Wrocław University of Science and Technology
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Dielectric characterization of electromagnetic composite barrier materials with plasma layers on nonwoven fabrics
Full text linkComposite materials are becoming more widely used in the technique of shielding electromagnetic field. Among these materials, textile materials with modified surfaces are of growing importance. Among them we can distinguish nonwoven fabrics coated with conductive plasma layers which are responsible for the phenomenon of reflection and attenuation of electromagnetic wave. These phenomena are related to the dielectric properties of composite material and its structure, in particular with the phenomena on the surfaces of interphase. In the paper, dielectric properties of plasma layer-polypropylene nonwoven fabric composite is reported. To determine these properties, measurements of transient and conduction currents were used. Dielectric response of the composite to an electric field is complicated, and is a function of both the physical structure of nonwoven and applied layer. Current measurements indicate the existence of build-in charge. Electrical conductivity is nonohmic but is controlled by several mechanisms, which include ion hopping, Schottky emission, space charge limited current, and Poole-Frenkel mechanism. The dielectric parameters vary depending on the morphology of substrate surface and on parameters of the plasma generating process
Dielectric characterization of EM composite barrier materials with plasma layers on nonwoven fabrics
Full text linkCurrently, one of the most extensively developing field of applications of composite materials, is engineering of materials used for shielding from electromagnetic fields. Composites of fabric materials with thin plasma layer can be used as shield for protection of people or electronic and electric power devices against of disadvantageous impact of electromagnetic fields. In the case of composite material containing conductive layer, conductive connection of the layer units is not necessary, although such connection reinforces screening properties. The capability of composite materials to shield electromagnetic fields are coherently associated with their dielectric properties - the response of a dielectric to an electric field is represented by its dielectric and electrical properties. The nature of the transient currents and conduction current are generally regarded as manifestation of different dielectric and electrical processes can be explained in terms of Jonscher universal dielectric theory. These phenomena are widely used in research the properties of plasma thin films. In the paper, dielectric properties of plasma layer-nonwoven fabric composite is reported
CONDUCTIVITY OF SOLID LAYERS POLLUTION ON SILICONE RUBBER IN HUMID AIR
Full text linkThe surface conductivity changes of solid layers deposited on silicone rubber under high humidity as a function of conditioning time in room conditions were studied. The measurements were carried out on flat samples in a glass hygrostat. It was shown that the surface conductivity of kaolin layer deposited on RTV-2 silicone decreases 4 times after 30 days of conditioning. However, the layer prepared from a natural dust from Glogow pollution test station shows different properties. The increase of layer hydrophobicity is related with the hygroscopicity decrease
PSPICE appliction for modelling of cap and pin insulator strings
Full text linkThe use of PSPICE program in HV engineering is shown. The calculation of voltage distribution along strings with standard cap and pin insulators, semi-conductive insulators and with both insulator types were performed. For calculation purpose a very known formula was used with constant stray capacitances. For PSPICE simulations the stray capacitances according to formulae proposed by Naito wee taken. Voltage measurement with a small air gap 10 mm sphere diameter were also carried out. The lightning and switching impulse flashover voltages were measured for both polarities
The role of gases in the pollution problem of outdoor insulators
No full textExperiments on the absorption of SO2 and CO2 by destilled water and by some electrolytic solutions have been conducted in laboratory and on the site. CO2 has been found to cause a decrease in the conductivity of alkaline solutions and an increase in that of CaCO3 and MgCO3 aqueous suspensions. The importance of the direct SO2 absorptions was proved as limited to the zones of extremely large concentrations of this gas in the air
Dielectric properties of polypropylene fabrics with carbon plasma coatings for applications in the technique of electromagnetic field shielding
Full text linkWithin the current work an attempt was made to use glow discharge low temperature plasma processing to produce carbon coatings on polypropylene unwoven fabric for electromagnetic field shielding applications. Layers were obtained from the gaseous phase (propane–butane). The influence of coatings on the dielectric buffer properties of modified fabrics was investigated. The Havriliak–Negami (HN) function precisely fits our relaxation data, hence the HN parameters could be used to control and optimize the processing of plasma coatings
Artificial aging of polymer insulation surface in a clean fog chamber and its evaluation
No full textIt is reported about electrical performance of room temperature vulcanizing (RTV) silicone rubber insulator coatings and epoxy insulators under accelerating aging in a clean chamber. The new type of solid layer used consists of a mixture of pure silicon dioxide and a filler agent (Perfil). The research was made to study the behaviour of light polluted indoor insulations under wet conditions (condensation). The current and partial discharges on the cylindrical model insulators were registered during the aging test. The evaluation of aging was made by measurement of contact nagle and voltage-current characteristics of condensed water deposits on the insulator surface. These tests were carried out in a given ambient conditions (relative humidity, temperature difference between insulator and air) as well as under impulse voltage. The measurements confirmed that the silicone coatings improve the indoor insulation performance under wet and pollution conditions
Intelligent wireless street lighting system
Full text linkWe propose an innovative wireless street lighting system with optimized management and efficiency. Wireless communication uses ZigBee-based wireless devices which allow more efficient street lamp system management, thanks to an advanced interface and control architecture. It uses many sensors to control and guarantee the optimal system parameters; the information is transferred point-by-point using ZigBee transmitters and receivers and is sent to a control terminal used to check the state of the street lamps and to take appropriate measures in case of failure. The system allows substantial energy savings with increased performance and maintainability
Výzkumy na jímačích ESE
Full text linkThe paper reviews about research of radioactive lightning rods carried out 30 years ago and about new measurements of early streamer emission terminals. Lightning damage on over 100 buildings equipped with ESE terminals in Malaysia and on one family house in Poland is reported. The main measure criterion was the breakdown voltage of the air gap consisted of the high voltage electrode (rod or plate) and a grounded radioactive or ESE terminal. These careful measurements show that the air gaps with ESE terminals have the same breakdown voltages as the air gaps with standard rods. Therefore the big protection zone of ESE terminals as claimed by their manufactures seem to be impossible
Assessing the benefits and risks of application of inverter drives in industry
Full text linkThis paper presents the impact assessment of converters installed in an industrial plant on the power quality in internal power grid of the plant. The analysis of real measurements showed that the installation of inverter drives, despite many benefits, as energy savings, that have been reported in the paper, can also cause many problems. We observed multiple issues related to failures in the control and automation systems that could be due to the interference generated by simultaneous operation of inverter drives