Wrocław University of Science and Technology
Repozytorium Eny Politechnika WrocławskaNot a member yet
431 research outputs found
Sort by
Influence of pollution layer thickness on flashover voltage of HV insulators
No full textThe pollution characteristics (the relationships of flashover voltage and SDD or maximum current Imax ) for insulators contaminated with uniform or nonuniform coatings with different thickness h are presented. The influence of the power of test voltage supply and the thickness as well uniformity of the pollution layer on obtained results of measurements is assessed. The flashover voltage and current registrations on a cap and pin insulator string are discussed for different thickness of pollution layer
Internal partial discharges test for metal oxide surge arresters
Full text linkProposals for testing of surge arresters performance under internal partial discharge stress by Sakshaug, Chrzan and Korycki have been presented
Composites Made of Polypropylene Nonwoven Fabric with Plasmas Layers
Full text linkEngineering of materials used for shielding from electromagnetic fields is currently one of the most extensively developing field of applications of composite materials (Bula et al., 2006; Jaroszewski & Ziaja, 2010; Koprowska et al., 2004, 2008; Sarto et al. 2003, 2005; Wei et al., 2006; Ziaja et al., 2008, 2009, 2010). The choice of suitable materials for the shields and their appropriate arrangement have an essential meaning. Development of lightweight and resistant to environmental exposure shielding materials is possible by using substrates of polypropylene and plasma technology (Ziaja&Jaroszewski, 2011). The shields for suppression of electric field were made in the form of composites of polypropylene unwoven fabrics with deposited plasma layers. Additional advantage of the application of the method is the possibility of plasma cleaning of a fabric surface and modifying its surface properties. The unique properties of pulse plasma make possible to obtain metallic and dielectric coatings on polypropylene fabrics, which are not achievable by standard methods. The coatings are characterized by a good adhesion to the substrates. The surface of the samples was examined in two ways: by metallurgical microscope Nikon MA200 and scanning microscope Quanta 200 in the low vacuum mode. To identify the structure of the obtained layers the X-Ray radiography was used. Additionally properties of the composites was studied using impedance spectroscopy. The method of impedance spectroscopy allows one to connect the measured frequency characteristics with the physical structure of tested material and the alternations in the structure. This method has been used by the authors to determine the properties of plasma layers deposited on a polypropylene nonwoven fabric (Jaroszewski et al., 2010a; Pospieszna et al., 2010; Pospieszna et al., 2010b)
Modeling of overhead transmission lines with line surge arresters for lightning overvoltages
Full text linkLightning is one of the most significant source of overvoltages in overhead transmission lines. The lightning overvoltages could lead to failure of the devices connected to the transmission line. A fundamental constraint on the reliability of an electrical power transmission system is the effectiveness of its protective system. The role of the protective system is to safeguard system components from the effects of electrical overstress. Surge arresters are an important means of lightning protection in distribution systems. Therefore, it is necessary to analyze influence of such overvoltages in order to applying the line surge arrester for improving the reliability of transmission line system. The method used to analyze the increase in voltage due to lightning was done by using the ATP/EMTP software This paper is aimed at analyzing the lightning performance improvement of a transmission line after installing line surge arresters
History of lightning protection in Poland
No full textThe history of lightning protection in Poland and its short overview in the world is given. The first lightning rod in Poland were installed in Rawicz by Christian Gottlob Stiegler and in Dęblin by Jowin Fryderyk Bystrzycki both in 1783. The third lightning rod was mounted next year on the king castle in Warsaw. The book Sposób Ubezpieczający śycie i Majątek od Piorunów (The manner protecting the live and real estate from lightning) published in 1784 by priest Josef Osiński is treated as a one from the first electrical works in Poland. The most meritorious polish researcher of lightning in XX century was Prof. Stanisław Szpo
Creeping discharges
No full textCreeping discharges were studied on a cylinder model insulator. The discharge theory worked out by Toepler was presented first. The transfer criterion of thread discharges into creeping discharges was explained. The flashover voltage of bushing was compared with the flashover voltage of post insulator. The effect of polarity reversal at lightning impulses was found
Impulse flashover of strings containing standard and semi-conducting disc insulators
Full text linkInsulators with semi-conducting glazes (SCG insulators) are used mainly in heavily polluted areas. Besides the well known application under such conditions, SCG insulators can be used for voltage upgrading in long strings supporting or replacing the grading electrodes. The paper describes electrical properties of SCG insulators including a one year-test carried out in a pollution test station. Measurements of the flashover voltage of insulator strings containing standard and SCG insulators under lightning and switching impulses are shown. The positive switching impulse flashover voltage of a string including 7 units of SCG insulators is about 19% higher than this of a string containing 7 standard insulators. The switching impulse flashover voltage of a string including 5 standard insulators and 5 SCG insulators is about 10% higher than of a string with 10 standard insulators. Under lightning impulse stress only small difference in flashover voltage is measured
Model of medium voltage metal oxide arrester
Full text linkModelling of MOA is necessary for many reasons and a considerable progress in this field has been made. It is very difficult to construct a general model of high voltage ZnO arrester in which we take into account a lot of factors, e.g. stray capacitance's, pollution, thermal processes, the response to fast transients and harmonics. Construction of a limited model for special purposes only seems to be a better idea. But even for such a limited, apparently simple task, a few models of medium voltage arrester in the low leakage region were proposed in literature. A method to determine the lumped parameters of an equivalent circuit model is proposed. The method is based on the published data which allows determination of the lumped parameters of an equivalent circuit model for the low leakage region. For the high leakage region the parameters were chosen based on our own experiments
Condition Monitoring & Fault Diagnosis System for Offshore Wind Turbines
Full text linkDue to the technological development, the electronic power progress and economic stake, through the use of Wound Rotor Induction Motor (WRIM) has taken more and more places in different domains (transport, energy production, electric drive..,) thanks to their robustness, efficiency and lower costs. Despite the performed work researches and the improvement that has been brought, these machines still remain the potential seats of failures both in stator and rotor levels. Consequently, WRIM faults detection is currently one of the centres of interest of several researches of both academic and industrial laboratories. In fact, this article addresses this problem by the use of Principal Components Analysis (PCA) for faults detection in Offshore Wind Turbine Generator (OWTG). An accurate analytic modelling of healthy and faulted OWTG is suggested to perform the data matrix needed for PCA method. Tests were achieved using a numeric simulator on Matlab/Simulink software. Analysis of OWTG simulation proves the efficiency of PCA method. Several simulation results will be presented and discussed
Fault Location in Power Networks with Mixed Feeders using the Complex Space-Phasor and Hilbert-Huang Transform
No full textThe paper introduces a practical approach to power system fault location in power networks using advanced fault signal processing. The three-phase fault voltages are converted to the vector of absolute values of its complex-space phasor. This vector represents fault travelling wave and it is further processed for fault location finding with the Hilbert-Huang transform. The simulation results, including single line to ground faults, faults in mixed feeders and high-impedance arcing faults, confirm the accuracy and practical applicability of the proposed approach