Pulse induced failures in bi-axially oriented polypropylene capacitors: Experimental investigation

An experimental study of the absorption of high energy pulses in bi-axially oriented polypropylene (BOPP) capacitors is reported in the paper. The pulse handling performance test is used to identify the material or mechanical problem characteristics developed in the capacitor. The experiments are focused on samples of different film metallization and crystallinity and the results are compared in terms of current pulse handling capability as well as the level of impulse breakdown voltage. To assess the impulse handling capability, the proposed deterioration parameter is the number of absorbed pulses and Weibull cumulative probability of failure is presented. Experimental findings reveal specific types of failure development through the gradually elevated energy pulse test. The observed failures are either accidental, or progressive and they are located at the electrode terminal, or in the capacitor volume. The accidental failures are accompanied by no significant change in the additionally measured capacitance and loss factor, however, the characteristic fault location is in the capacitor volume. The progressive failure is caused by the gradual degradation of the insulating material where both the capacitance and the loss factor give a preliminary information of the impending damage, dominantly occurring at the electrode terminals. Possible reasons accounting for the certain failure type are discussed

Analýza I(t) závislosti počas štrukturalizácie magnetických nanočastíc v magnetickej kvapaline

The previous experiments were devoted to observation of structuralization processes in magnetic fluids in dependence on time at constant value of homogenous magnetic fields. The average value of clusters of magnetite particles reached stabilized length that depended on volume concentration of magnetite particles in magnetic fluids. This work is oriented on observation and explanation of anomaly on dependences of current intensity (I) on time (t) in magnetic fluids with help of observation of structuralization processes results at respecting of space charge. This anomaly was detected at upper concentration of magnetite particles (>1%) on I(t) dependences in given time region that characterizes the change of energetic conditions in magnetic fluids

Monitorowanie zanieczyszczenia środowiska za pomocą cienkich elektrod metalowych przygotowanych przez fizyczne osadzanie z fazy gazowej

This work is focused on environmental pollution monitoring utilizing thin metal electrodes on glassy/ceramic substrates prepared by physical vapour deposition. Besides others, it is well known that environmental pollution on electrical insulation is one of the problems faced by distribution utilities and electricity transmission system. Due to this reason there is a need to deal with monitoring of environmental pollution as it strongly influences their capability to withstand the high-voltage stress without the breakdown. It is the aim of present work to propose new system for environmental pollution monitoring based on application of extra-thin metal electrodes. The influence of morphology and chemical composition of pollutants on the surface resistance and conductivity of selected insulators is also discussed.Artykuł dotyczy monitorowania zanieczyszczenia środowiska za pomocą cienkich elektrod metalowych na szklanych/ceramicznych podłożach przygotowanych przez fizyczne osadzanie z fazy gazowej. Widomym jest, że zanieczyszczenie środowiska odpadami izolacji elektrycznej jest jednym z problemów, przed którymi stoją firmy dystrybucyjne i system przesyłu energii elektrycznej. Z tego powodu istnieje potrzeba monitorowania zanieczyszczenia środowiska, ponieważ ma to duży wpływ niezawodność sieci wysokiego napięcia i jej awaryjność. Celem przedstawionych prac jest zaproponowanie nowego systemu monitorowania zanieczyszczenia środowiska w oparciu o zastosowanie bardzo cienkich elektrod metalowych. Omówiono także wpływ morfologii i składu chemicznego zanieczyszczeń na rezystancję powierzchniową i przewodnictwo wybranych izolatorów

Locomotor Activity of Ixodes ricinus Females in 900 MHz Electromagnetic Field

Mobile telecommunications technologies have become an indispensable part of people’s lives of all ages around the world. They affect personal life and social interactions and are a work tool in the work routine. Network availability requirements and the quality of the Internet connection are constantly increasing, to which telecommunications providers are responding. Humans and wildlife live in the permanent presence of electromagnetic radiation with just a minor knowledge of the impact this radiation has. The aim of our study was to investigate the effect of a 900 MHz electromagnetic field (EMF) on the locomotor behavior of female Ixodes ricinus ticks under laboratory conditions. Experiments were performed in the radiation-shielded tube (RST) test and radiation-shielded circular open-field arena placed in an anechoic chamber. Altogether, 480 female I. ricinus ticks were tested. In the RST arena, no differences in preference for irradiated and shielded parts of experimental modules were observed; in the open-field arena, the time spent and the trajectory passed was significantly longer in the part exposed to the EMF

Dielectric relaxation response of electrical insulating liquids under different natures of thermal stress

This study focuses on the dielectric relaxation response of insulating liquids based on mineral oil and synthetic ester in a thermal field.The research also offers the dielectric relaxation response of the magnetic nanofluid based on the investigated synthetic ester. The reason for investigating the synthetic ester-based nanofluid is that the temperature characteristics of the mineral oil-based magnetic nanofluid have already been investigated in several studies. Nanofluid based on synthetic ester is not sufficiently explored in this regard. The behavior of insulating liquids in the thermal field is divided into two parts. The first one points to the effect of temperature on the dielectric properties of the insulating liquids in the range from 293.15 K to 363.15 K. The insulating liquids show relaxation processes in the investigated frequency spectrum (1 mHz–3 kHz), which are dependent on temperature. The logarithm of the relaxation frequency decreases linearly with decreasing temperature according to Arrhenius' law. Mineral oil has the highest value of activation energy. In the second part, the results are focused on the influence of the rate of temperature increase on the dielectric parameters and moisture content of the investigated fluids. A slower increase in temperature causes an increase in polarization losses and a reduction in the distribution of relaxation times. In the case of base oils, also a reduction in activation energy. The change in the heating rate of the investigated liquids does not affect their moisture. Changes in dielectric parameters are not caused by changes in the moisture of insulating liquids, but by thermal aging

Frequency-Dependent Dielectric Spectroscopy of Insulating Nanofluids Based on GTL Oil during Accelerated Thermal Aging

Improving the dielectric properties of liquid-insulating materials is a current problem in research into the insulation system of a power transformer. Modern optimization of insulating liquids involves the potential use of unique synthetic esters enriched with nanoparticles. This study presents the results of the dielectric response of liquefied gas-based (GTL) insulating liquids during accelerated thermal aging. The dielectric relaxation spectroscopy method was used in the frequency domain to point out power losses as an imaginary part of a complex electric modulus. The relaxation spectra express the validity of applying this complex dielectric parameter. The polarization processes of the base oil alternately change position in the low-frequency band during thermal aging. Fullerene nanofluid undergoes three phases of dielectric loss changes during thermal aging. In the case of magnetic nanofluid, the effect of electric double-layer polarization disappeared after 500 h of thermal aging. It was found that with the gradual increase in the thermal aging time, there is no gradual increase in the dielectric losses investigated in the measured frequency spectrum. This study shows that the concentration of the two types of nanoparticles independently causes a different dielectric response to an applied AC electric field in the GTL base fluid

Magnetodielectric anisotropy in magnetic fluids in temperature interval from 20 °C to 80 °C

Substitution of transformer oil as insulator medium by magnetic fluid in transformers requires observation of electric properties of magnetic fluids at temperatures higher than 20 °C. That´s why important physical quantities were measured at temperature in interval from 20 °C to 80 °C. The magnetodielectric anisotropy was studied at the same temperature region. Two important quantities have been measured: specific electric conductivity and dielectric breakdown strength of magnetic fluids at volume concentrations from 0,185 % to 2 %. So the behavior of magnetic fluids as insulator medium could be observed at working conditions of transformers

Dielectric Properties of Electrical Insulating Liquids for High Voltage Electric Devices in a Time-Varying Electric Field

The motivation to improve components in electric power equipment brings new proposals from world-renowned scientists to strengthen them in operation. An essential part of every electric power equipment is its insulation system, which must have the best possible parameters. The current problem with mineral oil replacement is investigating and testing other alternative electrical insulating liquids. In this paper, we present a comparison of mineral and hydrocarbon oil (liquefied gas) in terms of conductivity and relaxation mechanisms in the complex plane of the Cole-Cole diagram and dielectric losses. We perform the comparison using the method of dielectric relaxation spectroscopy in the frequency domain at different intensities of the time-varying electric field 0.5 kV/m, 5 kV/m, and 50 kV/m. With the increasing intensity of the time-varying electric field, there is a better approximation of the Debye behavior in all captured polarization processes of the investigated oils. By comparing the distribution of relaxation times, mineral oil shows closer characteristics to Debye relaxation. From the point of view of dielectric losses at the main frequency, hydrocarbon oil achieves better dielectric properties at all applied intensities of the time-varying electric field, which is very important for practical use