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Degradation Processes in Shield-Centring Elements of Surge Arresters

Papliński P., Śmietanka H., Ranachowski P., Ranachowski Zbigniew, Wieczorek K., Kudela S. jr.

Archives of Metallurgy and Materials

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2023

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Vol. 68, iss. 1

237--242

EN

This paper presents the results of testing samples of shield-centering elements from medium-voltage surge arresters. The elements were made of TSE glass textolite. The elements have been dismantled from different operated surge arresters, which were subjected to discharge currents (short-circuit currents) of different intensity and duration. The discharge currents led to degradation of the tested elements with various degrees of advancement. The degradation was investigated using microscopic methods and energy-dispersive X-ray spectroscopy (EDS). Changes in the content of elements of the surface of textolite materials - as the degradation progresses - were documented. It was found that high discharge current flows resulted in melting of the organic binder, epoxy resin, especially its surface layer. Partial charring and even burning of the resin was noticeable. Furthermore, it was found that with increasing degradation on the surface of the TSE laminate, the carbon and oxygen content, which are part of the organic resin, decreases. Simultaneously the amount of silicon, calcium and aluminium, which are present in the glass fibres, increases. The charring effect of the resin and the formation of conductive paths result in a decrease in the performance of surge arresters and their subsequent failure.

2

Procesy degradacji w elementach tekstolitowych ograniczników przepięć

Śmietanka Hubert, Wieczorek Krzysztof, Ranachowski Przemysław, Ranachowski Zbigniew, Brodecki Adam

Przegląd Elektrotechniczny

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2022

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R. 98, nr 10

216--220

PL

W pracy przedstawiono wyniki badań próbek tekstolitowych elementów osłonowo-centrujących z eksploatowanych ograniczników przepięć SN. Prądy wyładowcze (zwarciowe) o zróżnicowanym natężeniu i czasie trwania spowodowały w tworzywie elementów efekty degradacji o różnym stopniu zaawansowania, które badano z wykorzystaniem metod mikroskopowych i mikroanalizy rentgenowskiej EDS. Udokumentowano zmiany w składzie elementarnym (zawartości pierwiastków) warstwy wierzchniej tworzyw tekstolitowych - w miarę postępu efektów degradacji. Wykazano, że tworzywa te posiadają niewystarczającą odporność na skutki awaryjnej pracy ogranicznika przy jego zawilgoceniu, które jest konsekwencją rozszczelnienia osłony.

EN

The work describes degradation effects in the structure of textolite shield-centering elements of operated MV surge arresters. As a result of acting inner partial discharges of diverse duration and power - the material underwent degradation of different degree of advancement. Using microscopic research techniques and EDS analysis, the authors found and documented changes of structure and chemical composition of the material surface, with the increasing degree of degradation. It has been shown that textolite materials have insufficient resistance to the effects of emergency operation of the arresters after moisture ingress, which is a consequence of unsealing of the housing.

3

Thermographic and Electrical Test of Medium Voltage Surge Arresters

Lisowska-Lis Agnieszka

Measurement Automation Monitoring

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2019

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Vol. 65, No. 2

60--63

EN

The paper presents the results of a thermal test (conducted with thermographic camera, coupled with an electrical test) of medium voltage metal–oxide surge arresters. Surge arresters (for Uc=18 kV) were tested for the leakage current and surface temperature: for 5 minutes under state 50 Hz alternating voltage 18 kV. The surface temperature of the MOAs correlates with an increase in leakage current. The result shows that the 0.6 mA AC leakage current in the medium voltage metal–oxide surge arrester (18 kV) is above the stable operating point, and the loss of electrical power is higher than the effective heat dissipation in the arrester. After 5 minutes of high voltage impact U = 18 kV, the surface temperature of the surge arrester was (4.32±0.55) K higher than the initial temperature. The IR camera can be used to detect the faults of ZnO metal–oxide surge arresters that lead to an increase in surface temperature.

4

Determination of residual stress distribution in high strength aluminum alloy after EDM

Mehmood S., Sultan A., Anjum N. A., Anwar W., Butt Z.

Advances in Science and Technology. Research Journal

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2017

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Vol. 11, no 1

29--35

EN

Thermal energy produced by discrete and random electric sparks in electric discharge machining (EDM) melts surface material. A portion of this molten material is removed and the remaining material resolidified by rapid cooling in a hydrocarbon oil. The effect of repeated heating and cooling of the surface and sub surface material with complex temperature gradients results in residual stresses in machined parts. The aim of this investigation is to determine the distribution of residual stresses in the depth of machined material with respect to discharge current, most important electric parameter during EDM. It is well known that surface finish is dependent on discharge current. Therefore, investigations were carried out for smaller discharge current levels i.e. 3, 6, 9, 12 ampere. Hole-drill strain gauge method is used for the determination of residual stresses in the depth of material. For comparison purposes, residual stresses are also determined for conventionally turned specimens. This study provided quantitative analysis of the residual stresses for various discharge current in EDM which is a key parameter in deciding the service life of material.

5

Study of the effect of localised axial magnetic field on discharge current using the Hall effect

Paingankar A., Chitra N., Shirodkar V.

Journal of Technical Physics

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1998

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Vol. 39, no 2

221-235

EN

The influence of localised axial magnetic field on discharge current in a low pressure, fry air dc discharge has been studied. The distinctive nature of the variation in discharge current was found to depend on the region to which the axial magnetic field was applied. In order to qualitatively explain this phenomenon, various plasma parameters in each region of discharge have been determined using Hall effect.