ABB REG650 User Manual

8.9.7.1 Start sensitivity
The trip start levels Current I2-1> and I2-2> of NS2PTOC are freely settable over a
range of 3 to 500 % of rated generator current IBase. The wide range of start setting
is required in order to be able to protect generators of different types and sizes.
After start, a certain hysteresis is used before resetting start levels. For both steps the
reset ratio is 0.97.
8.9.7.2 Alarm function
The alarm function is operated by START 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.
8.9.7.3 Logic diagram
Operation=ON
BLKST1
Inverse time
selected
IEC08000466-2-en.vsd
Inverse
DT time
selected
ST1
TR1
AND
OR
t1
BLOCK
a
b
a>b
Negative sequence current
I2-1>
IEC08000466-1-EN V2 EN
Figure 123: Simplified logic diagram for step 1 of Negative sequence time
overcurrent protection for machines (NS2PTOC)
Step 2 for Negative sequence time overcurrent protection for machines (NS2PTOC)
is similar to step 1 above except that it lacks the inverse characteristic.
ST1
IEC09000690-2-en.vsd
S
T A R T
OR
OR
ST2
TR2
TR1
ALARM
TRIP
tAlarm
IEC09000690 V2 EN
Figure 124: Simplified logic diagram for the START, ALARM and TRIP signals for
NS2PTOC
Section 8 1MRK 502 048-UEN A
Current protection
248
Technical manual

ABB REG650 Specifications

General

Brand	ABB
Model	REG650
Category	Protection Device
Language	English