Event under the auspices of the Ministry of Economy of Slovak Republic

Influence of temperature and high energy stresses on selected wideband characteristics of Metal-Oxide Varistor parameters

*Michał Bonk
Dept. of Electrical and Power Engineering, AGH University of

Pawel Zydron
Dept. of Electrical and Power Engineering, AGH University of Science and Technology, Krakow, Poland

Łukasz Fuśnik
Dept. of Electrical and Power Engineering, AGH University of Science and Technology, Krakow, Poland

Bartlomiej Szafraniak
Dept. of Electrical and Power Engineering, AGH University of Science and Technology, Krakow, Poland


     Last modified: 2017-06-17

Abstract
Gapless Metal-Oxide Varistors (MOV) are used for many years in systems limiting the surges arising in electrical power networks, at all voltage levels. Surge arresters used for protection of electrical installations and devices are currently produced mainly on the basis of ZnO varistors. Each overvoltage causes high energy stress, which degrades the internal structure of the varistor. As a result, it changes its properties, and by cumulative effects of aging processes reduces the lifetime. Diagnosis of surge arresters is performed to determine the degree of aging of their varistors structures. For this purpose, different testing methods are used. The report describes issues related to the application of wideband impedance spectroscopy (IS) for the experimental determination of some electrical and material parameters of low voltage surge arresters, subjected to the influence of aging factors. They are illustrated with results of tests performed to determine the effect of temperature and high energy stresses (current pulses 8 µs / 20 µs or 0.5 s AC burst waveforms) on some parameters describing the condition of the varistors. Modeling of varistor properties using electrical schemes is used for analysis of its structural changes.

 

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