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I.B. 17555C
7.0
TESTING THE DUAL-SOURCE POWER SUPPLY
The DSPS requires no maintenance or adjustment. Use
the following procedures to check for proper operation.
First, confirm or test Digitrip 3000 operation with ac
power applied, according to the guidelines of the
DT3000. Then, the following can be used to confirm that
the DSPS is functioning correctly.
7.1
IN-SERVICE TEST
THERE MAY BE LIVE VOLTAGES AND CURRENTS
PRESENT ON AND AROUND THE DIGITRIP 3000.
ONLY QUALIFIED PERSONS SHOULD BE PERMIT-
TED TO PERFORM ANY WORK ASSOCIATED WITH
THE EQUIPMENT. FAILURE TO FOLLOW SAFE
PRACTICE COULD RESULT IN SERIOUS INJURY,
DEATH AND/OR EQUIPMENT DAMAGE.
7.1.1 Some visible load current should be flowing in the
protected feeder circuit. It need not be full rated
load. Check all three phases.
7.1.2 Consider disconnecting trip circuits during this live
testing, although no tripping tests are called for in
the following.
7.1.3 Connect a dc voltmeter across Digitrip 3000 termi-
nals 5 & 6 on TB1. This is on the left side of the
relay as viewed from the rear.
7.1.4 With ac power applied, this dc meter should read
approximately 50 volts.
7.1.5 Connect an isolated ac multimeter across any one
phase ct input and observe the voltage drop, which
will be less – maybe much less – than 0.25 volt.
See Figure B-9.
7.1.6 Disconnect ac power from the relay. The front panel
and relay data communications may go away if the
load current is small.
Effective November 1999
CAUTION
7.1.7 The ac voltage drop across the ct input should rise
to a larger value, at least twice as large as when ac
was applied, and maybe approaching 0.5 volt as
shown in Figure B-9.
7.1.8 The dc voltage on terminals TB1 - 5 & 6 should cor-
respond very roughly to that from the plot in Figure
B-10, DSPS output voltage as a function of three-
phase current.
7.1.9 Disconnect instruments, restore ac power to relay,
reconnect trip circuits, and check for resumption of
front panel & communications operation.
7.2
LAB BENCH TEST
7.2.1 With ac control power applied, set the relay to trip
well below 9 A – any phase trip function is OK.
7.2.2 Apply more than 9 A to Phase A and confirm trip-
ping. Remove current and reset relay.
7.2.3 Remove ac control voltage – relay turns off.
7.2.4 Apply 9 A to Phase A again. Relay should power up
and trip. No need to recheck timing, but it may be
observed to be about 100 ms longer than for ac
control powered case. If test current is well above
10 A, avoid applying it for a long period.
7.2.5 Repeat step 3 for Phase B.
7.2.6 Repeat step 3 for Phase C. This time, use an iso-
lated ac multimeter to measure the voltage drop
across the Digitrip 3000 current input during the
test. Check the value against the "No Vac, 1 Phase
I" curve, the highest curve, of Figure B-9.
7.2.7 Apply ac control voltage again, with Phase C cur-
rent still applied, or reapply it. The voltage drop
shown on the multimeter should decrease to the
value for the "With Vac, 1 Phase I" curve of Figure
B-9. With ac power applied, this voltage will be
roughly half of the value without the ac power
applied.
Page B11
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