Triple-umbrella Type Glass Insulator

Triple-umbrella type glass insulator is the high-end subcategory of anti-pollution glass insulators. It adopts a progressive design with three layers of umbrella skirts, featuring an extremely high creepage ratio and excellent anti-pollution flashover capability. It is specifically developed for extremely harsh transmission scenarios such as severe pollution, high salt spray, and repeated icing. It is the core insulating component for 750kV and 1000kV ultra-high voltage lines.

1) Core structure and design features

• The three-layer umbrella skirt gradient configuration adopts a design of large umbrella + medium umbrella + small umbrella, with the largest diameter of the upper layer umbrella and the widest outward angle, which can effectively shield the middle and lower layers of umbrella skirts, blocking most of the dust, salt spray, condensation, etc. of pollution; the middle layer umbrella skirt takes on the protection of the large umbrella, further dispersing wind pressure and icing loads; the lower layer small umbrella is compactly arranged, maximizing the extension of the creepage path. The edges of all umbrella skirts are rounded and treated with anti-electrode discharge, reducing corona loss and radio interference, and improving the self-cleaning efficiency when washed by rainwater, reducing the residue of pollution.
• The basic structure and material body is composed of tempered glass pieces, hot-dip galvanized steel caps, high-strength steel feet, and special anti-aging cement adhesive. It inherits the core advantages of glass insulators such as zero-value self-breakage, arc resistance, and high mechanical strength. Damaged insulator pieces will automatically burst and fall off, allowing for direct visual inspection without the need for pole climbing detection.

2) Core advantages

• Ultra-high anti-pollution flashover performance: The creepage ratio can reach 30-40mm/kV, far exceeding that of double-sheath type insulators. It can effectively block the conductive path of pollution in severe industrial pollution and coastal high-salt spray environments, reducing the pollution flashover tripping rate by more than 30% compared to double-sheath type, fully meeting the insulation requirements of ultra-high voltage lines.
• Strong resistance to extreme working conditions: The symmetrical structure of the three-layer umbrella skirts significantly improves the wind vibration resistance and ice bridging resistance. It can withstand a wide temperature range of -40℃ to 70℃, suitable for extreme scenarios such as high-altitude areas with strong ultraviolet rays, repeated icing areas, and coastal areas with frequent typhoons.
• Significant operational economy: The shading design of the three-layer umbrella skirts + rounded umbrella edges make it difficult for pollution to adhere, and the pollution is easy to fall off after rain washing. The frequency of manual cleaning is reduced by 50% compared to double-sheath type; the zero-value self-breakage feature eliminates the need for individual piece detection, reducing the labor cost for operation and maintenance by 60% compared to porcelain insulators.

3) Applicable scenarios

• 750kV/1000kV ultra-high voltage transmission lines in severely polluted / coastal salt spray areas;
• Ultra-high voltage cross-sea projects in coastal areas with high salt spray and high humidity;
• Ultra-high voltage lines in high-altitude areas (≥3000m) and repeated icing areas (icing thickness ≥ 20mm);
• Transmission scenarios with high pollution and mechanical load in urban cores and large ports.

4) Selection and operation key points

• In severely polluted / coastal salt spray areas, prioritize selecting models with a creepage ratio of ≥35mm/kV;
• Ultra-high voltage lines need to match high-strength models with a rated mechanical breaking load of ≥210kN;
• In high-altitude areas, it is recommended to add UV-resistant coatings to extend the service life of glass components;
• In severely polluted areas, conduct inspections every 2-3 months, focusing on checking umbrella skirt cracks and rusting of steel caps and steel feet;
• In coastal areas, prioritize using stainless steel accessories or spraying anti-corrosion coatings on steel caps and steel feet;
• In repeated icing areas, it is recommended to combine with anti-icing devices to avoid the umbrella skirts being bridged by ice and causing flashover.