Schweitzer Engineering Laboratories SEL-311C - Out-Of-Step Characteristics; Use SEL-321 Relay Application Guides for the SEL-311 C; Table 3.6 Out-Of-Step Settings

3.22
SEL-311C Relay Instruction Manual Date Code 20060320
Distance, Out-of-Step, Overcurrent, Voltage, Synchronism Check, and Frequency Elements
Out-of-Step Characteristics
Out-of-Step Characteristics
The out-of-step (OOS) 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-311C makes these settings
automatically. Enable the advanced user settings to set these elements
individually (EADVS = Y).
Use SEL-321 Relay
Application Guides
for the SEL-311C
The out-of-step logic and settings in the SEL-311C are similar to those in the
SEL-321-5 Relay. Refer to SEL Application Guide 97-13: SEL-321-5 Relay
Out-of-Step Logic for additional information about applying the out-of-step
logic.
The timer setting UBOSBD, shown in Figure 3.17, 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-311C, the user can increase the adaptive setting UBOSBD in
multiples of setting UBOSBF. If UBOSBF is set at a multiplier of one, the
relay will calculate 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 will multiply the adaptive time
setting by four.
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.
Table 3.6 Out-of-Step Settings (Sheet 1 of 2)
Enable Setting: EOOS = Y
Block Zone Settings (Zone 1–Zone 4): OOSBn = Y, N (n = 1–4)
Out-of-Step Block Time Delay:
Pickup Ranges:
Pickup and dropout
accuracy for all timers:
OSBD
0.5–8,000.0 cycles, 0.25-cycle steps
±0.25 cycle and ±0.1% of setting
Enable Out-of-Step Tripping: EOOST = N, I, O
Out-of-Step Trip Time Delay:
Pickup Ranges:
OSTD
0.5–8,000.0 cycles, 0.25-cycle steps