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CARRIER RELAYING
RESTRAINING VOLTAGE
FROM CARRIER
WAVE DIAGRAMS
.INTERNAL FAULT
LOCAL
A
FILTER OUTPUT
LOCAL
8
OPERATIN&
c
---- -- -- - LOCAL
CARRIER
D
---- -- - D ISTANT CARRIER ____ __ __ _._
E
RECTIFIED CARRIER
AT
(RESTRAINING VOLTA&£>
RECEIVER
F
ON &RID OF
VOLTA&£
RELAY TUBE•(a>+<f)
G
PLATE CURRENT
OF R
A
L
E
H
RELAY
I
RELAY TRIP5
CURRENT
Fig. 2-The Relay Tube Circuit and Typical Wave Dia·
grams Of The Type HKB System.
relay tube positive.
The rectified output
the carrier receiver is connected
opposite polarity and i . s sufficient to
the effect of the voltage across R'c if carri
er
is received at
the same time that V2
conducting.
The voltage drop across
RB provides negative grid bias for the
trons.
The carrier transmitter
are conventional
carrier relaying units whose
construction
and
principle of operation
well known.
Response To Faults
Figure 2 shows
in detail
just described determine·
or
external
fault
exists.
circuit is shown
at the top
convenience.
The
"operating
trigger circuit" is the voltage drop Eo across
4
T
I �
EXTERNAL FAULT
,.:
e '
VOLTA&£
'
c
__.__. ._.
'
b
E'
'
F
Y TUBE
e:
'
H
RELAY DOES NOT TRIP I'
of
with
the
cancel
is
resistor
thrya
and
receiver
are
how
the circuits
whether an
internal
The
relay-tube
of Figure 2
for
voltage
from
"R'' RELAY
CURRENT
20
Fig. 3-Typical Overall Characteristics of the Type HKB
System.
R'c of Figure 1.
It is called operating volt
age, as it makes the
grid of the
positive, causing the flow of relay-tube plate
current.
The "restraining voltage from carri
er"
is the d-e output
ceiver
and
is so
named
operating
voltage
and prevents
plate
current in the relay
negative potential to its grid.
To see how the quantities
are utilized, consider first an internal fault.
The polarities
of the
voltages
at the two ends of the line are such
that, when the fault detectors operate, carri
er is transmitted
from both line terminals on
the same half-cycles (Figure 2, C and D) .
received and rectified
voltage (Figure 2, E) is applied to the
of the
relay tube
in series with the
ting voltage (Figure 2,
on the grid of the relay tube is the
these two voltages, and has the wave form
dicated at F on Figure 2.
The reference axis
at F
required
to cut off
the plate current of the
relay tube.
Consequently,
voltage
is above
this axis,
flows.
For an
internal
rect�fied carrier
voltage
cycles that the grid of the relay tube is made
180
relay
tube
ER of the
carrier re-
as
it
opposes the
the flow
of
tube
by
applying
shown in Figure 2
sequence-filter-output
The
c � rrier
restraining
grid
opera
The
net voltage
B).
sum
of
in
is the voltage
E c
when the net
grid
plate
current
fault,
there is
no
during
the
half
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