1100 kV直流SF6气体绝缘穿墙套管电场仿真分析

国产1100 kV直流SF6气体绝缘穿墙套管首次采用双层内屏蔽结构。为此,提出了1种气体电流密度计算方法用于仿真直流电压下的套管电场分布,对工频和直流电压下分别采用单层和双层内屏蔽结构时的套管电场分布进行了仿真分析,探讨了双层内屏蔽结构的电场调控能力,仿真分析了气体电离对电场分布的影响。结果表明:直流电压下套管外部表面电场分布不受内屏蔽电极配置方式的影响,但双层屏蔽结构相对于单层屏蔽结构能够减小套管内部电极的表面场强;套管外部空气电离达到一定程度后将引发屏蔽环表面起始的闪络,内部SF6气体电离达到一定程度后则更容易发生电离区附近的套管表面电晕放电。

一种新型的电离式MEMS气体传感器

实现了一种新型的电离式MEMS气体传感器,即线性阻抗电离式MEMS气体传感器。该传感器创新地采用了电导率而不是常用的击穿电压来检测不同的气体成分,这样可以避免高电压对器件的影响,提高器件工作状态的可重复性和稳定性。该器件在低压条件下不同气体组分中进行气体放电实验,测出了不同的伏安特性曲线和电导率值,从而证实了该器件的气体传感特性。

绝缘表面和气体导电与湿度的关系

湿度对绝缘体表面电导和气体电导有一定的影响，但通常在湿度传感器的研究中忽略了气体电导的贡献．本文通过特殊设计装置来区分表面电导和气体电导，并分别从实验和理论上进行了定性的研究．

直流电压下环氧浇注绝缘子的表面电场分析

针对直流气体绝缘设备电场分析及结构设计时气体侧模型的选择问题,以高压直流气体绝缘穿墙套管用环氧浇注绝缘子为研究对象,建立了直流电压下环氧浇注绝缘子的电场计算模型。其中,对气体侧分别采用离子迁移模型和线性模型,在直流电压下对环氧浇注绝缘子的表面电场进行了计算及分析。研究了不同气体电离率、外施电压、体积电导率等条件下两种模型对计算结果的影响及相互替换的条件,给出了直流电压下气体侧模型的选择建议。结果表明:离子迁移模型得到的绝缘子表面电场计算结果受气体中空间电荷不均匀分布的影响,随场强的变化呈现出较强的非线性;线性模型用以匹配离子迁移模型计算结果的气体电导率取值与气体电离率成正比,与外施电压等级成反比;当外施电压等级较高、绝缘子体积电导率较大时,固体侧电流在绝缘子表面电荷积聚过程中起主要作用,离子迁移模型与线性模型得到的计算结果差异较小。这时,线性模型计算时间更短,更适用于环氧浇注绝缘子的结构优化设计。

气固绝缘系统电场模型的建立与求解方法

针对目前气固绝缘系统直流电场计算所普遍采用的恒定电流场计算方法过于简化,尤其对于电流密度存在饱和现象的气体介质计算误差较大的问题,建立了基于介质内部和分界面上电荷驰豫过程的复合绝缘系统的电场模型,通过构建自由电荷密度方程并实时计算电荷产生的泊松场分布,获得了体电荷和界面电荷密度分布的暂态变化过程;建立了基于气体自然电离和离子迁移、扩散运动的弱电离气体的电导模型,准确表征了气体电流密度与场强的非线性关系。制作了常用于GIS/L的柱式绝缘子实验模型,测量了直流电压下绝缘子表面的电位分布,并与计算结果进行了对比,结果表明:计算得到的表面电位分布的整体变化趋势以及各电位峰位置均与测量结果吻合较好;发现弱电场下绝缘子配置嵌件时表面主要积聚同号电荷,强电场下则正好相反,同时负极性电压下的阴极发射电子过程将增大空气侧电流密度。

Ionic Conduction and Fuel Cell Performance of Ba0.98Ce0.8Tm0.2O3-α Ceramic

The perovskite-type oxide solid solution Ba0.98Ce0.8Tm0.2O3-α was prepared by high temperature solid-state reaction and its single phase character was confirmed by X-ray diffraction. The conduction property of the sample was investigated by alternating current impedance spectroscopy and gas concentration cell methods under different gases atmospheres in the temperature range of 500-900 ℃. The performance of the hydrogen-air fuel cell using the sample as solid electrolyte was measured. In wet hydrogen, the sample is a pure protonic conductor with the protonic transport number of 1 in the range of 500-600 ℃, a mixed conductor of proton and electron with the protonic transport number of 0.945-0.933 above 600 ℃. In wet air, the sample is a mixed conductor of proton, oxide ion, and electronic hole. The protonic transport numbers are 0.010-0.021, and the oxide ionic transport numbers are 0.471-0.382. In hydrogen-air fuel cell, the sample is a mixed conductor of proton, oxide ion and electron, the ionic transport numbers are 0.942 0.885. The fuel cell using Ba0.98Ce0.8Tm0.2O3-α as solid electrolyte can work stably. At 900 ℃, the maximum power output density is 110,2 mW/cm2, which is higher than that of our previous cell using Ba0.98Ce0.8Tm0.2O3-α （x〈≤1, RE=Y, Eu, Ho） as solid electrolyte.

Ionic Conduction and Fuel Cell Performance of Ba0.97Ce0.8Ho0.2O3-α Ceramic

The perovskite-type-oxide solid solution Ba0.97Ce0.8Ho0.2O3-α was prepared by high temperature solidstate reaction and its single-phase character was confirmed by X-ray diffraction. The ionic conduction of the sample was investigated using electrical methods at elevated temperatures, and the performance of the hydrogen-air fuel cell using the sample as solid electrolyte was measured, which were compared with those of BaCe0.8Ho0.2O3-α. In wet hydrogen, BaCe0.8Ho0.2O3-α almost exhibits pure protonic conduction at 600-1000℃, and its protonic transport number is 1 at 600-900 ℃ and 0.99 at 1000 ℃. Similarly, Ba0.97Ce9.8Ho0.2O3-α exhibits pure protonic conduction with the protonic transport number of 1 at 600- 700℃, but its protonic conduction is slightly lower than that of BaCe0.8Ho0.2O3-α, and the protonic transport number are 0.99-0.96 at 800-1000 ℃. In wet air, the two samples both show low protonic and oxide ionic conduction. For Ba0.97Ce0.8Ho0.2O3-α, the protonic and oxide ionic transport numbers are 0.01-0.11 and 0.30-0.31 respectively, and for BaCe0.8Ho0.2O3-α, 0.01-0.09 and 0.27-0.33 respectively. Ionic conductivities of Ba0.97Ce0.8Ho0.2O3-α are higher than those of BaCe0.8Ho0.2O3-α under wet hydrogen and wet air. The performance of the fuel cell using Ba0.97Ce0.8Ho0.2O3-α as solid electrolyte is better than that of BaCe0.8Ho0.2O3-α. At 1000 ℃, its maximum short-circuit current density and power output density are 465 mA/cm^2 and 112 mW/cm^2, respectively.

Mixed Conduction in BaCe0.8Pr0.2O3-α Ceramic

BaCe0.8Pr0.2O3-α ceramic was synthesized by high temperature solid-state reaction. The structural characteristics and the phase purity of the crystal were determined using powder X-ray diffraction analysis. By using the methods of AC impedance spectroscopy, gas concentration cell and electrochemical pumping of hydrogen, the conductivity and ionic transport number of BaCe0.8Pr0.2O3-α were measured, and the electrical conduction behavior of the material was investigated in different gases in the temperature range of 500-900℃. The results indicate that the material was of a single perovskite-type orthorhombic phase. From 500℃ to 900 ℃, electronic-hole conduction was dominant in dry and wet oxygen, air or nitrogen, and the total conductivity of the material increased slightly with increasing oxygen partial pressure in the oxygen partial pressure range studied. Ionic conduction was dominant in wet hydrogen, and the total conductivity was about one or two orders of magnitude higher than that in hydrogen-free atmosphere （oxygen, air or nitrogen）

Composite Cathode based on Mn-doped Perovskite Niobate-Titanate for Efficient Steam Electrolysis

Redox-active Mn is introduced into the B site of redox-stable perovskite niobate-titanate to improve the electrocatalytic activity of composite cathode in an oxide-ion-conducting solid oxide electrolyzer. The XRD and XPS results reveal the successful partial replacement of Ti/Nb by Mn in the B site of niobate-titanate. The ionic conductivities of the Mndoped niobate-titanate are significantly improved by approximately 1 order of magnitude in reducing atmosphere and 0.5 order of magnitude in oxidizing atmosphere compared with bare niobate-titanate at 800 ℃. The current efficiency for Mn-doped niobate-titanate cathode is accordingly enhanced by ,-25% and 30% in contrast to the bare cathode with and without reducing gas flowing over the cathode under the applied voltage of 2.0 V at 800 ℃ in an oxide-ion-conducting solid oxide electrolyzer, respectively.

Control of combustion area using electrical resistivity method for underground coal gasification

Underground coal gasification （UCG） is one of the clean technologies to collect heat energy and gases （hydrogen, methane, etc.） in an underground coal seam. It is necessary to further developing environ- mentally friendly UCG system construction. One of the most important UCG＇s problems is underground control of combustion area for efficient gas production, estimation of subsidence and gas leakage to the surface. For this objective, laboratory experiments were conducted according to the UCG model to iden- ti[y the process of combustion cavity development by monitoring the electrical resistivity activity on the coal samples to setup fundamental data for the technology engineering to evaluate combustion area. While burning coal specimens, that had been sampled from various coal deposits, electrical resistivity was monitored. Symmetric four electrodes system （ABMN） of direct and low-frequency current electric resistance method was used for laboratory resistivity measurement of rock samples. Made research and the results suggest that front-end of electro conductivity activity during heating and combusting of coal specimen depended on heating temperature. Combusting coal electro conductivity has compli- cated multistage type of change. Electrical resistivity method is expected to be a useful geophysical tool to for evaluation of combustion volume and its migration in the coal seam.

Analysis and design of resistance-wire heater in MOCVD reactor

Metal organic chemical vapor deposition(MOCVD) is a key equipment in the manufacturing of semiconductor optoelectronic devices and microwave devices in industry. Heating system is a vital part of MOCVD. Specific heating device and thermal control technology are needed for each new reactor design. By using resistance-wire heating MOCVD reaction chamber model, thermal analysis and structure optimization of the reactor were developed from the vertical position and the distance between coils of the resistance-wire heater. It is indicated that, within a certain range, the average temperature of the graphite susceptor varies linearly with the vertical distance of heater to susceptor, and with the changed distances between the coils; furthermore, single resistance-wire heater should be placed loosely in the internal and tightly in the external. The modulate accuracy of the temperature field approximately equals the change of the average temperature corresponding to the change of the coil position.

Vortex Lines and Monopoles in Electrically Conducting Plasmas

Based on the φ-mapping topological current theory and the decomposition of gauge potential theory, the vortex lines and the monopoles in electrically conducting plasmas are studied. It is pointed out that these two topological structures respectively inhere in two-dimensional and three-dimensional topological currents, which can be derived from the same topological term n^→·（Эin^→×Эjn^→）, and both these topological structures axe characterized by the φ-mapping topological numbers-Hopf indices and Brouwer degrees. Furthermore, the spatial bifurcation of vortex lines and the generation and annihilation of monopoles are also discussed. At last, we point out that the Hopf invaxiant is a proper topological invaxiant to describe the knotted solitons.

Geometrical structures, and electronic and transport properties of a novel two-dimensional β-GaS transparent conductor

Two-dimensional （2D） materials are highly promising for flexible electronics, and graphene is the only well-studied transparent conductor. Herein, density functional theory has been used to explore a new transparent conducting material via adsorption of H on a 2D β-GaS sheet. This adsorption results in geometrical changes to the local structures around the H. The calculated electronic structures reveal metallic characteristics of the 2D α-GaS material upon H adsorption and a large optical band gap of 2.72 eV with a significant Burstein-Moss shift of 0.67 eVo The simulated electrical resistivity is as low as 10^-4 Ω.cm, comparable to the benchmark for ITO thin films.

Characterization of the charge transport and electrical properties in solution-processed semiconducting polymers

The conventional charge transport models based on density- and field-dependent mobility, only having a non-Arrhenius tem- perature dependence, cannot give good current-voltage characteristics of poly （2-methoxy-5-（2＇-ethylhexyloxy）-p-phenylene vinylene） （MEH-PPV） hole-only devices. In this paper, we demonstrate that the current-voltage characteristics can give a good unified description of the temperature, carrier density mad electric field dependence of mobility based on both the Arrhenius temperature dependence and the non-Arrhenius temperature dependence. Fu^hermore, we perform a systematic study of charge transport and electrical properties for MEH-PPV. It is shown that the boundary carrier density has an important effect on the current-voltage characteristics. Too large or too small values of boundary carrier density will lead to incorrect cur- rent-voltage characteristics. The numerically calculated carrier density is a decreasing function of the distance to the interface, and the numerically calculated electric field is an increasing function of the distance. Both the maximum of carrier density and the minimum of electric field appear near the interface.