Pulsar TCF-10B, Системное руководство, Страница: 45 / 249

The value of
D
f depends on the bandwidth of the
TCF–10B set. For a bandwidth of 1,200 Hz,
D
f is
500 Hz. A bandwidth of 300 Hz yields a
D
f of 100
Hz, while the 600 Hz bandwidth
D
f can be either
250 or 100 Hz, depending on the setting of S5 on
the Transmitter Board. The center channel
frequency (f
C
) can vary from 30 to 535 kHz (in 0.5
kHz steps).
In the two-frequency systems, only f
H
and f
L
are
used. The two frequencies function differently and
take on different labels when operating with the
different types of protective relay systems.
2.3.1 Directional Comparison
Unblocking (Two-Frequency)
The higher frequency (f
H
), or “Block” frequency,
is transmitted continually as a blocking-type
signal during normal conditions, to indicate that
the channel is operative and to prevent remote
relay tripping when external faults occur.
For a fault sensed by the local overreaching pilot
relay, the transmitter is frequency-shifted to a low
frequency (f
L
), called “Unblock” frequency. The
transmitted power is normally 1 W, boosted to
10 W for the “Unblock” operation.
The Directional Comparison Unblocking system
will generally use the wide band, wide shift
(600 Hz BW, ±250 Hz Shift) TCF–10B carrier set.
Also, the most common power output level used
will be the 1 watt block and 10 watt trip. The type
of carrier applied with this scheme may be varied
from the normal for special circumstances, e.g.,
when matching the new TCF–10B equipment at
one end of the line with the older TCF, TCF-10, or
TCF-10A equipment at the other end. In this case,
you must apply the wide band, narrow shift carrier
(600 Hz BW, ±100 Hz Shift) to match the older
carrier characteristics.
2.3.2 Transfer Trip: Overreaching,
Underreaching or Direct (Two-
Frequency)
The higher frequency (f
H
), or “Guard” frequency,
is transmitted continually during normal condi-
tions. For a fault sensed by the overreaching (or
underreaching) pilot relay, the transmitter is
shifted to the low frequency (f
L
), called “Trip”
frequency.
When using the TCF–10B for any permissive
overreaching or underreaching line relay system,
you can apply any bandwidth set. However, the
best all around set to use will be the wide band,
wide shift (600 Hz BW, ±250 Hz Shift)
equipment. If signal-to-noise ratio is of concern,
however, you may use the narrow band set; on the
other hand, if relay speed is critical, you may
apply the extra wide band (1,200 Hz, ±500 Hz
Shift) equipment. If, in direct transfer trip
systems, security due to S/N is of concern, we
strongly recommend that you apply only narrow
band equipment. In any of these systems, the usual
power level combination will be 1 watt for guard
and 10 watts for the trip signal.
2.3.3 Phase Comparison
Unblocking: Dual or
Segregated (Two-Frequency)
Phase Comparison relays use square wave signals
for operation. The transmitter is keyed to a “Trip
Positive” (or Mark) frequency when the relay
square wave goes positive, and is keyed to a
“Trip-Negative” (or Space) frequency when the
relay square wave is at zero. The Trip Positive
frequency is frequency-shifted below f
C
; the “Trip
Negative” frequency is frequency-shifted above
f
C
. Either frequency can function as a trip or
block, depending on the local square wave.
For Phase Comparison systems, you can use only
the wide band with wide shift or extra wide band
TCF–10B. In the interest of conserving spectrum,
the wide band, wide shift channel is most
common. However, if speed is important, you may
apply the extra wide band set. The most often
applied power level will be 10 watts for both
“Trip-Positive” and “Trip-Negative”.
2.3.4 Three-Frequency Systems
The TCF–10B also provides for three-frequency
system applications (see Figure 2-13), e.g.,
Directional Comparison Unblocking with Direct
Transfer Trip, or Permissive Overreaching
Transfer Trip with Direct Transfer Trip. All three
frequencies are closely-controlled discrete
December 1996 Page 2–13
Chapter 2. Applications and Ordering Information
2