PROTECTIVE RELAYING APPARATUS OF THE UNBLOCK TYPE

摘要

Protective relaying apparatus for power transmission lines of the unblocking type which utilizes a fault signal from a remote portion of the protected line to initiate a normal transient blocking timer which in the absence of a local fault signal (within its timing period) will initiate a desensitizing operation and prevent the tripping of the local breaker due to the presence of transient and an additional timer arranged to be energized in response to a local fault signal and effective when timed out to initiate the normal transient blocking timer in the absence of the remote fault signal. In a modified form of the apparatus, the concurrent reception of the received and local signals (indicative of a fault in the line section protected thereby) deactivates the normal timer and prevents its further timing operation to increase the margin of coordination when transient blocking should not occur.