Abstract
Metal oxide varistors (MOVs) are widely used to protect electrical and electronic devices that are very vulnerable to surges due to the low insulation level of the equipment. MOVs deteriorate gradually due to manufacturing defects, mechanical and thermal stress, or repeated protective operations against surges. These defects result in the thermal runaway of MOV and finally lead to the explosion and electric fire of electrical and electronic devices due to a short circuit and a line-to-ground fault. Therefore, the reliable assessment of the condition of MOV deterioration is required for electrical and electronic equipment. However, when most accelerated degradation tests for the MOV have been performed to date, an 8/20 μs standard surge current is applied under de-energized conditions, which is unlike the actual operating environment. In this study, a surge generator was designed to apply a surge current to MOVs to monitor their deterioration. Three different types of leakage currents were measured to analyze the change rates of their electrical characteristics of MOVs by comparing them with the reference voltage variation. Furthermore, the condition assessment of MOV deterioration under energized and de-energized conditions was investigated.
Highlights
As the fourth industrial revolution has begun in earnest, a large amount of electrical and electronic equipment is being used in various fields in addition to advanced mechanical devices.Power semiconductor devices, which are composed of electrical and electronic devices, are very vulnerable to surges due to their low insulation level
There are no specific deterioration criteria for replacing a Metal oxide varistors (MOVs), and most are replaced at the same time or along with defective MOVs found by visual inspection [8]
The absorbed energies of decreased shows the comparisons of change rates in electrical parameters with MOV operating conditions. It can from 800 to 500 kJ and from 1200 to 600 kJ, respectively, at the Maximum continuous operating voltage (MCOV) compared with the be seen that the MOVs deteriorated more quickly when the magnitude of the MOV operating voltage de-energized condition until the reference voltage decreased to about 15%
Summary
As the fourth industrial revolution has begun in earnest, a large amount of electrical and electronic equipment is being used in various fields in addition to advanced mechanical devices. On-line measurement for the reference voltage, tests for the MOV are performed, standard surge current is applied under de-energized is impossible, and the an MOV is μs separated for off-line measurement. To date, when most the optimal parameter instead of the reference voltage and to perform the accelerated degradation accelerated degradation tests for the MOV are performed, an 8/20 μs standard surge current is test under de-energized conditions, which is unlike reliably the actual operating environment [11]. Characteristics, perform the accelerated degradation test under energized conditions to evaluate. 8/20 μs standard surge current, which can be synchronized with the AC power-frequency voltage to condition assessment the MOV deterioration de-energized replicate athe actual MOV operatingof environment. Surge andGenerator de-energized conditions was performed [6,13]
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