http://zet10.ipee.pwr.wroc.pl Electrical Engineering Repository latest documents pl Fri, 24 May 2013 12:41:14 CEST CDS Invenio 0.92.1 zbigniew.leonowicz@pwr.wroc.pl 1440 http://zet10.ipee.pwr.wroc.pl/img/cds.png http://zet10.ipee.pwr.wroc.pl Search this site: p http://zet10.ipee.pwr.wroc.pl/search http://zet10.ipee.pwr.wroc.pl/record/438In recent years we can observe rapid increase in the number of sources which generate the electromagnetic (EM) fields (like radio broadcasting, television, radio communication, cellular telephony), continuously extending range of applied frequencies and increasing power generated by those sources. The contemporary requirements of civilization lead to the necessity of applying more and more effective methods for shielding of electromagnetic fields, which take into account the specificity of modern devices and systems and the health of people living and working in the vicinity of these fields. Therefore, the choice of suitable materials for the shields and their appropriate arrangement have an essential meaning. Nowadays, one of the most dynamically developing areas of application for the new materials is the electromagnetic compatibility, more precisely development new materials for electromagnetic fields shielding. Content: Chapter 1 The basics of the electromagnetic shielding Janina Pospieszna Chapter 2 Electromagnetic shielding of lightweight and flexible composites Mariusz Ozimek, Maciej Jaroszewski, Jan Ziaja and Wiesław Wilczyński Chapter 3 Conducting polymers for electromagnetic interference (EMI) shielding Mahnaz M. Abdi, Anuar Kassim, Mehdi Jonoobi and Lim Hong Ngee Chapter 4 Polymer based nanocomposites for electromagnetic interference (EMI) shielding Veena Choudhary, S.K. Dhawan and Parveen Saini Chapter 5 Effects of changes of permissible values of the magnetic field intensity in the environment on the scope of protecting against the health effects of the 50 Hz electromagnetic fields Marek SzubaJaroszewski, MMon, 04 Feb 2013 21:02:48http://zet10.ipee.pwr.wroc.pl/record/438 http://zet10.ipee.pwr.wroc.pl/record/437The degradation of ZnO elements under AC or DC operating voltage and impulse current is described.Chrzan, K LTue, 08 Jan 2013 14:29:59http://zet10.ipee.pwr.wroc.pl/record/437 http://zet10.ipee.pwr.wroc.pl/record/436The long rod insulators with different profiles were shown. In the past the leakage distance was gradually increased because of increased pollution severity. Due to environmental improvement last years in Europe, the new insulator types with a short leakage distance can be applied now.Chrzan, K LTue, 08 Jan 2013 14:19:12http://zet10.ipee.pwr.wroc.pl/record/436 http://zet10.ipee.pwr.wroc.pl/record/435This paper gives the historical background of 250 year old question: should the Franklin rod tip be sharp or blunt ? The earlier works, the new field results from USA and own laboratory experiments are presented. The switching impulse tests were carried out with two different shapes of high voltage electrodes: rod or sphere and without additional dc bias voltage. In the arrangement with rod as high voltage electrode the smaller breakdown voltages were measured with sharp grounded electrode with negative impulse polarity. At the positive polarity the breakdown voltages do not depend on the shape of grounded electrode. The tests with spherical high voltage electrode showed, that breakdown voltages under negative polarity are practically the same for three different grounded electrodes. In spite of that, the remarkable differences in time to breakdown were noted.Chrzan, K LTue, 08 Jan 2013 14:05:06http://zet10.ipee.pwr.wroc.pl/record/435 http://zet10.ipee.pwr.wroc.pl/record/434The effect of fires on the flashover voltage of power lines has been investigated in Brazil, Mexico, Canada, USA, South Africa, Australia and Poland. The flashover voltage of outdoor insulation is reduced by hot air, conductive flame and colloidal smoke. The paper explains shortly the fire induced flashovers of air gaps. The safety aspect for firemen and other people caused by step potentials at the arcing point was described. The published works about deterioration of aluminum stranded conductors steel reinforced (ACSR) and detection of fire induced corona are briefly reported.Chrzan, K LTue, 08 Jan 2013 14:01:16http://zet10.ipee.pwr.wroc.pl/record/434 http://zet10.ipee.pwr.wroc.pl/record/433Frequency-tuned resonant test systems are, meanwhile, state-of-the-art for on-site testing and diagnostics on high-voltage plastic-insulated cables. The paper describes the basic idea and relations of this particular type of test systems. After experience with several commissioned systems, the technical data, especially the specific weight and the performance have been further optimised. A specially adapted diagnostic technique has been developed for the application together with test systems of variable fre-quency. Basic research on cable samples with different failures has obviously qualified AC voltage near to the power fre-quency to be the optimum test voltage wave shape. Resulting from these it is logical to apply this test voltage shape also on medium-voltage cable systems. An example is also introduced in this paper.Hauschild, W.Tue, 08 Jan 2013 13:56:00http://zet10.ipee.pwr.wroc.pl/record/433 http://zet10.ipee.pwr.wroc.pl/record/432Although the modern metal oxide elements are resistant to degradation caused by continuous operating voltage the degradation or destruction caused by current impulses, especially lightning currents, is still a serious problem. This phenomenon was the subject of the current study where single zinc oxide elements and 6 kV arresters manufactured in Poland were tested with 8/20 ms impulse currents. During our investigation the temperature and changes in current-voltage characteristics were recorded. These results indicate that even varistors that were stressed with high currents could reach saturation state in which following impulses did not cause any further degradation. Both single varistor elements and 6 kV arresters showed only little ageing if stressed with 0,5 kA impulses. The 6 kV arresters composed of 10 elements were able to withstand smaller currents than single varistors. Our findings suggest that a combination of sparking effects and less than optimal contacts are the cause varistor degradation.Chrzan, K LTue, 08 Jan 2013 13:49:51http://zet10.ipee.pwr.wroc.pl/record/432 http://zet10.ipee.pwr.wroc.pl/record/431This paper gives an overview of the acid rain problem in Europe, Poland and the Polish province of Silesia. The relationship between pH and water conductivity is shown. Different reactions between acid rain and particles are presented. Effects of temperature on the conductivity of H2SO4 solutions were studied. Finally, pollution flashover voltages and leakage currents on a model insulator that was contaminated with H2SO4 and other solutions were measured.Chrzan, K LTue, 08 Jan 2013 13:44:54http://zet10.ipee.pwr.wroc.pl/record/431 http://zet10.ipee.pwr.wroc.pl/record/430Varistor overtemperature above the ambient is an important state parameter of metal oxide surge arresters. The temperature monitoring using passive SAW sensors enables realisation of a surge counter function, an energy monitor, monitoring of electrical ageing and pollution stress. For temperature measurements during pollution tests of metal oxide arresters the not so advanced, TINY TALK sensors could be used. This method of temperature measurement was also applied in the field for temperature control of arresters tested at the pollution station near Głogów, Poland. The preliminary results during the first year of monitoring are presented and compared with results of similar measurements conducted in Germany close to the seacoast.Chrzan, K LTue, 08 Jan 2013 13:38:38http://zet10.ipee.pwr.wroc.pl/record/430 http://zet10.ipee.pwr.wroc.pl/record/429Flashover voltage of uniform and non-uniform polluted metal oxide arresters and their porcelain housings without internal parts was measured.Chrzan, K LTue, 08 Jan 2013 13:31:35http://zet10.ipee.pwr.wroc.pl/record/429