what is STUB protection in tranmission system and switch
yard area?
Answer Posted / abdelrahman hussein
The stub bus element protects for faults between two breakers in a breaker-and-a-half or ring bus configuration when the
line disconnect switch is open. At the same time, if the line is still energized through the remote terminal(s), differential
protection is still required (the line can still need to be energized because there is a tapped load on a two-terminal line or
because the line is a three-terminal line with two of the terminals still connected). Correct operation for this condition is
achieved by the local relay sending zero current values to the remote end(s) so that a local bus fault does not result in
tripping the line. At the local end, the differential element is disabled and stub bus protection is provided by a user-selected
overcurrent element. If there is a line fault, the remote end(s) trips on differential but local differential function and the DTT
signal (if enabled) to the local end are blocked by the stub bus logic, allowing the local breakers to remain closed.
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