Ametek UPLC-II System Manual page 63

open breaker. If this remote signal is received for 1,000 ms (1 sec) or longer, the carrier receiver logic inter-
prets this as an open breaker and allows the local end to trip whenever the local relays detect a fault.
An older system (STU unblock) is shown in Figure 3–24a & 24b, near the end of this chapter.
Table 3–4. Operation of the Directional Comparison Unblocking Scheme
OPERATION FOR EXTERNAL AND INTERNAL FAULTS
Type of Fault
External (F E )
Internal (F I )
G
Protected Line
1
Breaker 2 Trip Fault Detector (P
Figure 3–9. Basic Logic Diagrams for Directional Comparison Unblocking
January 2016
Events at Station G
P 1 operates.
f 1 channel shifts to unblock.
f 2 channel continues to
block.
No trip.
P 1 operates.
f 1 channel to unblock.
Loss of block and/ or receipt
of unblock (f 2 ) operates RR
or inputs AND.
Trip.
Breaker 1 Trip Fault Detectors (P
F
I
2
Power Line Carrier
Channel f 1 (G to H)
Power Line Carrier
Channel f (H to G)
2
)
2
Solid State Logic (per Terminal)
P
AND
Unblock
(See Figure 2-1)
Note: (X) Normally 4 Ms.
Chapter 3. applications
Events at Station H
P 2 does not see fault.
Loss of block and/or receipt
of unblock (f 1 ) operates RR
or inputs AND.
No trip.
P 2 operates.
f 2 channel shifts to unblock.
Loss of block and/or receipt
of unblock (f 1 ) operates RR
or inputs AND.
Trip.
)
Contact Logic (per Terminal)
1
H
F P
E
RR
52a
Timer
X
Trip
O
Key Transmitter
to Unblock
RR
Channel
Signal
Receiver
(F at H,
Trip 1
F 2 at G)
Coil
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