Abnormal phenomena and troubleshooting of polyester film capacitor in operation

Abnormal phenomena in operation of polyester film capacitor:

1. Oil leakage

Due to improper handling method, lifting the porcelain bushing, resulting in cracks in the flange welding joint, or excessive force on the fastening nut during wiring, resulting in damage to the welding part of the porcelain bushing and some defects in the product manufacturing process, which may cause oil leakage of the capacitor. At the same time, the temperature changes sharply and the internal pressure increases after the capacitor is put into operation. In addition, after a long time of operation, the paint layer of capacitor shell may be peeled off and the iron sheet is rusted, which is also one of the reasons for the leakage of capacitor in operation.

The result of the leakage of capacitor is that the impregnant is reduced, the upper part of the component is easy to be damped and broken down, so the capacitor is damaged, so it must be repaired in time.

2. Shell expansion

Due to the dissociation of the dielectric in the capacitor under the action of voltage, the gas will be separated from the dielectric due to the breakdown of some components or the discharge of the electrode to the shell. These gases will cause an increase in pressure in the sealed enclosure, causing the enclosure to expand. Therefore, the expansion of capacitor shell is a symptom of capacitor failure or failure. In the process of operation, if the capacitor shell expansion is found, measures should be taken in time. If the expansion is serious, it should be stopped immediately to avoid the expansion of the accident.

3. Capacitor burst

When the inner part of the capacitor breaks down between the poles or from the shell, the capacitor bank running in parallel will discharge it. At this time, the capacitor may burst due to the great energy. As the low-voltage capacitors are generally equipped with component protection fuse, this kind of accident often occurs in high-voltage capacitor banks without internal component protection. The results of capacitor explosion may endanger other electrical equipment and even cause fire in capacitor room (cabinet). In order to prevent the explosion accident of capacitor, in addition to strengthening the patrol inspection in operation, the protection device of internal components of capacitor is mainly installed to make the capacitor cut off from the power grid before the explosion accident.