Substation area back-up protecting method based on current differential principle

The invention belongs to the filed of power system relay protection, in particular to a substation area back-up protecting method which is based on a current differential principle and applicable to an intelligent transformer substation. According to the method, information such as analog quantity, switching value and the like is acquired on the basis of high-speed communication networks and inter-station data channels inside the intelligent transformer substation, back-up protecting areas are processed in areas, all faults inside the transformer substation and on outgoing lines are positioned rapidly, reliably and accurately through the current differential principle, and under the condition of failure of a main protection and a breaker, a back-up tripping instruction is issued to isolate fault elements. The method changes the state of the prior art that selectivity of traditional back-up protection is achieved through fit of fault electric quantity and time limit step, simplifies configuration and setting of the back-up protection and shortens movement time limit of the back-up protection.