Toshiba GR-200 Series Instruction Manual page 78

Permissive overreach protection (POP)
2.3.1
DEFCAR sends a trip permission signal in POP; and POP does not send a trip permission
signal for non-internal fault. Figure 2.3-1 shows POP scheme logic. The elements of OCD are
used to select a phase that should be tripped in CB.
When POP receives a trip permission signal, POP issues a trip signal on condition that
DEFCF has operated. To assure issuing a trip signal at the opposite terminal, POP continues
to send a trip permission signal for setting [TSBCT-DEF] after DEFCF stops. (Figure 2.3-2)
DEFCR is used for CRL as a revers looking element; DEFCF is used as a forward-looking
element, as shown in Figure 2.3-3. When DEFCR runs but DEFCF continues to stop for 20 ms
or more—even if DEFCF starts to run or DEFCR stops later—tripping CB at local terminal or
transmission of the trip permission signal is blocked for setting [TREBK-DEF].
In POP, users can delay the DEFCAR sending using settings [TDEFCF] and [TDEFCB].
Users can also delay the DEFCAR tripping using setting [TDEFC]. Thus, if users wish to carry
out the DEFCAR sending and the DEFCAR tripping separately, users should set a value for
the setting [TDEFCF] and another value for the setting [TDEFC]. For example, when 0 ms set
for the [TDEFCF] and 50 ms set for the [TDEFC], the DEFCAR sending is performed faster
than the DEFCAR tripping.
POP can provide ECHO and WKIT functions, which are used for the line having weak
infeed terminals. ECHO allows fast CB tripping at the terminal on which DEFCF has operated
when applied to the line having an open terminal or a weak infeed earth fault current terminal.
(Figure 2.3-4 to Figure 2.3-7)
When a trip permission signal is received if neither DEFCF nor DEFCR operates, ECHO
sends back the received signal to the opposite terminal. When CB is open, ECHO also sends
back the trip permission signal.
Once DEFCF or DEFCR operates, ECHO inhibits to send the echo signal for 250 ms by
delayed drop-off timer T1 even after DEFCF and DEFCR stop to operate.
In order to prevent any spurious echo signal from looping round between terminals in a
healthy state, sending ECHO signal is restricted for 200 ms by delayed pick-up timer T2. Echo
can operate using scheme switch [DEF-ECHO] On.
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6F2T0200 (0.15)
GRE200 (1,2)