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Power Automation and Protection Division
8.4
Outer blinder, 21 BO, setting (RU)
Similar to RT. It does not restrict tripping. Used mainly to detect out of step conditions.
For Example:
Set RU = 8.0 ohms for a blinder 8.0 ohms away from the line impedance.
8.5
Out of Step detection timer. (OST1)
This timer is started when the outer blinder, 21 BO, has operated but the inner blinder, 21 BI,
has not operated. If the timer times out, an out of step condition has been detected and OSB
is active.
For Example:
Set OST1 = 1.5 cycles.
8.6
Out of Step Trip on the Way in timer (OST2)
This timer is started when an Out of Step condition has been detected and the two blinders
have operated. Once it times out, a trip signal is issued for OST.
For Example:
Set OST2=2 cycle.
8.7
Out of Step Trip on the Way out timer (OST3)
This timer is started when an Out of Step condition has been detected and the OST2 timer has
timed out and both 21 BI are NOT operated. This permits controlling the time that the breaker
opens.
OST3 = 0.5 cycles
8.8
Out of Step Over-ride timer. (OSOT)
This timer is started once an Out of Step condition is identified (output of OST1). An OST signal
is generated if OSOT times out and the apparent impedance seen by the relay is inside Zone
2 or Zone 3 reach plus the RT blinde
For Example:
OSOT = 1600 msec
9.
TIME SETTINGS
REL 352 has an internal clock for event time tagging purposes. Even if the unit has lost its pow-
er supply the internal clock will continue running.
REL 352 Version 1.00
I.L. 40-201.9
5
5-11
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