lMoisture and dust on an insulator can create a conductive path across its surface, leading to flashover. Here's how it happens:
1. Moisture Effect : When humidity or rain deposits moisture on the insulator, it reduces the surface resistance. If the insulator is already contaminated with dust or pollutants, the moisture can dissolve these contaminants, forming a conductive layer.
2. Dust and Pollution : Accumulated dust, especially in industrial or coastal areas, contains conductive particles. Over time, this buildup can lower the insulation strength of the surface.
3. Leakage Current: The combination of moisture and dust allows a small leakage current to flow across the insulator, gradually increasing surface conductivity.
4. Dry Band Formation : As the leakage current flows, some areas may dry up due to heat, creating high-resistance dry bands. These bands can cause localized voltage stress and partial discharges.
5. Flashover : If the surface resistance drops significantly, a complete breakdown occurs, resulting in a flashover. This sudden discharge bypasses the insulation and may lead to system failures or outages.
How to minimize such issues?
Regular cleaning and proper insulation design (e.g., hydrophobic coatings or RTV silicone) help mitigate this issue.
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