Schweitzer Engineering Laboratories SEL-421-4 - Figure 5.38 Swing Center Voltage Slope Detection Logic

5.58
SEL-421 Relay Instruction Manual Date Code 20171021
Protection Functions
Out-of-Step Logic (Zero Settings)
The bottom input of AND Gate AND 5 asserts when the following is true:
➤ The absolute value of the SCV1 is above 0.05 and
➤ The enable out-of-step setting (EOOST) is either I, O, or C and the
positive-sequence impedance is in Zone 7 (Z1ZN7) or
➤ If out-of-step tripping is not selected (EOST = N), then the following
conditions must be true: the absolute value of the SCV1 is below
0.85 and the positive-sequence impedance is in the Starter Zone
(Z1ZNS)
When AND Gate AND 5 asserts, SD asserts. When SD asserts, the Latch in
Figure 5.37 asserts, causing OSB_I and OSB to assert.
Figure 5.38 includes two checks for Z1, the positive-sequence impedance:
whether Z1 is in the Starter Zone (see Figure 5.39) and whether Z1 is in Zone 7
(see Figure 5.32).
Figure 5.38 Swing Center Voltage Slope Detection Logic
AND 1
AND 2
AND 3
AND 4
SD
AND 6
AND 5
–0.0172
dSCV1_F
–0.0026
dSCV1_S
dSCV1_F
0.0172
dSCV1_S
0.0026
OSB_I
Z2P
Z5P
Z4P
Z3P
| dSCV1_UF |
0.55
0.23
| d2SCV1_UF |
0.20
EOOST = I, O, C
Z1ZN7
0.85
| SCV1 |
Z1ZNS
| SCV1 |
0.05
Timer 1
1.75
0
CYC
Timer 2
Timer 3
Timer 4
5
0
CYC
1.75
0
CYC
5
0
CYC
Timer 5
0
0.5
CYC
OR 1