电晕对HTV硅橡胶憎水性恢复的影响

为了解一种优异的高压外绝缘材料硅橡胶的憎水性恢复的影响。通过电晕加速老化试验,采用静态接触角法研究了高温硫化(HTV)硅橡胶在电晕老化不同时间后的憎水性恢复,结果发现,5kV的工频交流电压下电晕5min后,硅橡胶的憎水性暂时丧失;电晕老化后不同时间试样的憎水性恢复呈现出不同的变化趋势,其憎水性恢复率随着电晕老化时间的增加经历了"增加-降低-增加-降低"4个过程;同时在电晕老化一定时间后,即使经历足够长时间,其憎水性仍不能恢复到初始水平。因此硅橡胶的憎水性恢复快慢及恢复程度与电晕老化时间密切相关,并随之呈现出规律性的变化。     

电晕强度对HTV硅橡胶陷阱特性的影响

高温硫化(HTV)硅橡胶因具有优异的憎水性、憎水迁移性、憎水恢复性及其它显而易见的优越性而被广泛用作电力系统中合成绝缘子的外绝缘材料。为此,采用热刺激电流(TSC)技术对HTV硅橡胶在不同电晕强度老化后的陷阱特性进行了系统的试验研究,同时观测了硅橡胶在相应老化阶段表面形态的变化。试验结果表明,在不同的老化阶段,硅橡胶的陷阱特性变化呈现出不同的特点。随着电晕强度的增加,陷阱电荷量总体上呈增多趋势;在电晕作用时间较短时陷阱能级随电晕强度的增加而产生较小的变化;在电晕作用时间较长时,陷阱能级在电晕强度达到一定值时将被加深,之后随电晕强度的增加而逐渐变深。结合硅橡胶的扫描电子显微镜(SEM)结果,分析可知,电晕强度及电晕作用时间通过影响轰击硅橡胶表面的带电粒子的能量和持续时间,对其表面形态产生作用,进一步地引起硅橡胶陷阱分布特性的变化。     

交流电晕对超疏水及普通硅橡胶憎水性的影响

复合绝缘子优异的防污闪性能主要得益于硅橡胶材料表面的憎水性及其迁移特性。在近几年有关表面和界面的研究中,超疏水材料以其优异的超级憎水性和自清洁特性引起了电力行业研究人员广泛的关注。静态接触角大于150°,滚动角小于10°的材料表面被称之为超疏水表面。以往的研究表明,电晕放电是造成硅橡胶表面憎水性下降乃至丧失的主要因素之一。文中以自制的2种超疏水表面硅橡胶和1种普通表面硅橡胶为研究对象,开展了交流电晕对其憎水性及憎水恢复特性的影响研究。考虑到电晕后硅橡胶表面的滚动角会大于90°,文中用接触角滞后取代滚动角表征表面的自清洁能力。试验结果表明:普通硅橡胶表面的静态接触角和接触角滞后分别是113.2°和11.7°,而模板法制备的2种具有微观表面结构的硅橡胶的静态接触角均大于150°,接触角滞后均小于3°,具有良好的超疏水特性及自清洁特性;在电晕处理硅橡胶表面后及电晕后恢复的过程中,普通表面硅橡胶的憎水性及自清洁特性都明显不如超疏水表面硅橡胶;而对于两种超疏水表面,封闭式结构μc表面的憎水性及其恢复特性要优于开放式结构μ_o表面。     

硅橡胶合成绝缘子外绝缘老化性能研究

高温硫化(HTV)硅橡胶因其强憎水性、憎水迁移性和恢复性等优越性能,成为合成绝缘子外绝缘的首选材料。然而与无机材料相比,HTV硅橡胶更易受电晕、紫外辐射等因素的影响而老化。文章介绍了通过针-板电极系统模拟现实中的尖端电晕放电,用氙灯辐照对HTV硅橡胶进行紫外加速老化的研究过程。试验结果表明:电晕放电不同时间后硅橡胶表面的憎水性丧失是一个渐进的过程,而氙灯辐照对HTV硅橡胶表面憎水性影响不大,纯电场作用对硅橡胶表面的憎水性影响甚微;然而氙灯辐射后材料硬度有变大趋势,材料表面凹凸不平,粗糙度变大,并有填充物外露的趋势。     

紫外线老化对复合绝缘子硅橡胶憎水性的影响

硅橡胶复合绝缘子的优良耐污闪性能源自于硅橡胶材料的憎水性以及憎水迁移性。本文研究了紫外老化对硅橡胶憎水性影响以及硅橡胶表面积污后的憎水迁移性。研究结果表明：经小分子处理的硅橡胶经过2 000 h紫外线辐射后仍能够保持良好的憎水性,静态接触角仍能达到102.3°,憎水性等级为HC2级;硅橡胶上的污层在较短时间内具有了憎水性,憎水性等级能达到HC2~HC3。并对硅橡胶紫外老化机理以及憎水迁移性机理进行了分析。     

复合绝缘子电晕加速老化试验研究

为研究电晕对复合绝缘子老化性能影响,采用针-板电极模拟不均匀电场环境,以硅橡胶片材作为高温硫化硅橡胶展开试验.结果表明,电晕老化对材料表面具有一定的破坏,是造成材料憎水性下降及暂时性丧失的主要原因,温度越高,硅橡胶憎水恢复越快,恢复后憎水角越大;电晕造成材料拉伸强度和硬度有所下降,体积电阻率减小,介质损耗角增大、介电强度减小,电晕放电对电气性能影响较大.     

不同老化因素对互感器伞套老化影响的研究

通过扫描电子显微镜(SEM)和傅氏转换红外线光谱分析仪(FTIR)分析了硅橡胶伞套老化前后宏观表面结构变化和微观官能团变化,通过氙灯老化、湿热老化、电晕老化、户外自然老化和室内自然老化试验,研究互感器表面硅橡胶材料在不同因素影响下的理化、电气性能变化。结果表明:氙灯老化对硅橡胶硬度的影响最显著,硬度从37.0HA增加到45.40HA;湿热老化对硅橡胶镜像光泽度的影响最显著,镜像光泽度从75下降至40;自然户外老化对硅橡胶憎水性的影响最显著,静态接触角从115.4°下降至102.1°。通过测试老化硅橡胶的硬度、镜像光泽度、憎水性和表面电阻来评价各因素对硅橡胶伞套老化的影响大小,研究结果有助于对运行中的互感器老化程度进行监测。     

硅橡胶绝缘子粉化层憎水性变化的研究

硅橡胶绝缘子运行后会逐渐老化,伞裙表面出现粉化层。为研究粉化层对硅橡胶绝缘子表面憎水性的影响,通过红外光谱(IR)、扫描电镜(SEM)等手段对现场取回的硅橡胶绝缘子进行研究,测试硅橡胶绝缘子粉化层的微观结构和化学成分,进一步分析粉化层表面憎水性变化的原因。结果表明:绝缘子粉化层表面憎水性良好,但去掉粉化层后绝缘子表面憎水性明显下降。通过IR和SEM发现绝缘子的粉化层表面老化降解程度严重,硅橡胶材料主链上的分子键断裂,粉化层物质颗粒之间结构疏松,分子间相互作用力小,观察其微观形貌发现大量孔隙。因此水分不易附着在绝缘子伞裙表面,使运行老化后硅橡胶绝缘子表面仍具有良好的憎水性。     

自然老化硅橡胶材料表面憎水性及耐受特性的研究

研究硅橡胶材料的老化特性对于复合绝缘子的设计、选型及维护具有重要意义。以经过现场投样、自然老化后的复合绝缘子伞裙压片为研究对象,详细研究了硅橡胶材料自然老化前后在憎水性迁移特性、憎水性丧失特性、憎水性恢复特性上出现的差异,另外对材料受酸碱侵蚀后表面维持憎水性的能力也进行了研究。结果表明,老化对于材料憎水性能的影响较明显,上下表面由于存在日照、雨淋、积污和冲刷等因素的差异,老化程度不同,上表面的憎水性能表现的更差一些。     

交流电晕对复合绝缘子硅橡胶伞裙憎水性的影响研究

随着复合绝缘子在电力系统的广泛应用,电晕放电对其长期运行性能的影响是一个值得关注的问题。通过构建针-板电极系统,以清洁硅橡胶试片、人工染污硅橡胶试片、运行绝缘子伞裙试样为对象,系统地研究了在强烈交流电晕作用下硅橡胶伞裙材料的憎水性丧失和恢复过程。研究结果表明:在交流电晕持续作用下,硅橡胶材料的憎水性会逐步丧失,而人工染污和自然积污状态下的硅橡胶憎水性丧失进程相对缓慢,且稳定后的静态接触角也较高,适量的污秽层有利于复合绝缘子硅橡胶伞裙抵御电晕老化。在电晕作用后,由于硅橡胶材料内憎水性小分子硅氧烷的迁移作用,无论是清洁还是积污状态,表面憎水性均能在短时间内恢复到接近初始状态。     

Electrical and environmental stress and the hydrophobic stabilityof SIR, EVA and their blends

This paper treats the effects of electrical and environmental stresses on the hydrophobicity of polymers intended for use in nonceramic insulators. We investigated the effect of UV radiation, corona discharges, dry-band arcing, acid rain and water absorption on hydrophobic transfers in, and the aging of, room temperature vulcanized (RTV)-silicone rubber (SIR), high temperature vulcanized (HTV)-silicone rubber (SIR), ethylene vinyl acetate (EVA) rubber and the blends made from HTV-SIR and EVA. Acid rain had little influence on hydrophobicity in any of the samples. EVA and the blends with low silicone ratios to EVA allowed much larger reduction in hydrophobicity after or while subjected to the above stresses (except for acid rain) than did the silicone rubbers and a blend with a high silicone ratio to EVA. Salt-fog tests were conducted to correlate the hydrophobic stabilities of materials with leakage current levels thereon. The hydrophobic stability of the silicone rubbers was attributed to low-molecular-weight silicone components that were able to migrate and finally cover the aged surface layers. Because EVA possessed less fluid components and less chemical stability under electrical and environmental stresses, its hydrophobicity was readily reduced and hardly recovered, which led to higher current leakage and early material aging. For each material, the critical hydrophobic level permitting leakage current to develop was determined by adding a non-ionic wetting agent to saline water     

Effect of Hydrophobicity on Electric Field Distribution and Discharges Along Various Wetted Hydrophobic Surfaces

According to hydrophobicity and hydrophobicity transfer studies on silicone rubber surfaces, although the silicone rubber can transfer its hydrophobicity to various contaminants deposited on its surface, the hydrophobic states of water droplets on clean silicone rubber surfaces and on various contaminated silicone rubber surfaces were found to be different based on evaluation by contact angle measurement. Furthermore, surface discharge and aging of materials decreases the hydrophobicity of the surface. Focused on the difference of hydrophobicity and the effect of water droplets on the hydrophobic contaminated surfaces, some contrastive computations and tests of water droplets on various surfaces were carried out in this study. The results showed that the water droplets existing on the surface of silicone rubber materials might change the electric field and voltage distribution along the surface, and even reduced the initial voltage of the corona discharge, which was verified with a comparison test on a high voltage side of polymer insulator monitored by a photomultiplier tube (PMT) system. Since the leakage current provides much useful information to diagnose the state of outdoor insulation, this study investigates the time and frequency distributions of surface discharges on ceramic insulators, new room temperature vulcanized (RTV) silicone rubber coated insulators and aging RTV insulators with various hydrophobic states with the short time Fourier transform and Gabor transform methods. Then a correlation was found between the distribution of the spectrum of surface discharges and hydrophobicity via the joint time and frequency analysis of discharges on various hydrophobic surfaces.     

Effects of added silicone oils on the surface characteristics of silicone rubber

This paper reports on the effects of silicone fluids, used as processing agents, on the loss and recovery of hydrophobicity. The recovery of hydrophobicity was evaluated by the measuring the contact angle, the surface electrical resistance and the leakage current on a silicone rubber (SIR) surface. Two types of silicone fluids (A and B) having different chemical structures were selected from consideration of hydrophobicity and processability. SIR specimens were exposed to corona discharges in air and were analyzed using contact angle and surface resistance measurements. It was observed that the contact angle and the surface resistance increased gradually with increasing test time. The recovery of the hydrophobicity expressed as the contact angle and the surface resistance increased with increasing ratio of fluids A/B. The tracking and erosion resistances of SIR were investigated using the rotating wheel dip test. The leakage current of SIR decreased with increasing ratio of fluids A/B.     

紫外辐射对高温硫化硅橡胶性能影响初探

高温硫化(HTV)硅橡胶凭其强憎水性、憎水迁移性和恢复性等优越性能,成为合成绝缘子外绝缘的首选材料。然而,与无机材料相比,高温硫化硅橡胶更易受环境影响而老化,因此通过氙灯辐照对高温硫化硅橡胶进行紫外加速老化试验。采用静态接触角法测量和评价硅橡胶材料的憎水性,同时进行了硬度以及扫描电子显微镜(SEM)测试,另外采用image-pro plus 6.0软件对SEM图片进行测试分析。试验结果表明:短时氙灯辐照对高温硫化硅橡胶表面憎水性影响不大,材料硬度有变大趋势,材料表面凹凸不平,粗糙度变大,并有填充物外露的趋势。随着辐照时间增加,欲析出颗粒数目逐渐增多,颗粒大小逐渐变大,总面积增加。     

Surface recovery of silicone rubber used for HV outdoor insulation

Results of a study performed to obtain a better understanding of the material characteristics responsible for hydrophobicity recovery leading to a high wet surface resistance in silicone rubbers used for outdoor HV insulation, are reported. The samples were obtained from new and artificially aged HV insulators using HTV silicone rubbers (3 different formulations) as weathershed and RTV silicone rubbers (2 different formulations) as a protective coating. The main experimental facilities employed consist of a salt fog chamber for artificially aging the insulators, and a scanning electron microscope (SEM) for material studies. New results of practical significance that have emerged from this study are: (1) hydrophobicity recovery, predominantly due to diffusion of low molecular weight (LMW) silicone polymer chains, occurs with only a fraction (<20%) of the total LMW polymer content initially available in an unaged material surface, (2) LMW chain regeneration and hence surface hydrophobicity recovery occurs even after the initial supply of LMW polymer is depleted, and (3) hydrophobicity recovery is significantly affected by ambient temperature. The results show the same pattern for different formulations of HTV and RTV rubber materials studied. The X-ray Mapping feature in the SEM provides a visual indication of the diffusion process which is a noteworthy contribution     

电力外绝缘用硅橡胶清洗修复剂制备及性能研究

硅橡胶广泛应用于电力行业的复合绝缘子和防污闪涂料,然而长时间工况运行后,容易发生老化粉化、污秽沉积,降低了表面憎水性。电网中目前有上亿支硅橡胶绝缘子服役多年,研究能够清除表面污秽,修复硅橡胶老化层的新型清洗剂迫在眉睫。本文探究不同非离子表面活性剂含量和修复剂含量对清洗效率和憎水性的影响。实验表明非离子表面活性剂含量在3%时,洗净率最高达到95%。而修复剂含量为11%时,憎水性最好,其憎水迁移性最佳可以达到HC1级。通过扫描电镜分析,发现清洗后硅橡胶表面微孔和裂缝消失,表面平整,表明该清洗剂具有去除老化层和污秽,修复老化绝缘子的效果。这为继续研发硅橡胶清洗修复剂,延长绝缘子服役期限提供一定的理论和实践基础。     

Fractal phenomena. Dependence of hydrophobicity on surfaceappearance and structural features of SIR insulators

This paper reports the study of the dependence of hydrophobicity on the surface appearances and inherent chemical structure of the high-temperature vulcanized silicone rubber (HTVSR) insulator based on the fractal geometric principle. The fractal phenomena link the surface roughness with the hydrophobicity characteristics of silicone rubber (SIR) insulators. The rough surfaces of the insulators, no matter whether due to salt-fog aging or roughening by sandpaper, show the property of a fractal surface. According to the amount of hydrophobic material on the surface, surface roughness exerts different effects on the hydrophobicity of SIR insulators. Due to the behavior of fractal surfaces, the hydrophobicity of the appropriately roughened insulator can be enhanced, but depressed if dipped in hexane. Outdoor polymer insulating materials could be aged by environmental stresses and contaminants so that their surfaces become rough. The permanent change of surface roughness could be an indicator of aging state of the insulation material. The hydrophobicity of SIR insulators aged in salt fog in a fog chamber are investigated. During this aging, the inorganic filler and the hydrophobic groups in SIR are worn away so that the insulator surface becomes rough. The surface of the aged insulator becomes hydrophilic. After a subsequent rest, the hydrophobic polymer liquid in bulk diffuses and migrates to the insulator surface, which becomes more hydrophobic. Such a unique dependency of hydrophobicity on the surface appearance and chemical structure of SIR material is available for SIR insulator to maintain good contamination performances in outdoor applications     

高温硫化硅橡胶加速电晕老化试验分析及其寿命预测

高温硫化(HTV)硅橡胶属于有机材料,具有重量轻、憎水性好等优点,但也存在易老化的缺点。电晕是引起HTV材料老化的重要因素之一,因此对HTV进行了加速电晕老化试验,并对电老化后的试验样品进行了Fou-rier变换红外光谱(FTIR)分析。试验结果表明,随着老化时间的增加,HTV电晕老化速率会越来越慢。根据基于陷阱理论的聚合物电老化寿命公式及电晕老化前后HTV的红外光谱变化分析HTV的寿命模型,确定了寿命公式中的待定系数,得到了HTV老化寿命的定量表达式。此方法可为建立硅橡胶材料的老化模型和寿命评估提供参考。