There occurred simultaneously three failures with multiple equipment in recently

one accident was the ground fault which took place on two 500 kV lines at the same time

another was the fault which took place simultaneously on the line and the bus

the third one was the fault on buses in different substation at the simultaneous time.The protection action was analyzed based on equipment wiring

transient fault recorder and the inspection result of the scene of the accident.With the development of the power system

failure mode was more and more complicated.The accidents discussed show that the multiple equipment failures would affect the routine protection theory and grid security.To this problem

research and practice about the protection system based on wide area measurement should be put forward.