Wuhan UHV specializes in producingseries resonance (also known as series resonance withstand voltage equipment). Next, we will share with you the application of series resonance withstand voltage equipment in GIS systems.
The method of measuring AC withstand voltage using avariable frequency series resonance test deviceis to change the inductance and frequency in the test circuit to make the circuit in a resonant state. This method can meet the requirements of high voltage and high current testing.
When using afrequency conversion series resonant devicefor AC withstand voltage testing, 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. If there are defects or abnormalities, the experiment should be carried out after cleaning;
2. Adjust the gap between the protective balls to a discharge voltage of 105% to 110% of the test voltage, and conduct three consecutive tests without significant differences. Check the reliability of the overcurrent protection device operation;
3. If it is found during the experiment that the pointer of the voltmeter swings greatly, the test substance makes abnormal noises, the indication of the milliampere meter increases sharply, or the test substance emits smoke, fire, or continuous spark discharge on the insulation surface, the voltage should be immediately reduced. After hanging a ground wire on the high-voltage side, the cause should be identified;
4. The test site should be fenced off, warning signs should be hung, and a dedicated person should be assigned to supervise;
5. After connecting the wires according to the test wiring diagram, a dedicated person should check and confirm that there are no errors, including the lead to ground distance, safety distance, etc., before preparing for pressurization;
6. Before applying pressure, check if the regulator is in the zero position. Confirm that it is in the zero position before applying pressure, and only after shouting "high pressure at home" can the operation be carried out;
7. Before the experiment, the insulation surface of the tested equipment should be wiped clean, and the outer shell of the test equipment, the tested sample, and the non tested winding should be reliably grounded. For multi oil equipment, the oil should be kept still for a certain period of time according to relevant regulations before conducting the test. For example, for large capacity transformers, the oil should be kept still for 12-24 hours, and for 3-10kV transformers, the oil should be kept still for 6-12 hours;
8. During the boosting process, the changes in the voltmeter and other instruments should be monitored. When the additional test voltage is 0.5 times, the capacitance current of the tested equipment should be read; When the additional voltage is raised, start calculating the time, then read the capacitor current. After the time is up, slowly decrease the voltage to zero, and then disconnect the power supply;
9. Regarding the boosting speed, it can be slightly faster when the test voltage is below 30%. Afterwards, the boosting should be uniform, about 5% of the test voltage per second, or increased to an additional test voltage for 10-15 seconds;
10. For devices without clear regulations, the general withstand time is 1 minute; The withstand voltage time of insulating rods and other tools is 5 minutes. After the experiment is completed, the ground wire should be hung in a timely manner, and then the relevant parts should be contacted without any heating phenomenon;
11. The insulation resistance and absorption ratio of the tested equipment should be measured before and after the experiment, and the results of the two measurements should not be significantly different.
