Degradation assessment of metal oxide varistors using a statistical experimental design

Abstract

The proliferation of metal oxide varistor (MOV) arresters in various industries prompts the need to improve reliability thereof. This is only achievable through first expanding current knowledge of these devices, particularly with regard to degradation mechanisms. Currently, there are no methods available to conclusively evaluate factors suspected of influencing degradation. This study investigates two such factors, namely, microstructural composition and distorted voltage supply (harmonic distortion). Furthermore, a statistical experimental design methodology is proposed to definitively assess the significance of the effects of these factors on the degradation of MOV arresters. The experimental methodology comprises thermally accelerated degradation under distorted and nondistorted voltage and scanning electron microscopy. Samples from three different manufacturers are used for the study. Results indicate that the differences in microstructural composition, owing to manufacturing differences, have a significant effect on the failure rate and, thus, on the reliability of MOV arresters. Distorted supply voltage is also found to have a significant effect on the failure rate of MOV arresters. © 2018 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

A Bibliometric and Comprehensive Review on Condition Monitoring of Metal Oxide Surge Arresters

“…Changes in the microstructure of aged varistor blocks demonstrate the effects caused by the degradation process [ 87 ]. The chemical differences in microstructures result in different degradation patterns [ 88 ]. The techniques that are applied to analyze the microstructure are divided between Optical microscopy (OM), Scanning electron microscopy (SEM), X-ray diffraction (XRD) and Energy-dispersive spectrometry (EDS) [ 7 ].…”

“…In their study, Bokoro and Doorsamy [ 88 ] presented an experimental statistical design methodology, based on the use of SEM, in order to evaluate the influence of microstructural composition and a distorted voltage supply on the degradation of the arresters. In their work, de Salles et al [ 87 ] also investigated the effect of operating temperature on degradation caused by current impulses.…”

Effects of Dopants and Processing Parameters on the Properties of ZnO-V2O5-Based Varistors Prepared by Powder Metallurgy: A Review

“…Most commercial ZnO-based varistors are composed of ZnO-Bi 2 O 3 systems with up to 8–12 MO dopants and typically yield ZnO grain sizes (d ZnO ) of 10–100 μm and a depletion length of the doped GBs of 50–100 nm, a breakdown field (E B ) of 2–3 kV/cm, and a nonlinear coefficient of about 40–50 [ 52 , 56 , 59 , 80 , 81 , 82 ]. MOVs with coarse-grained microstructures (mean d ZnO > 30 µm) and lower E B values are used for low-voltage (LV) applications, while MOVs with fine-grained microstructures (mean d ZnO < 10 µm) are required for high-voltage (HV) and medium-voltage (MV) applications [ 59 , 83 ].…”

Mapping Reliability Predictors of Low-Voltage Metal Oxide Surge Arresters Using Contour Plots

“…To ensure reliable surge protection in power systems, electronic and data circuits: condition monitoring and reliability assessment of MOSA devices is essential practice to be adhered to [7], [8]. Besides thermal stress having proven to be an important non-electrical contributing factor to the reliability reduction, power system harmonics have been reported to be significant aggravating factor to reliability reduction phenomenon of metal oxide surge arresters (MOSA) [9]− [11]. A mathematical model proposed in [12], predicts life acceleration, and hence reliability reduction of MOSAs for a given percentage content of harmonic-distortion in the voltage stress.…”