Measurement Of Space Charge Distribution Research Articles

Portable space charge measurement system using the pulsed electrostatic method

The pulsed electroacoustic (PEA) method is used to measure space charge distributions in insulating materials. A high-resolution PEA measurement system and signal procedure has been discussed in previous papers. Since the signal procedure is necessary for high-resolution measurement, the system must include a computer. In this paper, a new PEA system without signal processing is introduced. In order to eliminate the inevitable signal distortion of the conventional PEA method, the new system employs a new voltage waveform generator, one that is different from the very narrow pulse generator used in conventional PEA systems. Using the new waveform, designed based on the impulse response of the measurement system; the output signal can show the space charge distribution directly, without the need to conduct deconvolution. Thus, space charge distributions can be measured on site, such as in a factory, with a portable oscilloscope. The spatial resolution of the space charge measurement of the system is 10 /spl mu/m, which is the same as that of conventional PEA systems. Such a portable PEA system can contribute to various industrial applications.

Piezo-PWP and PEA methods for measuring space charge in solid dielectric

In this paper, a new illation of the principle of PWP (Pressure Wave Propagation) method is presented, and the results, after comparing the PWP method with the PEA (Pulsed Electro-Acoustic) method, indicate that the two methods very resemble with each other in physics. In order to testify the conclusion, the measurement of space charge distribution in XLPE by using the combined system of piezo-PWP/PEA has been corried out, and the experimental results confirm the conclusion.

Space charge behavior in polymer film based on increment of capacitance under AC high field

AbstractPolymer materials have excellent dielectric and insulation properties; however, those properties in AC high field region have not been known well. Recently we established an evaluation method of high‐field AC dissipation current waveform of polymer materials 1. AC dissipation current waveforms of polyethylene and polypropylene films show nonlinear distortion in AC high‐field region. This nonlinearity was thought to be related to the behavior of AC space charge formation in the sample near electrodes. The properties of space charge formed under AC high field at power frequency seem to differ from those formed under DC high field. The measurement of AC space charge distribution is not so easy due to the resolution limit of the space charge measurement.We studied the dielectric properties of biaxially oriented polypropylene (BOPP) film under AC high field up to 120 °C. It was found that tan δ, AC dissipation current (Ixr), and unbalanced component of capacitive current (ΔIxc) increased when the temperature became higher. In particular, ΔIxc increased above some threshold field and was considered to be due to the AC space charge formation. This AC space charge layer near electrode is thought to be formed due to carrier injection under AC high‐field application. Usually, the carrier mobility becomes smaller on lowering the temperature. Most of the carriers injected from the electrode are trapped near the electrode in the sample film. But in the high‐temperature region, the carrier mobility becomes larger and the carrier injection starts to increase from lower field. Many more carriers are injected from the electrode. It is thought that some of the injected carriers are trapped inside the sample film; the others go through the sample to the opposite side. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 141(2): 8–16, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10018

PEA空間電荷分布測定装置の高分解能化と金属中の圧力波減衰の測定

The pulsed electroacoustic(PEA) method has been used to measure space charge distributions in insulations. Since the resolution of ordinary PEA systems is over 10 microns, it is difficult to observe space charges in thin specimens, such as a film which is less than 100 microns-thick. In order to improve the resolution of the current PEA system, the attenuation of pressure waves in the bottom electrode and the frequency bandwidth of the piezoelectric sensor were concerned. In this paper we introduce the new PEA system which has super high resolution of 6 microns.

Measurement of space-charge distributions in solid insulators underrapidly varying voltage using the high-voltage, high-speed pulsedelectro-acoustic (PEA) apparatus

A new high-voltage, high-speed pulsed electro-acoustic (PEA)apparatus for real-time measurements of space-charge distribution in solidinsulators subjected to rapidly varying voltages is described. Very high-ratePEA measurement is accomplished with the use of a high-speed real-time dataacquisition module known as the `Eclipse' unit and a purpose-builthigh-voltage FET switch pulse generator. Real-time space-charge measurementswith good phase resolving capability can be made under time varying appliedstresses, e.g. voltage transients or ac conditions. The high-field PEA systemhas been used to investigate the space-charge dynamics in polyethylene samplesstressed by 0.2 and 50 Hz sinusoidal ac voltages.

Estimation of conductivity and permittivity of water trees in PE from space charge distribution measurements

Using an improved pulsed electroacoustic system which is capable of measuring space charge distribution at minimum intervals of 25 /spl mu/s, the charge distribution inside water-treed polyethylene (PE) was examined. From the results, the frequency dependencies of conductivity and permittivity were examined for water trees grown in PE. The conductivity of the water-treed region is found to be >10/sup 10//spl times/ higher than that of non-treed regions, while the permittivity increase is only slight.

LDPEフィルムの絶縁破壊発生までの過渡的空間電荷と外部回路電流の同時測定

LDPEフィルムの絶縁破壊発生までの過渡的空間電荷と外部回路電流の同時測定

Influence of divergent electric fields on space-charge distribution measurements by elastic methods

Elastic methods are presently being used to study the space charge distributions in insulators. They are limited in their interpretation to simple geometries whereas real systems often involve complex structures such as the case for divergent electric field regions. The authors propose a general theory for the interpretation of the data obtained by the pressure-wave-propagation method and the electro-acoustic method. This model makes it possible to study crystals, isotropic solids, or fluid samples of any geometry, containing charge and dipole distributions and also submitted to divergent electric fields such as produced by treeing or defects. A comparison is made with existing models in the case of simple geometries, such as planar or coaxial. It is shown that classical results are justified in the case of a planar sample. However, a correction has to be introduced in more complex geometries, even in coaxial ones. Indeed, some experiments show the associated difference. The model also emphasizes the similarities of the two elastic methods of measurement both for the analytical and experimental point of view.

Space- and surface-charge analysis of plasma-preprocessed PTFE thin films

The space- and surface-charge behavior of corona-charged polytetrafluoroethylene thin films after plasma processing were studied experimentally by space-charge density distribution measurement and thermally stimulated discharge current (TSDC) measurement. The effect of the antistatic process using low-pressure discharge plasma and charge elimination process dipping in tap water was examined. The surface composition of the samples which were plasma- processed was analyzed with X-ray photoelectron spectroscopy (XPS) to study the mechanisms of antistatic process. It was found that charge elimination of plasma-processed samples was enhanced, independently of the kind of processing gas during the plasma processing. Oxygen and nitrogen atoms were observed from the XPS measurement of plasma-processed samples. In particular, a large amount of nitrogen atoms was found on the surface of the samples plasma processed in pure nitrogen gas. The samples plasma processed in pure nitrogen gas showed a large hetero TSDC peak at room temperature before the charge-elimination process. This might be due to nitrogen atoms on the sample surface that were generated during plasma processing.

Measurement of space charge distribution in epoxy resin

Internal space charge behavior of insulating materials has recently attracted attention of many researchers, and a large number of experimental studies were carried out by using the materials for dc cables, such as XLPE, LDPE, and HDPE. Epoxy resins are used for insulation under strong electric fields in power apparatus and in electronic devices, and we investigated the behavior of internal space charge using the pulsed electroacoustic method. Two types of epoxy resins were studied: insulation-grade and craft-grade. When dc electric fields were applied to the craft resins treated by immersing them into room-temperature water for 8 and 24 h, positive and negative charges accumulated near the anode and the cathode, respectively, and the charge distribution changed with the immersion time. On the other hand, no charge was observed in the insulation-grade epoxy resin. Next, we treated the samples by immersing them into 100 °C water for 8 h. When the sample was treated for 8 h, hetero charge distribution, which means positive charges near the cathode and negative charges near the anode, was observed. This result is consistent with a previous paper reporting that by chemical analysis, secondary decomposition had occurred. These results show that water and temperature influence the internal space charge behavior of epoxy resins. © 1999 Scripta Technica, Electr Eng Jpn, 129(3): 9–16, 1999

Analysis and discussion on conduction current based on simultaneous measurement of TSC and space charge distribution

A new analysis of conduction current distributed in dielectrics based on simultaneous measurements of thermally stimulated current (TSC) and time dependent space charge distribution is proposed. A new system pulsed electro-acoustic (PEA) method has been developed to enable simultaneous measurement of the TSC and the dynamic space charge and electric field distributions as a function of temperature within insulators. With the new system, the relationship between the TSC and the time dependent electric field distribution in electron beam (e-beam) irradiated PMMA has been investigated. From the time dependent electric field, the displacement current in dielectrics is obtained. The TSC is a typical external current which is represented as an addition of the displacement current and a conduction current in dielectrics. This paper makes it clear that the conduction current as a function of position is determined by the simultaneous measurement of the external current and the dynamic space charge distribution.

A relation between the space charge distribution and TSDC spectrum of corona charged PTFE thin films

A space charge density distribution measuring system based on a PPP (piezoelectrically induced pressure pulse wave) method was constructed. The pressure pulse wave is generated by a pulse-driven piezoelectric PVDF (polyvinylidene fluoride) thin film used as a piezoelectric pulse generator. A thin aluminum plate is used as a shield electrode to electrically separate the pressure pulse generator and the sample holder. This thin shield electrode reduces attenuation and dispersion of the pressure pulse wave compared to the former system. The spatial resolution of the system is estimated to be about 7 μm, based on the PPP response to a sheet charge that is artificially placed on a dielectric thin film. Using space charge distribution measurements and TSDC (thermally stimulated discharge current) measurements, the charge behavior of the corona-charged PTFE Teflon TM (polytetrafluoroethylene) thin films was studied.

Influence of the tacticity dependent microstructure on the space charge distribution of poly[vinyl chloride

The aim of this study is to investigate the influence of the tacticity dependent microstructure on the ability of PVC to accumulate space charge. In this connection the Thermal Step Method developed at ‘Laboratoire d'Electrotechnique de Montpellier’ is used to measure space charge distribution in poled samples. Three PVC samples of different tacticity are studied. We show that the space charge increase substantially with isotacticity. An explanation to this phenomenon is also provided.

Laser thermoacoustic modulation for space charge measurement

A new method for measuring the space charge distribution in polymer insulators has been developed. This frequency method is based on the thermoacoustic signal which propagates into the insulator when a chopped laser beam is modulated in intensity and focused on the surface of the sample. This method has been used for measuring space charge distribution in a polyethyleneterephtalate sample.

Measurement of space-charge distributions in insulators under very rapidly varying voltage

In this paper we describe a new instrument for real-time measurements of space charge distributions in insulators submitted to rapidly varying voltages. It is illustrated with the pressure wave propagation method but can also be adapted for use with the pulsed electro-acoustic method. A new acoustic generator has been designed to produce high amplitude pressure pulses, at a high rate, and with good reproducibility. This generator, made of a thin transducer coupled with a waveguide and a backing medium, responds with a pressure pulse when a step voltage is applied. A special sample holder with a signal decoupling circuit, and a storage unit have been developed. The described instrument allows for measurements at a rate of 3200 Hz. Its potentialities are illustrated by studying the evolution of space charge in polyethylene samples stressed by both pulsed and 50 Hz ac voltages.

電子線照射によりPMMA中に蓄積させた3次元空間電荷分布の測定

電子線照射によりPMMA中に蓄積させた3次元空間電荷分布の測定

パルス静電応力法による空間電荷分布の計測と熱刺激電流測定により考察したポリエーテルスルホンの自発電流

パルス静電応力法による空間電荷分布の計測と熱刺激電流測定により考察したポリエーテルスルホンの自発電流

Measurement of the internal space charge distribution of an anti-electrostatic discharge polymer

Charged dielectrics can cause an electrostatic discharge (ESD) that damages electronic circuits because of the electromagnetic noise associated with the discharge. Newly developed anti-ESD polymers are expected to be 'anti-ESD polymer insulating materials', but the mechanism of their action against ESD has not been explained. Since the anti-ESD polymers contain some kind of polymer solid electrolyte, they should be able to be characterized by the behavior of their internal space charge. By measuring the space charge distribution of an anti-ESD polymer using the pulsed electroacoustic method under DC electric field, we found that the polymer was effective in preventing ESD because the internal space charge near the surface partially compensates the electric field of the external charge on the surface. We also found indications that the internal space charge behavior is related to the dispersion of the polymer solid electrolyte. >

ポリイミドフィルムの空間電荷蓄積現象の観測

ポリイミドフィルムの空間電荷蓄積現象の観測

Pulsed electro-acoustic method for measurement of space charge distribution in power cables under both DC and AC electric fields

A modification of an earlier technique, to measure the distribution of space charge in the insulation of a coaxial cable, under both DC and AC electric fields, is described. The mathematical analysis is developed on the basis of acoustic waves propagating in media with cylindrical geometry. In order to measure the charge distribution in AC electric fields at any phase angle, a phase shift technique has been employed. The method of calibration of charge density is given, and the charge distribution in the insulation (2 mm in thickness) of XLPE cable has been measured under DC voltages (+or-40 kV, at room temperature) and AC voltage (17 kV peak, at 24 degrees C and 105 degrees C).