Method for starting longitudinal differential protection by using fault component

The invention discloses a method for staring longitudinal differential protection by using a fault component. The method mainly comprises the following steps of: after power side longitudinal differential protection meets three conditions, including a protection starting action criterion, a zero sequence or negative sequence positive direction action criterion and a zero sequence differential protection action criterion, starting a fault component; transmitting a fault component starting signal to weak feedback side longitudinal differential protection through an optical fiber channel; and if protection is not started after the weak feedback side longitudinal differential protection receives a power side fault component starting signal, and meets the zero sequence differential protection action criterion, starting driving protection, so that differential protection on both sides can act. Due to the adoption of the method, the problem of insufficient staring sensitivity of weak feedback side longitudinal differential protection during a high-resistance ground fault is solved.