Sel 411L - Figure 3.109 Dependable Power-Swing Block Detector Logic (EOOS = Y); Figure 3.110 Relay Word Bit DOSB Is the or Combination of DOSBY1 and DOSBY

P.3.171
Date Code 20151029 Protection Manual SEL-411L Relay
Protection Functions
Out-of-Step Logic (Zero Settings)
Figure 3.109 Dependable Power-Swing Block Detector Logic (EOOS = Y)
Figure 3.110 shows DOSB, the OR combination of the output from
Figure 3.108 (DOSBY1) and the output from Figure 3.109 (DOSBY). Only
Relay Word bit DOSB is available; DOSBY1 and DOSBY are for internal use
in the relay.
Figure 3.110 Relay Word Bit DOSB Is the OR Combination of DOSBY1 and
DOSBY
Three-Phase Fault
Detector
Figure 3.111 shows the logic diagram of the three-phase fault detector. If a
three-phase fault occurs on a transmission line during a power swing, a step
change occurs in the SCV1 waveform. This step change can be identified
when the second derivative of SCV1 has a higher than usual value.
Furthermore, the SCV1 has a low value and its rate of change is very small.
These properties are taken into account in the three-phase fault detector so as
to implement a very fast detector, independent from the swing speed. Three-
phase faults will be detected with a minimum and maximum time delay of two
and five cycles, respectively.
DIR5 = F
DIR4 = F
Z5P
Z4P
Z3P
Z2P
OSB
TRIP
SERCAB
SERCBC
MAB1I
XAB1I
MBC1I
XBC1I
SERCCA
MCA1I
XCA1I
X7ABC
Z1MAG
| Z1F
k
— Z1F
k — 1
| • 8 • NFREQ
DIR3 = F
0
0.25
CYC
0
0.25
CYC
0
0.25
CYC
0
1.5
CYC
0
0.125
CYC
0
1.5
CYC
DOSBY
0
1.5
CYC
0
60
CYC
DOSBY1
DOSBY
DOSB