In view of the cascading trip induced by backup relays that affects the safe operation of the system and may even cause blackout

after investigating the defects of the existing backup protection

this paper presents a new wide area backup protection strategy based on WAMS to identify the flow transfer. A new concept of flow transfer relativity factor (FTRF) is proposed to estimate the flow distribution after flow transfer occurs

and the strict definition and calculating method are presented. The simulation in a threemachine network shows that the widearea backup protection strategy proposed to identify flow transfer works well.