Transfer Matrix-Based Differential Protection of Transmission Lines

In this paper, a new differential integrated line protection scheme is presented. A central computer or relay in a control center provides protection for multiple transmission lines. The transmission line may be modeled by a transfer matrix similar to a dipole circuit, which relates the local bus current and voltage signals to the remote units. However, the transfer matrix of the line is not applicable when a fault occurs on the associated line. This concept is applied in the proposed method for fault detection. Simulation results verify that the novel integrated protection scheme, using the proposed method, operates correctly for the various test cases. The proposed method resolves several shortcomings of the existing transmission line protection schemes. It works accurately for high-resistance faults and has the feature of unit protection in identifying the faulted line. Using one central relay significantly decreases the overall cost of protection equipment in the system. The proposed integrated protection scheme detects the faults approximately one cycle after the fault occurrence, which is very fast among other proposed methods.