02/ 2011
BENNING ST 720
24
- If necessary, the testing voltage of the R
ISO
(insulating resistance) measurement can be
reduced to 250 V
DC
by means of the
-key
5
. The selected testing voltage is briefly shown
on the display
8
. Press the key again to switch back to the preset testing voltage of 500 V
DC
.
- Switch the test object on.
- Press the
-key
2
to start the automatic testing procedure.
- The test starts with measuring the protective conductor resistance R
PE
. If R
PE
is higher than
the admissible limiting value, the measured value of R
PE
will be shown on the display and
a will appear next to the R
PE
symbol. "FAIL" appears on the display to confirm that the
measurement has been stopped.
- If R
PE
is lower than the admissible limiting value, the measured value of R
PE
is shown and
a
appears next to the R
PE
symbol. Now, the R
PE
measurement is carried out again with
reversed polarity and the highest measured value of both measurements will be displayed.
After the R
PE
test has been passed, the test of the insulating resistance is started.
- If "Lo LOAD" is shown on the display, please check whether the test object is switched on.
- Press the key
2
to continue the testing procedure in case of the load being too low (R
L-N
> 6 kΩ).
- If "HIGH LOAD“ is shown on the display, this indicates an excessive load (R
L-N
<< 14 Ω,
I
LAST
(I
LOAD
) > 16 A) of the test object. There might be danger of a short-circuit or of an earth
fault. Check whether there is a short-circuit between the external conductor (L) and neutral
conductor (N) of the test object.
- If there is no short-circuit, you can continue with the testing procedure by pressing the key
2
.
- If the insulating resistance R
ISO
is higher than the admissible limiting value, a
appears
next to the R
ISO
symbol.
BENNING ST 720 in mains operating mode:
- The BENNING ST 720 interrupts the testing procedure after the R
ISO
(insulating resistance)
measurement and requests the user to switch the mains voltage of 230 V to the test socket
1
by showing a flashing "I
LEAK
" symbol. Make sure that the test sample is protected and
press the
key
4
to measure the protective conductor current by means of the differential
current measurement method.
- The protective conductor current measurement (differential current measurement method)
only starts as soon as the mains voltage is correct applied.
