Distinct degradation processes in ZnO varistors: Reliability analysis and modeling with accelerated AC tests

Hadi Yadavari, Mustafa Altun*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

1 Citation (Scopus)


In this study, we investigate different degradation mechanisms of zinc oxide (ZnO) varistors. We propose a model that shows how Vv (defined as DC varistor voltage when a 1-mA DC current is applied) changes with time for different stress levels. For this purpose, accelerated degradation tests are applied for different AC current levels and voltage values are then measured. Different from the common practice in the literature that considers degradation with only decreasing Vv values, we demonstrate either an increasing or a decreasing trend in the Vv parameter. The tests show a decreasing trend in Vv for current levels above a certain threshold and an increasing trend for current levels below this threshold. Considering both of these degradation mechanisms, we present a mathematical degradation model. The proposed model exploits the physics of the degradations for a single-grain boundary that is the core structure of a ZnO varistor. To validate the proposed model, we perform Monte Carlo simulations and the results are compared with those obtained from accelerated AC tests. As a summary of this study, we introduce a conceptual accelerated AC test methodology to analyze the reliability of the new ZnO varistor.

Original languageEnglish
Pages (from-to)3240-3252
Number of pages13
JournalTurkish Journal of Electrical Engineering and Computer Sciences
Issue number4
Publication statusPublished - 2017

Bibliographical note

Publisher Copyright:


This work was done in cooperation with Arcelik A.S¸. and supported by the TÜBİTAK (Scientific and Technological Research Council of Turkey) University–Industry Collaboration Grant Program #5130034. We are grateful to Burak S¸al from İstanbul Technical University for his help with the experiments and Ahmet Ferit Co¸san and Bari¸s Ocak from Arc¸elik A.S¸. for their feedback and discussions.

FundersFunder number


    • AC tests
    • Degradation
    • Reliability analysis and modeling
    • ZnO varistors


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