The method of AC withstand voltage for the complete set of variable frequency series resonance test equipment is to change the inductance and frequency in the test circuit, and the circuit is in a resonant state. This method can meet the testing requirements of high voltage and high current. When conducting the AC withstand voltage test for the complete set of variable frequency series resonance test equipment, the following points should be noted:
1. Before the experiment, it is necessary to understand whether the non-destructive testing items of the tested equipment are qualified.
2. A fence should be set up at the test site. Hang warning signs and assign dedicated personnel for supervision;
3. The insulation surface of the equipment to be tested should be cleaned before the test, and the test equipment, test object shell, and non test winding should be reliably grounded. For multi oil equipment, the test should be conducted after a certain period of oil static according to relevant regulations. For example, for large capacity transformers, the oil should be left to stand for 12-24 hours; For 3-10kV transformers, the oil should be left to stand for 6-12 hours;
4. Adjust the gap between the protective balls to ensure that the discharge voltage is between 105% and 110% of the test voltage. Conduct three consecutive tests without significant differences and check the reliability of the overcurrent protection device operation;
5. After wiring according to the series resonance test wiring diagram, a dedicated person should check and confirm that there are no errors (including grounding distance, safety distance, etc.) before preparing for pressurization;
6. Before applying pressure, check if the regulator is in the zero position and confirm that the pressure regulator is in the zero position before applying pressure. Operation can only be carried out after high voltage is applied;
7. For the boosting speed, when the test voltage is less than 30%, it can be slightly faster, and then the boosting should be uniform, about 5% of the test voltage, or 10-15 seconds when the rated test voltage rises;
8. During the boosting process, monitor the changes in the voltmeter and other instruments. When the rated voltage is 0.5 times, read the capacitance current of the tested equipment. When the voltage rises to the rated voltage, start calculating the time. Then read the current of the capacitor, slowly reduce the voltage to zero after time, and then disconnect the power supply;
9. In the experiment, if it is found that the pointer of the voltmeter swings greatly, there is abnormal noise from the test sample, the milliampere meter reading increases sharply, the test sample smokes or catches fire, and continuous spark discharge occurs on the insulation surface. The voltage should be immediately reduced, and the cause should be identified after hanging a grounding wire on the high-voltage side;
10. If the tested equipment is not specified, the general voltage withstand time is 1 minute. The withstand voltage time of insulation rods and other electrical appliances is 5 minutes. After the experiment is completed, hang the grounding wire in a timely manner and then contact the relevant components without heating;
11. The insulation resistance and absorption rate of the tested equipment should be measured before and after the test, and the results of the two measurements should not be significantly different.