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.
In this paper a charging kinetics of cross-linked polyethylene (XLPE) under electronic beam irradiation in scanning electron microscope (SEM) is quantified by the evaluation of trapped charge. The effect of thermal aging at different temperatures ranged from 80°C to 140°C is highlighted and analyzed. The variation of charging process of XLPE is monitored with measuring the influence current, leading...
This research work presents the distribution of the electric field in point-barrier-plane air gaps taking into account the presence of a space charge under electric stress. A new approach of numerical simulation has been applied to study the barrier effect on the electric field distribution using COMSOL Multiphysics®. The introduction of an insulating barrier leads to a reduction of the electric field...
A scanning electron microscope (SEM) is employed to investigate the Thermal aging effect on the surface potential decay of cross-linked polyethylene (XLPE) under electron beam irradiation. We have subjected the material to the X-ray spectra monitored with X-ray spectrometer attached to the special adapted arrangement of SEM. The variation of charging process of XLPE is monitored with measuring the...
High voltage cables are permanently subjected to electrical and thermal operating constraints, leading to their progressive degradation and deterioration. The control and the identification of the thermal aging parameters of high voltage insulation require the use of several characterization techniques. In this work we have presented some results carried out from the use of different characterization...
This paper presents an experimental investigation on transformer oil subject to impulse voltage. The dynamic impedance of the mineral oil samples was determined from the instantaneous ratio of voltage and current characteristics at the instant of breakdown. A dedicated test cell was constructed to contain the insulating oil. A sphere-sphere electrodes gap of variable length was used for the experiments...
In this paper, we propose three prediction algorithms using the artificial neural networks to generalise some characteristics describing the electrical arc propagation on polluted insulators. For that purpose, three Radial Basis Function Gaussian (RBFG) networks with one output have been elaborated. The difference between these configurations consists in the nature of the input and output units. The...
The present experimental carried out investigations aimed at elucidating the effect of earth discontinuity on the breakdown voltage of short rod-plane air gap (40 to 140 mm) under negative lightning impulses (−1.2/50μs). We also carried out investigations on electric field measurement on the surface of a discontinuous plane of a rod-plane air gap arrangement. For this purpose, we used a probe with...
Some Artificial neural network algorithms have been used to predict properties of high voltage electrical insulation under thermal aging in term to reduce the aging experiment time. In this paper we present a short comparison of the obtained results in the case of Cross-linked Polyethylene (XLPE). The theoretical and the experimental results are concordant. As a neural network application, we propose...
Dielectric interfaces can have a significant effect on the insulating performances of HV apparatus. The oil/solid interface represents a relatively weak component of an insulation system in power transformer. Therefore, when we are considering the effect of oil breakdown in oil filled transformer, we should consider the interactions which electrical discharges may have with solid surfaces. This work...
In this paper we present results of carried out investigations on the influence of insulating barriers on AC prebreakdown current of long point-plane transformer oil gaps up to 12cm. The insertion of an insulating barrier leads to an important prebreakdown current decrease. The barrier acts as a geometrical and electrostatic obstacle for the disruptive discharge. We present in the paper a comparison...
The control of the dielectric permittivity and losses of solid insulators, through an understanding of the origin of their dipole relaxation and ionic conduction processes, is essential for their use in electrical insulation. Dielectric Spectroscopy is a powerful tool in the investigation of dipolar and conduction in electrical insulating materials. In particular, the localisation of space charges...
This paper presents the result of study on radial temperature distribution of XLPE cable. The distribution characteristic analyzed with the finite volume method (FVM). Result obtained indicates that the radial temperature distribution of the XLPE cable do not flattened distribution because of the difference in thermal conductivity in each layer. It is shown that the highest distribution radial temperature...
The risk of breakdown in mineral insulating oil constitutes a critical part in the insulation of high voltage apparatus such as transformer. This paper presents an experimental investigation on transformer oil dynamic breakdown characteristics when subjected to AC voltage. Breakdown tests were carried out on mineral oil samples using a sphere-sphere electrode test cell for various gap lengths 1 mm,...
In this paper, we present an experimental study on the properties of mineral oils under AC breakdown conditions. Breakdown tests were carried out on mineral oil samples using a sphere-sphere electrode test cell for various gap lengths 1 mm, 2.5 mm and 5 mm and at different voltage speed ramps: 0.5 kV/s, 2 kV/s and 3.5 kV/s. The dynamic impedance of the mineral oil samples was determined from the instantaneous...
Dielectric spectroscopy is a powerful tool in the investigation of dipolar and conduction in electrical insulating materials. In particular, the localisation of space charges at crystalline - amorphous interfaces in a semicrystalline polymer, such as low density polyethylene LDPE, provides on internal field which could be unfavourable to the insulating properties of the polymer. A physical displacement...
The major aim of our investigations is the computation of the voltages induced by an external transient electromagnetic excitation, especially due to the lightning discharge coupling to overhead transmission line networks. In this paper we propose a hybrid method for evaluating the electromagnetic field radiated by lightning The Agrawal et al. model coupling model will be used in order to analyse...
In this paper we propose a hybrid method for evaluating the electromagnetic field radiated by lightning. The proposed method is a combination between the images method and the finite difference time-domain (FDTD) method. We first calculate the magnetic field with the images method and then; the electric field based partially on the FDTD method. The suitability of this method (hybrid method) is checked...
In this paper, we present the electrical and physic-chemical behaviours of oil in high voltage transformers, under thermal ageing. Continuous thermal ageing tests were made on transformer oil BORAK22 during 5000 hours at two different temperatures 80degC and 120degC. Here, every 500 hours, the dielectric losses factor, the relative permittivity and the resistivity were measured. Other properties such...
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.
This communication describes work and gives results focused on the application of Differential Scanning Calorimetry (DSC) 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 four different temperatures have been analyzed. This study shows also the effect of aging on the melting peak temperature...
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.