Institute of Fundamental Technological Research

The objective of this examination was to test the aging resistance of the aluminous porcelain material C 130 type, when exposed to direct current (DC) high voltage. Long-term exposure to high DC voltages can potentially lead to various negative effects, in particular ionic current development in the porcelain material. This process may reduce the mechanical strength and, consequently, cause a failure. This problem has been noticed in the case of glass disc insulators. The samples were examined using the 3-point bending test, ultrasonic and microscopic analysis. No recordable degradation effects were found. Long-term impact of DC high voltage did not reduce the mechanical parameters or change the microstructure of the porcelain material.

DC high voltage, aluminous porcelain C 130, 3-point bending test, mechanical strength

The application of the acoustic emission (AE) method for the detection and recording of partial discharges (PD) occurring in a medium voltage switchgear model was presented in this paper. The results of AE measurements were presented in the form of spectrograms. The acoustic emission effect occurred when the applied voltage level reached values from 10 kV to 30 kV. The authors used devices and probes EA to record PD using the acoustic method. The presented equipment can also be intended for industrial applications. The original accomplishment of the presented work is the achievement of successful and repeatable results of partial discharge measurements using the acoustic method.

Partial Discharges (PD), Acoustic Emission (AE), Registration of Acoustic Emission signals

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.

ogranicznik przepięć, tekstolit szklany TSE, prąd wyładowczy (zwarciowy), metoda EDS

The aim of this work was to investigate the effects of the currents flowing through surge arresters on the internal insulating textolite structure. The samples were removed from high-voltage arresters that were taken out of service due to malfunction or failure. Discharge (short-circuit) currents of diverse intensities and durations caused degradation effects of varying degrees of advancement in the material of the tested elements. The samples were examined using microscopic methods. The use of the microanalysis technique EDS (energy-dispersive X-ray spectroscopy) made it possible to register changes in the elemental composition of the surface layer of the textolite materials, along with the intensification of the degradation effects. It was found that the high discharge current flows were subject to melting, charring and even burning of the organic adhesive. These effects caused serious changes in the content of elements in the top layer of the textolite and were the cause of a reduction in the service life, durability and reliability of the surge arresters. It was shown that the textolite materials had insufficient resistance to the effects of the emergency operation of the arresters after moisture ingress, which was a consequence of unsealing of the housing. A solution to this problem proposed by the authors could be the use of silicone elastomer as a covering of the textolite internal structure of surge arresters.

surge arrester, TSE glass textolite, discharge (short circuit) current, EDS method

The paper presents results of investigation of microstructure and micro-hardness for material of ZnO varistors applied to 110 kV surge arrester and surge arrester counter. The research combined two pairs of varistors, each consisted of one varistor subjected before to operation, while the other one was brand new unit and constituted a reference. All varistors were made of the same material by the reputable manufacture. The tests revealed a different degree of the material degradation for varistors subjected before to operation. This also refers to different degradation mechanism observed for the material of these varistors, if typical effects of degradation of aged ZnO varistors were considered as a reference. Physical state of spinel in the microstructure had a significant impact on the material degradation, however a considerable loosening of the microstructure associated with bismuth oxide was observed too. It was surprising, since the precipitates of the bismuth oxide phase most often showed very good binding to the ZnO matrix and high resistance to associated electrical, thermal and mechanical effects. The degradation effects in the ZnO matrix proved to be limited only.

surge arrester, surge arrester counter, MO varistors, microstructure of ceramics, ceramic material degradation

Celem prezentowanej pracy było znalezienie zależności pomiędzy parametrami mikrostruktury warystorów, a prądem płynącym przez ogranicznik przepięć dla różnych poziomów napięcia. Badania zostały wykonane na losowo wybranej populacji beziskiernikowych ograniczników przepięć w osłonach polimerowych, przeznaczonych do pracy w sieci średniego napięcia. Wykonano pomiary przebiegów referencyjnych dla badanej populacji ograniczników. Przyjęto jako kryterium oceny udział wyższych harmonicznych w przebiegu prądu. Praca stanowi wstęp do szerszego zakresu badań, prowadzonych w ramach wspólnych działań laboratoriów Instytutu Energetyki i Instytutu Podstawowych Problemów Techniki PAN.

beziskiernikowy ogranicznik przepięć, warystor ZnO, mikrostruktura ceramiki, analiza FFT