2 Functions
146
7UT613/63x Manual
C53000-G1176-C160-2
Figure 2-62 Tripping characteristic of the restricted earth fault protection depending on the
phase angle between 3I
0
” and 3I
0
' at 3I
0
” = 3I
0
' (180
o
= external fault)
It is possible to increase the tripping value in the tripping area proportional to the arith-
metic sum of all currents, i.e. with the sum of the magnitudes „IrestREF=“ i.e.
„IrestRE2=“ Σ | I |=|I
L1
|+|I
L2
|+|I
L3
|+|I
Z
| (Figure 2-63). The slope of this re-
straint characteristic can be set.
Pickup Normally, a differential protection does not need a „pickup“, since the condition for a
fault detection is identical to the trip condition. As with all protective functions the earth
fault differential protection has a pickup that displays a precondition for tripping and
defines the fault inception instant for a number or further activities.
As soon as the fundamental wave of the differential current exceeds 85 % of the
pickup value, fault detection is indicated. In this aspect, the differential current is rep-
resented by the sum of all in-flowing currents.
Figure 2-63 Increasing the Pickup Value
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