In this paper

the accident prediction is made for some fault operation mode of 500 kV substation

and the operation mode is modeled and analyzed by PSCAD simulation platform

and the impact of series-inner closing loop on power network by using medium switch is studied. The results show that when the bus voltage

amplitude and outgoing load are all in unfavorable conditions

the closing loop impulse current is large

which may have adverse effects on the operation of power equipment and power grid.It provides the effective suggestion for the operation personnel to deal with the emergency situation.