550 kV GIS is one of the most important equipments for the construction of 500 kV power network in China.The GIS is upgraded based on type ZF8-550/3150-50 GIS
with the rated current of 4 000 A and the rated short time withstanding current of 63 kA.This paper introduces the current carrying capability of main circuit and earthing circuit
the flow capacity
the caculation of dynamic thermal stability and the calculation of closing speed of fast making earthing switch
as well as their test results.The effectivity of the measure to reduce VFTO is verified through test.