ABB RELION 670 Series Technical Manual page 445

1MRK 502 066-UUS B
ANSI11000297 V1 EN-US
Figure 237: Block diagram of zone 1
The functionality included in zone 1:
• Comparator to detect, if the operating impedance has entered inside zone 1 offset mho
characteristic.
• All three phase-to-phase loops are implemented separately.
• Forward and reverse reach values are provided in percentage of impedance base value at
generator.
• Trip time delay is provided.
Comparator characteristics
The comparator consists of offset mho characteristics. Three individual comparators are provided
in the three phase-to-phase loops. The offset mho characteristic is as shown in figure 238.
Technical manual
BLOCK
BLKZ
Comparator
V3P
<
ZAB
I3P
EnableZone1
Z1Fw
Z1Rev
Comparator
<
ZBC
EnableZone1
Z1Fw
Z1Rev
Comparator
<
ZCA
EnableZone1
Z1Fw
Z1Rev
pickupZone1
Timer Logic
tripZone1
OR
tOpDelayZ1
opModetZ1
ANSI11000297_1.en.vsd
Section 7
Impedance protection
439