Boundary protection of EHV transmission lines using multi-channel frequency comparison technique

This paper reports a new development in boundary protection (BP) techniques, the multichannel frequency comparison (MCFC) technique. The new development is in the key part of the BP relays, the transient current signal analysis and processing unit. The fault transient signals are captured by the specially designed transient detection unit, then are decomposed into a series of frequency components by using the proposed multi-channel filtering technique. The energies contained in the output signals of the filters are calculated at the corresponding frequencies. The levels of the energies at different frequency bands are used to distinguish between the internal and external faults. Simulation results have shown that the proposed techniques can significantly enhance the reliability and security of the BP relays