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7UT51 v3
or
Let a
= 49k factor, Address 2502 X I
2
I1
where I1 is the test current Figure 16.13:
a1 and a2 must be less than 1 (I1 > Address
X I rated)
49 Tcont, Address 2403 and 2503 are in
minutes.
The time for a 49 warning based on temperature rise
is calculated as such (no preload):
≈ 49-1 T
49-1 T
warn
trip
Address 2404 in decimal format
≈ 49-2 T
49-2 T
warn
trip
Address 2504 in decimal format
For any group of 49 settings, the trip time decreases
as the test current increases. The maximum test
current for the tests below is 20 amps (4 amps for a
7UT51 rated for 1 amp). Using this current, calculate
49 T
now. Also estimate 49 T
trip
Testing the 49 elements with the desired, in-service
settings is strongly recommended. However, if those
settings would result in unpractical warning and trip
times, decrease Address 2403 or 2503. The
recommended minimum 49 warning time – if setting
changes are made – is about 2 minutes, giving a trip
time of [2-3] minutes. If the desired settings result in
warning times faster than 2 minutes, do not change
the settings.
The 7UT51 continually calculates the temperature rise
of the winding or object. Therefore, prior testing or
loading of the 7UT51 will make the test results below
unpredictable unless the temperature rise is forced to
zero. Changing Address 2401 (2501) to OFF, waiting
at least one minute, and then resetting Address 2401
(2501) to the desired setting accomplish this.
Note: These steps must be done before , and
in- between , all tests for 49 warning times and
49 trip times.
PRIM-2330C
(for 49-2)
Objsec
Θ
X 49 ALRM ,
Θ
X 49 ALRM ,
warn.
16.7.2
Warning, Temperature:
Addresses 2404, 2403 and
2402 (49
2504, 2503, and 2502 (49
Connect the 7UT51 using the example and the
accompanying Figure 16.13. The timer is used with
the Signal Relay 2 contact in this test.
49-1 Temperature Warning
1. Set Address 2401 = OFF. Wait at least one
minute with this setting. Set up the test during the
wait.
2. Any Source 1 current magnitude between {[1.2 X
Address 2402 X I
NsecWx
I
]} and 20 amps (4 amps) can be used. The
Objsec
alarm time decreases as the current increases.
The following is recommended. If 49-1T
minutes for a current of 20 amps (4 amps), lower
the current to get a warning time of about 2
minutes. Otherwise, use a current magnitude of
20 amps (4 amps).
3. Set the timer to start on the application of current,
and stop on the closure of the Signal Relay 2
contact.
4. Set Address 2401 for the desired setting.
5. Apply the current.
6. Observe the LEDs and the Signal Relay 1 contact
during the tests.
7. Turn off the current after the alarm but before the
trip. If the trip occurs, there is no problem.
Turning off the current before the trip saves time in
reading the LCD.
8. Record the value from the timer.
9. Record the LEDs and LCD, and reset.
10. Follow step 1 if any other testing is done.
49-2 Temperature Warning
Follow steps 1-10 for 49-1, except use Address 2501
in steps 1 and 4, Address 2502 in step 2, and 49-2
T
in step 2.
warn
Bench Testing
1) ; Addresses
-
] or [1.2 X Address 2402 X
< 2
warn
16
2)
-
175
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