Zmmmxu Settings - ABB RED650 Applications Manual

1MRK 505 393-UEN B
7.1.3.10
Line differential protection RED650 2.2 IEC
Application manual
This setting opens an opportunity to enable phase-to-earth measurement for phase-
to-phase-earth faults. It determines the level of residual current (3I0) above which
phase-to-earth measurement is activated (and phase-to-phase measurement is
blocked). The relations are defined with the equation.
IN Re leasePE
× ³
3 I
0
100
EQUATION2548 V1 EN-US
Where:
INReleasePE
the setting for the minimum residual current needed to enable operation in the
phase-to-earth fault loops in %
I the maximum phase current in any of the three phases
phmax
By default, this setting is set excessively high to always enable phase-to-phase
measurement for phase-to-phase-earth faults. This default setting value must be
maintained unless there are very specific reasons to enable phase-to-earth
measurement. Even with the default setting value, phase-to-earth measurement is
activated whenever appropriate, like in the case of simultaneous faults: two earth
faults at the same time, one each on the two circuits of a double line.
One specific situation where the INReleasePE setting should be altered is for cross-
country faults in high impedance earthed networks, in order to make sure that
operation is phase-to-earth. This is particularly important when using phase
preference logic, since it is only working per phase, not for phase-to-phase
measurement. The limit should be set so that it will be exceeded during a cross-
country fault.

ZMMMXU settings

ZZeroDb
Minimum level of impedance in % of range (ZMax-ZMin) used as indication of
zero impedance (zero point clamping). Measured values below ZZeroDb are forced
to zero.
ZHiHiLim, ZHiLim, ZLowLim and ZLowLowLim
All measured values are supervised against these four settable limits. It provides
the attribute "range" in the data class MV (measured value) with the type
ENUMERATED (normal, high, low, high-high and low-low) in
ZMFPDIS.ZMMMXU.
ZLimHys
Hysteresis value in % of range (ZMax-ZMin), common for all limits. It is used to
avoid the frequent update of the value for the attribute "range".
×
I
ph max
Section 7
Impedance protection
(Equation 75)
GUID-42F340C5-93CC-40AE-B67D-DC1B7D0520DA v1
133