直流电场下低密度聚乙烯纳米介质空间电荷特性的数值分析(英文)

The dynamic characteristics of space charge in nanocomposite of low-density polyethylene (LDPE) mixed with inorganic nano- fillers. Different from previous qualitatively theoretical works, we investigated the influence of trap depth, trap volume charge density and injection barrier height on the space charge and the electric field distribution in the nanocomposite under a DC external electric field (100 MV/m) systematically and quantificationally, through numerical simulations based on a bipolar charge transport model. The simulation re- sults showed that, the increase of trap depth would severely distort the balanced electric field distribution with the highest and the lowest electric field of 119 MV/m and 47 MV/m, respectively. It is concluded that the introduction of nanofillers creates more deep traps, which would block space charges by capturing most of them in the vicinity of electrode and hence reduce the local electric field largely. Further theoretical analysis of the simulation indicates that both the high permittivity and the low local electric field of the nanocomposite contri- buted to the increase of injection barrier height, and almost no charge could overcome an injection barrier higher than 1.25 eV. At last, a mechanism of space charge suppression in the LDPE nanocomposite was presented.     

高空核电磁脉冲模拟器横电磁波喇叭天线瞬态场简化计算方法（英文）

For conveniently calculating the radiated electric field of transverse electromagnetic(TEM) horn antenna,an approximate simplified analytical calculation method is suggested.This method divides the horn to a system of V-antennas and superimposes the fields of all V-antennas to obtain the field of the TEM horn.The method is compared with the traditional analytical method and numerical method.The obtained results suggest that the proposed method is valid,simple and that it can fastly calculate the radiated electric field of the TEM horn antenna in an arbitrary space with an arbitrary excitation voltage.Based on this method,radiation of the TEM horn antenna of a high-altitude electromagnetic pulse(HEMP) simulator is simulated.Rise time,pulse width,peak value of electric field,and field distribution are analyzed.Results show that the TEM horn antenna can be used in HEMP simulators: the near field waveform is closer to the standard waveform than to the far field waveform; the standards for the rise time and the peak value of electric field are easily satisfied; the pulse width of the radiated field can be increased by broadening the pulse width of an excitation source and by making the antenna of a proper length     

混响室频率搅拌技术研究（英文）

The radio frequency(RF)modes of reverberation chamber(RC) in different frequency ranges are calculated to develop frequency-stirring techniques for RCs.An experimental system is built with a two-port vector network analyzer,of which one port is connected to a transmitting antenna located in a corner of a RC,and the other port is connected to a receiving antenna located in the working area of the RC.The parameter S21 is obtained in eight different locations of the receiving antenna for discussing the number of RF modes and the stirring bandwidth.It is found that the lowest useable frequency of a RC is determined by the RC’s dimension:the larger the dimension is,the lower the lowest useable frequency is.S21 at the lowest useable frequency is about-20 dB,and it is more stable than that at lower frequencies when the frequency increases.Increasing the bandwidth would result in a smoother dependence of S21 on frequency,which shows that frequency stirring is effective.In a RC with frequency stirring,the standard deviations of three individual field components and the total field are within the specified tolerance,i.e.the electric field distribution is uniform.Meanwhile,the electric field’s magnitude is characterized by the Chi-distribution with two degrees of freedom or the Rayleigh distribution,and the square of the magnitude is characterized by the Chi-square distribution with two degrees of freedom or the exponential distribution.Therefore,both good uniformity and good behavior of the electric field can be obtained if the RF modes in the RC are sufficient.     

陡脉冲电场作用下细胞电场力的仿真计算(英文)

The basic characteristic of electric field is that the substance in the field is in operation by the stress. Under external electric fields,there is strong distribution of electric fields on the inside and outside surfaces of cell membrane. In virtue of the difference of the permittivity among membrane,cytoplasm and extracellular medium,there must be electric field stress on the surface of the membrane. The goal of the study is to research the irreversible electrical breakdown (IRE) mechanism of the malignant tumor cells under steep pulsed electric field (SPEF) from the views of mechanics. Electric field stress of plasma membrane under steep pulsed electric field is calculated and simulated both on malignant tumor cells and on the normal cells. The calculation results show that,in addition to a compressive stress normal to the membrane plane,transverse traction stresses are generated in the lateral plane of the membrane. The lateral stress will reduce the membrane tension significantly,leading to electroporation and rupture. At the same electric field strength,the transverse traction stress on malignant cell membrane is greatly larger than the one on normal cell membrane. Therefore,compared with the normal cells,the malignant tumor cells are more sensitive under the steep pulsed electric field. Namely,steep pulsed electric field can selectively destroy the malignant tumor cells,which proved the safety of treating malignant tumors by steep pulsed electric field.     

多层有机绝缘结构真空沿面闪络特性和机理研究(英文)

In order to further investigate the surface flashover mechanism in vacuum, the surface flashover and electric field distribution of multilayer organic insulation structure are studied and developed based on the previous studies. The samples of multilayer organic insulation structure are prepared by inserting multilayer organic composite material with different relative permittivity between the electrode and the dielectric. Two multilayer organic insulation structures are prepared in this study. One is the cylindrical samples, the other is 45° samples. The impulse (1.2/50 μs) and DC flashover voltages in vacuum are tested, and the electric field distributions of two insulation structures are analyzed by ANSYS. It is found that these two insulation structure could effectively improve the surface flashover performance in vacuum. The results indicate that the highest impulse first flashover voltage of cylindrical samples reaches 65 kV and increases by 25% under im- pulse voltage. The highest first flashover voltage of /c samples reaches 81 kV and increases by 32% under impulse voltage. The results of electric field simulation demonstrate that different mechanisms exist between 45° insulation structure and cylindrical structure.     

多路架空输电线交错区域电场的3维模型分析(英文)

This work is carried out to predict the special distribution of electric field induced by multi-circuit intersecting overhead high-voltage (HV) transmission lines (TLs) within a large range without any expensive and time-consuming computation. The two main parts of the presented methodology are 1) setting up a three-dimensional (3D) model to calculate the electric field based on combining ca- tenary equations with charge simulation method and 2) calculating the hybrid electric field excited by multi-circuit intersecting TLs using coordinate transformation and superposition technique. Examples of different TLs configurations, including a 220 kV single-circuit hori- zontally configured TLs, a 500 kV single-circuit triangularly configured TLs and a combination of the 220 kV TLs and the 550 kV TLs, are illustrated to verify the validity of this methodology. A more complicatal configurations, including a 500 kV double-circuit TLs and two 220 kV single-circuit horizontally configured TLs, are also calculated. Conclusions were drawn from the simulation: 1) The presented 3D model outperforms 2D models in describing the electric field distribution generated by practical HV TLs with sag and span. 2) Coordinate trans- formation and superposition technique considerably simplify the electric field computation for multi-circuit TLs configurations, which makes it possible to deal with complex engineering problems. 3) The electric field in the area covered by multiple intersecting overhead TLs is distorted and the hybrid electric field strength in some partial region increases so sharply that it might exceed the admissible value. 4) The configuration parameters of the TLs and the spatial configuration of multi-circuit TLs, for instance, the height of TLs, the length of span and the intersection angle of multiple circuits, influence the strength and the distribution of hybrid electric field. The influence regularities sum- marized in this paper can be referred by future TL designs to meet the electromagnetic environmental protection regulations.     

两相体中正脉冲放电分枝的现象和机理(英文)

Discharge branching is a general phenomenon in atmospheric-pressure air,dense gases,and two-phase mixtures(TPMs).In this work,an ultraviolet imaging device is utilized to investigate the branching of positive pulsed discharges in TPMs.Comparison among the captured images indicates that the branching is caused by the voltages and the macropartilces in the discharge channels combining together.The interaction of macroparticles with ions,electrons or photons is one reason for the branching behavior of pulsed discharges.The generation of electrons at the discharge front closely relates to the work function of dielectric macroparticles,which is a key parameter influencing the electron-emission ability of macroparticle surfaces.The electric field alteration under various applied voltage in TPMs,which is calculated by a two-dimension finite element method,is the other reason for the guiding effect of macroparticles on the streamers compared with in the air.     

采用多电极结构的大面积表面介质阻挡放电特性(英文)

Surface gas discharge(SGD)plasmas have potential applications in the fields of active flow control,gas purification,heat transfer enhancement,etc.In order to obtain a uniform,stable and large-area SGD at atmosphere,a multi-electrode SGD plasma generator is designed in this paper.The major features of this newly-designed SGD plasma generator is as follows:the air-exposed upper grounded electrodes are made of nine tungsten wires and flush mounted on the dielectric PTFE barrier layer,while the lower powered electrode is made of a copper foil and encapsulated inside the PTFE material to avoid the ignition of the gas discharges below the dielectric barrier layer.The measurements on the electrical characteristics,fast imaging of discharges and the preliminary numerical analysis on the electric field distributions suggest that the multi-electrode configuration of the plasma generator plays a crucial role in enhancing the local electrical field,and subsequently,leads to the stable,quasi-uniform and large-area surface discharges.     

热处理前后非脱气交联聚乙烯的介电性能和机械性能分析

In order to investigate the influence of cross-linking byproducts on dielectric and mechanical properties of 110k V cross-linked polyethylene(XLPE)cable insulation,we selected the undegassed XLPE cable insulation which is heated at 70℃in laboratory for different duration in terms of heating time,to prepare XLPE samples with different mass loss ratio.We carried out Fourier transform infrared spectroscopy(FTIR)test,electric breakdown test at 50 Hz,pulsed electro-acoustic(PEA)measurement and tensile test for XLPE samples.In FTIR spectrogram,the characteristic absorption peaks were observed to appear at 1 680 cm-1 and 1 600 cm-1,which can be related to two kinds of cross-linking byproducts includingα-methylstyrene and acetophenone.The intensity of these absorption peaks decreases with the increase of mass loss ratio.It can be proposed that the mass loss of XLPE samples in the process of thermal treatment is caused by volatiliztion ofα-methylstyrene and acetophenone.Therefore,the change of mass loss ratio can reflect the change of content ofα-methylstyrene and acetophenone in the process of thermal treatment.The results of electric breakdown test showed that the reduction ofα-methylstyrene and acetophenone leads to the enhancement of electric breakdown strength at 50 Hz.PEA measurement results showed that heterocharge is produced and accumulated when cross-linking byproducts are present,whereas no heterocharge is found whenα-methylstyrene and acetophenone are absent.The formation of heterocharge is attributed to ionization of cross-linking byproducts under electric stress.Based on these results,it can be suggested that when AC electric field is applied on XLPE samples,the occurrence of ionization of cross-linking byproducts results in the increase of free carriers in XLPE insulation,leading to a lower electric breakdown strength.The results of tensile test showed that tensile strength is proportional to the mass loss ratio of XLPE samples,which suggests that cross-linking byproducts can reduce the tensile strength of XLPE insulation.     

热处理前后非脱气交联聚乙烯的介电性能和机械性能分析（英文）

In order to investigate the influence of cross-linking byproducts on dielectric and mechanical properties of 110k V cross-linked polyethylene(XLPE)cable insulation,we selected the undegassed XLPE cable insulation which is heated at 70℃in laboratory for different duration in terms of heating time,to prepare XLPE samples with different mass loss ratio.We carried out Fourier transform infrared spectroscopy(FTIR)test,electric breakdown test at 50 Hz,pulsed electro-acoustic(PEA)measurement and tensile test for XLPE samples.In FTIR spectrogram,the characteristic absorption peaks were observed to appear at 1 680 cm-1 and 1 600 cm-1,which can be related to two kinds of cross-linking byproducts includingα-methylstyrene and acetophenone.The intensity of these absorption peaks decreases with the increase of mass loss ratio.It can be proposed that the mass loss of XLPE samples in the process of thermal treatment is caused by volatiliztion ofα-methylstyrene and acetophenone.Therefore,the change of mass loss ratio can reflect the change of content ofα-methylstyrene and acetophenone in the process of thermal treatment.The results of electric breakdown test showed that the reduction ofα-methylstyrene and acetophenone leads to the enhancement of electric breakdown strength at 50 Hz.PEA measurement results showed that heterocharge is produced and accumulated when cross-linking byproducts are present,whereas no heterocharge is found whenα-methylstyrene and acetophenone are absent.The formation of heterocharge is attributed to ionization of cross-linking byproducts under electric stress.Based on these results,it can be suggested that when AC electric field is applied on XLPE samples,the occurrence of ionization of cross-linking byproducts results in the increase of free carriers in XLPE insulation,leading to a lower electric breakdown strength.The results of tensile test showed that tensile strength is proportional to the mass loss ratio of XLPE samples,which suggests that cross-linking byproducts can reduce the tensile strength of XLPE insulation.     

大气压针板介质阻挡放电中微流注、电晕和辉光放电相互转换研究（英文）

To discuss the modes of dielectric barrier discharge(DBD) between needle-to-plane electrodes in air,DBD is generated and observed on a needle-to-plane device at atmospheric pressure air.Fast images of the DBD are taken by using a charge couple device(CCD) cinema with a macro lens,while the electrical and photo-electricity waveforms of the DBD are recorded.The current waveforms show that under an applied voltage of 3 kV,there are numerous short current pulses in both positive and negative half-periods of discharges.However,under 6 kV,there are still the numerous short current pulses in the positive half-periods,but only one wide current pulse in each negative half-period.This difference is also found in the photoelectric signals.The streamer,corona and glow discharges are observed from the images of the discharges at different applied voltages.The structure of glow discharge in the negative period is exactly the same as that of the low pressure glow discharge.However,in the positive period of discharge there is always a streamer.In the negative period of discharge,while the applied voltage increases,the transition from corona to glow discharge is observed.The progress of a transition between streamer and glow discharge at 6 kV during one period is analyzed.The glow discharge appearance is determined by two factors: the discharge current is limited to a certain extent by the dielectric layer; the charges deposited on the dielectric layer during the last half period enhance the intensity of the electric field.At an insufficient applied voltage,the cathode drop leads to no glow discharge,but Trichel pulses.     

半绝缘砷化镓光电导开关表面闪络电场的实验研究(英文)

With its unique features, photoconductive semiconductor switch (PCSS) is generally recognized today as a promising power electronic device. However, a major limitation of PCSS is its surprisingly low voltage threshold of surface flashover (SF). In this paper, an experimental study of surface flashover of a back-triggered PCSS is presented. The PCSSs with electrode gap of 18 mm are fabricated from liquid encapsulated czochralski (LEC) semi-insulating gallium arsenide (SI-GaAs), and they are either un-coated, or partly coated, or en- tirely coated PCSSs with high-strength transparent insulation. The SF fields of the PCSSs are measured and discussed. According to the experimental results, the high-dielectric-strength coating is efficient in both reducing the gas desorption from semiconductor and increasing the SF field: a well-designed PCSS can resist a voltage up to 20 kV under the repetition frequency of 30 Hz. The physical mechanism of the PCSS SF is analyzed, and the conclusion is made that having a channel structure, the SF is the breakdown of the contaminated dielectric layer at the semiconductor-ambient dielectric interface. The non-uniform distribution of the surface field and the gas desorption due to thermal effects of semiconductor surface currents are key factors causing the SF field reduction.     

材料时频域屏蔽效能及其强电磁场测试（英文）

To describe the shielding ability of materials accurately and comprehensively,the frequency-domain and time-domain shielding effectiveness(SE) of material is investigated.The relevance between them was analyzed based on the minimum phase method,and the time-domain SE can be derived from frequency-domain SE.The SE of an energy selective surface(ESS) made of a novel material is investigated,and the relationship between SE and radiation field intensity are analyzed.The results show that not only material,but also the intensity of radiation electric field shows influence on SE in its frequency; for some materials,the dependence of SE on radiation electric field intensity needs to be considered.Therefore,it is necessary to research on the SE of shielding material in high-intensity electromagnetic environment.     

金属氧化物避雷器周围电场强度的测量与仿真(英文)

The study of the electric field around a surge arrester is useful for design procedures and diagnostic tests. The current work com- putes the electric field around a medium voltage gapless surge arrester using 2D and 3D representation of the arrester. The 2D simulation design, which is described in IEC 60099-4 Standard, cannot include the non symmetrical parts of the arrester geometry and the test arrange- ment. 3D simulation procedures have the advantage that takes into account these asymmetries, giving more accurate results for each measurement position. In order to confirm the suitability of the created models, the simulation results of the electric field, using the 2D and 3D edition of PC Opera, are compared with recorded measurements, which are obtained in laboratory using appropriate calibrated field meters.     

微结构内纳秒脉冲空气放电中微通道的形成及高能电子的产生过程(英文)

The investigations results of the different types of high-voltage nanosecond atmospheric discharges(diffusive in the gaps "wire(cathode)-plane", "rod(cathode)-plane", spark "point-plane" and in homogeneous gaps "plane-plane", as well as streamerless discharges in homogeneous gaps "plane-plane") are present. It was found out that the current channels prints, left on the electrodes surface, has the microstructure. The microstructure is a cluster(up to 1 000) of the microchannels of 1~30 μm diameters almost evenly distributed on the channels section. It was found out that in some cases the discharges develop in the regime of microstructuring of the current channels, are accompanied by generation of high-energy electrons and x-ray radiation. In this case the generation of high-energy component is stipulated by the electrons runaway in the microchannels. The calculation results of the electric field in clusters of parallel microchannels in the frameworks of the model of a bundle of parallel long cylindrical conductors are present. It is shown that in the clusters with many microchannels in the result of mutual attenuation of their fields maximum strength of the radial field could be lower than the critical one, which is necessary for ionization multiplication and expansion. This provides long existence of microchannels groups of microns radii in the high-voltage nanosecond discharges. A physical model of the streamerless discharge microstructure formation at the result of instability development of the ionization process in the avalanche stage is developed. It was established that the instability has long wave character and leads to formation of self-similar spatial structure. It is shown that the microstructure of the streamer discharges could be explained in the frameworks of this model. Three-dimensional numerical simulation of dynamics of microchannels system of high-voltage nanosecond discharges in the air of atmospheric pressure is performed in hydrodynamic approximation. It is established that fast(≈10 ns) expansion and significant decreasing of the gas concentration in the microchannels takes place at the expense of ohmic heating of the microchannels. It is shown that the microchannels expansion provides increase of electric field and gas concentration ratio up to the values that are sufficient for high-energy electrons beams and bremsstrahlung generation in them.     

High-resolution impedance mapping using electrically activated quantitative phase imaging

Retrieving electrical impedance maps at the nanoscale rapidly via nondestructive inspection with a high signal-to-noise ratio is an unmet need,likely to impact various applications from biomedicine to energy conversion.In this study,we develop a multimodal functional imaging instrument that is characterized by the dual capability of impedance mapping and phase quantitation,high spatial resolution,and low temporal noise.To achieve this,we advance a quantitative phase imaging system,referred to as epi-magnified image spatial spectrum microscopy combined with electrical actuation,to provide complementary maps of the optical path and electrical impedance.We demonstrate our system with high-resolution maps of optical path differences and electrical impedance variations that can distinguish nanosized,semi-transparent,structured coatings involving two materials with relatively similar electrical properties.We map heterogeneous interfaces corresponding to an indium tin oxide layer exposed by holes with diameters as small as~550 nm in a titanium(dioxide)over-layer deposited on a glass support.We show that electrical modulation during the phase imaging of a macro-electrode is decisive for retrieving electrical impedance distributions with submicron spatial resolution-and beyond the limitations of electrode-based technologies(surface or scanning technologies).The findings,which are substantiated by a theoretical model that fits the experimental data very well enable achieving electro-optical maps with high spatial and temporal resolutions.The virtues and limitations of the novel optoelectrochemical method that provides grounds for a wider range of electrically modulated optical methods for measuring the electric field locally are critically discussed.     

Study on Electromagnetic Environment of AC-DC Hybrid Transmission Lines

With the expansion of electricity demand,transmission corridors are becoming scarce.AC and DC circuits running parallel to each other and sharing the same right-of-way or even the same tower become a possible option.Due to the existence of the adjacent line,space electromagnetic field and corona of another line may be changed.Different characteristics of two line types make the electromagnetic field of transmission corridors become more complex.Hybrid line is viewed as a whole.The calculation contains surface gradient,ground level electric field,radio interference and audible noise.Interaction between the two line types is considered.The calculation results show that the interaction is mainly concentrated in the inner corridor.In the role of DC electric field,AC electric field is no longer symmetrical and ground level electric field is significantly enhanced.Under the negative DC voltage,the positive corona of the waveform is significantly strengthened,and it is inhibited under the positive DC voltage.It is better to erect the positive DC line near AC line.     

高压下非均匀电场中局放机理的建模

Partial discharges in air in non-uniform electric field occur in surroundings made of high curvature elements.The equivalent electrode system,needle-plane refers both to external components of high voltage insulating systems and to micro sharpness in the internal structure of those systems.The ionization zone,accumulation of space charge and formation of corresponding current pulses depend on electrode configuration,voltage level,pressure,temperature and humidity of air.The assessment of pressure influence on discharge mechanism in non-homogenous electric field has been performed on the basis of empirical density distributions of discharge charges at different voltage levels,electrode distance,curvature of high voltage electrode and taking into account solid dielectric barrier in serial configuration.The measurement results obtained at variable voltage level yield the influence of electric field strength in the needle electrode zone.While increasing voltage,a deviation from normal distribution may be observed that reveals other forms of discharge.     

开孔不规则金属腔体电磁耦合实验研究（英文）

In order to study electromagnetic field coupling to irregular cuboid enclosures,tests of shielding effectiveness are performed using a hollow irregular truncated pyramid with a square aperture.The electric field distribution inside the enclosure with different sizes of the square aperture is measured within the frequency range of 5~1 000 MHz.The experimental results are in a good agreement with the stimulation results obtained by using computer simulation technology(CST)code.It is shown that the aperture size affects shielding effectiveness at low frequencies,at which shielding effectiveness decreases with the decreasing aperture size.The effect of the aperture size vanishes and shielding effectiveness improves by more than 12 dB when polyurethane absorbent fills the enclosure.     

HVAC输电线路损耗和空间电场的改进计算方法（英文）

An improved method for calculating the corona power loss and the ground-level electric field on HVAC transmission lines induced by corona is proposed.Based on a charge simulation method combined with a method of successive images,the proposed method has the number and location of the simulated charges not arbitrary.When the surface electric field of a conductor exceeds the onset value,charges are emitted from corona into the space around,and the space ions and the surface charges on each sub-conductor are simulated by using the images of the other sub-conductors.The displacements of the space ions are calculated at every time step during corona periods in both the positive and the negative half cycles.Several examples are calculated by using the proposed method,and the calculated electric field at the ground level and the corona power loss agree well with previous measurements.The results show that simulating 12 charges in each conductor during 600 time steps in one cycle takes less time while guarantees the accuracy.The corona discharge from a 220 kV transmission line enhances slightly(less than 2%) the electric field at the ground level,but this effect is little from a 500 kV line.The improved method is a good compromise between the time cost and the accuracy of calculation.