Megger INGVAR, Руководство пользователя

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48 ZP-BH05E BH0654BE
8 APPLICATION EXAMPLES
8
A
pplication examples
8.1 Testing a low-voltage
circuit breaker
The following sections explain how to test a low-volt-
agecircuit breaker.
1]
Start by measuring the overcurrent stage’s
tripping limit and the tripping time.
2]
Then measure the tripping limit and tripping
time for the instantaneous unit.
Measuring the tripping limit
(normal generation)
Current is generated continuously and gradually in-
creased until the breaker trips. When the breaker trips
the current shown on the display is frozen and the
current is interrupted. When current first is generated
for a load (while the current is being set), INGVAR
adapts itself so that all subsequent generation opera-
tions start at the current’s zero-cross-over points. This
ensures minimized transient DC offset when the injec-
tion is initiated.
1]
Basic settings:
OPERATE OFF
CURRENT ADJUST Lower than the tripping
limit
HOLD function ON
AUTO OFF STOP INPUT
2]
Set the stop condition to INT.
3]
Press
TIME
to start generation.
4]
Increase the current until tripping occurs (the
LATCH lamp lights up).
5]
The current value frozen when tripping oc-
curred can now be read from the display.
Note You can read out the highest current value
during an operation by pressing
ESC
repeat-
edly until "max" appears after a current value.
This value should be used for test objects
whose impedance changes during the opera-
tion.
Measuring the tripping time
1]
Set the current to an ample margin above
the tripping limit. The procedure is described
in section 7.3. Use the I/30 function (step 2 to
6 in section 7.3) if you want to set the cur-
rent without operating the breaker.
Note: Disable the INT -function when you are
using I/30.
2]
Settings:
HOLD ON
AUTO OFF STOP INPUT
STOP INPUT INT
3]
Press
TIME
or
MOM
to start generation .
4]
Read the time and the current presented on
the display.
Instantaneous trip unit
measurement
When you test the instantaneous pick-up you can
provide a manually-controlled momentary current
injection by pressing the
MOM
button. This permits you
to find the instantaneous trip unit’s lowest operating
current without tripping the overcurrent stage.
1]
Basic settings:
OPERATE OFF
CURRENT ADJUST Close to the tripping
limit
HOLD function ON
2]
Set the stop condition to INT.
3]
Select a suitable current setting.
4]
Press
MOM
briefly. The time throughout which
current is generated must be shorter than
the overcurrent stage’s tripping time. You
can also use limited-time current generation
(
MAX TIME ). See section 7.13 "Measuring
operating limits".
5]
Change the current setting somewhat and
repeat from step 3 above until you find the
lowest current that provides tripping of the
instantaneous trip unit.