New Type Power Line Carrier Relaying System with Directional Comparison for EHV Transmission Lines

This thesis suggests and studies a new type power line carrier protective relaying system with directional comparison for EHV transmission lines. It consists of the following three important improvements: (a) Adoption of the phase compensator type directional relay suggested and studied by the authors which can operate correctly in two phase operating conditions of the protected line;(b) with constant circulation of carrier frequency blocking current;(c) to take advantage of sudden decrease of received carrier signal level in case of internal three phase faults. Theoretical analysis, experimental data and field operating experience are given.