High-speed differential protection of parallel teed transmission lines

This paper presents high-speed differential protection algorithm for parallel-teed transmission lines. The algorithm uses distributed parameter models of the transmission lines and synchronized sampling of data at the terminals of the line. A method that takes the unsynchronised data and generates synchronised information is described. The proposed algorithm uses a segregated scheme, facilitates the coordination of multiphase tripping and reclosing on HV and EHV parallel-teed transmission lines. A relaying system design based on the proposed algorithm is also discussed The proposed system was tested extensively by using data that was generated by using the EMTDC and sample power systems. Results show that the system remains stable during normal operation of the power system and during external faults. The relaying system is sensitive and fast and does not jeopardize security. Some test results are included in the paper