Ametek UPLC CU44-VER04, Руководство по применению

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May 2012 Page 3–33
Chapter 3. Applications
3
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
and FD
2
).
FD
1
, the carrier start unit, is set more
sensitively than FD
2
and permits the
local square wave signal to key the
“ON/OFF” carrier transmitter. FD
2
,
set with a higher pickup than FD
1
, is
used to arm the system for tripping.
For transmission lines less than 100
Table 3–4. Directional Comparison Schemes for External and Internal Faults.
* For external faults, the CS unit or timer x/o assure that a blocking signal is established.
SCHEME FOR EXTERNAL AND INTERNAL FAULTS
Type of Fault Events at Station G Events at Station H
External (FE)
For external faults, the
CS unit or timer x/o
assure that a blocking
signal is established.
P1 operates; S1 does not see
fault. Blocking signal received
from station H. RR back con-
tacts open (or 1 signal negates
AND).
No trip.
S2 operates to key transmitter.
Blocking signal sent to station
G. P2 does not see fault.
No trip.
Internal (FI) P1 operates; S1 may or may
not operate, but P1 operation
prevents transmission of a
blocking signal.
Breaker 1 tripped.
P2 operates, S2 may or may
not operate but P2 operation
prevents transmission of a
blocking signal.
Breaker 2 tripped.
Protected Line
G H
1 2
Trip Breaker 1 Trip Breaker 2
Sequence
Network
Squaring
Amplifier
Delay
Circuit
Comparison
Circuit
Three Phase
and Neutral
Single Phase
Output
Sequence
Network
Squaring
Amplifier
Delay
Circuit
Comparison
Circuit
Three Phase
and Neutral
Single Phase
Output
Channel
Figure 3–30 Phase-Comparison Blocking, Basic Elements.