WITH RELATIVE IIIST.l.IITAMEOUS
POLAR tTY AS SHOWN, THE
D I RECTIONAL U N I T CONTACTS CLOSE
I N STAMTANEOUS
OVERCURREin UNIT
{UPPER CYL.UIIIT)
SATURATUIG
TRAIISFORMER
\IIOUCTIOII D I S C
U N I T
D I RECTIOIIAL U II I T
(LOWER CYL.UIIIT)
CHASS I S OPERATED
SHORT I N G SWITCH
RED HANDLE
TEST SWI TCH
CURRENT TEST JACK
TEI
M
UI
A
L
185A421
Fig. 3. Internal Schematic of the Type IRV Relay in the
Type FT31 Case.
Instantaneous Overcurrent Unit (I)
Range
Taps
0.5- 2
Amps
0 . 5
0.75
1.0
1 . 25
1 . 5
2
1-4
1 . 0
1 . 5
2. 0
2. 5
3.0
4. 0
2-8
2
3
4
5
6
8
4- 16
4
6
8
9
12
16
10-40
10
15
20
24
30
40
20-80
20
30
40
48
60
80
Time Overcurrent Unit
Range
Taps
.5- 2 . 5 0 . 5
0 . 6
0 . 8
1 . 0
1 . 5
2.0
2 . 5
2-6
2
2.5
3
3 . 5
4
5
6
4- 1 2
4
5
6
7
8
10
1 2
The tap value i s the minimum current required to
just close the relay contacts.
The time vs. current characteristics for the time
overcurrent unit are shown in Figs.
4
to
10.
These
characteristics give the contact clo sing time for the
various time dial settings when the indicated multi
pl es of tap vaJue current are applied to the relay,
The time vs. current characteristics for the in
stantaneous overcurrent unit is shown in Fig.
1 1.
The time vs. current characteristics for the
directional unit is shown in Fig.
1 2.
4
T r i p C i rc u i t
The relay contacts will safely close
3 0
amperes
at
250
volts d.c. and the seal-in contacts of the indi
cating contactor switches will safely carry this cur
rent long enough to trip a circuit breaker.
The indicating contactor switch has two tap s
that provide a pickup setting of
0 . 2
or
2
amperes. To
change taps requires connecting the l ead located in
front of the tap block to the desired setting by means
of a screw connection.
C y l i n der U nit C o ntacts
The moving contact assembly has been factory
adjusted for low contact bounce performance and
should not be changed.
The set screw in each stationary contact has
been shop adjusted for optimum follow and this ad
justment should not be disturbed.
T r i p C i rc u i t C o n stants
Indicating Contactor Switch -
0 . 2
ampere tap -
6 . 5
ohms d-e resistance
2.0
ampere tap -
0. 15
ohms d-e resistance
Aux i l iary Switch ( C S- 1 )
The auxiliary switch op erating time i s approxi
mately
5
mil liseconds.
48-250
volt d-e relay
d- e resistance
-
1 1 6 5 ohm s
24
volt d-e relay
d-e resistance
-
1 10
ohm s (note that series re
sistor is a fixed
100
o hm resistor).
D i recti onal U n i t
Th e IRV relay i s intended for phase fault pro
tection and the directional unit has its maximum
torque when the current l eads the voltage by appro x
imately
30
°.
The directional unit minimum pickup is
1.2
volts and
4
amperes at its maximum torque angl e
for the
4
to
1 2
ampere range relays and
1 .
2
volts and
2
amperes for the
0.5
to
2.5
ampere and the
2
to
6
ampere range relays.
The directional unit should be connected using
the current in one-phase wire and the potential acro ss
the other two phase wires. This connection is com
monly referred to as the
90
•connection. When utilizing
the
90
• connection the maximum torque of the relay
occurs when the fault current lags its
100%
P.F.
position by approximately
60
•. See Fig.
15.
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