Operation
14
The three soft keys now assume different functions. Press the left hand key labelled ‘VIEW’ to bring
back into view, sequentially, the breakdown voltage values of each individual test and the average
value.
Press the ‘NEW’ key to return to the start of the ‘5 MINUTE TEST’ followed by the left hand ‘START’
key to repeat a test sequence or the ‘MENU’ key to return to the main menu.
Note:– At any time during a test sequence the right hand control key, labelled ‘STOP’, can be used to
end a test and return to the first screen (see figure 4) display for the test option chosen.
AS 1767, BS 148, BS 5874, CEI 10-1,
G
OCT 6581, IEC 156, IP 295, NFC 27-221, SABS 555, UNE 21
and VDE 0370 tests
1. On pressing the ‘START’ key ‘TEST 1’ is initiated. The display screen appears similar to that shown
in figure 5.
The sub-display area indicates that a 3 minute initial oil sample stand time is being undertaken and
the time is being counted down to zero.
2. After the initial stand time is complete the high voltage is switched on and slowly applied to the oil
sample. The screen display appears similar to that shown in figure 6.
The sub-display shows the voltage applied to the oil sample; this voltage is rising at the rate of 2 kV/s.
It continues until breakdown occurs (or up to maximum). The high voltage warning light is illuminated
during this time. The number of the test in the sequence is shown and the words ‘IN PROGRESS’
appear.
3. When breakdown occurs (or if the maximum voltage is reached) the test voltage is cut off, the ‘kV’
warning light goes out and the test set begins its oil sample stirring period. The stirrer rotates for a
period of 1 minute and the previous breakdown voltage is retained on the display. The display screen
appears similar to that in figure 7.
The time remaining for stirring is shown alternately with the words ‘STIRRING’, unless stirring is
continuous (see page 6).
4. When stirring has finished the test set begins its oil sample intermediate standing period which lasts
for 1 minute. Again the time remaining for standing is shown alternately with the words ‘STANDING’
and the previous breakdown voltage is still retained on the display. The display screen appears
similar to that in figure 8.
5. The test voltage then begins to rise again as in step (2) above, this time for ‘TEST 2’, and the cycle
of events repeats.
6. For these specifications there are 6 consecutive tests. After the test voltage has been cut off on the
last test, the display screen shows the average breakdown voltage value from the 6 tests in the
sequence. The display screen appears similar to that in figure 9 or figure 10 if the PASS/FAIL option
is enabled. The BS 148 test includes the recommended pass limit and shows pass or fail as well as
the actual average breakdown voltage.
The three soft keys now assume different functions. Press the left hand key labelled ‘VIEW’ to bring
back into view, sequentially, the breakdown voltage values of each individual test and the average
value in turn.
Note:– UNE 21 test differs from the above as follows:– Initial stand time is 10 minutes, stir time 1 minute,
intermediate stand time 4 minutes and the result is presented as the mean and standard
deviation from the last 5 out of 6 tests.
Note:– NFC 27-221 test differs from the above in that the result is the mean of the last 5 our of 6 tests.
Note:– At any time during a test sequence the right hand control key, labelled ‘STOP’, can be used to
end a test and return to the initial test screen.
Press the ‘NEW’ key to return to the start of the selected test sequence. Press the left hand ‘START’
key to repeat a test sequence or the ‘MENU’ key to return to the main menu.
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