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Producers of windings of electrical machines require totally fixed winding after impregnation. They require not only high mechanical strength of impregnation resin, but even completely filled winding by impregnating resin. Then is winding more compact and provide better endurance to voltage spikes when speed is controlled by frequency converter. Article compares properties of thixotropic resin and...
This paper deals with the analysis of perspective and environmentally-friendly electrical insulating liquids for electrical engineering. In the experimental part, dielectric properties of the most common vegetable oils were analyzed and compared with those of their constituents converted from triglyceryl esters to methyl esters: soybean oil, sunflower oil, rapeseed oil, peanut oil, cottonseed oil...
The article deals with the issue of delay lines on the basis of surface acoustic waves for the application in single-mode oscillators. Based on the theoretical analysis concrete delay lines are proposed.
This contribution is dedicated to the issue of increasing of operational safety, reliability and diagnostics of cables and wires in the energy sector. The selected factors which need to be considered when choosing the methods of diagnostics of cables and wires are highlighted. It informs and extends the knowledge about the issue for responsible persons of individual operations of electrical power...
The authors want to introduce the different voltage wave shapes which are currently used for offline partial discharge diagnosis and their impact on partial discharge parameters. A literature survey gives a brief overview among several respective recent and past publications. The main scope of this paper is about the influences of the frequency of the test voltage on partial discharge defects. Selected...
Amorphous silicon carbide in various forms, thin films or bulk structures, is a longer period used in microelectronics, power electronics, sensors and mechanical engineering. Thin films of n-doped amorphous silicon carbide (a-SiC:H) in combination with crystalline silicon representing heterostructure for the solar cells were object of this study. DC and AC measurements and subsequent analyzes were...
The paper deals with the identification of the furnace power transformer state. The furnace transformer was subjected to several prophylactic measurements. Their results are summarized and described in the article. In spite of that it is not a standard power oil transformer there was selected appropriate procedures and practices with respect to international standards. Identified failure was confirmed...
The high voltage diagnostics must follow the actual state of the industry devices and the problems related to diagnostics methods. One of the diagnostic methods necessary to be solved at this time is the partial discharge detection, diagnostics and analyses in HVDC systems. There is no standardized method for detection of partial discharges in HVDC systems supplied with DC voltage. The presented study...
Article presents theoretical and experimental analyses of possible effect of short-circuit forces on the transformer windings. The first part of the article is focused to the establishment and activity radial and axial forces during short circuit. It shows dimensions, direction and of course caused mechanical stress. Equation shows basic dependencies of these mechanical forces created in the transformer...
ZnO based surge protective devices have been made and characterized both morphological (SEM microscopy and interferometry) and electrical (U/I characteristic and dielectric spectroscopy). SEM microscopy analyzes revealed that the disks of metal oxides sintered at 12000C present a homogeneous distribution of ZnO grains, without pores and well-defined intergranular limits. It was also found that Ag...
Demands on current electrical insulating systems have increasing trend toward tolerance to environmental safe conditions. This trend of course subsequently requires finding a new way in the field of application of materials compatible with the surrounding environment, e.g. easy biodegradable. This applies particularly for electrical insulating liquids used in distribution transformers since their...
In order to determine the durability of polymer coatings using investigation techniques based on X-rays diffraction and combined techniques for thermal analysis (TG-DTA-DTG), were determined the changes of structure and of their thermo-oxidative characteristics (6 different paint types having different characteristics) after exposure to UV radiation (60W/m2 in range of 300–400nm). The experimental...
Paper deals with the analysis of thermal processes in oil power transformers. By means of the mathematical analysis and experimental measurements it is possible to diagnose of distribution oil transformers in terms of mechanical strength of winding. Analysis of warming at varying loads is very importance, since allows determining the load capacity and overload of the transformer under various operating...
Nowadays, the LED technology is still more and more forthcoming technology. LED luminaires slowly replace traditional luminaires because their energy consuming in comparison with light output expressed by means of luminous efficacy lm/W increase to higher values what certainly save electrical energy consumption. At the present the popular way traditional light sources are replaced by LED retrofit...
This article presents the experience of partial discharges monitoring inside high voltage oil power transformers under operation obtained in two last years. The presence of partial discharges inside paper insulation is one of the crucial phenomena in high voltage transformers influencing their lifetime. The applied ultrahigh frequency measurement system enables not only to detect partial discharges...
In this paper a review is given of computing procedures for evaluation of the absorption current and recovery voltage measurements in dielectric systems. The method based on the recovery voltage measurement is treated in details and compared with some selected methods used in this field. All computing procedures were applied to the dielectric data acquired on aged PVC cables. In the final assessment,...
Solar modules under ordinary working condition are exposed to amount of degradation factors which deteriorate their properties. The most important degradation of PV modules during operation are optical, electrical and thermal degradation. The result of these factors is performance degradation of the modules, or even can caused their fault. It is important to find the cause of the fault and its timely...
This work deals with the models for modelling various kinds of discharge activity in the insulation systems. Models represent the failures in insulation systems as well as simultaneous action of these failures in the insulation system. The first part of the work deals with the distribution of types of partial discharge in respect of their displays when measuring the phase distribution of apparent...
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