ABB Relion 670 Series Technical Reference Manual page 305

1MRK505222-UUS C
Technical reference manual
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.
DeltaIA
DeltaVA
Sequence based
function
AB fault
OR
AG fault
3 Phase fault
IA Valid
BLOCK
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
a>b
a
FaultPriority
c
then c=a
Adaptive release
b
dependent on result
else c=a
from Delta logic
a<b
a
c
then c=b
b
OR
else c=a
&
Section 6
Impedance protection
PU_A
en06000386_ansi.vsd
299