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Directional Overcurrent Ground Relays
Types IRP, IRC and IRD
Upon completion of steps 1 or 2 above, apply 5
amps and gradually increase to 80 amps. Note,
high current to be applied only momentarily.
Plug adjustment is then made per Table 2 (page
11) such that the spurious torques are reversed.
The plugs are held in position by upper and lower
plug clips. These clips need not be disturbed in
any manner when making the necessary adjust-
ment.
The magnetic plug adjustment may be utilized to
positively close the contacts on current alone.
This may be desired on some installations in
order to insure that the relay will always trip the
breaker on zero potential.
e. The core adjustment is used to eliminate any
unwanted spurious torques that may be present
when the relay is energized with voltage alone.
Apply 120V AC to terminals 4 (+) and 5 for IRD
and terminals 6 (+) and 7 for IRP and adjust core
so that contacts just open.
7.4.2 Time Overcurrent Unit (CO)
Contacts
The index mark on the movement frame will coincide
with the "0" mark on the time dial when the stationary
contact has moved through approximately one-half of
its normal deflection. Therefore, with the stationary
contact resting against the backstop, the index mark
is offset to the right of the "0" mark by approximately
.020". The placement of the various time dial posi-
tions in line with the index mark will give operating
times as shown on the respective time-current
curves.
Minimum trip Current
The adjustment of the spring tension in setting the
minimum trip current value of the relay is most con-
veniently made with the damping magnet removed.
With the time dial set on "0", wind up the spiral spring
by means of the spring adjuster until approximately
6-3/4 convolutions show.
Set the relay on the minimum tap setting, the time
dial to position 6.
With auxiliary switch (Aux) contacts blocked closed,
adjust the control spring tension so that the moving
contact will leave the backstop at tap value current
+1.0% and will return to the backstop at tap value
current -1.0%.
Time Curve Calibration
Install the permanent magnet.
Apply the indicated current per Table 3 (page 11) for
permanent magnet adjustment (e.g. IRP-8, 2 times
tap value) and measure the operating time. Adjust
the permanent magnet keeper until the operating
time corresponds to the value of Table 3.
Apply the indicated current per Table 3 for the elec-
tromagnet plug adjustment (e.g. IRP-8, 20 times tap
value) and measure the operating time. Adjust the
proper plug until the operating time corresponds to
the value in Table 3. (Withdrawing the left hand plug,
front view increases the operating time and with-
drawing the right hand plug, front view, decreases
the time.) In adjusting the plugs, one plug should be
screwed in completely and the other plug run in or
out until the proper operating time has been
obtained.
Recheck the permanent magnet adjustment. If the
operating time for this calibration point has changed,
readjust the permanent magnet and then recheck the
electromagnet plug adjustment.
7.5 INDICATING CONTACTOR SWITCHES (ICS/I)
AND (ICS/T)
For proper contact adjustment, insert a .030" feeler
gauge between the core pin and the armature. Hold
the armature closed against the core pin and gauge
and adjust the stationary contacts such that they just
make with the moving contact. Both stationary con-
tacts should make at approximately the same time.
The contact follow will be approximately 1/64" to
3/64".
Close the contacts of the CO and pass sufficient dc
current through the trip circuit to close the contacts of
the (ICS/T). This value of current should not be
greater than the particular (ICS/T) tap setting being
used. The operation indicator target should drop
freely bringing the letter "T" into view.
Close contacts of instantaneous overcurrent unit (I)
and directional unit (D). Pass sufficient dc current
through the trip circuit to close contacts of the (ICS/I).
This value of current should not be greater than the
particular (ICS/I) tap setting being used. The opera-
41-133S
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