Experimental investigation between short circuit making performance and closing speed of direct acting earthing switch

The capability of existing MV metal enclosed switchgear is restrained by its poor short circuit making performance of earthing switch. A new type of direct acting earthing switch with rated voltage 12kV is designed for better short circuit making capability in this paper. A series of different springs which supply different forces and different main circuit arrangement patterns which produce different electro-dynamic forces are manufactured in order to supply different closing speeds. Therefore corresponding experiment switch peak current of 80kA are performed to study the relationship between closing speed and making capability. The results of experiments show that the capability of short circuit making increases with the rising of closing speed and the electrical durability of the earthing switch is at least 8 times when the max measuring closing speed is 3.82 m/s especially. The research on direct acting earthing switch in this paper is meaningful for large capacity MV metal enclosed switchgear.