Silicone rubber of composite insulators is extensively utilised because of its superior hydrophobicity and hydrophobicity transfer characteristics, especially in heavily polluted environments. This work investigates the hydrophobicity transfer process of silicone rubber materials with different insoluble substances and explores the impact of microscopic parameters on hydrophobicity transfer. Experiments employed diatomaceous earth and kaolin of various particle sizes and origins as inert substances to analyse their effects on hydrophobicity transfer characteristics. Results indicate that diatomaceous earth, with its porous structure, facilitates faster transfer compared to the dense structure of kaolin. Pore size and specific surface area are critical parameters influencing transfer rates. Larger outer pores accelerate the initial 'fast process' while smaller inner pores govern the subsequent 'slow process' Fractal characteristics of pores also affect transfer efficiency with higher fractal dimensions leading to more extensive transfer. The hydrophobicity transfer process in silicone rubber involves dynamic diffusion influenced by the complexity of internal channels and surface structures. Enhanced understanding of these mechanisms can improve the performance and reliability of composite insulators in polluted environments.

This paper comprehensively applies seismic load calculations, finite element simulation, and modal analysis to explore the seismic performance of I-shaped and circular section column insulators under seismic dynamic loads. By comparing and analyzing, the study reveals the performance differences of insulators with different cross-sectional shapes in seismic de-sign, providing a scientific basis for the external insulation design of high-voltage DC converter stations.

In order to obtain the bird streamer flashover characteristics in high altitude areas, the discharge of DC V-type string insulators was studied in high-altitude test base at 4300 m in Tibet. The study results show that medium viscosity bird streamer is easy to form a continuous channel and cause flashover. The flashover probability of positive polarity transmission lines is slightly higher than that of negative. The conductivity of bird excrement almost has no effect on the flashover probability in the range of 1.9∼20.9 mS/cm. To increase the vertical air gap distance can reduce bird streamer flashover probability. Based on the experiment results, the recommended vertical air gap distance values of ±400 kV DC transmission line were proposed. Considering the influence of wind and bird streamer falling angle, the protection radius was set 3.5 m at 3500∼5000 m altitude area. Bird streamer flashover is a mixed discharge of air gap breakdown and the surface discharge along the bird streamer channel, at the altitude of 4300 m area, the minimum breakdown potential gradient is about 2.1 kV/cm, and the discharge between bird streamer and shielding ring can be approximately equivalent to rod-rod gap discharge.

The deterioration at the sheath-core interface of composite insulator is a crucial problem, which can lead to fracture fault. However, the study on the sheath-core interface delamination failure of the composite insulator is just at the preliminary stage both inland and abroad. The thesis focuses on the sheath-core interface performances of the composite insulator in operation. In addition, the key parameters are put forward through water diffusion test and dye penetration test, to describe the interface performances quantitively, including interfacial leakage current and deterioration area ratio. Moreover, this paper also researches the effect of sheath-core interface defects on decay-fracture of the composite insulator through finite-element simulation, with regard to water content and non-uniform electric field. It has been found that the existence of the air gap defects can make the local electric field distortion rate up to 186.4%, and the temperature rise is 1.8K. As the moisture absorption rate increases from 0% to 100%, the electric field distortion rate increases from 73% to 160%, the temperature increments increased from 1.4K to 19.8K. These results are consistent with the physical and chemical properties analyses of typical decay-fracture composite insulator. The research suggests that strong external electric field near high-voltage side of the insulator and water permeation process have impacts on material deterioration and interface defects. The interface defects can cause partial discharge, which lead to the permeation of the acidic liquid into the interface and acceleration of the interfacial degradation. The research results can provide some references to operation and maintenance of composite insulators for hot and humid rain-fed areas in southern China.

Mastering the bird dropping flashover characteristics of AC transmission line tower clearance in areas above 4,000 m and taking reasonable measures to prevent bird dropping fault are the key to ensure the safe and stable operation of transmission lines in high-altitude areas. For V and I insulator strings of 500 kV line and I insulator strings of 330 kV line commonly used in high-altitude areas, the bird dropping flashover discharge test was carried out under rated operating voltage and highest operating voltage respectively, and flashover probability at different falling positions of bird droppings was obtained. The easy flashover scope of bird droppings on both sides of 3.5 m and 3.0 m of V and I insulator strings of 500 kV line and 2.0 m of I insulator strings of 330 kV line is determined. According to the structural characteristics of tangent towers and tension towers on AC line, the layout scope and measures of bird thorn and thorn plate are put forward. The research results can provide a basis for the bird dropping flashover prevention fault of AC transmission lines in areas above 4,000 m.

In order to study the discharge phenomena of plastic film overlapping on UHV DC transmission lines and explore the cause of flashover fault of a ± 800 kV UHV line, an experimental study is conducted on the flashover characteristics of plastic film with three different gap distances of 1.0 m, 2.0 m and 11.5 m, and the relationship between flashover voltage and plastic states, including dry and wet state, spreading and rolling state, is studied through analyzing the equivalent salt density of three typical areas on the surface of plastic film. The results show that, when the gap distance is 1.0 m and 2.0 m, the gap flashover potential gradients of wet plastic film are 1.22 kV/cm, 0.96 kV/cm, 0.82 kV/cm and 0.7 kV/cm respectively for the spreading out and rolling up state; When the gap distance is 11.5 m, the gap flashover potential gradient of the wet plastic film is 0.56 kV/cm. Under the condition of moisture, the plastic film in rolling up state is more prone to flashover than that in spreading out state, and the average flashover potential gradient decreases with the increase of gap distance. Finally, the causes for the failed three times of restart of a ± 800 kV UHV line caused by short circuit of plastic film is analyzed.

A concentrated treatment used on the residual pollution layer in the Obennaus and its improved models is inappropriate for establishing the propagation model of an arc along the pollution layer surface. Therefore, discretising the residual pollution layer is innovatively proposed. The residual pollution layer is discretised into several infinitesimal pollution layer elements with various characteristics along the vertical direction from the arc root to the ground electrode. Quantitative relationships between the surface conductivity of a pollution layer element and several variables, including salt deposit density, water film thickness, temperature, and time, are concluded based on experimental data and relevant theories. A distribution factor that determines leakage current densities in a pollution layer is defined. A residual pollution layer surface resistance model based on the discretisation, relational expressions, and distribution factor is established. A comparison of the proposed model with the results observed in the experiments with and without a partial arc shows that the proposed model is reasonable.

Birds’ activities may cause short-circuit damages of transmission line (TL), especially in the areas without tall trees and other vegetation. ±400 kV Qaidam-Lhasa DC TL with an average altitude of about 4650 m in China is the highest DC TL in the world. Since November 2011 to the end of January 2017, there have been a total of 102 short-circuit damages, including 95 damages caused by birds. The damages were mainly caused by the defecation of birds. This paper analyzes the characteristics and causes of flashover damages of the Project. Moreover, A survey of birds along the TL was carried out by using line transect method and point count method, and then the comprehensive improvement measures for such bird-related outages were put forward. The results show that a total of 26 species of birds are involved in the damages, mainly including large or clustered birds such as Gyps himalayensis, Aegypius monachus, Buteo hemilasius, Buteo buteo and Corvus corax. The damages often occur at night in winter and spring. The prevention measures shall be dominated by guiding type and supplemented by isolation type and expulsion type, and focus on the treatment of tension tower. Through improvement, the outages have been greatly reduced from 2018 to now.

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 ultrahigh 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 steep-front impulse voltage tests.

典型空气间隙的击穿电压特性是外绝缘设计的重要依据,为研究电位悬浮体对空气间隙击穿电压的影响,文中以简化的组合间隙放电模型为研究对象,实验研究了悬浮导体长度和高压电极形状对组合空气间隙击穿电压的影响特性和变化曲线.基于实验数据和观测到的放电现象,文中在考虑子间隙的击穿顺序和流注通道压降的基础上,建立了组合间隙击穿电压的计算模型.利用该模型对含有电位悬浮导体的组合间隙击穿电压进行了计算,结果表明,文中提出的计算模型得到的击穿电压计算值和实验数据相比,相对误差小于5％,说明该方法对于计算含有电位悬浮导体的组合空气间隙击穿电压具有一定的适用性.

青藏±400 kV柴拉直流输电线路自2011年11月投运后,截至2017年9月,共发生了115次对地短路故障.首先分析上述故障原因和特点并在西藏高海拔试验基地开展了模拟鸟粪闪络试验研究,在此基础上提出了相应的治理措施.研究结果表明:青藏线大部分短路故障是由鸟粪闪络所引起,涉鸟故障的主要鸟种有大鵟、高山兀鹫、秃鹫、金雕等猛禽类鸟类.故障多发生在海拔4500～5000m地区,春季和冬季的鸟粪闪络故障相对高发,故障时段主要集中在21:00—次日凌晨8:00之间,耐张杆塔的故障数高于直线杆塔,正极性的故障数略高于负极性.结合前期治理经验和模拟鸟粪试验,提出了综合性的治理措施:在横担3.5m防护半径内规范布置防鸟刺和针板,适当增加垂直方向上间隙距离.青藏线经上述措施治理后,大幅降低了线路鸟粪闪络故障率.

Scanning electron microscope (SEM) has been widely used in the field of materials science because of its excellent microscopic amplification performance, but it is seldom used in the field of high voltage. SEM can visually reproduce the micro morphology of the mandrel surface and find the defects that are difficult to be observed by the naked eye, which is convenient for the experimenters to summarize the micro morphology characteristics of the aged core rod and determine the equivalence between the accelerated aging test in the laboratory and the actual aged samples in operation. In this paper, SEM was used to observe the surface of the core rod samples after heat aging, acid soaking and electric erosion, and the results were compared with the actual decay-like aged samples in operation. The results show that the serious degradation of epoxy resin, the exposure of glass fiber, the uneven fracture and the failure of interface between fiber and resin can be clearly seen by SEM. At the same time, it can also find the residue on the fiber after the epoxy resin is powdered and the bubbles and cavities formed when the epoxy resin is degraded. Meanwhile, SEM can be used to find the similarity between the laboratory aging sample and the actual sample, and prove the equivalence between them to a certain extent.

为掌握高海拔地区直流架空输电线路的鸟粪闪络特性,在海拔高度为4 300 m的西藏羊八井高海拔试验基地对直流V串绝缘子的鸟粪闪络问题进行了试验研究.研究表明:中等黏度的鸟粪易于形成连续的鸟粪通道,闪络概率较高,且正极性的鸟粪闪络概率略高于负极性;在1.9～20.9 mS/cm的电导率范围内,鸟粪电导率对鸟粪闪络概率影响很小;增加垂直间隙距离可降低鸟粪闪络概率.基于试验提出了±400 kV柴拉直流线路垂直间隙距离推荐值,考虑风偏修正和鸟类泄粪角度的影响,在4 500～5 000 m海拔地区,防护半径宜设置为3.5 m.鸟粪闪络属于空气间隙击穿与沿鸟粪通道沿面放电相结合的混合放电过程,在海拔高度4 300m处,其间隙最低击穿电位梯度约为2.1 kV/cm,鸟粪与均压环间隙的放电可近似等效为棒-棒间隙.

Abstract A new type of composite insulator mechanical failure named decay-like fracture happens rather often in UHV AC transmission lines. However, the cause from the point view of electric field is not clear. To investigate the effect of electric field on the occurrence and development mechanism of decay-like fracture, the 3D tower-conductor-insulator models for ZB2-type and CZ34-type transmission tangent towers are established and analysed based on the finite element simulation. The conclusion can be drawn that the tower type has a significant effect on the electric field distribution along the axial direction of the insulator string, and the degradation is more likely to occur in high-voltage side of the B-phase string, which is consistent with the fracture failure investigation. Simulation results also show that the withstand electric field strength is 297kV/m. The distribution of surface potential and electric field under the actual operating voltage provide a new idea for the condition monitoring of the decay-like fracture of UHV AC composite insulators in transmission lines, as well as a reference for further research in the field of decay-like fracture failure.

Power girds in different countries face different types of threats and in China the threats severely affecting grid reliability were in the past large power outage accidents caused by pollution flashovers. First records of pollution flashover accidents in China can be traced back to 1950s in industrial areas in Northeast and East China. Thereafter, such accidents occurred occasionally, but after 1...

在线监测设备的可靠工作对电源性能有较高的要求,为提升取能电源的供电性能,基于无源元件设计了1套TA取能电源。为了解决TA取能电源难以兼顾高取能效率和避免饱和的难题,选取高磁导率的纳米晶合金作为铁芯材料,通过理论分析和仿真研究,分析匝数、负载阻抗对取能效率的影响;同时采用肖特基二极管组成稳压泄流通路抑制铁芯饱和。利用整流桥和直流–直流变换器(DC-DC)模块实现稳定直流电压的输出,通过有限元电磁–热耦合仿真并结合试验设计合理的电源装置。该电源装置可在导线电流在17～1 100 A范围内为摄像头负载提供1.5 W以上的电能。

Contamination withstand performance of power equipment adopting silicon rubber as external insulation is dominated by its hydrophobicity. To reveal hydrophobicity transfer mechanism of various non-soluble pollutant on silicon rubber surface, several inert materials of similar chemical component were selected, including Kaolin, Kieselguhr, and silicon dioxide microspheres. Static contact angle tests at various transfer times are performed to obtain the hydrophobicity transfer characteristics of various pollutants. Scanning electron microscope (SEM) test and mercury intrusion porosimetry (MIP) of these inert materials are also carried out to observe the topographical microstructure. Results show that the variations between static contact angle and hydrophobicity transfer time perform great distinction depending on the microscopic properties of inert material. According to MIP and SEM analysis of Kieselguhr, two kinds of pores are found, which play different part on hydrophobicity transfer process. It is proposed that there are two patterns superimposed in hydrophobicity transfer process. One was the “fast process”, determined by the large pore among inert material particles, controlled hydrophobicity transfer speed in first 10 hours. While the other was the “slow process”, resulted by the small pore in inert material particles, determines the final static contact angle. In conclusion, the hydrophobicity transfer process from silicone rubber surface to pollutant surface is a superposition effect of the two transfer processes, especially for porous inert materials. This paper has researched the concrete hydrophobicity transfer process considering the influence of non-soluble pollutant microcosmic characteristics. The results have great significance for hydrophobicity transfer theory and guidance value for outdoor insulation practice of transmission line.

为研究降雨条件下空气间隙的操作冲击放电特性,通过实验对比研究获得了干燥和淋雨条件下间隙距离为10～60 cm球-板、棒-板间隙正极性操作冲击放电曲线。研究表明淋雨造成球-板间隙正极性操作冲击击穿电压降低幅度大于棒-板间隙;雨量大小对棒-板间隙击穿电压的影响不明显;雨量为0.5～3.9mm/min时,直径10cm球电极间隙距离30cm,操作冲击击穿电压较干燥条件降低15.8%～32.6%;雨水电导率为100～2000μS/cm时,击穿电压随电导率的增加而降低,但随着间隙距离的增加,球-板、棒-板间隙操作冲击击穿电压降低幅度减弱,且雨水电导率对球-板间隙操作冲击击穿电压的影响更为明显;雨水的存在会使放电时延较干燥时有变短趋势,使间隙在波前击穿的几率增大,且雨水通道会影响放电的发展路径。

针对现阶段直流系统接地故障检测所使用的频率注入法会给直流系统带来较大纹波和受到分布电容影响较大的问题,提出了在正负直流母线间串联交流电源并在母线增加短路电容通路的方法以提高检测精度.即根据两次变频注入交流信号得到故障支路的漏电流建立两个二元方程以在规避分布电容影响的前提下精确求得接地电阻.该方法向母线投入一个大电容支路,既能有效规避母线分布电容给测量带来的误差,又满足国家电网的规定,向系统注入的小信号在纹波规定范围内,还从计算上规避了支路分布电容的影响.该方法有效减小了由于传感器测量精度和分布电容对直流系统绝缘检测带来的误差,降低了绝缘检测设备漏报误报概率,提高了检测精度并使用实验仿真验证了方法的可行性.

研究有关复合绝缘子伞形的标准和文献资料,结合对水平安装的复合绝缘子伞形积污特性对比分析、伞裙受力特性研究,优化设计出了一种用于d或e级污秽等级的超特高压耐张复合绝缘子伞形结构,并通过人工踩踏试验和人工污秽试验,对伞形设计进行了验证,取得了预期的效果.