Method for preventing fault actions of line longitudinal differential protection caused by non-fault phase secondary current abrupt change

A method for preventing fault actions of line longitudinal differential protection caused by non-fault phase secondary current abrupt change comprises the following steps: 1) measuring a phase difference current Idphi, wherein the Idphi is a phase braking current; and 2) when the formula of Idphi>k1Irphi, Idphi>Imkl.Idphi>k2Ir-other is satisfied simultaneously, eliminating the condition of non-fault phase secondary current abrupt change, and turning on the phase difference streaming relay. In the formula, Idphi is a phase difference current, Irphi is a phase braking current, Imkl is a difference threshold, Ir-other is the comprehensive braking amount of the two other phases, k1 and k2 are coefficients, phi=a, b, c, other=bc, ac, ab, wherein a, b and c stand for three phases. The method has the following beneficial effects: through the main criterion of the non-fault phase saturated discrimination, the fault phase electrical character amount is used as the braking factor in a non-fault phase action equation, t