Directional control
SEMOD168247-145 v2
The directional function (ZDSRDIR) which is able to cope with the condition at voltage reversal,
shall be used in all IEDs with conventional distance protection (ZMCPDIS,ZMCAPDIS). This
function is necessary in the protection on compensated lines as well as all non-compensated
lines connected to this busbar (adjacent lines). All protections that can be exposed to voltage
reversal must have the special directional function, including the protections on busbar where
the voltage can be reversed by series compensated lines not terminated to this busbar.
The directional function is controlled by faulty phase criteria. These criteria must identify all
forward and reverse faults that can cause voltage reversal. Setting of the corresponding reach
of the impedance measuring elements is separate for reactive and resistive reach and
independent of each other for phase-to-earth and for phase-to-phase measurement.
It is also necessary to consider the minimum load impedance limiting conditions:
Setting of zone 1
SEMOD168247-150 v3
A voltage reversal can cause an artificial internal fault (voltage zero) on faulty line as well as on
the adjacent lines. This artificial fault always have a resistive component, this is however small
and can mostly not be used to prevent tripping of a healthy adjacent line.
An independent tripping zone 1 facing a bus which can be exposed to voltage reversal have to
be set with reduced reach with respect to this false fault. When the fault can move and pass
the bus, the zone 1 in this station must be blocked. Protection further out in the net must be
set with respect to this apparent fault as the protection at the bus.
Different settings of the reach for the zone (ZMCPDIS) characteristic in forward and reverse
direction makes it possible to optimize the settings in order to maximize dependability and
security for independent zone1.
Due to the sub-harmonic oscillation swinging caused by the series capacitor at fault
conditions the reach of the under-reaching zone 1 must be further reduced. Zone 1 can only be
set with a percentage reach to the artificial fault according to the curve in
99000202.vsd
p
100
80
60
40
20
0
100 %
80
60
40
20
C
%
IEC99000202 V1 EN-US
Figure 116: Reduced reach due to the expected sub-harmonic oscillations at different
degrees of compensation
Section 7
1MRK 505 343-UEN B
Impedance protection
182
Application manual
Содержание Relion 670 series
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