1-42
ALPS Advanced Line Protection System
GE Power Management
1.10 OUT-OF-STEP TRIPPING (OPTIONAL)
1 PRODUCT DESCRIPTION
1
Figure 1–23: OST MHO CHARACTERISTIC
Figure 1–24: OUT-OF-STEP TRIPPING LOGIC
1.10.3 OUT-OF-STEP DETECTION
The actual out-of-step detection in the OST option is accomplished by a software algorithm. This algorithm is represented
by the logic diagram shown in Figure 1–24: OUT-OF-STEP TRIPPING LOGIC on page 1–47.
The operation of the logic diagram in is explained below; this discussion assumes that Protection Setting 1702: NUM-
BRCHAR = 3 and all three OST Mho characteristics are used.
1.
The power swing enters the OUTER characteristic. Thus AND61 will have one input from the OUTER and a second
input from OR61 since NOT61 has no input. If the swing impedance remains between the OUTER and MIDDLE char-
acteristics for the pickup setting of TLOS1, TLOS1 operates, seals in one input of AND61.
When a fault occurs, the OUTER and MIDDLE characteristics operate almost simultaneously, and the MIDDLE blocks
AND61 through NOT61 thus preventing TLOS1 from operating.
2.
The swing now enters the MIDDLE characteristic but remains outside the INNER characteristic. One input of AND62 is
energized by TLOS1, a second input is proved by the MIDDLE, and the last is supplied by NOT62. If the swing imped-
ance remains between the MIDDLE and INNER characteristics long enough for TLOS2 to pick up, TLOS2 seals in the
Outer
Middle
Inner
Swing Line
R
X
Zf
Zr
OUTER
MIDDLE
INNER
NUMBRCHAR
=
2
NUMBRCHAR
=
2
TRIP OUT
TRIP IN
TLOS1
TLOS2
TLOS3
TLOS4
61
62
63
63
65
70
65
63
64
62
61
61
66
62
64
68
A = 1 - 100
ms
OST
A
A
A
0
A
A
0
A
0
(REF.)
