全尺寸交流500 kV输电杆塔复合横担的雷电闪络特性

架空输电线路(OTL)一直以来都是电力传输的主要方式。随着输电电压和输电容量的迅速提高,输电杆塔的尺寸也随之增加,造成土地资源的大量占用。考虑到线路复合绝缘子的优异性能,复合横担有望成为这一问题的解决方案。在本文中,作者制备了一个安装有复合横担的全尺寸交流(AC)500 kV输电杆塔,并施加了不同极性的雷电过电压。借助高速相机记录了流注-先导放电的过程,确认了闪络的主要路径。通过测量闪络电压并根据空气密度和湿度对结果进行修正,证实了放电的极性效应。继而,根据杆塔结构和闪络特性计算了杆塔的耐雷水平。基于全尺寸试验的结果与分析,确认了复合横担的可行性,并提出了结构优化方案。

Effect of UV radiation aging on creepage discharge characteristics of high temperature vulcanized silicon rubber at high altitude

The physicochemical properties and creepage discharge characteristics of aged high temperature Vulca nized(HTV)silicone rubber materials were investigated by ultraviolet radiati on(UV)aging method in this study.The experimental results show that as the aging time increases,the creepage discharge flashover voltage increases first and then decreases.But the aging time has little effect on the creepage discharge inception voltage.With the aging time prolonged,the discharge endurance time of HTV silicone rubber is shortened,and the creepage discharge development velocity is accelerated.In the short time of applying voltage to aging material,the magnitude of discharge in creases rapidly.According to the partial discharge characteristic parameters of creepage discharge,the whole creepage discharge process is partitioned into four stages.Compared with unaged HTV silicone rubber,the aged HTV silicone rubber has less fluctuation in performance parameters and a clear trend.The study found that UV aging not only affects the physicochemical and hydrophobic properties of the HTV silicone rubber,but also accelerates the development of creepage discharge under AC voltage.

Inhibiting liquid permeation into silicone rubber by superhydrophobic coating for prolonged service life

Liquid permeation into silicone rubber(SR)may lead to the degradation or complete failure of the composite insulators.Aiming to inhibit liquid permeation,two kinds of superhydrophobic coatings are applied to the SR surface.The liquid permeation properties of SR with different types of liquids are investigated,and the Langmuir diffusion model is applied to analyse the experimental data.The results show that the composite superhydrophobic coating can effectively inhibit liquid permeation by reducing the contact area between the surface and liquid,and the stable structure of the composite coating can maintain the performance after the liquid permeation and effusion.However,the nano‐particle coating without the polymer binder experiences severe performance degradation during the immersion test,and it cannot restrain the liquid permeation anymore after it loses the superhydrophobicity.As a validation of the effective protection,the insulation resistivity change was measured.The resistivity decreases sharply for the pristine SR after water permeation;however,the decrease is much smaller for the coated SR.The current study not only provides new insight into the liquid permeation properties of SR with different surface wettability but also suggests an effective measure to prevent liquid permeation into SR.

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

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.

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

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.

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

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.

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

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.

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

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.

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

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.