The breakdown of the insulation outside the vacuum interrupter generally occurs when the sealing ring of the moving or static end breaks down between the shield and the contact along the surface of the porcelain shell, because the internal insulation of this part is relatively weak, once the external insulation If it is broken down, it will cause the whole product to be unusable. So what are the reasons for the breakdown of the outer insulation?

The main reasons for the breakdown of the insulation outside the vacuum interrupter are as follows:

1. The outer surface of the porcelain shell of the product is not well treated, and there is dirt and so on.

2. When the epoxy resin or silicone rubber transition layer is bonded to the outer surface of the product ceramic shell, there is an air gap formed by poor bonding quality.

3. During the pouring process of epoxy resin, bubbles are generated on the surface of the porcelain shell.

4. Because the linear expansion rate of epoxy resin and product ceramic shell and stainless steel or oxygen-free copper sealing ring is different, this will lead to increased residual stress, and further lead to peeling and cracking of the casting interface.

The above casting defects will cause the product to act like a capacitor under the high-voltage alternating electric field. When the accumulated charge reaches a certain level, the external insulation will be broken down due to local discharge. Generally speaking, the breakdown of the outer insulation is irreversible, so once the breakdown occurs, the entire product will be scrapped

At present, there are many manufacturers of vacuum interrupters, whether it is an assembly line or manual operation, because of the different processing techniques, the products have different effects on the insulation breakdown. The manufacturers can perform partial discharge tests on the products before they leave the factory. The product will not have insulation breakdown phenomenon.