Measurement Of Space Charge Distribution Research Articles

Electronic properties of polyethylene naphthalate as derived from photo-stimulated discharge, luminescence experiments and quantum chemical calculation

The electronic properties of thin films of poly(ethylene 2,6-naphthalate)—PEN, are investigated based on their photo-physical (optical absorption, photoluminescence) and electrical (space charge distribution, photo-stimulated discharge) behavior. Photo-stimulated currents are associated with optical absorption of the material leading to space charge dissipation as demonstrated by space charge distribution measurement. Based on this set of experimental results and quantum chemical calculation performed on PEN macromolecular system, we propose a new scheme for the electronic levels of PEN. This scheme allows understanding the mechanisms at play in photo-stimulated discharge. One of the main conclusions of our work is that photo-stimulated current measurements do not probe the energy level of traps. Detrapping of charges results from a two-step process where the photon energy is absorbed by chromophores that restitute a part of this energy to trapped charges through various mechanisms. Moreover, the new scheme allows discussing the components of the luminescence excited under different stresses, being electric field, electronic and UV irradiation, charge recombination and thermal activation.

Blending Modification Technology of Insulation Materials for Deep Sea Optoelectronic Composite Cables

The insulation layer of deep-sea optoelectronic composite cables in direct contact with high-pressure and highly corrosive seawater is required for excellent water resistance, environmental stress cracking resistance (ESCR), and the ability to withstand high DC voltage. Although high-density polyethylene (HDPE) displays remarkable water resistance, it lacks sufficient resistance to environmental stress cracking (ESCR). This article is based on a blend modification approach to mixing HDPE with different vinyl copolymer materials (cPE-A and cPE-B). The processing performance and mechanical properties of the materials are evaluated through rheological and mechanical testing. The materials’ durability in working environments is assessed through ESCR tests and water resistance experiments. Ultimately, the direct current electrical performance of the materials is evaluated through tests measuring space charge distribution, direct current resistivity, and direct current breakdown strength. The results indicate that, in the polyethylene blend system, the rheological properties and ESCR characteristics of HDPE/cPE-A composite materials did not show significant improvement. Further incorporation of high melt index linear low-density polyethylene (LLDPE) material not only meets the requirements of extrusion processing but also exhibits a notable enhancement in ESCR performance. Meanwhile, copolymerized polyethylene cPE-B, with a more complex structure, proves effective in toughening HDPE materials. The material’s hardness significantly decreases, and when incorporating cPE-B at a level exceeding 20 phr, the composite materials achieve excellent ESCR performance. In a simulated seawater environment at 50 MPa, the water permeability of all co-modified composite materials remained below 0.16% after 120 h. The spatial charge distribution and direct current resistivity characteristics of the HDPE, cPE-A, and LLDPE composite systems surpassed those of the HDPE/cPE-B materials. However, the HDPE/cPE-B composite system exhibited superior dielectric strength. The application of composite materials in deep-sea electro–optical composite cables is highly promising.

Migration behavior of space charge packet researched by using electron beam irradiation and real-time space charge distribution measurement in piezo-pressure wave propagation (PWP) method

The space charge packet is a special sort of space charge phenomenon that is characterized by the migration of aggregated space charge in the form of a packet in the sample. Currently, most of the experimental and simulation studies on the generation and migration of space charge packets focus on the space charge packets with positive polarity in polyethylene and their cross-linking products, while the characteristics of the space charge packets with negative polarity still need studying. This paper presents an integrated experimental system for studying space charge packet with negative polarity, which enables experimental studies combining electron beam irradiation technique and real-time space charge distribution measurement. The beam flux for electron beam irradiation is controlled by a metal grid with an optical fiber-electric relay, and the space charge distribution measurement is performed by the piezo- pressure wave propagation method. The system achieves a withstand voltage value of 17 kV and a measuring resolution of 25 ns for space charge distribution measurement and is suitable for experimental studies of various material samples with different thickness ranges under different electric fields. In this work, the migration behaviors of space charge packets with negative polarity in polypropylene (PP) and polymethyl methacrylate (PMMA) samples under different applied electric fields (15, 20, 25, 30 kV/mm) are studied by using the experimental system. The relationship between the migration properties of carriers with negative polarity (electrons) and the electric field can be extracted from the experimental results. The “negative differential mobility” phenomenon is found for both materials, i.e. the migration rate decreases with the increase of the electric field. The threshold electric field for the “negative differential mobility” phenomenon of electrons in PP sample is about 26.0 kV/mm while the threshold electric field for the “negative differential mobility” phenomenon of electrons in PMMA sample is 19.5 kV/mm, and the phenomenon disappears at an electric field of 27.5 kV/mm. The electric field where the "negative differential mobility" phenomenon of electrons appears and disappears in different materials can be extracted by using the experimental system proposed in this paper.

Analysis of uncertainties in the measurement of the space charge distribution in dielectrics

The results obtained from the commonly used space charge distribution measurement methods are frequently apparent and one-dimensional results of a localized area; moreover, random errors can be caused by various factors. In this work, three factors—sample thickness uniformity, pressure wave intensity uniformity, and space charge distribution uniformity—that may cause measurement uncertainties are examined. The analysis and evaluation of the experimental data are affected by the measurement uncertainties, which are particularly noticeable in experiments on semiconductive electrode-flat polyethylene samples that use the laser-induced pressure propagation method. These factors are investigated separately using several auxiliary experiments, including laser beam spot energy distribution measurements and space charge distribution measurements, at different measurement positions on the same uniform sample. A clear and intelligible model is developed to discuss the influence of these factors on the uncertainties in the space charge distribution measurement in dielectrics.

Study of contact conditions at conductor/insulator interfaces used in space charge distribution measurements

Interfaces play a major role on charge injection in dielectrics under high voltage. As a consequence, space charge distribution measurements under high voltage may depend on the chosen interface conditions during the tests. In this paper, it is shown that various mountings of an insulating polymer (polyethylene) in a space charge distribution measurement setup develop very different intrinsic dipoles at the interfaces generating in turn an interface voltage that may interact with energy levels between the electrode and the insulator and thus with injection laws. These dipoles are minimal when the insulating polymer has hot-pressed carbon-loaded polymer electrodes or is coupled with silicone oil to carbon-loaded EVA electrodes. On the contrary aluminum coating or direct contact with aluminum in presence of silicone oil for the coupling generates large dipoles compared to gel coupling or with gold coating. The measurements were carried out with an ultra sensible pressure-wave-propagation measurement setup under very low electric field (±30 V/mm at most) for calibration purpose. Aluminum and stainless steel was used for the setup wave-guide in order to check its influence. Interface voltage up to 5 V could be estimated with an uncoated sample in contact with aluminum through silicone oil.

Development of Space Charge Distribution Measurement System with High Positional Resolution at High Temperature using a Pulsed Electro-Acoustic Method

Development of Space Charge Distribution Measurement System with High Positional Resolution at High Temperature using a Pulsed Electro-Acoustic Method

Bulk topological signatures of a quasicrystal

We show how measuring real space properties such as the charge density in a quasiperiodic system can be used to gain insight into their topological properties. In particular, for the Fibonacci chain, we show that the total onsite charge oscillates when plotted in the appropriate coordinates, and the number of oscillations is given by the Chern number of the gap in which the Fermi level lies. We show that these oscillations have two distinct interpretations, obtained by extrapolating results from the two extreme limits of the Fibonacci chain -- the valence bond picture in the strong modulation limit, and perturbation around the periodic chain in the weak modulation limit. This effect is found to remain robust at moderate interactions, as well as in the presence of disorder. We conclude that experimental measurement of the real space charge distribution can yield information on topological properties in a straightforward way.

Space charge effect and application in solid insulation dielectrics

<p indent="0mm">Space charge effect and its application in solid insulation dielectrics are long-term issues with continuous development. The study of space charge effect is of great significance to high-voltage direct current (HVDC) transmission. This paper summarizes the development history and research progress of space charges in solid dielectrics, from the aspects of measurement technologies, damage, suppression, application, and simulation, etc. Currently, the most widely used space charge distribution measurement technologies can be roughly divided into two categories, acoustic effect technique and thermal effect technique, whose spatial resolution and application range are different. For the acoustic effect technique, pressure wave propagation method and pulsed electro-acoustic method are most commonly used with proven technique. The spatial resolutions of these two are similar, both can reach an average of <sc>10 μm.</sc> With extremely narrow pulses, the highest spatial resolution can reach about <sc>1 μm.</sc> The thermal effect techniques, such as thermal pulse method and laser intensity modulation method, have more advantages in spatial resolution and practicability, especially for micron-thick film detection. Future research may focus on the more widely application of space charge distribution measurement technologies to electrical equipment in operation. For the trap parameters and charge storage properties of insulation dielectrics, there is still a lack of reliable and practical measurement technologies. The results of the isothermal decay method are more reliable and credible, but the required measurement time is too long. Therefore, it has been rarely used in practice in recent years. The most commonly used methods, thermal stimulated discharge current method and photo stimulated discharge method, each has its own disadvantages. And their results for the same sample are quite different for mutual corroboration. In recent years, some researchers are more focused on piezo-stimulated current method, but this method is still in a preliminary stage of experiment and application. In general, the space charge effect has pros and cons. On one hand, space charge accumulation in solid insulation dielectrics may cause electric field distortion and discharge damage, eventually lead to breakdown and destruction of insulation. In order to prevent these damages, many effective methods have been proposed, such as surface modification of insulation dielectrics and material modification by additives. However, these methods have not yet been practically used in industrial applications. On the other hand, space charge effect also has many efficient applications. One of the most important applications is electret, a dielectric material that quasi-permanently stores real charges in surface or volume traps. A large number of significant contributions have been published on preparation process, charge characteristics and applications of electrets. The simulation research of space charges can mainly be divided into physical model research of space charge behavior and data processing of experimental results. The development of space charge simulation is relatively backward compared to other research fields as the physical model of space charge behavior has not yet been built completely. The issues of space charge effect and its application are involved with multiple factors. Although some technical and theoretical developments have been achieved in recent years, there are still some uncertain questions remained to be explored.

Measurement of Space Charge Distribution in Epoxy/Fullerene Nanocomposite at High Temperature under High DC Stress

Measurement of Space Charge Distribution in Epoxy/Fullerene Nanocomposite at High Temperature under High DC Stress

Correction to: Measurement of Sheet-like Space Charge Distribution and Signal Calibration of Insulator XLPE Using PEA Method

Correction to: Measurement of Sheet-like Space Charge Distribution and Signal Calibration of Insulator XLPE Using PEA Method

Space Charge Distribution Measurement in FEP Film Irradiated by Proton

Space Charge Distribution Measurement in FEP Film Irradiated by Proton

Measurement of Sheet-like Space Charge Distribution and Signal Calibration of Insulator XLPE Using PEA Method

Long-distance power transmission requires durable and high-performance cables with insulators resistant to dielectric breakdown. However, space charge can cause dielectric breakdowns by affecting the electrical characteristics inside the insulator as it is injected, generated, or moved inside the insulating materials. In this study, the sheet-like space charge distribution of the insulator cross-linking polyethylene (XLPE) was measured using the pulsed electro acoustic (PEA) method. As compared to the existing method, a more convenient method was designed and produced using NI’s PXI System and LabVIEW software. Furthermore, a signal calibration program was developed to correct the distortions of the measured signals. The accuracy and reliability of the space charge distribution signals were improved by correcting the distortions of the signals.

다중 유전체에서의 공간전하 분포 측정 및 신호 보정에 대한 연구

다중 유전체에서의 공간전하 분포 측정 및 신호 보정에 대한 연구

Space Charge and Electric Field Analysis on Contaminated XLPE Insulator

&lt;p&gt;Nowadays, XLPE cable has been widely used because it has better resistance than other cables. XLPE insulation has unique features including a high dielectric strength and high insulation resistance. A lot of researches based on hardware and software have been conducted to prove the effectiveness of XLPE cable such as AC and DC applications and Space Charge Distribution measurement under HVDC at High Temperature. This research focused on analysis of space charge and electric field on XLPE cable with effect of non-uniform contamination layer by using Quickfield Software. Non-uniform contaminations have been applied along XLPE cable using Arsenic Tribromide (AsBr3), Boron Bromide (BBr3), Ethylene Dichloride (CH2C1), Formic Acid (CH1O2), Formamide (CH3NO) and Alcohol element. Presence of these contamination elements represent of underground contamination. The size and layer of the contamination were non-uniform type. From the results, it is shown that lower dielectric constant of contamination will affect more on charge of XLPE insulation. As a conclusion, it can be seen lower dielectric constant value of contamination element greatly affecting the performance of XLPE insulation. Furthermore, size of contamination also influences the content of charge in contamination where the bigger the contamination size, the more charge contained in the contamination.&lt;/p&gt;

Effects of electric field and temperature on space charge characteristics in double-layered polytetrafluoroethylene films

As the core component of composite insulation for dry-type high-voltage equipment, polytetrafluoroethylene (PTFE) films are subjected to high temperatures and complex electric fields. Therefore, this study explores the effects of electric field and temperature on the space charge characteristics of double-layered PTFE films based on the measurement of space charge distribution in double-layered PTFE films under different DC voltages and temperatures using the pulsed electro-acoustic measurement system. Results show that more charges accumulated in the PTFE sample subjected to a positive electric field during polarization and the space charges dissipated more rapidly during depolarization compared with those subjected to a negative electric field. The existence of a PTFE/PTFE interface increased the density of trap and deepened the trap. The positive charges that accumulated at the PTFE/PTFE interface during polarization gradually held a dominant position with the increase of temperature. Finally, the formation of charge in the PTFE/PTFE interface mainly depended on two factors. When the applied DC voltage was not large, the charge formation was mainly dominated by the Maxwell-Wagner polarization effect. When the voltage increased to a certain threshold, the charge formation was mainly caused by the charge injection and migration characteristics.

High-resolution pulsed electro-acoustic (HR PEA) measurement of space charge in outer space dielectric materials

The pulsed electro-acoustic (PEA) method is used for thirty years for measuring space charge distribution in dielectric materials [1]. However, this method was limited to at least 150 μm thick films characterization. For some applications, in spatial industry for example, 50 μm thick outer space dielectric materials must be analyzed. A high resolution optimized measurement system is discussed in this paper in order to expand performances and ranges of this method. To design it, a new pulse generator has been conceived and an optimized acoustic detector, key of the PEA method, has been realized and validated. The optimized High-Resolution PEA apparatus allows to obtain calibration signal with 50 μm thick dielectric materials that can be used to obtain the characteristic transfer function of the PEA system, essential step to use the data processing to find space charge distribution to characterize thinner dielectric materials.

Investigation on relationship between breakdown strength enhancement of composites and dielectric characteristics of nanoparticle

In this work, the relationship between dielectric characteristics of nanoparticle and its effects on dielectric breakdown strength of Epoxy was investigated. The dielectric characteristic was tailored through silica surface encapsulation on TiO2. It was found that in contrast to raw TiO2, addition of TiO2@SiO2 core-shell nanoparticle obviously improved the dielectric breakdown strength of epoxy resin. Meanwhile, peculiar increase of resistivity was also observed. Based on the results, a mechanism through barrier effect by electric double layer was proposed to explain this enhancement, which was regarded closely associated with the highly polarizable and surface insulating features of TiO2 after silica encapsulation. Experimental validation was also conducted with permittivity and space charge distribution measurement of composites. It was concluded that the high polarizability and surface insulativity firstly favored formation of the double layer, synergistically from which the resulted space charge in homo-pattern then suppressed excessive charge injection through Coulomb repulsive interaction, and improved electrical strength by retarding exorbitant localized field occurrence which had been found to be direct cause of breakdown when it exceed a critical value.

Electric field and space charge distribution measurement in transformer oil struck by impulsive high voltage

Transformer oil is widely used in power systems because of its excellent insulation properties. The accurate measurement of electric field and space charge distribution in transformer oil under high voltage impulse has important theoretical and practical significance, but still remains challenging to date because of its low Kerr constant. In this study, the continuous electric field and space charge distribution over time between parallel-plate electrodes in high-voltage pulsed transformer oil based on the Kerr effect is directly measured using a linear array photoelectrical detector. Experimental results demonstrate the applicability and reliability of this method. This study provides a feasible approach to further study the space charge effects and breakdown mechanisms in transformer oil.

Measurement and modeling of electric field and space-charge distributions in obstructed helium discharge

Axial and radial variations of electric field have been measured in dielectric shielded 0.025 m diameter parallel plate electrode with 0.0065 m gap for 1.6 mA, 2260 V helium dc discharge at 1.75 Torr. The axial and radial electric field profiles have been measured from the Stark splitting of 21S→11 1P transition through collision induced fluorescence from 43D→23P. The electric field values showed a strong radial variation peaking to 500 kV/m near the cathode radial boundary, and decreasing to about 100 kV/m near the anode edge, suggesting the formation of an obstructed discharge for this low nd condition, where n is the gas density and d is the gap distance. The off-axis Stark spectra showed that the electric field vector deviates from normal to the cathode surface which permits longer path electron trajectories in the inter-electrode gap. Also, the on-axis electric field gradient was very small and off-axis electric field gradient was large indicating a radially non-uniform current density. In order to obtain information about the space charge distribution in this obstructed discharge, it was modeled using the 2-d axisymmetric Poisson solver with the COMSOL finite element modeling program. The best fit to the measured electric field distribution was obtained with a space charge variation of ρ(r) = ρ0(r/r0)3, where ρ(r) is the local space charge density, ρ0 = 6 × 10−3 Coulomb/m3, r is the local radial value, and r0 is the radius of the electrode.

Surface temperature measurement for space charge distribution measurements with thermal methods

The implementation of space charge measurements based on thermal perturbation on thin films requires an improvement of the temperature distribution estimation at the surface and in the depth of dielectric materials for getting reliable space charge profile measurements. Absolute temperature variations are needed, both in time and space. The present contribution addresses surface temperature measurements based on either thermoelectric or bolometric effects. Both responses have been measured on coppercoated silicon nitride layers and gold-coated polypropylene films heated with a Nd:YAG laser pulse. It is shown that high temporal resolution thermal response can be obtained through the bolometric response and that the information appears nearly independent on the nature of the coating electrode. The setup developed provides good signal to noise ratio for heated electrodes of a few ohm resistance. Strategies are still to develop to get the temperature profile in the insulating sample layer.