Grid Jibei Electric Power Co.Ltd.Research Institute North China Electric Power Research Institute Co.LtdBeijing100045People's Republic of China Department of Electrical Engineering State Key Lab of Power SystemTsinghua UniversityBeijing100084People's Republic of China Department of Electrical and Computer Engineering University of ConnecticutStorrsConnecticut06269USA

In the present work,a field brittle fracture composite insulator was collected and examined with the purpose of obtaining a better understanding of the failure features.Firstly,the macroscopic and microscopic fractography of this fractured composite insulator was observed confirming that the classical brittle fracture morphology features appeared in this field failed composite insulator.Secondly,the X-ray photoelectron spectroscopy(XPS)analysis was performed on the fracture surface of the glass-fibre-reinforced polymer rod.By examining the XPS survey spectra and high-resolution XPS spectra for nitrogen,sulphur,silicon,calcium,aluminium,boron and carbon elements,the type of the glass fibre and the acid source responsible for this brittle fracture composite insulator were confirmed.Furthermore,the oxidation of the silicate network of glass fibre at the fracture surface was first observed,meanwhile,the oxidation of the epoxy resin matrix was also observed.The leaching of non-silicate constituents leading to a high-silica glass fibre was also observed;moreover,in comparison with the calcium and aluminium elements,the boron element resides in the silicate network was more preferential to be leached.The present work provides an insight into the brittle fracture in high voltage composite insulator from chemical properties point of view.

关键词： fracture composite insulator

Effects of liquids immersion and drying on the surface properties of HTV silicone rubber:characterisation by contact angle and surface physical morphology

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High Voltage 2019年第1期4卷 49-58页

作者： Yanfeng Gao xidong liang Weining Bao Shaohua Li Chao Wu Yingyan Liu Yuanji Cai State Grid Jibei Electric Power Co.Ltd Research InstituteNorth China Electric Power Research Institute Co.LtdBeijing100045People's Republic of China Department of Electrical Engineering State Key Lab of Power SystemTsinghua UniversityBeijing 100084People's Republic of China

High-temperature vulcanised(HTV)silicone rubber composite insulator has been widely used in extra-high and ultra-high transmission lines due to its excellent electrical and mechanical performance.In practice use,liquids may encounter the composite insulator intermittently and can lead to the degradation and deterioration of silicone rubber.In the present research,the effects of liquids immersion and subsequent drying on the surface properties of HTV silicone rubber were investigated by means of the contact angle measurement and surface physical morphology measurement which was further analysed in terms of the discrete wavelet transform method,multiresolution signal decomposition algorithm,and three-dimensional fractal dimension calculation.Based on the experimental results,the mechanism of the loss and recovery of the hydrophobicity of HTV silicone rubber surface during the liquids immersion and subsequent drying processes were further explained by taking into consideration the embedded water molecules(and/or hydrated ions)on the HTV silicone rubber surface and the synergy of the increase in roughness/fractal dimension and low molecular weight siloxanes diffusion.This study is helpful for better understanding of the change of surface properties of HTV silicone rubber caused by environmental and electrical stresses.

关键词： rubber surface immersion

Study on liquids diffusion into and relevant corrosion behaviour of glass fibre reinforced polymer used in high voltage composite insulator

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High Voltage 2020年第1期5卷 53-61页

作者： Yanfeng Gao xidong liang Weining Bao Chao Wu Shaohua Li Yingyan Liu Yuanji Cai State Grid Jibei Electric Power Co.Ltd Research InstituteNorth China Electric Power Research Institute Co.LtdBeijing100045People's Republic of China Department of Electrical Engineering State Key Lab of Power SystemTsinghua UniversityBeijing100084People's Republic of China Department of Electrical and Computer Engineering University of ConnecticutStorrsConnecticut06269USA

Long-term liquids diffusion tests were performed on glass fibre reinforced polymer(GFRP)used in high voltage composite insulator.The plate-shaped GFRP specimens were immersed in three types of liquids,which high voltage composite insulator would encounter in practice,including deionised water,NaCl solution and nitric acid solution for a period of 4000 h.Chemical reaction and physical dissolution complicated the diffusion processes,which could be divided into three types based on the features of diffusion curves.Fourier transform infrared spectroscopy,scanning electron microscopy and optical interferometry were employed to investigate the chemical property,two-dimensional(2D)and 3D surface morphologies of GFRP.The results revealed that the surface layer of GFRP was destroyed to some extent depending on the type and concentration of the liquid,the maximum of profile height deviation of GFRP surface was proposed to evaluate the extent of the corrosion of GFRP,the greater the profile height deviation,the more serious the corrosion of GFRP.The present work is helpful for a better understanding of the diffusion behaviour of liquids into GFRP used in high voltage composite insulator as well as in other industry applications.

关键词： corrosion diffusion composite

水分侵入高温硫化硅橡胶扩散行为的仿真研究(一):数值建模与计算

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中国电机工程学报 2024年第1期44卷 341-352,I0028页

作者：左周周颖梁曦东罗兵王婷婷刘书棋王乾刘书明新型电力系统运行与控制全国重点实验室(清华大学电机系) 北京市海淀区100084 南方电网科学研究院有限责任公司广东省广州市510663

硅橡胶复合绝缘子在高湿多雨环境下容易发生劣化,但由于受到实验方法和观测表征技术的限制,难以判断硅橡胶复合材料中水分的来源及侵入路径。借助数值建模与可视化仿真,通过两篇系列论文分别研究液态水和气态水在高温硫化硅橡胶内部的... 详细信息

硅橡胶复合绝缘子在高湿多雨环境下容易发生劣化,但由于受到实验方法和观测表征技术的限制,难以判断硅橡胶复合材料中水分的来源及侵入路径。借助数值建模与可视化仿真,通过两篇系列论文分别研究液态水和气态水在高温硫化硅橡胶内部的扩散行为,该文是系列论文第一篇。首先,基于Langmuir扩散模型研究水分侵入过程的数值建模方法,结合时域有限差分法和牛顿–拉夫逊法实现精确建模与高效解算。然后,使用MATLAB软件编程,对高温硫化硅橡胶内部的液态水扩散行为开展仿真,实现对自由态水分和结合态水分的解耦,获得液态水侵入过程的时空分布及质量演变规律。通过硅橡胶样品吸水增重实验,验证数值模型和仿真的正确性。最后,研究氢氧化铝和温度两种因素对水分扩散行为的影响,揭示亲水性氢氧化铝填料和温度对水分侵入过程的影响规律。所提出的数值仿真方法可为研究水分侵入复合绝缘子提供新的思路。

关键词：外绝缘硅橡胶水分扩散行为数值建模

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高温后预损伤混凝土的轴压试验研究

混凝土与水泥制品 2024年第4期 26-30页

作者：王连坤梁锡东郭一彬刘杰林文皓五邑大学土木建筑学院广东江门529020

对不同预损伤程度下C30混凝土试件进行了高温(200、350、500℃)后轴心抗压试验,获取了试件的应力-应变全曲线,分析了高温对预损伤试件的质量损失率、峰值应力、峰值应变、弹性模量等的影响。结果表明:在相同温度下,预损伤程度越高的混... 详细信息

对不同预损伤程度下C30混凝土试件进行了高温(200、350、500℃)后轴心抗压试验,获取了试件的应力-应变全曲线,分析了高温对预损伤试件的质量损失率、峰值应力、峰值应变、弹性模量等的影响。结果表明:在相同温度下,预损伤程度越高的混凝土试件破坏越早;在相同预损伤程度下,高温温度越高,试件破坏越早;与温度相比,预损伤程度对试件轴压破坏的影响更大;各试件的质量损失率随着温度的升高而增加;预损伤程度越高,高温温度越高,试件的轴心抗压强度越低;随着温度的升高,各试件的峰值应力降低,峰值应变增加,上升段的斜率变小;各试件的弹性模量均随着温度的升高而降低。

关键词：预损伤高温质量损失率轴压力学性能

考虑旅客换乘的高铁列车停站方案-票额分配鲁棒优化

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系统工程理论与实践 2022年第8期42卷 2196-2209页

作者：张玉利梁熙栋周超越宋士吉北京理工大学管理与经济学院北京100081 清华大学自动化系北京100084

随着我国高速铁路客运量的迅速增长,旅客出行需求时空波动性大,跨线换乘旅客多等特征凸显,对列车停站和票额分配方案的制定提出了更高要求.本文通过构造基于条件概率的不确定性集,刻画旅客出行需求的不确定性,并建立考虑旅客换乘行为的... 详细信息

随着我国高速铁路客运量的迅速增长,旅客出行需求时空波动性大,跨线换乘旅客多等特征凸显,对列车停站和票额分配方案的制定提出了更高要求.本文通过构造基于条件概率的不确定性集,刻画旅客出行需求的不确定性,并建立考虑旅客换乘行为的列车停站方案-票额分配联合鲁棒优化模型,提升高速铁路运输组织方案的鲁棒性和灵活性.提出了行-列生成算法对模型进行有效求解,并针对子问题设计基于库恩-塔克条件的精确算法和基于问题结构性质的近似算法.利用京沪线高铁运营数据的计算实验表明考虑换乘的联合优化方案具有更高的客流满足率和更少的停站时间,行-列生成算法具有很高的收敛速度和求解精度.在运行方案制定过程中,应综合考虑旅客出行需求的不确定性和换乘行为,兼顾服务效率和服务水平进行决策.

关键词：高速铁路停站方案票额分配鲁棒优化行-列生成算法