A new current differential protection scheme for Teed transmission lines

This paper presents a current differential protection scheme for Teed transmission lines using superimposed components. Basing on the characteristics of the superimposed currents in Teed feeders, a unique differential criteria was proposed and analyzed under different operating conditions. This criteria inherently has sufficient sensitivity for internal faults and stability for external faults. Particularly, it copes well with both the internal high resistance faults on a heavily loaded feeder and the out-feeder problem. Extensive simulation studies were conducted on a typical EHV teed line model using EMTDC package. Theoretical analysis and simulation results demonstrates that the new differential scheme provides adequate reliability and fast operating response for a variety of system and fault conditions