Development of GPS synchronized digital current differential protection

This paper describes a newly developed digital current differential protection scheme for power transmission lines. The proposed protection is different from existing ones in two aspects: one is the use of GPS time information to implement synchronized sampling at all terminals of the protected line; the other is the application of a new differential algorithm based on fault component instantaneous value. To evaluate the performance of the protection scheme, both an EMTP simulation study on the new algorithm and dynamic simulation tests on the prototype of the protection are conducted. The test results have proved the correctness of the new algorithm and the feasibility of the whole protection scheme. This paper starts with a brief introduction to the overall configuration of the protection scheme, then focuses on the description of principles of GPS based synchronized sampling and the new differential algorithm. Simulation results are also presented