Pulsar TC-10B, User Manual

Page: 25 / 190

terminal determines whether a fault
is internal or external.
Fault detectors are used to determine
whether a fault has occurred and to
supervise tripping. The fault
detectors must be overreaching, i.e.,
set sensitively 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
detectors 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.
October 2003 Page 2–3
Chapter 2. Applications and Ordering Information
2
Table 2–1. 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 (F
E
)
For external faults, the
CS unit or timer x/o
assure that a blocking
signal is established.
P
1
operates; S
1
does not see
fault. Blocking signal received
from station H. RR back
contacts open (or 1 signal
negates AND).
No trip.
S
2
operates to key transmitter.
Blocking signal sent to station
G. P
2
does not see fault.
No trip.
Internal (F
I
) P
1
operates; S
1
may or may not
operate, but P
1
operation
prevents transmission of a
blocking signal.
Breaker 1 tripped.
P
2
operates, S
2
may or may not
operate but P
2
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 2–2. Phase-Comparison Blocking, Basic Elements.