GE Power Management LPS-O Line Protection System 1-
11
1 PRODUCT DESCRIPTION 1.4 AUXILIARY PROTECTION FUNCTIONS
1
Figure 1–5: OSB R-X DIAGRAM
When MOB (A-B) picks up during the power swing, it applies the lower input to AND202. The top input is
present from the NOT via OR202, since MT (A-B) has not operated yet. The AND202 output energizes timer
TL1.
If the impedance stays between the MOB and MT characteristics for the pickup time of TL1, an OSB output
results. The OSB output is routed back to the top input of AND202 via OR202 to seal-in the OSB output for as
long as MOB is picked up. The OSB output resets 50 ms after the swing-impedance locus leaves the MOB
characteristic. The same logic is repeated for the distance functions associated with phase pairs B-C and C-A,
and all three phase-pair outputs energize TL1. OSB is always routed to block tripping of:
1. All functions (Protection Setting 1303,
BLOCKWHAT
= BLKALL)
2. All distance functions (Protection Setting 1303,
BLOCKWHAT
= BLKDIST)
3. Only the phase distance functions (Protection Setting 1303,
BLOCKWHAT
= BLKPHAS)
4. No functions (Protection Setting 1303,
BLOCKWHAT
= BLKNONE)
For 2 and 3 above, each of the four distance zones (Zones 1, 2, 3, or 4) may be selected to be blocked (or not)
via Protection Settings 1304 through 1307 (
BLOCKZ1
,
BLOCKZ2
,
BLOCKZ3
, and
BLOCKZ4
).
Timer TL1 has an adaptive pickup feature with an initial pickup setting of 30 ms for the first slip cycle, with the
pickup delay becoming progressively lower during successive slip cycles. This adaptive pickup provides
improved capability to maintain the out-of-step output during the increasing slip frequencies that are typically
encountered after the first slip cycle.
MT
ZONE 2/
ZONE 3/
ZONE 4
MOB
SWING IMPEDANCE
LOCUS
X
R
MT (Zone 2 / Zone 3 / Zone 4)
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