CALCULATION OF TOWER SURGE IMPEDANCE WITH JORDAN’S EQUATIONS
+ Alberto De Conti, + Silvério Visacro and ++ Euler G. Silva
+ LRC – Lightning Research Center, UFMG – Federal University of Minas Gerais, Brazil
++ CEB – Companhia Energética de Brasília, Brazil
Proceedings of XIX International Conference on Electromagnetic Disturbances, Bialystok, Poland, September 23–25, 2009, pp. 35–40.
Abstract: In this paper, lightning strikes to two different tower configurations are investigated with new surge impedance equations derived from Jordan’s theory. An electromagnetic model is used to test the validity of the obtained results and comparisons are made with equations traditionally used in the literature. The good agreement between the results obtained with the proposed equations and the electromagnetic model used as reference suggests that in certain conditions the transmission line modeling of towers can still be a useful tool for estimating lightning strikes to tall objects, at least from an engineering perspective.
Index terms: Lightning, tower modeling, surge impedance.
RELATION BETWEEN THE ELECTRODE SURFACE CONDITION AND RADIATED EM FIELD INTENSITY DUE TO MICRO GAP DISCHARGE AS THE LOW VOLTAGE ESD
+ Ken Kawamata, ++ Shigeki Minegishi and +++ Osamu Fujiwara
+ Hachinohe Institute of Technology, Hachinohe Japan
++ Tohoku Gakuin Univ., Tagajo Japan
+++ Nagoya Institute of Technology, Nagoya Japan
Proceedings of XIX International Conference on Electromagnetic Disturbances, Bialystok, Poland, September 23–25, 2009, pp. 91–93.
Abstract: The micro-gap discharge shows a very fast transition duration of about 32 ps or less. In addition, the breakdown field strength was examined to corroborate the very fast transition durations of about 32 ps. Also, a relationship between breakdown field strength and radiated electromagnetic field intensity was examined in the experimental study. As a consequence of the experiment, the breakdown field strength was very high; about 80 MV/m in low voltage discharging of below 350 V. The average radiated electromagnetic field intensity is proportional to the breakdown field strength in the discharge gap. And so, the electrode surface effect was confirmed that the received electromagnetic field intensity has a cyclic variation with the cleaning of electrode surface. The radiated electromagnetic field intensity suddenly increased just after the cleaning.
Index terms: Micro-gap discharge, low voltage discharge, ESD, radiated electromagnetic field intensity, electrode surface effect.
MICROWAVE RADIATION SHIELDING EFFECTIVENESS OF COMPOSITE LIQUID-CONTAINING MATERIALS IN DEPENDENCE ON HYGROSCOPIC PROPERTIES OF THE COMPOUNDS
Natallia Kolbun, Tatiana Pulko, Leanid Lynkou
Belarusian State University of Informatics and Radioelectronics 6, P. Brovki Str., Minsk, Belarus, 220013
Proceedings of XIX International Conference on Electromagnetic Disturbances, Bialystok, Poland, September 23–25, 2009, pp. 98–103.
Abstract: Composite shielding materials based on capillary-porous matrixes impregnated with liquid solutions possessing resistive and dielectric losses for microwave electromagnetic radiation (EMR) are developed. Meeting the objectives the EMR attenuation obtained by the proposed materials can be higher than 12–19 dB, with the reflection level lower than – (2–8) dB in the frequency range 8 GHz to 11.5 GHz. A Study of the liquid content dynamics upon the surface of a non-sealed sample revealed that synthesis of 40–60% mass solution results in stabilization of liquid content of capillary-porous matrix at the level not lower than 100–108% mass of the initial value.
Index terms: Composite shielding material, electromagnetic radiation, absorption.
ELECTROMAGNETIC SHIELDS WITH MOISTURE LOADED NATURAL CARBONACEOUS POWDERY FILLERS
Belarusian State University of Informatics and Radioelectronics
Proceedings of XIX International Conference on Electromagnetic Disturbances, Bialystok, Poland, September 23–25, 2009, pp. 119–120.
Abstract: The possibility of producing cost-effective and weight-effective electromagnetic shields by using powdery shungite, taurite and charcoal dispersed in polymer binder is shown. They have the value of transmission coefficient from –10 dB to –24 dB.
Index terms: Carbonaceous materials, shungite, taurite and charcoal, electromagnetic shields.
SIMULATION OF LOOP CURRENTS INDUCED BY LIGHTNING CURRENTS OF DIFFERENT WAVEFORMS
Tomasz Maksimowicz, Karol Aniserowicz
Bialystok Technical University
Proceedings of XIX International Conference on Electromagnetic Disturbances, Bialystok, Poland, September 23–25, 2009, pp. 141–144.
Abstract: Simulation examples of loop currents induced by lightning strokes are presented. Differences which occur while using different formulas describing lightning current waveforms have been revealed. Results of using popular equations: double exponential and the one proposed in international standards, for different types of cloud-to-ground lightning strokes, are presented.
Index terms: Lightning, induced current, simulation.
CURRENT TRAVELLING WAVES IN MODELING OF LIGHTNING STRIKE TO A COMMUNICATION TOWER USING A VOLTAGE SOURCE
Bialystok Technical University
Proceedings of XIX International Conference on Electromagnetic Disturbances, Bialystok, Poland, September 23–25, 2009, pp. 157–160.
Abstract: The paper presents an analysis of the application of an ideal voltage source for numerical modeling of a direct lightning strike to a communication tower. Current travelling waves in the tower are of primary concern in this analysis since they strongly affect the total lightning current injected to the tower. A tower of 62 m height and a current wave-shape recommended for representation of subsequent return strokes are taken into consideration. The results of the analysis are presented as opposed to the results obtained using an ideal current source.
Index terms: Current travelling waves, direct lightning strike, communication tower, numerical modeling.
TIME-FREQUENCY DOMAIN ANALYSIS OF OPERATION OF SURGE PROTECTIVE DEVICE IN BUILDING ELECTRICAL INSTALLATION
Bialystok Technical University
Proceedings of XIX International Conference on Electromagnetic Disturbances, Bialystok, Poland, September 23–25, 2009, pp. 161–165.
Abstract: Numerical analysis of nonlinear operation of surge protective devices in large electrical and electronic installations during lightning strikes often requires also taking into account electromagnetic phenomena. Computer simulation methods make possible analyses of various electromagnetic threats. However, there is no single program which allows for direct simulation of all these effects to a desired extent. The paper presents a combined time-frequency domain approach for analysis of the operation of surge protective devices in the electrical installation of a building.
Index terms: Electromagnetic phenomena, nonlinear phenomena, numerical analysis, surge protective device.
CONSIDERATION OF LIGHTNING PROTECTION ON MEDIUM VOLTAGE UNDERGROUND CABLES WITH SHIELD WIRE
Michael A. Omidiora and Matti Lehtonen
Electrical Engineering Department, Helsinki University of Technology (TKK), Finland
Proceedings of XIX International Conference on Electromagnetic Disturbances, Bialystok, Poland, September 23–25, 2009, pp. 230–236.
Abstract: Medium Voltage (MV) underground cables are more costly to maintain than any other type of power line. They are mostly used as connections from generating plants and substations to serve the loads for the life of the installation. They are also the predominant feeder type in urban distribution networks and are increasingly being considered even in rural MV networks. Lightning strokes to ground can cause overvoltage build-up or severe damage to any underground cables in their proximity. Therefore, necessary care must be taken to prevent the cables from this environmental disturbance. Lightning protection of medium voltage underground cables is studied in this paper. Simulation of an underground cable with a shield wire is made to investigate protection against lightning discharges around the cable. The performance of the protection scheme is investigated with the Finite Element Method (FEM) considering different soil structures and resistivities. Finally, the failure rates of the underground cable with and without a shield wire are compared based on the real lightning statistics in Finland. It is expected that the results will further understanding of the need for lightning protection on medium voltage underground cables.
Index terms: Shield wire (SW), FEM (finite element method), lightning discharge, ground flash density (GFD), electric field intensity, underground cable (UC), overvoltage, soil resistivity.
MEASUREMENT OF THE SHIELDING EFFECTIVENESS OF SLOTTED ENCLOSURE WITHIN 30–1000 MHz RANGE USING GTEM CELL
Bialystok Technical University, Faculty of Electrical Engineering, POLAND
Proceedings of XIX International Conference on Electromagnetic Disturbances, Bialystok, Poland, September 23–25, 2009, pp. 255–258.
Abstract: Shielding effectiveness measurement of a small slotted enclosure model using a comb generator and GTEM cell within range from 30 to 1000 MHz has been described. Comparison with results of numerical simulation calculated with a WIPL-D package has been presented.
Index terms: Shielding effectiveness, slotted enclosure, GTEM cell, comb generator.
ANALYSIS OF SEPARATION DISTANCES BETWEEN LPS AND DEVICES ON THE BUILDING ROOF
Andrzej W. Sowa
Białystok Technical University
Proceedings of XIX International Conference on Electromagnetic Disturbances, Bialystok, Poland, September 23–25, 2009, pp. 283–288.
Abstract: Lightning protection of structures very often requires the information about a minimum separation distances between the external lightning protection system LPS or elements with lightning currents and devices on the building roof. In analysis of such distances one of important information is the lightning current distribution in elements
Index terms: Separation distance, lightning discharge, lightning current distribution.
INVESTIGATION OF THE EARLY PHASE OF LIGHTNING CURRENTS AS SOURCE OF ELECTROMAGNETIC DISTURBANCE
Visacro Silvério, Murta Vale Maria Helena, Teixeira André M.N.
LRC – Lightning Research Center – UFMG Federal University of Minas Gerais Av. Antonio Carlos 6.627 Pampulha – 31270.901 – Belo Horizonte – BRAZIL
Proceedings of XIX International Conference on Electromagnetic Disturbances, Bialystok, Poland, September 23–25, 2009, pp. 314–317.
Abstract: Experimental current waves of first negative downward lightning strokes measured at the base of a short instrument tower are presented. The features of such waveforms are discussed specifically in relation to the early stage preceding the flow of the return current, including the comparison to the features of attempted leaders. The pulses of these stages were evaluated as a non-relevant source of electromagnetic disturbance.
Index terms: Lightning currents, early phase of lightning currents, electromagnetic disturbance.
MODELLING OF ELECTRIC DISCHARGE EFFECT ON FERRO-CONCRETE
+ Juozas Žvinys, + Kazimieras Juzenas, ++ Rasa Kandrotaite Janutiene, +++ Saulius Gudzius, ++++ Vilandas Cˇeslevicius
+ Department of Manufacturing Technologies, Kaunas University of Technology
++ Department of Engineering Graphics, Kaunas University of Technology
+++ Department of Electric Power Systems, Kaunas University of Technology
++++ Department of Building Structures, Kaunas University of Technology
Proceedings of XIX International Conference on Electromagnetic Disturbances, Bialystok, Poland, September 23–25, 2009, pp. 338–341.
Abstract: Influence of electric discharges on microstructure of armature steel was investigated. The studied samples were made of a reinforced concrete and affected by simulated lightning discharges. Metallographic analysis applying optical microscope LMA combined with video camera YCH15 was carried out. Pictures of the affected structure were also picked out by an electron scanning microscope SEM EVO 50 as well using a secondary electron detector SE. Changes of the material structure showed possibilities to model the impact of natural lightning on steel or steel reinforced concrete and analyze their properties.
Index terms: Lightning, electric discharge, steel, microstructure, ferro-concrete, armature, failure. EMC