Out-Of-Step Blocking - GE ALPS Instruction Manual

1.4 AUXILIARY PROTECTION FUNCTIONS
1
IA LEADS
VA BY 90°
IB LEADS
VB BY 90°
IC LEADS
VC BY 90°
If sufficient load current is flowing prior to the fault there is no output from OR1, indicating that no charging current is
detected, and AND3 is not blocked, since there is no output from AND2. If an unbalanced fault subsequently occurs, FD
blocks AND1 to prevent an AND2 output. AND3 is allowed to produce an output when the remote breaker opens, provided
there is sufficient charging current to operate one or more of the three charging-current-detectors that are the inputs to
OR1. The capacitive charging current must be 60 mA or more (secondary phase current) to assure operation of ROD. If the
fault is still present as indicated by an output from OR3, an ROD trip follows the expiration of the TL20 security time delay.
Figures 1–7: OSB R-X DIAGRAM and 1–8: OSB LOGIC DIAGRAMS represent the functional logic diagrams for out-of-step
blocking and an R-X diagram depicting an assumed swing-impedance locus superimposed on the associated distance
relay characteristics. For an out-of-step condition, the impedance locus will first enter the MOB characteristic, then later
enter the MT (phase-distance trip function) characteristic.
When MOB (A-B) picks up during the power swing, it applies the middle input to AND201. The top input is present from the
NOT via OR202, since MT (A-B) has not operated yet. The bottom NOT input of AND202 is satisfied, since it is assumed
that no phase is open, and 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. OSB can be selected to block tripping of:
1. All functions (Protection Setting 1603: BLOCKWHAT = BLKALL)
2. All distance functions (Protection Setting 1603: BLOCKWHAT = BLKDIST)
3. Only the phase distance functions (Protection Setting 1603: BLOCKWHAT = BLKPHAS)
4. No functions (Protection Setting 1603: BLOCKWHAT = BLKNONE)
For selections 2 and 3, each of the four distance zones (Zone 1, 2, 3, or 4) may be individually selected to be blocked or not
via Protection Settings 1604 through 1607 (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; the pickup delay
becomes progressively lower during successive slip cycles. This improves the capability to maintain the out-of-step output
during the increasing slip frequencies typically encountered after the first slip cycle.
1-14
1
1
F A U L T
D E T E C T O R 3
A N Y Z O N E 2
P H A S E - D I S T A N C E
3
F U N C T I O N
A N Y Z O N E 2
G R O U N D - D I S T A N C E
F U N C T I O N
Figure 1–6: REMOTE-OPEN DETECTOR LOGIC (ROD)
ALPS Advanced Line Protection System
1 PRODUCT DESCRIPTION
2
2
T L 2 0
A
4
TRIP
0
A = 10 - 100
R e m o t e O p e n . v s d

1.4.4 OUT-OF-STEP BLOCKING

GE Power Management