ABB RELION REX640 Technical Manual page 768

Section 4
Protection functions
762
When the reset period is initiated, the time for which START has been active is saved.
If the fault reoccurs, that is, the negative-sequence current rises above the set value
during the reset period, the operate calculations are continued using the saved values.
If the reset period elapses without a fault being detected, the operate timer is reset and
the saved values of start time and integration are cleared.
Inv. curve B
The inverse time equation for curve type B is:
k
t s
[ ]
=
2 2
I
I
   
S
2
 −
  
I I
 r   r 
GUID-8B2C61FA-1705-4C05-BAA4-6FFFE5F2E858 V1 EN
t[s] Operate time in seconds
k Machine time Mult
I Negative-sequence current
2
Start value
I Set
S
Rated current
I Set
r
1MRS759142 C
(Equation 193)
REX640
Technical Manual