7. TEST
METHOD
The test method consists of submitting the oil to an electric field from a continuously increasing AC
current until the oil is perforated because its dielectric properties are surpassed (insulation
properties). When this occurs, on the display is shown the disruptive voltage in kV.
If we wanted to obtain the dielectric strength of the oil (kV/cm), we would have to divide the value
shown on the display (kV) by the distance between electrodes (cm). In the case of the IEC-156
standard, this distance is 0,25 cm, therefore, if we multiply by 4 (1/0,25=4) the value shown on the
display, we obtain the dielectric strength value of the oil (kV/cm).
7.1- Positioning the test cell in the chamber
Open the door of the equipment and place the test cell (filled with the sample of oil) inside the
chamber, introducing the contacts in the holes on the bottom of it (sockets of the high voltage
transformer). Press firmly until the pieces fit. This is important, because the equipment could
work wrong if there was a bad connection.
7.2-
Stirrer
If it is desired to use the stirrer, it will be necessary to introduce the teflon coated magnet inside
the cell, being it clean and dry. The teflon coated magnet will automatically locate in its site
when introducing the cell in the chamber.
