Fault evaluation and selection logic
The phase selection logic has an evaluation procedure that can be simplified according
to figure 153. Only phase A is shown in the figure. If the internal signal 3 Phase fault is
activated, all four outputs PICKUP, PU_A, PU_B and PU_C gets activated.
a
b
a>b
then c=a
else c=a
c
DeltaIA
DeltaVA
FaultPriority
Adaptive release
dependent on result
from Delta logic
a
b
a<b
then c=b
else c=a
c
OR
AB fault
AG fault
Sequence based
function
OR
3 Phase fault
IA Valid
&
BLOCK
PU_A
en06000386_ansi.vsd
ANSI06000386 V1 EN
Figure 153: Simplified diagram for fault evaluation, phase A
Load encroachment logic
Each of the six measuring loops has its own load (encroachment) characteristic based
on the corresponding loop impedance. The load encroachment functionality is always
activated in faulty phase identification with load encroachment for mho (FMPSPDIS,
21) function but the influence on the zone measurement can be switched Enabled/
Disabledin the respective impedance measuring function.
The outline of the characteristic is presented in figure
154. As illustrated, the resistive
reach in forward and reverse direction and the angle of the sector is the same in all four
quadrants. The reach for the phase selector will be reduced by the load encroachment
function, as shown in figure
154.
Blinder
Blinder provides a mean to discriminate high load from a fault. The operating
characteristic is illustrated in figure 154. There are six individual measuring loops with
the blinder functionality. Three phase-to-ground loops which estimate the impedance
according to
1MRK505222-UUS C Section 6
Impedance protection
299
Technical reference manual
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