Advertisement
I.L. 41-973.5Q
or inserted by locking two nuts on the stud and then
turning the proper nut with a wrench.
For detailed FT case information, refer to I.L. 41-076.
Where the potential to ground impressed on the
relays can exceed 700 volts, a drainage reactor in
conjunction with its surge protectors, or the reactor in
conjunction with 700 volt carbon-block arresters, is
recommended. For details, see Protection of Pilot-
Wire Circuits, AIEE Committee Report, paper 58-
1190, AIEE Transactions, 1959, Volume 78, Part III B
pp. 205-212. Also, see AIEE Special Publication S-
117, Applications and Protection of Pilot-Wire Cir-
cuits for Protective Relaying, July 1960.
7.
ADJUSTMENTS AND MAINTENANCE
The proper adjustments to insure correct operation of
this relay have been made at the factory and should
not be disturbed after receipt by the customer. If the
adjustments have been changed, the relay taken
apart for repairs, or if it is desired to check the adjust-
ments at regular maintenance periods, the instruc-
tions in the succeeding sections should be followed.
7.1.
Acceptance Tests
The following tests are recommended when the relay
is received from the factory. If the relay does not per-
form as specified below, the relay either is not prop-
erly calibrated or it contains a defect. (Relays must
be tested in the case.)
7.1.1.
Indicating Contactor Switch (ICS)
Close the contact of the tripping unit and pass suffi-
cient direct current through the trip circuit to close the
contacts of the ICS unit. This value of current should
not be greater than the particular ICS tap setting
being used (0.2 or 2.0). The indicator target should
drop freely.
7.1.2.
PMA and PMA-1 Relays
Alarm Unit (1)
Set the primary tap on 120 volts. Connect a variable
resistor of approximately 20,000 ohms in series with
a low-range dc milliammeter across terminals 6 and
7 with the instrument positive connected to terminal
7. Apply 120 volts at rated frequency to terminals 4
and 5. Adjust the 20,000 ohm resistor to obtain a cur-
rent of one mA dc. For a three-terminal line relay, use
8
Courtesy of NationalSwitchgear.com
a 10,000 ohm resistor and set the current to 2 mA dc.
At this value, the moving contact of the alarm or mon-
itoring relay unit (1) should float between the two sets
of stationary contacts. In the PMA relay, the ground
alarm unit (5) contact should also float. (This contact
will also float when the relay is deenergized.)
Increase and decrease the one or two milliampere
monitoring current to check the calibration values
listed in Tables 4 and 5.
Ground Unit (5)
Reconnect the 20,000 ohm resistor. For the PMA
relay only, short terminals 7 and 3. The contact of the
ground alarm unit (5) should close to the right when
the relay is energized. Remove the short, and con-
nect it between terminals 6 and 3. The ground alarm
unit (5) should close to the left. The action of the
monitoring unit (1) contact is of no significance in this
simulated pilot-wire ground test. To check the pickup
current of the ground detector, first remove to the
20,000 ohm resistor from terminals 6 and 7. Connect
a 0-1 dc milliammeter in series with a variable resis-
tor of about 50,000 ohms between terminals 3 and 6.
The ground unit should close its left-hand contact at
approximately 0.3 mA dc. With the milliammeter and
resistor connected between terminals 3 and 7, the
right-hand contact should close at 0.3 mA dc.
7.1.3.
PMD and PMD-1 Relays
Alarm and Ground Units
Connect an adjustable 20,000 ohm resistor (or
10,000 ohms for a 3-terminal relay) in series with a
dc milliammeter across terminals 6 and 7 with the
instrument positive connected to terminal 7. Apply
rated dc voltage to terminals 8 and 9 with positive on
terminal 9. Now check the PMD and PMD-1 relays,
following the procedure given in the previous section
for the PMA and PMA-1 relays, respectively. Note,
however, that terminal 5 of the PMD relay corre-
sponds to terminal 3 of the PMA relay.
7.1.4.
PM-2, PM-3, and PM-23 Relays
Alarm Unit (2)
Apply a variable dc voltage of approximately 20 volts
to relay terminals 8 and 9 (terminal 9 positive) of the
PM-2 or PM-23 relay. Adjust the voltage to obtain a
reading of one mA on the relay milliammeter. The
monitoring polar unit (2) contacts should float.
Advertisement
