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The study of electrical properties of poly (ethylene terephthalate), (PET), has attracted great interest since it is used in commercial applications such as insulation in capacitors and as a charge storage device in foil electret transducers. For an accurate evaluation of its insulating and electret qualities the underlying physical mechanisms for charge transport have to be understood. Two processes...
On heating metal 1-polymer- metal 2 systems above room temperature, open-circuit voltages are generated between the two dissimilar electrodes [1–4]. Ieda et al. [1, 2] were the first to suggest that these open-circuit voltages, Voc, were of electrochemical origin. Several other explanations of the phenomenon have been put forward [3–6] but most of them neglect the central fact, i.e. the oxidation...
It is well known that most fluids of low viscosity are penetrable into polyethylene and that some fluids such as acetophenone and silicone oil used as additives have the capability of inhibiting tree initiation or growth in polyethylene. Additives having such a capability are attractive to the insulation industry because the inhibition of tree initiation or growth implies the extension of the service...
The Curie-v. Schweidler law at low field strengths in thin films of aluminumoxide results from a volume polarization. The elementary process is caused by protons which tunnel between two metastable positions. The proton density in the samples under investigation is npr ≈ 6.1020 cm− 3.
In recent years, gas insulated apparatus has been widely employed in power engineering. In future, the application of SF6 for the GIS may be implemented to gas cables as well as in the other electrical apparatus. Thus, it is considered that the development of simple methods for the detection of gaseous components can be important, from the view point of the maintenance and of the usage of gas mixtures.
PVDF and its copolymers have been developed very recently and therefore there are only few manufacturers is the world. Because of unique structure these materials are able to sustain harsh thermal, chemical, electrical and even ultraviolet environment. Low smoke and low flame spread make their use possible in plenum as well as in computer wiring and host of equipments as mentioned earlier. This is...
The results presented in this paper reveal a number of interesting features of the poling of PVDF: Room-temperature poling yields, depending on the applied field, no polarization at all or a spatially uniform polarization. In contrast, poling at elevated temperatures yields generally a nonuniform polarization with the poled region located close to the positive electrode at low fields, but extending...
When an ac voltage stress is applied to a ZnO varistor in the pre-breakdown region, a through current (leak-age) constantly flows through the device. This current consists of a resistive component and a capacitive component, the magnitude of the latter being several times greater than that of the former. In spite of this relatively lower value of IR, it is the key parameter responsible for Joule heating...
The ferroelectric properties of poly(vinylidene fluoride) [1] have recently stimulated interest in similar properties of its copolymers with other fluorocarbons. While copolymers with trifluoroethylene have been studied extensively from a ferroelectric viewpoint, (e.g. ref. 2–5), others have not. Yet, copolymers with tetrafluoroethylene are of particular interest in relation to the homopolymer because...
It has been established by a number of investigators [1]–[4] that the statistics of breakdown of liquid dielectrics change with forced liquid motion. More specifically, the distribution of liquid breakdown voltage shifts with increasing velocity from the extreme value distribution that characterizes stationary fluids to a Gaussian distribution [2],[3]. This is quite significant from the practical...
TSDC from XLPE demonstrates that charge storage is extremely complicated and can be affected by external parameters such as outgassing, wetting, and the gaseous charging medium.
This paper briefly reviews three areas of concern relating to aging effects in silica-based lightguides. In all cases, further work is necessary to quantitatively predict the lifetime behavior of lightguides in a given operating environment.
A dielectric submitted to a prolonged electrical stress will fail at nominal field levels often one or two orders of magnitude below the short term breakdown field. The damage typically consists of multiply branched hollow channels of ∼ µm diameter (electrical trees) which originate at a point of local field enhancement. Another family of damage structures consists of channels much finer in diameter...
The influence of the kinds of impurities in the core and manufacturing process of the core on the radiation resistance was investigated for 6 kinds of pure silica core optical fibers. We have obtained the following results: 1. The radiation resistance of OD doped fiber was good and the initial loss before irradiation was low also although the total hydroxide molecule content was low. on doped fiber...
The effects of γ-ray radiation of 60Co on two optical fibers having different OH concentration and a bundle fiber have been investigated in the visible region. The radiation induced attenuation increases with the increment of total irradiation dose exhibiting peaks at around 460 nm and 600–630 nm in the optical fibers having OH. It has been found that radiation induced loss is related linearly to...
Pd characteristics for MLC capacitors with different relative permittivities, porosity, and void size distributions were evaluated. The results show that: 1. Pd is a strong function of and increases with the increase of the applied field. 2. Higher dielectric constant, which gives a bigger field enhancement, also enhances the Pd activity. 3. The source of Pd is the ionization discharge across the...
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