P.3.157
Date Code 20151029 Protection Manual SEL-411L Relay
Protection Functions
Out-of-Step Logic (Conventional)
Figure 3.95 Load-Encroachment Characteristics
Out-of-Step Logic (Conventional)
The relay offers both conventional and settingless (zero-setting) out-of-step
(OOS) functions. To use the conventional OOS function, set EOOS = Y. To
use the zero-setting OOS function, set EOOS = Y1.
The out-of-step (OOS) logic determines whether a power swing is stable. This
relay logic can be set to either block distance protection or allow tripping
when the measured positive-sequence impedance (Z
1
) remains between inner
Zone 6 and outer Zone 7 longer than either the OOS blocking delay (setting
OSBD) or the OOS tripping delay (setting OSTD), respectively (refer to
Figure 3.96).
NOTE: E50Q must be set to 1 or
greater for enabling 67Q1T override of
OOS blocking for Zone 1 (see
Figure 3.121, Figure 3.124, and
Figure 3.127).
The OOS logic detects all power swings that enter the OOS characteristics,
even if a single-pole open condition exists (Relay Word bit SPO equals
logical 1). If either negative-sequence directional element 67QUBF or
67QUBR (67Q1T for Zone 1) picks up during a power swing and a single-
pole open condition does not exist (Relay Word bit SPO equals logical 0), the
ZLIN
(Load In
Region)
(180˚)
(90˚)
X1
PLAR
PLAF
NLAR
NLAF
ZLF
ZLR
(270˚) (—90˚)
ZLOUT
(Load Out
Region)
(0˚)
R1
Table 3.85 Load-Encroachment Logic Relay Settings
Name Description Range
Default
(5 A)
ELOAD Load encroachment Y, N Y
ZLF Forward load impedance () (0.25–320)/I
NOM
9.22
ZLR Reverse load impedance () (0.25–320)/I
NOM
9.22
PLAF Forward load positive angle () –90.0 to +90 30.0
NLAF Forward load negative angle () –90.0 to +90 –30.0
PLAR Reverse load positive angle () 90.0–270 150.0
NLAR Reverse load negative angle () 90.0–270 210.0
Table 3.86 Load-Encroachment Logic Relay Word Bits
Name Description
ZLOAD ZLIN OR ZLOUT
ZLIN Import load impedance detected
ZLOUT Export load impedance detected
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