A New Digital Relaying Scheme for Parallel Transmission Line.

This paper presents a scheme for the protection of parallel transmission line having two different configurations (geographical locations). In the proposed scheme, the six line currents at a common end of a parallel line or three line currents at a separate end of a parallel line are decomposed using wavelet packet transform (WPT) in order to derive the operating quantities for relay operation. The proposed scheme provides stability against close-in faults, more sensitivity towards high resistance faults and reliability for discriminating in-zone and out-zones faults during complete loss of generation at one of the buses. When the conventional relay, without an intuitive directional element, fails to trip for a remote end fault located in the vicinity of remote bus, the proposed method solves the said problem and also avoids the voltage signal used in conventional relays. Furthermore, the suggested scheme completely avoids the requirement of a distance algorithm as a backup protection in case of the disconnection of one line (due to maintenance or fault). Moreover, the proposed scheme analyzes solves the problem of simultaneous same phase fault on parallel lines. To validate the proposed scheme, numerous computer simulations have been carried out on realistic data of part of the Indian 400 kV power transmission system network. [ABSTRACT FROM AUTHOR]