02/ 2011
BENNING ST 720
25
step 1 of 2:
- After a measuring time of 5 seconds or by pressing the key
4
, mains polarity will be reversed
and the protective conductor current will be measured with reversed mains voltage ("L/N" -
"N/L"). The highest measured value of both measurements will be displayed. (step 2 of 2)
step 2 of 2:
- If the protective conductor current is lower than the admissible limiting value, a
will be
shown next to the I
LEAK
symbol.
- The overall test is considered to be passed, if "PASS" is shown on the display.
As an alternative:
BENNING ST 720 in battery operating mode (without mains supply):
-
Similarly, a
will be shown next to the I
EA
symbol, if the protective conductor current I
EA
(al-
ternative leakage current measurement method) is lower than the admissible limiting value.
- The test is considered to be passed, if "PASS" is shown on the display.
See figure 4:
Testing of devices of protection class I (devices with protective conduc
-
tor and accessible conductive parts which are connected to the protective
conductor)
Note on measuring the protective conductor resistance:
-
Alternatively, the measurement of the protective conductor resistance R
PE
can be car-
ried out as permanent measurement (max. 4 minutes). For this purpose press the key
2
for approx. > 5 seconds until the
symbol appears on the display. Check the con-
necting line of the test object by bending it over the entire length in order to detect
weak points or a break of the protective conductor. The BENNING ST 720 continuously
records the current measured value on the display and stores the maximum value in the
memory. By pressing the key
2
again, the measurement is carried out with reversed
polarity. Press the key
2
again to indicate the maximum value of R
PE
on the display and
to continue the testing procedure as described in section 8.2.1.
Note on measuring the protective conductor current in mains operating mode:
- Alternatively, the measurement of the protective conductor current I
LEAK
can be carried out
as permanent measurement (max. 30 seconds). Press the key
4
for approx. > 5 seconds
to start permanent measurement. After 30 seconds, the polarity of the mains voltage will be
reversed automatically ("L/N" - "N/L"). By pressing the key
4
earlier, the mains voltage po-
larity reversal can be activated manually and by pressing the key
4
again, the measurement
can be stopped.
Note on measuring the contact current:
- Accessible conductive parts which are not connected with the protective conductor have to
be tested as described in section 8.2.2. For measuring the contact current (direct measure-
ment method), the BENNING ST 720 has to be operated with a mains voltage of 230 V.
- During contact current measurement by means of the direct measurement method, no part
of the test object must have a connection to the earth potential. The test object must be
