Functions
46
7UM62 Manual
C53000-G1176-C149-3
.
Figure 2-14
Definition of the Parameters
and
The setting value of the direction straight line results from the short-circuit angle of the
feeding network. As a rule, it will be > 60°. The current pick-up value results from the
short-circuit current calculation. Acceptable pick-up values are situated at about (1.5
to 2)
⋅
I
N, G
. A tripping time delay of (TI>>
≈
0.05 s to 0.1 s). is required to ensure that
the effect of the transient phenomena is eliminated.
Application
Example: Motor
Protection
For motors that have no separate current transformers in the starpoint, Figure 2-15
shows how to use the I>> stage as ”differential protection”. The configuration of the
protection function depends on the transformers. Since this application is most likely
to be used for replacements in an existing system, the settings of that system should
be the basis for this.
Figure 2-15
I>> Stage Used as “Differential Protection”
Z
Line
I
L1
U
L1
ϕ
L
=
LINE ANGLE
Direction straight line
FOR
WAR
D
REV
ERS
E
(li
ne)
(Ge
ner
ato
r)
I
L, S1
I
L, S2
I>> Stage
Stage I>, Ip>
7UM62
Motor
