Faulty phase identification with load encroachment for mho (FMPSPDIS) function
is designed to accurately select the proper fault loop in the Distance protection
function dependent on the fault type.
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.
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, UBase and SBase as applicable.
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
222:
1MRK 506 369-UEN B Section 8
Impedance protection
Line distance protection REL670 2.2 IEC 287
Application manual
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