Space Charge Measurement Techniques Research Articles

Space charge measurements for multilayer heterogeneous composite films by thermal pulse method

Multilayer composite films are suitable for high-temperature and high-electric-field insulation, but the accumulation of space charge may lead to the degradation of their insulating properties. However, few studies have been reported on space charge distribution in multilayer composite thin films due to the limitations of space charge measurement techniques. In this study, using Al2O3/PI and BOPP/PI composite structural samples as numerical examples, we proposed a method for calibrating electric fields in multilayer heterogeneous structures and combined it with the Tikhonov regularization algorithm, and successfully reconstructed the electric field distribution inside the samples. Based on this, the experimental results show that the reconstruction of the overall electric field in the BOPP/PI composite samples is consistent with the combined electric field reconstructed after the individual measurements of each layer, which further confirms the feasibility and validity of the use of thermal pulse to measure the charge distribution in multilayer heterogeneous composite films.

Space Charge Behavior in Epoxy‐Based Dielectrics: Progress and Perspective

AbstractEpoxy‐based dielectrics are extensively used in grid‐connected energy systems and modern microelectronics as electrical insulation, adhesive, and packaging components. However, space charge accumulation in epoxy‐based dielectrics is a foremost factor threatening device stability and lifespan, especially under conditions of high voltage direct current and high temperatures during long‐term operation, and thus are investigated systematically. This article reviews the state‐of‐the‐art progress in understanding and regulating the space charge behavior of epoxy‐based dielectric materials. The development of space charge measurement techniques is first introduced. Then, experimental observations of macroscopic space charge characteristics in epoxy dielectrics under different conditions, along with the advancement of nanofiller‐doping strategies for improving space charge suppression capabilities, are discussed and emphasized. Afterward, simulation progress based on the bipolar charge transport models and quantum chemistry calculations are summarized to provide some insight from a microscopic perspective. It is concluded by providing a brief summary and highlighting future research opportunities in inhibiting space charge accumulation of epoxy‐based dielectrics for practical applications in power equipment and electronic devices.

Atomic force microscopy developments for probing space charge at sub-micrometer scale in thin dielectric films

Charge injection and accumulation in dielectrics are phenomena at the origin of different kind of failure of devices. To improve the understanding of involved mechanisms, space charge measurement techniques have been successfully developed. However, their spatial resolution is incompatible with thin films or interfaces studies. In this paper, the contribution of techniques derived from Atomic Force Microscopy (AFM) to space charge measurement is investigated. First of all, localized charges injection is studied using classical Kelvin Force Microscopy (KFM). Secondly, we propose a new method called EFDC (Electrostatic Force Distance Curve) which allows direct measurement of electrostatic force induced by trapped charges. EFDC sensitivity to lateral localization of charges is demonstrated. Finally, comparing the results obtained by EFDC and KFM highlights the relative merit of each technique.

Progress and Prospects in PEA Space Charge Measurement Techniques - [Feature Article

Space charge measurements using electro-acoustic techniques have dramatically improved in the past 20 years. They have revealed many interesting phenomena in dielectrics. The author believes that the technique is progressing continuously, and that the progress expands the range of applications and raises new topics in research on dielectrics. To make the PEA method more acceptable, it could be high time to discuss measurement protocols, including a standard material for evaluation of systems. Editing a good practice guide will be helpful to users who are not familiar with acoustic physics. Then, it is essential for users to discuss space charge behavior in dielectrics not only by using space charge profiles by electro-acoustic techniques, but with additional evidence obtained by other techniques and chemical information of materials under test. Especially, the simultaneous measurement of space charge, temperature, luminescence, and other possible physical values will definitely help our understanding of dynamic phenomena in solid dielectrics.

Two-dimensional structure of charge packets in polyethylene under high dc fields

The puzzling behavior of space charge inside solid dielectrics has been revealed by space charge measurement techniques. In particular, positive and negative “charge packets” propagating through the bulk with a repetitive character are thought to be related to prebreakdown mechanisms. Here, we investigated the space charge distribution in a lateral direction by using our recently developed two-dimensional pulsed electroacoustic setup and discovered that the structure of the charge packets is not homogeneous in the lateral direction. This could change drastically the common view as regards their generation and propagation mechanisms as well as their relationship to breakdown.

Space charge and charge trapping characteristics of cross-linked polyethylene subjected to ac electric stresses

This paper reports on the result of space charge evolution in cross-linked polyethylene (XLPE) planar samples approximately 220 µm thick. The space charge measurement technique used in this study is the pulsed electroacoustic method.There are two phases to this experiment. In the first phase, the samples were subjected to dc 30 kVdc mm−1 and ac (sinusoidal) electric stress levels of 30 kVpk mm−1 at frequencies of 1, 10 and 50 Hz ac. In addition, ac space charge under 30 kVrms mm−1 and 60 kVpk mm−1 electric stress at 50 Hz was also investigated. The volts-off results showed that the amount of charge trapped in XLPE sample under dc electric stress is significantly bigger than samples under ac stress even when the applied ac stresses are substantially higher.The second phase of the experiment involves studying the dc space charge evolution in samples that were tested under ac stress during the first phase of the experiment. Ac ageing causes positive charge to become more dominant over negative charge. It was also discovered that ac ageing creates deeper traps, particularly for negative charge.This paper also gives a brief overview of the data processing methods used to analyse space charge under ac electric stress.

Space charge distribution measurement methods and particle loaded insulating materials

In this paper the authors discuss the effects of particles (fillers) mixed in a composite polymer on the space charge measurement techniques. The origin of particle-induced spurious signals is determined and silica filled epoxy resin is analysed using the laser-induced-pressure-pulse (LIPP) method, the pulsed-electro-acoustic (PEA) method and the laser-induced-thermal-pulse (LITP) method. A spurious signal identified as the consequence of a piezoelectric effect of some silica particles is visible for all the method. Moreover, space charges are clearly detected at the epoxy/silica interface after a 10 kV mm−1 poling at room temperature for 2 h.

Space charge profile measurement techniques: recent advances and future directions

Some of the advances in space charge measurement techniques over the last 5 years are described. It is concluded that significant further improvements in spatial resolution are unlikely in the next 5 years, except in the case of the LIMM technique implemented using very short laser pulses, where spatial resolution approaching 100 nm might be achievable. It is suggested that existing space charge techniques be combined with conducting atomic force microscopy (CAFM), with the aim of correlating 3-dimensional space charge profiles and 2-dimensional conductivity maps and thus providing a more complete picture of charge transport through dielectrics, particularly in future work on nanodielectrics. Since CAFM samples are typically 5-10 nm thick, it would be necessary to operate the equipment at higher voltage (say 1000 V) so that samples not less than 10 /spl mu/m thick, e.g. polymers, could be investigated. This seems feasible.

Establishment of Space Charge Measurement Technique in Samples with Variation of Temperature

The aim of this research work is to establish an accurate measurement technique using pulsed electro-acoustic method for observing a dynamic space charge behavior in insulating materials during elevating temperature under high electric stress. When the high electric stress is applied to the dielectric materials, so-called space charge accumulates in the bulk of dielectrics. It is said that space charge accumulation strongly affects the characteristics of electrical conduction and breakdown strength in dielectrics. Therefore it is necessary to observe the space charge formation in dielectric materials. It is well known that the space charge accumulation in the insulating materials strongly depends on temperature of materials. However, most of the space charge measurement has been carried out at room temperature except for a few reports. It seems that these have been still remained some difficulties for measuring the charge distribution during elevating temperature. Therefore, in this research work, we would like to establish the measurement technique for dynamic behavior of space charge accumulation in insulating materials at high temperature under high electric stress.

空間電荷計測技術の最前線

空間電荷計測技術の最前線

Progress in space charge measurement of solid insulating materials in Japan

The space charge measurement technique may be applied to diagnostic technology for high-voltage machines in the near future. The authors review the progress in the various methods of space charge measurement in Japan. >

Space charge measurement techniques and space charge in polyethylene

Recently, several new techniques such as LIPP, PIPS, PEA and TP methods have been developed to measure directly the space charge distributions in insulating polymers. Many papers have been published on space charge in insulating materials. In this paper, the space charge measurement techniques and space charge in polyethylene are reviewed. The space charge distributions in polyethylene depend strongly upon additives (antioxidants, antistatic agents, etc.), oxidation products, byproducts from the crosslinking reaction (acetophenone, etc.). Some of them enhance electron (or hole) injection from the electrode and, as a result, homo space charge is formed. Ionic carriers are supplied from some impurities to form hetero space charge. Space charge distributions are also sensitive to the electrode material and the interface between different materials. From the space charge behavior observed, the space charge effects on the high-field conduction and breakdown phenomena have been discussed quantitatively and some of the high-field phenomena in polyethylene have been elucidated. >

A DLTS study of the effects of boron counterdoping on the gap states in n-type hydrogenated amorphous silicon

The technique of Deep Level Transient Spectroscopy (DLTS) and related space charge measurement techniques have been applied to a series of 300 vppm phosphine (PH 3) doped, 0–44 vppm diborane (B 2H 6) counterdoped samples of hydrogenated amorphous silicon ( a-Si:H). The trends in the resulting density of states, g(E), show: (1) A large increase of g(E) at ≈0.4 to 0.6 eV from the valence band, comparable in magnitude to the total number of B atoms introduced; (2) A smaller decrease in the midgap dangling bond states on the order of ≈2.5% of the added B; (3) A drop in the number of occupied shallow states ≈0.5%; and (4) A quantitative assessment of the degree of autocompensation which shows roughly five compensating midgap states removed for every six shallow acceptor states introduced by B.