The Infona portal uses cookies, i.e. strings of text saved by a browser on the user's device. The portal can access those files and use them to remember the user's data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser.
The following topics are dealt with: electrical insulation; dielectric phenomena; aging; partial discharges; treeing; nanodielectrics; outdoor insulation; charge storage; flow electrification; field mapping; dielectric polarization; high field phenomena; surface flashover; biodielectrics; and breakdown phenomena.
In order to fully understand a certain property of a material or to clarify the mechanism of a phenomenon, research must be done with scientific rigor and a scholarly approach. The first three pioneers who introduced the rigorous scholarly approach into the field of electrical insulation research in Japan are Profs. Inuishi, Ieda, and Yahagi. Researchers and students have been inspired by their work...
In this paper, we focused on the breakdown lifetime characteristics under repetitive surge voltage application for nanocomposite enameled wires. Experimental results revealed that the nanocomposite enameled wires exhibited the longer breakdown lifetime as high as 1000 times of conventional enameled wires under surge voltage application. The relationship between the surge breakdown voltage V and the...
In view of the coming major asset replacement wave of power grid components, new lifetime prediction tools are developed to assist asset managers in making technically and economically sound decisions. This paper discusses the modeling technique based on the concept of quality parameters applied to paper insulated systems. The concept of quality parameters was recently introduced for power transformers...
Measurements of bias-dependent deflections and strain in EAPap, as well as water absorption were carried out. Model simulations have also been performed to probe the role of the various internal mechanisms. Our simulation predictions yield good agreement with the measured data on EAPap deflections. The modeling suggests that internal ion content and its migration, water absorption leading to a non-uniform...
Dc conductivity and ac impedance measurements were made in air and in vacuum on samples of low density polyethylene to which nano-sized and micro-sized ZnO particles and a dispersant had been added. The samples were 150-200 mum thick. The temperature range was 30-70degC. The temperature dependence of the vacuum dc conductivity in samples containing the dispersant and 10% w/w nanosized ZnO followed...
This work deals with the study of the physical properties of solid dielectric materials intended for the applications of the electrical engineering. In order to improve these properties, it is allowed today that the incorporation of nanoloads in these materials can have a great influence. During their use, these materials are subjected to combined constraints (electric, thermal, mechanical, environmental...
Whenever a polymeric material is subjected to an electrical stress, imperfections such as protrusions, contaminants and microvoids, will all act as points where the field is enhanced, causing the degradation processes to be initiated. However, as manufacturing technology improves, insulation systems are of higher quality and their interfaces smoother. The reduction in concentration and size of impurities...
An environmental chamber has been built at Arizona State University (ASU) for purpose of establishing a long-term aging test of All Dielectric Self Supporting (ADSS) fiber optic cable. Six ADSS cables are subjected to UV radiation, salt fog, clean rain and mechanical tension in the aging chamber. This paper briefly compares aging characteristics of six ADSS cables subject to various lengths of time...
We have applied a remaining service life diagnostic technology to phenol insulators of power distribution equipment. Application of chemical evaluation and the Mahalanobis-Taguchi (MT) method enabled us to diagnose the insulators' degree of deterioration with great accuracy and nondestructively on-site. Time was defined as the end of service life when electrical discharge was initiated and a remaining...
The steep voltage pulses associated to modern Adjustable Speed Drives (ASDs) stimulate the capacitive coupling between the stator and the rotor, resulting in stray shaft and bearings voltages. These latter act on the dielectric grease employed for lubricating the bearings and may cause the breakdown of the film. The associated Electric Discharge Machining (EDM) currents deteriorates the bearings performance...
Thermal endurance tests have been carried out on low voltage cable specimens insulated with two PYC-based compounds. Specimens have been aged at three test temperatures (110, 120 and 130degC) with the induced-current method. A proof-test procedure, based on withstand-voltage tests, has been chosen for determining specimen times to the end-point. During thermal aging some physical quantities -i.e....
We consider that electrical tree initiation is caused by collision impact of electrons which are accelerated in polymer free volume by electric field. It is expected that gas in free volume in SiR affects the electrical tree initiation characteristics. The electrical tree initiation voltage is increased by vacuum evacuation, SF6 impregnation, and air re-impregnation after vacuum evacuation. It is...
Tracking of a plug for household appliance connected to an outlet is considered as one of causes of fire, which is occasionally observed when dust is accumulated in the space between the plug and the outlet and wetted by dew condensation. By carrying out a series of fundamental studies, surface current were recorded and analyzed, which flowed on the surface of a cord plug during accelerated tracking...
Short circuit of a stator winding is one of the most probable faults of induction motors. Once the fault occurs, the current waveform flowing in the winding will be distorted from sinusoidal depending on the degree of short circuit fault. In a series of experiments using induction motors with artificially introduced short circuit fault in stator windings, current waveforms were recorded and analyzed...
X-ray diffraction has been applied to reveal the effect of thermal aging on the crystallinity variation of XLPE insulation cables. The changes in the crystalline phase of XLPE during aging at different temperatures have been analyzed. The carried out investigations pointed out that thermal aging at temperatures above the melting temperature of XLPE have a great effect on the crystallinity variations.
Despite the continuing growth of polymeric insulation systems, paper and oil are still routinely used in many items of high voltage plant as the dielectric material. In such systems the oil provides a convenient medium for sampling in order to indicate plant condition. However, in order to understand the ageing of oils in plant, and more importantly, to predict the remaining lifetime, requires controlled...
Deterioration with water tree phenomenon is the one of typical problem on the electrical insulation of the high-voltage class power cable. A water tree which bridges a cable insulation between inner and outer screen makes the insulation resistivity low, then it is possible to apply the conventional way, such as leakage current measurement and so on. However, for an un-bridged one, which induces the...
The behavior of the oil-paper insulating systems of transformers is primary determined by paper and oil basic properties. Recent studies are concerned to study of using synthetic oils instead of traditionally used petroleum based oils. This study monitors the influence of oil type on the final insulating system properties. The main degradation factor -temperature -is respected and properties under...
It has been shown that the supply waveforms generated by the power converters play a major role in inverter-fed traction motor insulation degradation. The electrical characterization of these insulating materials is often carried out through aging tests which may provide estimation of life under different stress levels and conditions. However, deeper investigation of aging phenomena due to supply...
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.