ABB RELION 670 Series Technical Manual page 572

Section 8
Current protection
Where
I
NS
I
Pickup
ResetMultip
8.14.7.1 Pickup sensitivity
The trip pickup levels Current
3 to 500 % of rated generator current
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.
8.14.7.2 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
during short-time unbalanced conditions.
8.14.7.3 Logic diagram
CurveType1=Definite
Negative sequence current
I2-1>
Operation=Enabled
BLK1
BLOCK
CurveType1=Inverse
ANSI08000466 V4 EN-US
Figure 300: Simplified logic diagram for step 1 of Negative sequence time overcurrent
Step 2 for Negative sequence time overcurrent protection for machines (NS2PTOC, 46I2) is similar
to step 1.
566
is the measured negative sequence current
is the desired pickup level in pu of rated generator current
is multiplier of the generator capability constant
time of inverse time characteristic
I2-1> and I2-2> of NS2PTOC (46I2) are freely settable over a range of
tAlarm is provided for the alarm function to avoid false alarms
a
a>b
b
AND
protection for machines (NS2PTOC, 46I2)
K equal to setting K 1 and thus defines reset
IBase . The wide range of pickup setting is required in order
0-t1
0
0-txMin
Inverse
0
AND
1MRK 502 066-UUS B
GUID-1D038486-7086-466F-A92F-30E1A47D0298 v3
GUID-1B932D89-3233-4841-977A-5B61346B057B v2
GUID-71553DAF-374C-4980-82D8-D3AF79861C5B v3
OR
PU_ST1
ANSI08000466-4-en.vsd
Technical manual