Pickup Sensitivity - ABB REG650 Technical Manual

Section 8
Current protection
8.9.7.1
8.9.7.2
242



ResetMultip
[ ]
=
ResetTime s



I

NS

 
I
Pickup
ANSIEQUATION2111 V1 EN
Where
I is the measured negative sequence current
NS
I is the desired pickup level in pu of rated generator current
Pickup
ResetMultip
is multiplier of the generator capability constant
reset time of inverse time characteristic

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.



⋅
K K 1

 2

 −
1

 
1MRK 502 043-UUS B
(Equation 68)
K equal to setting K 1 and thus defines
Technical Manual