Comparison of engineering failures and seismic responses of 500 kV transformer-bushing systems in the 2022 Luding earthquake

Cemented and mechanically clamped types of end fittings(fitting-C and fitting-M)are commonly used in transformer bushings.During the Luding Ms 6.8 earthquake that occurred in China on September 5,2022,all transformer bushings with the two types of end fittings in a 500 kV substation were damaged.Post-earthquake field investigations were conducted,and the failures of the two types of bushings were compared.Two elementary simulation models of the transformer-bushing systems were developed to simulate the engineering failures,and further compute their seismic responses for comparison.The results indicate that the hitch lugs of the connection flange are structurally harmful to seismic resistance.Fitting-M can decrease the bending stiffness of the bushing due to the flexible sealing rubber gasket.Since it provides a more flexible connection that dissipates energy,the peak accelerations and relative displacements at the top of the bushing are significantly lower than those of the bushing with fitting-C.Compared with fitting-C,fitting-M transfers the high-stress areas from the connection flange to the root of the porcelain,so the latter becomes the most vulnerable component.Fitting-M increases the failure risk of the low-strength porcelain,indicating the unsuitability of applying it in high-intensity fortification regions.

±400 kV直流穿墙套管用环保气体的绝缘特性

400 kV直流穿墙套管为连接外部电场和内部阀厅的重要设备,然而现有研究中环保型气体——干燥空气、CO_(2)以及C_(4)F_(7)N(全氟异丁腈)混合气体的数据并不完全适用于直流穿墙套管,因此研究直流穿墙套管典型电场结构的环保型气体的绝缘特性有重要意义。该文首先仿真分析了±400 kV直流穿墙套管的电场分布,得到穿墙套管内部整体电场分布呈现出两端低中间高的特征,电场强度最大值出现在中间穿墙筒体屏蔽罩端部圆弧处,并根据穿墙套管典型位置电场强度与不均匀度设计了不同类型的电极;其次,在正负极性直流电压下通过试验研究了0.5~1.0 MPa气压范围内不同电极形式、不同电极距离的干燥空气和CO_(2)的击穿特性,以及0.1~0.6 MPa气压范围内球板电极、同轴电极下不同电极距离的C_(4)F_(7)N/CO_(2)混合气体击穿特性,并将三种气体在相同条件下进行对比。试验结果表明:在气压过高时,干燥空气、CO_(2)及C_(4)F_(7)N/CO_(2)混合气体的击穿电压会呈现饱和现象;在相同条件下,干燥空气的绝缘性能是CO_(2)的1.18倍,球板电极下,0.9 MPa干燥空气直流负极性击穿电压可达0.4 MPa SF_(6)混合气体负极性击穿电压的77.2%,可用于±400 kV直流穿墙套管中。

Variable-based Ramberg-Osgood constitutive model of power spinning bushing

The influences of power spinning process parameters on the mechanical properties of spinning parts were analyzed with an SXD100/3-CNC numerical control power spinning machine.The unidirectional tensile tests were carried out.Based on the experimental data,a ternary quadratic regression equation was established by orthogonal experiment.The Ramberg-Osgood constitutive model of tin-bronze connecting rod bushing was obtained.Referred to the constitutive relation of macroscopic incremental,the incremental elastoplastic constitutive relation of spinning parts was deduced based on the Mises yield criterion and kinematic hardening model.The results can be applied to the elastoplastic analysis in finite element numerical simulation.

一种新的Bush型分形曲面及其维数

在 Bush型分形曲线的基础上 ,首先构造了一种分形曲面 ,然后研究这种曲面的分形维数及光滑性。得到了曲面的 Box维数 ,Packing维数的计算公式以及 Hausdorff维数的下界估计式。

Bush型函数的分形维数及其奇异性

本文给出了一类无处可微的连续函数──Ｂｕｓｈ型函数的Ｂｏｘ维数的精确值及其Ｈａｕｓｄｏｒｆｆ维数的下界估计值，同时讨论了Ｂｕｓｈ型函数的奇异性特征．

压合衬套冷挤压对耳片孔残余应力分布的影响

文章利用压合衬套冷挤压工艺对7050铝合金耳片孔进行挤压强化,并采用X射线应力测定仪对残余应力进行检测,研究冷挤压强化对耳片孔残余应力分布的影响。实验结果表明:压合衬套冷挤压工艺使耳片孔产生了明显的残余压应力,并沿孔壁径向形成了一定深度的残余压应力层;相同相对挤压量下,挤出端残余压应力明显高于挤入端,且残余压应力值随着相对挤压量增大而变大;在相对挤压量为2.5%时,挤出端残余压应力最大值为-384.2 MPa,并形成了约14 mm残余压应力层。通过显微硬度计对强化后的试样进行检测,检测结果表明,强化后的试样沿孔壁径向形成了约4.5 mm的组织硬化层,最大显微硬度提升达到了18.1%。冷挤压强化后孔壁沿径向形成了残余压应力层和组织硬化层,提高了耳片孔抗疲劳性能。

用Bush型函数构造分形纹理图

给出一类以Bush型函数构造分形纹理图的方法。用hx方法构造的纹理图可以事先确定其精确的Box－counting维数和Packing维数等分形量，因而可广泛应用于图像分析和图像处理中。

Bush有限单元原理及其在航天器结构建模中的应用

利用大量的数值计算确定了MSC.NASTRAN软件中广义弹簧单元(Bush)刚度阵的解析表达式,通过对比Bush元与剪切梁元的刚度阵,推导了Bush元参数与剪切梁刚度参数的对应关系,并利用展开状态的太阳翼结构和大型桁架结构的静力和动力分析验证了推导结果。该研究揭示了Bush有限单元的原理和所有输入参数的物理含义,有助于Bush元在结构有限元分析中的准确使用。

Bush型函数图像的K-维数

研究一类基于实数的Cantor级数表示的分形函数———Bush型函数图像的K-维数.得到了这类函数图像的K-维数的上、下界估计式.指出在基于实数的b进制表示的情形下,这类函数图像的K-维数等于其box维数与pack ing维数.

发动机曲轴轴瓦装配工艺对装配精度影响的仿真研究

针对发动机曲轴轴瓦装配工艺对装配精度的影响问题,分析了螺栓拧紧力矩下的轴瓦变形规律以及等效应力,拟定7个装配工艺方案,利用有限元仿真对各方案进行了验证,得到不同拧紧顺序下轴瓦应力分布及变形规律,采用轴瓦内径圆度误差评估了装配精度,并将轴瓦圆度优化结果与实验结果进行了对比分析。研究结果表明,优化方案的轴瓦圆度误差降至0.0038 mm,保证了装配精度;轴瓦内径差实测值的平均值为0.0300 mm,仿真结果为0.0324 mm,两者误差为7%,说明仿真结果和实验结果基本一致。

基于某车稳定杆台架试验仿真和路谱疲劳仿真方法对比研究

介绍了稳定杆台架试验仿真分析方法和基于路谱疲劳仿真分析方法,对比两种仿真方法的优异。在ABAQUS环境下对台架进行仿真分析,Bushing单元模拟稳定杆衬套,输入Bushing单元6个方向上的刚度模拟稳定杆衬套实际状态。基于路谱疲劳仿真分析,通过多体动力学输入的载荷谱结合单位载荷下的静态应力结果,通过疲劳耐久专业分析软件Femfat计算出其疲劳寿命。

某矿山球磨机电机轴瓦降温系统优化

某矿山为有效控制球磨机的轴瓦温度,针对球磨机电机轴瓦易受外部环境温度影响而出现高温的问题,进行了轴瓦降温措施研究。结合球磨机实际使用情况及设备结构形式,分析了电机轴瓦升温原因及当前常规降温措施的优缺点,制定了轴瓦降温系统优化方案,并进行了现场试验。试验结果表明:通过优化方案的实施,球磨机电机轴瓦温度得到了有效降低,彻底解决了外部环境因素对球磨机电机轴瓦的负面影响。

基于YOLOv8的变压器套管红外图像发热缺陷识别

变压器作为电力系统的关键设备,其安全可靠运行显得尤为重要,变压器套管的发热缺陷是影响其运行可靠性的重要因素之一。针对变压器套管红外图像发热缺陷识别问题,引入YOLOv8目标检测算法。首先,分析了变压器套管发热缺陷的产生原因、传统变压器套管发热缺陷红外识别方法及其存在的不足。其次,对比分析了中值滤波、引导滤波两种不同去噪方法。然后,设计增广、增强+增广两种不同方法构建数据集,基于YOLOv8算法分别进行训练。最后,在测试集上进行对比实验,结果表明,增强+增广处理后训练所得模型的识别精确率提高了3%、召回率提高了2.3%、平均精度均值提高了0.8%。

Application of the Finite Element Method in the Glass Fiber Bushing Research

Design and optimization of bushing at present mainly use the traditional experience method.The relevant research that adopts computer simulation to carry on the operation behavior of the bushing has appeared in recent years.How to use the finite element method to research bushing was introduced in the article.Physics fields and many relevant parameters of one real bushing were calculated.Through the results of calculation,it indicate that the finite element method is very useful in bushing research of designing and optimizing.

A finite element analysis of a large thrust elastic metal-plastics bearing bush for a hydraulic turbine

Presents the study on the pressure and friction fields of the lubricant film on the surface of a large thrust elastic metal plastic bearing bush in a hydraulic turbine using the method of finite element analysis and the stress and displacement fields in the vertical direction of the bush surface obtained to provide a theoretical basis for the design of contour lines and investigation into the causes for destruction of bushes, and concludes with test results that 1) the stress on the surface of the bush is not uniform; 2) a tension stress tends to occur near the oil ingress and egress edges but it is minor; 3) the biggest displacement in the vertical direction appears where x=84 and Y=1 153 and has a value of 0.022 mm; 4) the deformation of the bearing bush is harmful to the maintenance of lubricant film.

Experimental Investigation on the Bush Inner Surface Temperature of a High Speed Spiral Oil Wedge Sleeve Bearing

The temperature of bush inner surface temperature is measured by using infrared thermometer and transparent bearing,and temperature rise is measured by using thermocouple. The influence of rotating speed and axial location on the bush inner surface temperature is studied,and the influence of supply pressure and rotating speed on the temperature rise is analyzed. The results show the bush inner surface temperature and temperature rise of spiral oil wedge hydrodynamic bearing increase with the increase of rotation speed. In axial direction,the temperature is higher around the oil return hole. The temperature rise decreases with the increase of supply pressure. The highest temperature of bush inner surface and temperature rise are higher at higher speed,so the temperature rise is the fundamental reason which restricts the increase of rotation speed for high speed sleeve bearing.

Characteristics of non-magnetic nanoparticles in magnetically fluidized bed by adding coarse magnets

The fluidization behavior of SiO2, ZnO and TiO2 non-magnetic nanoparticles was investigated in a magnetically fluidized bed （MFB） by adding coarse magnets. The effects of both the amount of coarse magnets and the magnetic field intensity on the fluidization quality of these nanoparticles were investigated. The results show that the coarse magnets added to the bed lead to a reduction in the size of the aggregates formed naturally by the primary nanopartieles. As the macroscopic performances of improved fluidization quality, the bed expansion ratio increases whilst the minimum fluidization velocity decreases with increasing the magnetic field intensity, but for TiO2 nanoparticles there exists a suitable magnetic field intensity of 0.059 6 T. The optimal amounts of coarse magnets for SiO2, ZnO and TiO2 non-magnetic nanoparticles are 40%, 50% and 60% （mass fraction）, respectively. The bed expansion results analyzed by the Richardson-Zaki scaling law show that the exponents depend on both the amount of coarse magnets and the magnetic field intensity.

Analysis of radial stiffness of rubber bush used in dynamic vibration absorber

In order to study the influence of the structural parameters of the rubber bush on its radial stiffness, the constitutive relation of rubber materiel is used to obtain the calculation formula of the dimensionless radial stiffness coefficient. The obtained theoretical result is consistent with previous research results in both long rubber bushes and short rubber bushes. The simulation case was conducted by the finite element method to verify the correctness of the theory. The axial compression experiment was conducted to obtain the parameters needed in the simulation. The result shows that the percentage difference between the theoretical result and the simulation one is only 2.75%. A series of simulations were conducted to compare with previous work, and the largest magnitude of the percentage difference is only about 5%. Finally, the radial stiffness experiment was conducted by using a dynamic vibration absorber, and the influence of the structural parameters of the rubber bush on its radial stiffness is obtained. The result shows that the radial stiffness of the rubber bush increases with the increase in the length and the inner radius, but decreases with the increase in the outer radius.

Study on Heating Uniformity of Pt-Rh Alloy Bushing for Producing Flexible Glass

The numerical simulation for temperature distribution of Pt-Rh alloy bushing was carried out using a thermal-electric module in ANSYS Workbench finite element analysis software.The effects of side wall thickness,plug thickness,the angle of two side walls and electrode structure on the uniformity of temperature distribution were investigated.Meanwhile,the contrastive analysis results of bushing with and without glass melt were discussed.The simulation results show that,when the homogeneous glass melt flows through bushing,the temperature difference between the center and both ends of bushing is decreased significantly,but the temperature distribution at both ends of bushing is still affected by heating non-uniformity of bushing.Compared with side wall thickness,plug thickness and the angle of two side walls,electrode structure plays a greater role in adjusting heating uniformity of bushing.

Earthquake Response and Isolation Layer Parameter Effect of Seismic Isolation Systems of Transformers With Bushings

国内外震害表明，变压器在地震中的破坏型式多样，易损性极高。隔震技术是一项能够有效降低地震反应的新型抗震技术，而变压器及套管隔震层的设计和参数选择与普通结构有较大的差异。首先，建立了大型电力变压器及套管隔震体系的多质点分析模型，采用Matlab软件编写计算程序，分别输入人工地震波和Taft地震波，对变压器及套管隔震体系的地震响应进行分析；最后，开展了隔震层等效水平网0度、等效阻尼比、双线性恢复力模型的屈服剪力系数及屈服后刚度等参数的地震响应影响分析。分析结果表明：合理设计变压器及套管隔震体系的隔震层参数，可有效降低变压器及套管的地震响应；另外，通过隔震层的参数分析，得到了相关参数的合理取值范围。该研究对今后变压器及套管隔震体系的设计具有参考与指导作用。