Toshiba GRL100-101A, Инструкция по эксплуатации

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generated and used to reset the receiving current data from terminal B to zero. Thus, terminal A
does not need to operate unnecessarily in response to fault F2.
Terminal B detects that terminal A is out-of-service with the out-of-service detection logic and
resets the receiving current data from terminal A to zero, and so does not operate in response to
fault F1.
The signal STUB ON also brings the local tripping into three-phase final tripping.
Through current for a close-up external fault
In the close-up external fault shown in Figure 2.2.12.3, a large fault current may flow through
current transformers CT1 and CT2 at terminal A and a small fault current flows in at terminal B.
This large through fault current may cause an erroneous differential current if the characteristics
of CT1 and CT2 are not identical.
CT1 CT2
GRL100 GRL100
Terminal B
Terminal A
Figure 2.2.12.3 Through Fault Current
The models 503 and 513 have individual input terminals for CT1 and CT2 secondary current.
Thus, sufficient restraining current can be obtained by summing the scalar values of CT1 and
CT2 secondary currents.
In this manner, terminal A can have sufficient restraining current against the erroneous
differential current mentioned above and demonstrate correct non-operation. But terminal B
cannot have a sufficient restraining current and may operate in response to the fault incorrectly.
To cope with this, the GRL100 has a scheme switch [T.F.C] and the scheme logic of the
differential protection shown in Figure 2.2.2.1 is switched to that of Figure 2.2.12.4. When the
[T.F.C] is set to "ON" locally or at the remote terminal, tripping commands are output under the
condition that the differential protection operates at both ends.
In this case, the tripping time is delayed by the transmission time of the remote terminal
operation signal.