A new directional relay for the protection of EHV transmission lines based on the detection of transient voltage signals

This paper presents the application of a new directional relaying technique for the protection of EHV transmission lines using fault generated high frequency voltage transients. The technique utilises a specially designed transient detection unit to detect fault generated transient voltage signals. A multi-channel filter unit is then applied to the captured signals to extract the desired bands of signals. The filter outputs are then fed to a spectral energy circuit where their associated spectral energy levels are calculated. These levels can be compared to establish the direction of the fault