4.1 In addition to this section, use IEEE Standard 4 to determine other requirements necessary for conducting test methods and making measurements using alternating voltages. Procedures to ensure accuracy should follow the requirements of IEEE Standard 4. Calibration(s) shall be traceable to national standards and should be conducted annually or more often.
4.1.1 Test Voltage - The test voltage shall be an alternating voltage having a frequency in the range from 45 to 65 Hz, normally referred to as power-frequency voltage.The voltage waveshape should approximate a sinusoid with both half cycles closely alike, and it should have a ratio of peak-to-rms values equal to the square root of 2 within more or less 5%.
4.1.2 Generation of the Test Voltage - The test voltage is generally supplied by a transformer or resonant circuit. The voltage in the test circuit should be stable enough to be practically unaffected by varying current flowing in the capacitive and resistive paths of the test circuit. Non disruptive discharges in the test circuit should not reduce the test voltage to such an extent, and for such a time, that the disruptive discharge(breakdown) voltage of the test specimen is significantly affected. In the case of a transformer, the short-circuit current delivered by the transformer should be sufficient to maintain the test voltage within 3% during transient current pulses or discharges, and a short circuit current of 0.1A may suffice.
4.1.3 Disruptive Voltage Measurement - Design the measurement circuit so the voltage recorded at the breakdown is the maximum voltage across the test specimen immediately prior to the disruptive breakdown with an errorn og reater than 3%.
4.2 Circuit-Interrupting Equipment - Design the circuit used to interrupt the disruptive discharge through the specimen to operate when the voltagea cross the specimen has collapsed to less than 100V. It is recommended that the circuit design limit the disruptive current duration and magnitude to low values that will minimize damage to the disks and limit formation of non-soluble materials resulting from the breakdown,but consistent with the requirementsof4.1.1.
4.3 Voltage Control Equipment - Use a rate of voltage rise of 3kV/s. The tolerance of the rate of rise should be 5% for any new equipment. Automatic equipment should be used to control the voltage rate of rise because of the difficulty of maintaining a uniform voltage rise manually. The equipment should produce a straight-line voltage-time curve over the operating range of the equipment. Calibrate and label automatic controls in terms of rate-of-rise.
4.4 Measuring Systems - The voltage shall be measured by a method that fulfills the requirements of IEEE Standard No.4, giving rms values.
4.5 Connect the electrode such that the voltage measured from each electrode with respect to ground during the test is equal with in 5%.
5. Electrodes
5.1 The electrodes shall have parallel faces and axes in a coincident horizontal line when mounted in the cup. Construct the electrodes of polished brass as disks 25.4mm(1.0in.) in diameter more or less 2%, and at least 3.18mm(1/8 in.) thick, and with sharp edges. The sharp edge shall have a quarter circle radius no greater than 0.254mm(0.010in.).
6. Test Cup
6.1 Construct the cup of a material having high dielectric strength, that is inert to any of the cleaning or test liquids.The cup material shall not absorb moisture or the cleaning and test liquids. The vector sum of the resistive and capacitive current of the cup, when filled with oil meeting the requirements of Specifification D3487, shall be less than 200 µAat 20 kV, at power frequency. Construct the cup so that no part is less than 12.7mm(0.5in.) from any part of the electrode disk. The cup shall be designed to permit easy removal of the electrodes for cleaning and polishing, verification that the sharp edge is within the specified tolerance, and to permit easy adjustment of the gap spacing. The top of the cup shall be maintained at least 25.4mm(1.0in.) above the top of the electrodes.