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terminal exists; therefore, ECHO is not required in BOP. WIKT is not applicable in BOP; hence,
the weak infeed terminal cannot operate.
(i) Countermeasure of current reversal (CRL)
BOP has the countermeasure of current reversal, as well as PUP. (For more information of
CRL, see section 2.12.6)
(ii) Scheme logic
Figure 2.12-5 and Figure 2.12-6 show BOP scheme logic. In BOP, trip block signals (DISCAR-
S: used for the external carrier communication) and (INT.DISCAR-S-*: used for the integral
carrier communication) are observed when the logic level in BOP is equal to “1”. Conversely, a
trip block signal is not observed when the logic level is equal to “0”.
In BOP, a trip block signal is not transmitted. If the reverse overreaching element
operates while the forward overreaching element does not operate, a trip block signal is
transmitted.
A trip block signal is not sent for setting [TREBK-dis] even after the local terminal issues
a trip signal so that command tripping at the remote terminal is secured.
The selection of either the single-phase trip (1P) or the three-phase trip (3P) is carried
out when the trip block signal is not received.
The delayed pick-up timer [TCHD-dis] is provided to allow for the transmission delay for
receipt of the trip block signal from the remote terminal in the event of a forward external
fault.
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