ABB Relion 670 series - Page 582

8.16.7.4 Logic diagram
GUID-0A1565A4-74E1-4171-968B-50529AABF192 v2
PickupCurr
X
a
b
a>b
Voltage
control or
restraint
feature
Inverse
DEF time
selected
Inverse
time
selected
OR
ANSI10000214-2-en.vsd
PU_OC
TROC
MinPh-Ph Voltage
MaxPhCurr
0
0-tDef_OC
ANSI10000214 V2 EN-US
Figure 307: Simplified internal logic diagram for overcurrent function
AND
a
b
b>a
MinPh-PhVoltage
BLKUV
ANSI10000213-2-en.vsd
DEF time
selected
PU_UV
T R U V
0
0-tDef_UV
PickupVolt
Operation_UV=Disabled
ANSI10000213 V2 EN-US
Figure 308: Simplified internal logic diagram for undervoltage function
8.16.7.5 Undervoltage protection
GUID-96171DC7-9F8E-47B4-BE0D-E1B9EE214612 v5
The undervoltage step simply compares the magnitude of the measured voltage quantity with the
set pickup level. The undervoltage step picks up if the magnitude of the measured voltage
quantity is lower than the set level.
The pickup signal starts a definite time delay. If the value of the pickup signal is one for longer
than the set time delay, the undervoltage step sets its trip signal to one.
This undervoltage functionality together with additional ACT logic can be used to provide
functionality for overcurrent protection with undervoltage seal-in.
Section 8 1MRK 502 066-UUS B
Current protection
576
Technical manual