8
S&C Instruction Sheet 663-590
Table 2
Table 2. Inspection Procedures for Pad-Mounted Gear Equipped with AT-12 Source-Transfer Control
①
Item
Procedures
Voltage-sensor signal
adjustments and
measurements
1 . Place the MANUAL/AUTOMATIC operation selector switch in the
Manual position, and decouple both operators from their
associated Mini-Rupter Switches . (Switching operations will result in temporary service interruptions if the operators are coupled) .
2 . Measure the voltage-sensor signal for each phase of the preferred source and alternate source using a voltmeter having an input
impedance of at least 5000 ohms per volt .
3 . If the measured voltage differs from 2 .5 Volts, “scrub” the associated potentiometer by rotating the adjustment screw back and
forth 10 to 12 times . Then, adjust the setting to obtain a 2 .5-Volt reading . (Note that a 2 .5-Volt voltage-sensor signal is appropriate
only when the system is at nominal voltage . If the system voltage is higher or lower than the nominal voltage; the required
voltage-sensor signal is 2 .5 volts × actual system voltage ÷ nominal system voltage .)
Switch operators
1 . With the MANUAL/AUTOMATIC operation selector switch in the
Manual position, open the preferred-source operator by
pressing the appropriate OPEN pushbutton . After opening, the operator should recharge in less than 25 seconds .
2 . Close the alternate-source operator by pressing the appropriate CLOSE pushbutton . This operator should also recharge in
less than 25 seconds .
3 . Return both operators to their original positions .
Time delay on loss of
source and return of
source (“62P,” “62A,” and
“2P” Timers)
1 . Place the MANUAL/AUTOMATIC operation selector switch in the
Automatic position and note the position of the AUTOMATIC/
HOLD RETURN selector switch .
2 . If the AT-12 control is in the
Automatic Return mode:
a . Simulate a prolonged loss of preferred-source voltage by pressing and holding in the SIMULATE-LOSS-OF-SOURCE test
switch for the preferred source . Verify the time to initiate transfer is within ±20% of the setting on the “62P” timer . Also confirm
the source voltage lamp for the preferred source extinguishes .
b . Now, release the test switch to simulate a return of the preferred-source voltage . Verify the time to initiate back transfer is within
±20% of the setting on the “2P” timer . Confirm the source voltage lamp for the preferred source relights .
3 . If the AT-12 control is in the
Hold Return mode:
a . Simulate a prolonged loss of preferred-source voltage by pressing and holding in the SIMULATE-LOSS-OF-SOURCE test
switch for the preferred source . Verify the time to initiate transfer is within ±20% of the setting on the “62P” timer . Also confirm
the source voltage lamp for the preferred source extinguishes .
b . Release the test switch to simulate a return of the preferred-source voltage, and wait a sufficient length of time to verify back
transfer does not occur . Confirm the source voltage lamp for the preferred source relights .
c . Now, simulate a loss of alternate-source voltage by pressing and holding in the SIMULATE-LOSS-OF-SOURCE test switch for
the alternate source . Verify the time to initiate back transfer if within ±20% of the setting on the “62A” timer . Confirm the source
voltage lamp for the alternate source extinguishes, and then release the test switch .
TABLE CONTINUED
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