Impact of Surface Morphology on Arcing Induced Erosion of CuW Contacts in Gas Circuit Breakers

In this paper, the impact of surface morphology of contacts, in particular different microstructural parameters like size and distribution of contact ingredients, on contact erosion in high voltage gas circuit breaker is investigated. It is demonstrated that the size and contiguity of copper and tungsten zones play a key role in contact erosion so that the mass loss in one specific contact after interruption of the rated short-circuit current is 2.5 times higher than that of another one, with the same dimensions and material composition. It is shown that the arc roots tend to be formed on larger copper zones and if the zones are not confined by tungsten area, the arc cross section expands resulting in a higher evaporation rate of copper areas. In addition, it is emphasized that ejection of tungsten particles after evaporation of surrounding copper areas is another mechanism leading to more contact erosion, which has to be taken into consideration in contact erosion modeling along with molten contact splash and vaporization.