Effects of multiple impulse currents on the microstructure and electrical properties of metal-oxide varistors

The multiple impulse currents that are associated with a lightning ground flash have a stronger degradation effect on the electrical properties of metal oxide varistors than single pulses. It has been found that this degradation is associated with the formation of cracks extending between the contact surfaces of the devices which are filled with an amorphous material. These defects probably develop because of the formation of highly localized conduction paths during the application of the current pulses.<
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