Characteristic of large current making switch to verify making performance of high voltage switchgear

The test to verify the making performance of high voltage switchgear is required and the standard also requires the making test. We have developed a large current making switch (rated voltage of 180 kV, trigger energy of 5.5 kJ) to mainly apply to making tests of high voltage switchgears, such as short-circuit making and out-of-phase. In this kind of test is important that the gap withstand high voltage before trigger and ignite with small time delay. Our development targets for a making switch were set up (1) Making current to be made : 63 kA. (2) Minimum voltage to make triggering possible : 2 kV. (3) Time delay : 200 microsecond or less. We investigated the performance of gas gap switches with Sulfur Hexafluoride (SF₆) gas as an insulation medium to find the most suitable conditions for the purpose. It was confirmed that the large current making switch almost achieved the target time delay of 200 ms when the gap length 30 mm, SF₆ gas pressure is 0.4 MPa and trigger energy is 5.5 kJ and withstand AC200 kV at a voltage enduarance test. It was applied to a short circuit making test of 420 kV GCB and the test result satisfied the standard.