Toshiba GR200 Series Instruction Manual page 211

terminal, the CB at the terminal is tripped in permission overreach protection (POP).
In other words, POP can determine if the fault exists inside the protected line based on
the overlapping operation of the forward overreaching elements at both terminals. ZCSF/ZCGF
elements are used for the forward overreaching element.
†Note: POP sends a trip permission signal when the forward overreaching element
operates. Thus, multiplex signaling channels or one channel for each direction is
required in POP. This is because that the terminal sending signals shall not trip
erroneously due to reception of its own sending signal if an external fault occurs in
the zone of forward overreaching element.
Operation of echo (ECHO) and week infeed trip (WKIT)
(ii)
POP has an echo function (ECHO) and a weak infeed trip function (WKIT) in order that the
line including an open terminal or a weak infeed terminal can be protected by POP. Thus, POP
enables to trip CBs fast at both terminals for any fault along the whole length of the protected
line. (For more information of ECHO and WKIT, see section 2.12.5)
Countermeasure of current reversal (CRL)
(iii)
When a fault exist on one of parallel lines, tripping CBs sequential may cause a current
reversal on another of parallel lines. The current reversal results in the false operation of POP,
hence, countermeasure logic is provided for the current reversal (CRL). (For more information
of CRL, see section 2.12.6)
Criterion of POP tripping
(iv)
POP at the local terminal issues either a single-phase tripping signal or a three-phase trip
signal when the following conditions are satisfied:
Trip permission signal is received from the opposite terminal
✓
The current reversal has not been observed
✓
One of the following conditions is established:
✓
The forward overreaching element operates.
⚫
When On is set for scheme switch [Dis-WIKT], the undervoltage element UVL†
⚫
(UVLS or UVLG) operates and the forward overreaching element and the
reverse looking element have not operated.
†Note: UVL is provided in the function of protection common (PROT_COMMON).
For more information, see Chapter
Scheme logic
(v)
Figure 2.12-3 shows POP scheme logics. POP sends a trip permission signal for the opposite
Relay application: Protection common
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6F2S1914 (0.49)
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GRL200 (Soft 033 & 037)