What is surface discharge?
There are many suspension and pin insulators, transformer bushings and wall bushings in the power system and many of them are exposed in the air. When the voltage of these insulators reaches a certain value, the air on the surface of these insulators will discharge, which is called discharge along the surface of solid medium, or surface discharge for short.
When the surface discharge runs through the two poles, surface flashover is formed. The surface discharge voltage is lower than the discharge voltage in the air. The surface discharge voltage is related to the uniformity of the electric field, the surface state of the solid medium and the meteorological conditions.
What is insulator flashover?
When the gas or liquid dielectric around the solid insulation is broken down, the phenomenon of discharge along the surface of the solid insulation is called flashover.
What causes pollution flashover of the insulators?
In dirty areas, there are many industrial dirt particles on the surface of composite insulators. These dirt particles will form a conductive liquid film on the insulator surface when they are wet, which will significantly reduce the withstand voltage of the insulation and the flashover voltage will become very low. This is why insulator insulation is very easy to flashover under dirty and wet conditions. Dirt and moisture are necessary conditions for pollution flashover. Composite insulator that is only dirty but not wet will not cause flashover.
How to prevent flashover of insulators?
(1) Increase basic insulation. For example, increase the number of insulators and increase the distance of surface discharge to meet the leakage ratio distance specified by the pollution classification.
(2) Strengthen cleaning. The porcelain insulation in the dirty area must be cleaned regularly to keep the surface of the porcelain insulation clean to prevent flashover. Live water flushing is an effective means.
(3) Use dust-proof coating. When the effective leakage ratio distance of porcelain insulation in the dirty area cannot meet the requirements and the cleaning workload needs to be reduced, silicone oil, beeswax and other methods are often used to increase the flashover voltage and prevent flashover accidents.
(4) Silicone rubber insulators has better performance to prevent flashover.
