Design of Multifunctional Integrated Coating And Self-Cleaning Mechanism Research for Composite Insulators in Alpine Heavy Contaminated Areas

Composite insulators are widely used in power grid construction due to their excellent hydrophobicity, light weight, and ease of installation. 

However, in extreme environments characterized by the combination of Alpine conditions (low temperature, ice accretion) and Heavy contamination (industrial dust, salt deposition), their surface performance faces severe challenges. These include loss of hydrophobicity, significant reduction in pollution flashover voltage, and drastically increased risk of ice flashover, posing serious threats to grid security and stability. This article focuses on developing a multifunctional integrated coating aimed at simultaneously addressing the challenges of anti-icing, anti-pollution, and self-cleaning for insulators in alpine heavy contaminated regions, and delves into its underlying mechanisms.

The Dual Threat of Alpine Heavy Contaminated Environments

1. Heavy Contamination

Pollutants such as industrial emissions, salt fog, and dust deposit on the insulator surface, forming a conductive layer. Under humid conditions (fog, dew, light rain), the contaminated layer absorbs moisture and dissolves, leading to a sharp increase in surface conductivity and leakage current. This significantly raises the risk of pollution flashover accidents. The hydrophobicity transfer and recovery of traditional silicone rubber materials may fail or be delayed under high contamination levels.

2. Alpine Conditions/Icing

 Low temperatures alone can reduce the elasticity of silicone rubber, potentially affecting hydrophobicity. More critically, precipitation in cold weather easily leads to ice accretion on the insulator surface. Ice coverage directly shortens the creepage distance. Moreover, the melting ice forms continuous water films or water droplets bridging the sheds, drastically lowering the ice flashover voltage. Ice encapsulation also completely eliminates hydrophobicity.

3. Synergistic Effect

Contaminants act as condensation nuclei, accelerating the ice accretion process. Simultaneously, contaminants dissolve into the meltwater, forming a more conductive electrolyte, further exacerbating the ice flashover risk. Ice encapsulation also renders traditional self-cleaning by wind and rain ineffective.

Solution: Design Philosophy of Multifunctional Integrated Coating

1. Superhydrophobic/Anti-Icing Functional Layer:

Micro/Nano Structure: Construct hierarchical nano/micro rough structures (e.g., nanoparticles, micropillar arrays) to maximize air entrapment and form a stable air cushion.

Low Surface Energy Materials: Modify with low surface energy substances such as fluorinated silanes or silicone resins to confer superhydrophobicity (static contact angle >150°, sliding angle <10°).

Anti-Icing Mechanism:Superhydrophobicity significantly delays water droplet freezing time (ice delay); extremely low ice adhesion strength (as low as tens of kPa) enables easy ice shedding under gravity, wind, or slight vibration (active de-icing). Low surface energy also inhibits ice crystal spreading and adhesion.

2. Photocatalytic Self-Cleaning Functional Layer:

Active Component: Uniformly disperse highly active photocatalytic nanoparticles (e.g., TiO₂, ZnO, g-C₃N₄, and their modified/composites) within the coating.

Self-Cleaning Mechanism:

Photodegradation of Organic Contaminants:Under natural light (especially UV), photocatalysts generate reactive oxygen species (ROS), efficiently degrading adhered organic pollutants (e.g., industrial oils, bird droppings, plant exudates, biofilms) by mineralizing them into small molecules like CO₂ and H₂O.

Hydrophilic Conversion (Optional):Some photocatalysts (e.g., TiO₂) become superhydrophilic (contact angle near 0°) under light, facilitating rainwater spreading into a thin film that washes away hydrophilic inorganic particles (e.g., dust, coal ash). Hydrophobicity recovers after light ceases.

Synergistic Effect:Photocatalytic degradation disrupts the adhesion and encapsulation of inorganic particles by organic matter, making inorganic particles easier to be washed away by rain, achieving overall cleaning. A clean surface also helps maintain superhydrophobicity.

3. Hydrophobicity Transfer and Recovery Enhancement Layer:

Material Selection:Use modified silicone materials with excellent inherent hydrophobicity and hydrophobicity transfer capability as the coating matrix.

Mechanism:Ensures that even if surface-active substances are partially depleted due to aging, abrasion, or severe contamination, hydrophobic small molecules from the coating matrix can rapidly migrate to the surface, restoring or maintaining a certain level of hydrophobicity to suppress leakage current growth.