A New Backup Protection for Transmission Lines Based on Substation-area Current Information

At present, when current transformer (TA) circuit of transmission line is broken, the method of blocking backup protection is usually adopted, which will cause short-circuit faults to be unable to be cleared in time. To solve the problem, a new transmission line backup protection based on substation-area current information is proposed in the paper. Based on the TA non-fault phase current information and substation-area current information, the breaking phase current of TA can be reconstructed by the new protection. By judging the reconstructed current and zero-sequence voltage of transmission line, it is determined whether the backup protection will be unblocked after TA circuit breaking. Finally, the effect of new protection is verified by simulation. The simulation results show that the impedance and zero-sequence current of transmission line can be calculated accurately by the new protection after TA circuit breaking, and ensures that short-circuit faults can be cleared timely and accurately by backup protection.