High-voltage voltage divider breakdown troubleshooting measures case

作者： GOZ Electric 时间：2024-05-24 09:25:42 阅读：18

    Based on the principle of air breakdown, the following failure mode analysis is proposed: From the filling process, it can be seen that vacuuming is required for 5 to 8 minutes during the filling of silicone gel in high-voltage components. Since the high-pressure divider is a hollow, semi-sealed structure, it is inevitable that some air will leak out of the high-pressure divider. As the silicone gel solidifies, a low pressure state will be formed inside the high-pressure divider. According to According to Paschen's law, refer to the curve in Figure 3, the air insulation voltage strength will decrease significantly. Due to different degrees of air leakage, the degree of reduction in insulation voltage strength is also different. We conducted experimental verification of the above theoretical analysis: we took 8 new high-voltage voltage dividers. 4 of them kept their original structure, 4 of them had their ceramic shells removed, and they were applied to 8 kV withstand voltage before infusion, and they all worked normally. Then, the perfusion conditions of the upper components of the missile were simulated for silicone gel perfusion and vacuuming. After the silicone gel solidified, the pressure was tested and it was found that three of the four high-voltage dividers that maintained the original structure broke down within 2 to 4 kV. Four voltage dividers without ceramic casings still work normally with a withstand voltage of 8 kV. This reproduces the fault. Three voltage dividers that broke down within 2 to 4 kV were taken out of the silicone gel, cracked the ceramic casing, and then re-tested to withstand voltage, and then returned to 8 kV withstand voltage. They worked normally, indicating that the air pressure does have an impact on the withstand voltage. Obvious impact.

1. Solutions

     In view of the above situation, we stopped using high-voltage voltage dividers with ceramic shells without perfusion. It was decided to temporarily use a high-voltage voltage divider that removes the ceramic shell and is filled with silicone gel. The structure is as shown. In order to verify that the high voltage divider is filled with silicone gel. To see whether it meets the temperature stability requirements, four high-voltage voltage dividers with ceramic shells removed and filled with silicone gel were subjected to high and low temperature tests of 55°C and 0°C respectively. The standard test voltage is 4 kV. The test data of the partial pressure indication value can be Meet the usage conditions of high-voltage components. Since silicone gel is highly viscous and elastic, and cannot maintain a regular shape, an improved design was proposed based on the above. As shown, a structure in which silicone gel is poured into a ceramic shell is used, and silica powder is added to the silicone gel to enhance the hardness. . The high-voltage voltage divider with this structure has passed various environmental adaptability assessments.

2. Conclusion

     Through the above theoretical analysis and experimental research on the breakdown failure mode of high-voltage voltage dividers, we have obtained an important high-voltage device design principle: due to anti-vibration and insulation requirements, high-voltage components need to be evacuated and filled with silicone gel, so high-voltage devices should Try to avoid hollow semi-sealed structures. If a hollow structure is used. There must be clear air tightness requirements for devices to prevent local low air pressure from causing a decrease in insulation strength.