CIRCUTOR OT2-60D - Manual (Page 12)

DIELECTRIC STRENGTH TESTER FOR ISOLATING OILS OT2-60D --------- Page 12
7. OPERATING THE EQUIPMENT
There are standard tests specified (ASTM D877, ASTM D1816) for testing dielectric
oils. This manual provides step-by-step instruction on operation of the OT2-60D in
conjunction with the necessity of following the aforementioned test specifications.
Many facilities have their own in-house test standards structured around the IEC
specifications, and this manual is not to supercede these. The purpose of this section
is to explain the capabilities of this test set in real-world applications.
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. Ensure that setup has been accomplished as noted in Setting Up the Equipment.
7.2. After checking the Test cell for proper electrode tightness, spacing and
cleanliness, fill the selected oil vessel with sample oil to the level specified in
the IEC-156 Standard. The test sample oil temperature must be at or
below 100C to avoid damage to oil vessel.
7.3. Gently stir the oil test sample release trapped air on sides of test cup. Avoid
creating any additional air into the test solution.
7.4. Place the filled test cell onto the bushing cradle toroids. Open the door of the
equipment and place the test cell (filled with the sample of oil) inside the
chamber.
7.5. Close the door, since if it is not closed, the protection circuit will prevent the
operation of the equipment.
7.6. Allow the sample to stand for a minimum of three minutes. If the VDE cell
used, plug the line cord from the stirring assembly into the receptacle in the
test chamber.