Toshiba GRZ100-211B, Instruction Manual

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6 F 2 S 0 8 3 4
Figure 2.4.3.8 shows the current reversal logic. The current reversal logic is picked up on
condition that reverse looking Z4 has operated and forward overreaching zone 2 or zone 3 have
not operated, and the output CRL immediately controls the send signal to a trip block signal and at
the same time blocks local tripping. If the condition above continues longer than 20ms, the output
CRL will last for the TREBK setting even after the condition above ceases to exist.
≥
1
TREBK
[ZONESEL]
CRL
Z2
Z3
Z4
&
0.01 – 10.00s
0 t
20ms
t 0
"Z3"
"Z2"
737:REV_BLK-A
738:REV_BLK-B
739:REV_BLK-C
740:REV_BLK-S
214:REV_BLK
Figure 2.4.3.8 Current Reversal Logic
The operation of the current reversal logic and its effect in the event of a fault shown in Figure
2.4.3.7 (a) are as follows. As shown in Figure 2.4.3.7 (b), the current reversal logic of terminal A2
operates (CRL = 1) immediately after the fault occurs. This operation lasts for TREBK setting
even after the current is reversed and Z3 operates, continuously blocking the local tripping and
transmitting a trip block signal to the terminal B2.
Even if overlap arises due to current reversal on the operation of Z3 at terminal A2 and terminal
B2, it will disappear while the current reversal logic is operating, thus avoiding false tripping of
the healthy line of parallel lines. When a current reversal occurs in the direction opposite to the
above, the current reversal logic at terminal B2 will respond similarly.
Current reversal logic is not picked up for internal faults, thus not obstructing high-speed
operation of any protection scheme.
2.4.3.7 Phase Selection Logic
Every command protection has phase selection logic for single-phase tripping. Figure 2.4.3.9
gives details of the phase selection logic displayed in blocks in Figures 2.4.3.1 to 2.4.3.4.
Tripping command signal TRIP of each command protection can be classified by the phase
selection logic as a single-phase tripping command or a three-phase tripping command. If the
distance measuring element for earth fault Z3G (or Z2G depending on the setting of the scheme
switch [ZONESEL]) is operating when a TRIP is input, a single-phase tripping command S-TRIP
is output to the phase in which the phase selection element UVC is operating. If the UVC is
operating with two or more phases, a three-phase tripping command M-TRIP is output.
The undervoltage detection element UVLS, not shown in Figure 2.4.3.9, is used for the phase
selection logic as phase fault detector. The UVLS is also used for fault location.
If the distance measuring element for phase fault Z3S (or Z2S) is operating when a TRIP is input,
a three-phase tripping command M-TRIP is output.
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