Toshiba GRL100-701B Instruction Manual page 66

The following elements have fixed setting values or their settings are interlinked with other
elements listed above. So no setting operation is required.
Element Setting
Z4BS
Fixed to 1.5Ω
(Fixed to 7.5Ω) (*1)
Z4S θ(*2) Interlinked with Z3S θ
Z4BS θ(*3) Interlinked with ZBS θ
BRRS θ Fixed to 75°
BRLS Interlinked with BRRS
BRLS θ Interlinked with BFLS θ Angle of reverse left blinder BRLS
Z4G θ(*2) Interlinked with Z3G θ
Z4BG θ(*3) Interlinked with ZBG θ
BRRG θ Fixed to 75°
BRLG Interlinked with BRRG
BRLG θ Interlinked with BFLG θ Angle of reverse left blinder BRLG
(*1) Ohmic values shown in the parentheses are in the case of 1 A rating. Other ohmic values are in
the case of 5 A rating.
(*2) Valid only when mho-based characteristic is selected by ZS-C and ZG-C.
(*3) Valid only when quadrilateral characteristic is selected by ZS-C and ZG-C.
The reverse looking elements Z4 (G,S), BRR (G,S) and BRL (G,S) must always operate for
reverse faults for which the forward overreaching element of the remote end operates. The
following setting coordination is required.
When zone 2 is selected as the forward-looking element,
Z4 setting = 1.2 × (Zone 2 setting at remote end)
When zone 3 is selected,
Z4 setting = 1.2 × (Zone 3 setting at remote end)
In both cases,
BRR setting = 1.2 × (BFR setting at remote end)
2.3.2.4 Blocking Overreach Protection
Application
In blocking overreach protection (BOP), each terminal normally transmits a trip permission
signal, and transmits a trip block signal if the reverse looking Z4 operates and the forward
overreaching element does not operate. Tripping of the local circuit breaker is performed on
condition that the forward overreaching element has operated and a trip permission signal has
been received. As the forward overreaching element, it is possible to use zone 2 or zone 3.
If signal modulation is performed by an ON/OFF method, the signal is not normally transmitted
and a trip block signal is transmitted only when the reverse looking element operates. Tripping is
performed on condition that the forward overreaching element has operated and no signal has been
received. In this signaling system, the signal transmitted is a trip block signal and transmission of
this signal is only required in the event of an external fault. Therefore, even if power line carrier is
used, there will be no failure to operate or false operation due to attenuation of signals caused by
signal transmission through the fault.
The BOP receives a trip permission signal all the time. Therefore, when a forward external fault
occurs, the infeed terminal on which the forward overreaching element has operated attempts to
perform instantaneous tripping. At this time, at the remote outfeed terminal, the reverse looking
element operates and transmits a trip block signal. This signal is received at the infeed terminal
after a channel delay time. Therefore, a short delay is required for the tripping to check for the
reception of a trip block signal.
Remarks
Z4 reverse offset reach
Characteristic angle of Z4 mho element
Angle of Z4 directional element
Angle of reverse right blinder BRRS
Reverse left blinder
Characteristic angle of Z4 mho element
Angle of Z4 directional element
Angle of reverse right blinder BRRG
Reverse left blinder
 65 
6 F 2 S 0 8 5 0