Functions
66
7UM62 Manual
C53000-G1176-C149-3
Definite-Time
Trip Stage
High negative phase-sequence currents can only be caused by a two-pole power
system short circuit which must be covered in accordance with the network grading
plan. For this reason, the thermal characteristic is cut by a selectable, definite-time,
negative phase-sequence current stage (address
and
(see Figure 2-21).
Please also observe the instructions regarding the phase rotation (phase sequence)
provided in Sections 2.3 and 2.43.
Figure 2-21
Tripping Zone of the Unbalanced Load Protection
Figure 2-22
Logic Diagram of the Unbalanced Load Protection
I
2
t
Thermal
trip stage
Unbalanced load
Tripping zone I
2
>>
I
2 adm
I
2
>>
Unbalanced load stage I
2adm.
FNo. 05146
I
L1
I
L2
I
L3
FNo. 05143
Tripping
matrix
FNr.05156
&
&
FNr.05160
FNr.05158
&
FNr.05165
FNr.05152
FNr.05159
FNo.05161
0
1
I
2
I
n
---
2
t
∆
⋅
å
I
2
I
CO
Reset
I
2
=0
OR
TMin
TRIP CMD