What is the effect of humidity on the dielectric strength of insulating paint?
Published on:
2024-10-14
- Increased humidity leads to decreased dielectric strength
- When the ambient humidity increases, the water vapor molecules in the air will be adsorbed on the surface of the insulating paint, and under the action of the electric field, these water molecules may be ionized to produce ions. For example, in an environment with high relative humidity (e. g., greater than 70%), water molecules will form a water film on the surface of the insulating paint. These ions in the electric field will be directional movement, the formation of leakage current.
- With the further increase of humidity, moisture may penetrate into the interior of the insulating paint, destroying the molecular structure and internal electric field distribution of the insulating paint. This makes it possible for the insulating varnish to break down at lower voltages, resulting in a decrease in dielectric strength. In general, for every 10% increase in humidity, the dielectric strength of the insulating paint may decrease by 10%-20%.
- In addition, under high humidity environment, hydrolysis reaction may occur inside the insulating paint. For insulating varnishes containing ester bonds, amide bonds and other chemical bonds, water molecules will react with these chemical bonds, so that the chemical structure of the insulating varnish changes, thereby reducing its dielectric properties. For example, in a polyester insulating varnish in a high humidity environment, the ester bond may be hydrolyzed to generate carboxylic acid and alcohol, which may impair the insulating properties of the insulating varnish.
- Effect of Low Humidity Environment on Dielectric Strength
- In low humidity environment (such as relative humidity less than 30%), the dielectric strength of insulating varnish can usually maintain a good state. Because the dry environment reduces the interference of moisture on the insulating paint, the electric field distribution inside the insulating paint is relatively stable.
- However, too low humidity may cause static electricity problems. Electrostatic accumulation may produce high voltage pulse, when this high voltage pulse acts on the insulating paint, although it may not directly lead to the breakdown of the insulating paint, but may cause partial discharge, long-term down will also produce some damage to the dielectric properties of the insulating paint.
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