Pickup Sensitivity - ABB Relion Technical Manual

1MRK 502 048-UUS A
8.9.7.1
8.9.7.2
8.9.7.3
Technical manual

Pickup sensitivity

The trip pickup levels Current I2-1> and I2-2> of NS2PTOC (46I2) are freely settable
over a range of 3 to 500 % of rated generator current IBase. The wide range of pickup
setting is required in order to be able to protect generators of different types and sizes.
After pickup, a certain hysteresis is used before resetting pickup levels. For both steps the
reset ratio is 0.97.
Alarm function
The alarm function is operated by PICKUP signal and used to warn the operator for an
abnormal situation, for example, when generator continuous negative sequence current
capability is exceeded, thereby allowing corrective action to be taken before removing the
generator from service. A settable time delay tAlarm is provided for the alarm function to
avoid false alarms during short-time unbalanced conditions.
Logic diagram
Negative sequence current
a
a>b
b
I2-1>
Operation=Enabled
BLK1
BLOCK
ANSI08000466 V3 EN
Figure 123: Simplified logic diagram for step 1 of Negative sequence time overcurrent
protection for machines (NS2PTOC, 46I2)
Step 2 for Negative sequence time overcurrent protection for machines (NS2PTOC, 46I2)
is similar to step 1 above except that it lacks the inverse characteristic.
DT time
0-t1
selected
0
AND
Inverse
Inverse time
selected
Section 8
Current protection
TRST1
OR
PU_ST1
ANSI08000466-3-en.vsd
271