Siemens SIPROTEC 7UT613 series Manual page 146

2 Functions
Pickup
146
Figure 2-62 Tripping characteristic of the restricted earth fault protection depending on the
phase angle between 3I
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
straint characteristic can be set.
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
" and 3I ' at 3I
0 0
| + | I | + | I | + | I
L1 L2 L3 Z
o
" = 3I ' (180 = external fault)
0 0
| (Figure 2-63). The slope of this re-
7UT613/63x Manual
C53000-G1176-C160-2