Figure 561: Defined zones
The impedance is continuously monitored for detecting an out of step condition.
When the impedance enters inside from the outer blinder, the out of step detection
timer is triggered. If impedance remains between outer and inner blinder for the
duration of the
Swing time
setting, output SWING is activated. If the impedance
enters the mho circle in zone 1, out of step blocking ( OSB) for zone 1 is detected
and output OSB is activated, or if the impedance enters the mho circle in zone 2, OSB
for zone 2 is detected and output OSB_Z2 is activated if setting
Zone 2 enable
is set
to “Yes”. Both OSB and OSB_Z2 can be activated if the impedance passes through
zone 1 and zone 2 while inside the mho circle. The OSB or OSB_Z2 output deactivates
when impedance exits and remains outside the mho circle and the inner blinder for
a duration of five cycles.
Activation of the OPERATE output depends on the
Oos operate mode
selected. The
available options are “Way in”, “Way out”, and “Adaptive”. If the “Way in” option is
selected, the function triggers the delay timer after detecting an OSB condition.
When the set
Operate delay time
has elapsed, the OPERATE output is activated.
When using the “Way in” option, the zone-related settings and zone slip counters are
not applicable.
If the “Way out” option is selected, after detecting an OSB condition, the function
further checks if impedance exits the outer blinder. On exiting the outer blinder, Way
out timer defined by
Operate delay time
setting is triggered and the respective zone
slip counter is incremented after the set
Operate delay time
has elapsed. If the slip
counter value is equal to the set number of slips in the respective enabled zone, the
OPERATE output is activated. If the swing impedance passes through both zone 1
and zone 2, only the zone 1 slip counter is incremented. The zone 2 slip counter is
incremented if the impedance passes through the Mho circle but only through the
zone 2 portion. The zone 3 slip counter is incremented if the impedance misses the
1MRS759142 F
Protection functions
REX640
Technical Manual
1009
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