The heavy load transfer that is common in many transmission networks may in some cases be
in opposite to the wanted fault resistance coverage. Therefore, FMPSPDIS has an built-in
algorithm for load encroachment, which gives the possibility to enlarge the resistive setting of
both the Phase selection with load encroachment and the measuring zones without interfering
with the load.
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
On.
7.8.3
Setting guidelines
SEMOD154771-1 v2
SEMOD154782-4 v6
GlobalBaseSel: Selects the global base value group used by the function to define (IBase),
(
UBase) and (SBase).
INRelPE: The setting of INRelPE for release of the phase-to-earth 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
INBlockPPto give
priority to open phase-to-earth loop.
INRelPE 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.
INBlockPP: The setting of INBlockPP 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 245)
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 7
1MRK 505 343-UEN B
Impedance protection
264
Application manual
Summary of Contents for Relion 670 series
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