High levels of safety are required for substation facility switchgear in foreign countries, and so they have been equipped with grounding switches of which main circuits are connected to the grounding potential. When grounding switches are mistakenly turned on while voltage is being applied, a short circuit current of several tens of kA is also produced together with the associated preceding arc discharge between contacts. There is a danger of conduction failure if the contact damage is significant.
By conducting electromagnetic field analysis and theoretical calculations to accurately analyze the timing at which preceding arc discharge occurs, the impact of wear on contacts, and the contact pressure relationship when short-circuit current is conducted, it has been possible to realize highly-reliable switching operation with appropriate contact load.
Example of detailed observation of preceding arc discharge between grounding switch contacts