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3-48
Line Current Differential, Distance, Out-of-Step, Overcurrent,
Date Code 20011112
Voltage, Synchronism Check, and Frequency Elements
SEL-311L Instruction Manual
O
UT
-
OF
-S
TEP
(OOS) C
HARACTERISTICS
The out-of-step detection logic detects stable or unstable power swings. When the positive-
sequence impedance remains between Zones 5 and 6 longer than the OOS blocking delay (setting
OSBD), or the OOS tripping delay (setting OSTD), the relay makes a decision to either block
tripping or to allow tripping.
The OOS relay word outputs are used for alarming or controlling other equipment.
Normally, the Zone 5 and Zone 6 bottom reactance and left resistance element settings are mirror
images of the top reactance and right resistance element settings (e.g., X1B5 = -X1T5). The
SEL-311L Relay makes these settings automatically. Enable the advanced user settings to set
these elements individually (EADVS = Y).
Note:
The out-of-step logic cannot be used when setting Z1ANG is less than 45 degrees. In
that case, setting EOOS must equal N.
Use SEL-321 Relay Application Guides for the SEL-311L Relay
The out-of-step logic and settings in the SEL-311L Relay are the same as those in the SEL-321-5
Relay. Refer to
Application Guide 97-13: SEL-321-5 Relay Out-of-Step Logic
for applying the
out-of-step logic in the SEL-311L Relay.
The timer setting UBOSBD, shown in Figure 3.37, is an adaptive setting calculated by the relay.
This adaptive setting, which is the expected duration of the swing within the inner blinders, is
based on the actual time it takes for the swing to travel between the Zone 6 and Zone 5 blinders
prior to moving into inner blinders. If the swing stays between the inner blinders for a period
longer that UBOSBD cycles, an unblock signal is asserted.
In the SEL-311L, increase the adaptive setting UBOSBD in multiples of setting UBOSBF. If
UBOSBF is set at a multiplier of one, the relay calculates the expected time to traverse the inner
blinders based on the rate at which the swing transitions from Zone 6 to Zone 5. Similarly, if
UBOSBF is set at a multiplier of 4, the relay multiplies the adaptive time setting by four.
Enable Setting:
EOOS = Y
Block Zone Settings (Zone 1–Zone 4):
OOSB
n
= Y, N (
n
= 1–4)
Out-of-Step Block Time Delay:
OSBD
Pickup Ranges:
0.5–8,000.0 cycles, 0.25-cycle steps
Pickup and dropout accuracy for all
timers:
±0.25 cycle and ±0.1% of setting
Enable Out-of-Step Tripping:
EOOST = N, I, O
Out-of-Step Trip Time Delay:
OSTD
Pickup Ranges:
0.5–8,000.0 cycles, 0.25-cycle steps
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