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TY P ES I R P, I RC AND I R D R ELAYS
ne ctor s crew in the desired t ap , the rel ay will j ust
close its contacts at the tap value current.
Since the tap block connector screw car
C A U T I O N
ries
operating current, b e sure that the screw i s
turned tight.
In order to avoid opening the current transformer
circuits when changing tap s under load, connect the
sp are tap screw in the desired tap position before re
moving
the other tap s crew from the ori ginal tap
po sition.
D i recti o n al U n i t s ( D)
No setting is required.
l n di eati n g Co n t a c to r Sw i t c h ( I C S/ 1 a n d I C S/ T)
No setting is required on the ICS units except the
selection of the
0 . 2
or
2.0
selection is made by connecting the lead located in
front of the tap block to the desired setting by means
of the connecting screw.
A u x i l i ary S w i t c h ( C S- 1 )
No setting required on the CS- 1 unit except for the
selection of the required
on the taPPed resistor.
This connection can be made
by referring to Fig.
2 1 .
I N S T A L L A T I O N
The
relays should be mounted on switchbo ard
p anels or their equivalent in a location free from dirt,
moisture , excessive vibration and heat.
relay vertically be means of the t wo mounting studs
for the type FT projection case or by means of the
four mounting hol e s on the flange for the semi-flush
type FT case.
Either of the studs or the mounting
screws may be utilized for grounding the rel ay.
electrical connections may be made directly to the
terminal s by means of s crews for steel panel mount
ing or to terminal stud s furnished with the rel ay for
thick panel mounting.
The terminal studs may be
easily removed or inserted by locking two nuts on the
studs and then turning the proper nut with a wrench.
For detail information on the FT Case refer to
I . L .
4 1-076 .
The external a·c connections of the directional
overcurrent relays are shown
If no voltage polarizing source is to be connected to
the IRD relay, short-circuit the voltage polarizing
circuit at the terminals of the relay.
20
ampere tap setting.
This
24, 4 8 , 125
or
250
voltage
Mount the
The
in
Figs . 1 8 , 1 9 and
20.
A D J U S T M E N T S
A N D
The proper adjustments to insure correct operation
of this relay have been made at the factory.
ceipt of the relay, no customer adjustment s , other
than those covered under " SETTINGS" , should b e
required.
A c c ep ta n ce C h e ck
The fo llowing check is recommended to insure
that the relay is in proper working order;
Instantaneous Overcurrent Unit ( I)
1.
Contact Gap - The gap between the stationary
and moving contacts with the relay in the de-ener
gized po sition should b e approximately
2.
Minimum Trip Current - The normally-closed
contact o f the directional unit should be blocked open
when checking the pick-up of the overcurrent unit.
The pick-up of the overcurrent unit can be checked
by inserting the tap screw in the desired tap hole and
applying rated tap value current.
± 5%
clo se within
of tap value current.
Directional Unit ( D)
Contact Gap - The gap between the stationary
1.
contact and moving contact with the relay in the de
energized p o sition should b e approximately
2.
Sensitivity - The respective directional units
should trip with value of energization and phase angle
relationship as indicated in Tabl e
3 .
be no spuriou s closing torques when the operating
circuits are energized per Table
circuits short circuited for the voltage polarized units
and open-circuited for the current pol arized units.
Time Overcurrent Unit (CO)
1. Contacts - The index mark on the movement
frwne will coincide with the "O" mark on the time
dial when the stationary contact has moved through
approximately one-half of its normal deflection. There
fore, with the stationary contact resting against the
backstop , the index mark is offset to the right o f the
"0"
mark by approximately
the various time dial positions in line with the index
mark will give operating times as shown on the re
spective time-current curves.
2 .
Minimum Trip Current - Set the time dial to
position
with the auxiliary switch (C8- 1) contacts
6
M A I N T E N A N C E
Upon re
. 0 20 ".
The contact should
. 0 20".
1 .
2
with the pol arizing
The placement of
. 0 20".
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