The load encroachment algorithm and the blinder functions are always activated in the
phase selector. The influence from these functions on the zone measurement
characteristic has to be activated by switching the setting parameter
LoadEnchMode
for the respective measuring zone(s) to
Enabled
.
8.8.3
Setting guidelines
SEMOD154771-1 v2
SEMOD154782-4 v6
GlobalBaseSel
: Selects the global base value group used by the function to define
IBase
,
VBase
and
SBase
as applicable.
INRelPG
: The setting of
INRelPG
for release of the phase-to-ground loop is by default
set to 20% of
IBase
. The default setting is suitable in most applications.
The setting must normally be set to at least 10% lower than the setting of
3I0BLK_PP
to give priority to open phase-to-ground loop.
INRelPG
must be above the
normal un-balance current (3I
0
) that might exist due to un-transposed lines.
The setting must also be set higher than the 3I
0
that occurs when one pole opens in
single pole trip applications.
3I0BLK_PP
: The setting of
3I0BLK_PP
is by default set to 40% of
IBase
, which is
suitable in most applications.
I1LowLevel
: The setting of the positive current threshold
I1LowLevel
used in the
sequence based part of the phase selector for identifying three-phase fault, is by default
set to 10% of
IBase
.
The default setting is suitable in most cases, but must be checked against the minimum
three-phase current that occurs at remote end of the line with reasonable fault
resistance.
IMaxLoad
: The setting
IMaxLoad
must be set higher than the maximum load current
transfer during emergency conditions including a safety margin of at least 20%. The
setting is proposed to be according to equation
:
IMaxLoad
=1.2 ILoad
EQUATION1614 V2 EN-US
(Equation 194)
where:
1.2
is the security margin against the load current and
ILoad
is the maximal load current during emergency conditions.
The current ILoad can be defined according to equation
.
Section 8
1MRK 504 163-UUS A
Impedance protection
318
Transformer protection RET670 2.2 ANSI
Application manual
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