Single Phase-Comparison Blocking, Current Only - Ametek UPLC CU44-VER04 Applications Manual

Table 3–4. Directional Comparison Schemes for External and Internal Faults.
SCHEME FOR EXTERNAL AND INTERNAL FAULTS
Type of Fault
External (F E )
For external faults, the
CS unit or timer x/o
assure that a blocking
signal is established.
Internal (F I )
* For external faults, the CS unit or timer x/o assure that a blocking signal is established.
sitively enough to operate for all internal
phase and ground faults.
Because overcurrent fault detectors
are normally used, voltage trans-
formers are not required. Such a
scheme is current only. Fault detec-
tors should be set above maximum
load, yet operate for all internal
faults. Distance fault detectors,
which require voltage transformers,
are used on heavy-loaded or long
lines when distance supervision is
required.
3.5.3 Single Phase-
Comparison
Blocking, Current
Only
In the current only system, the
UPLC™ is used with two overcur-
rent fault detectors (FD
l
FD , the carrier start unit, is set more
1
sensitively than FD and permits the
2
local square wave signal to key the
"ON/OFF" carrier transmitter. FD
set with a higher pickup than FD
used to arm the system for tripping.
For transmission lines less than 100
May 2012
Events at Station G
P 1 operates; S 1 does not see
fault. Blocking signal received
from station H. RR back con-
tacts open (or 1 signal negates
AND).
No trip.
P 1 operates; S 1 may or may
not operate, but P 1 operation
prevents transmission of a
blocking signal.
Breaker 1 tripped.
and FD ).
2
,
2
Figure 3–30 Phase-Comparison Blocking, Basic Elements.
, is
1
Events at Station H
S 2 operates to key transmitter.
Blocking signal sent to station
G. P 2 does not see fault.
No trip.
P 2 operates, S 2 may or may
not operate but P 2 operation
prevents transmission of a
blocking signal.
Breaker 2 tripped.
G
Protected Line
1
Three Phase
and Neutral
Sequence
Network
Single Phase
Output
Squaring
Amplifier
Channel
Delay
Circuit
Comparison
Circuit
Trip Breaker 1
Chapter 3. Applications
H
2
Three Phase
and Neutral
Sequence
Network
Single Phase
Output
Squaring
Amplifier
Delay
Circuit
Comparison
Circuit
Trip Breaker 2
Page 3–33
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