Ground Wire Type Glass Insulator

Ground wire type glass insulators are specialized insulating devices designed for the overhead ground wires (lightning protection wires) of transmission lines. Their main function is to support and insulate the ground wires, preventing discharge between the ground wires and the towers, and they possess lightning protection, anti-wind vibration, and aging resistance properties. They are suitable for ground wire systems of transmission lines with voltages ranging from 110kV to 1000kV.

1) Core structure and design features

• The lightweight and compact design of ground wire type glass insulators has a smaller umbrella skirt diameter and a lower structural height compared to line insulators. The overall weight is lighter, adapting to the low mechanical load characteristics of the ground wires. The umbrella shape mostly adopts single umbrella or shallow double umbrella structures, and the creepage distance only needs to meet the insulation requirements of the ground wires, without the need to pursue high creepage ratio. It balances economy and practicality.
• The basic composition and material mainly consists of tempered glass components, hot-dip galvanized steel caps, steel feet, and high-grade cement adhesive. It inherits the core advantages of glass insulators such as zero-value self-breakage, arc resistance, and vibration resistance. The steel caps and steel feet are made with thickened hot-dip galvanizing process, providing stronger corrosion resistance and enabling adaptation to the harsh outdoor environment.
• The connection method mostly adopts ball socket type connections, which are convenient for installation and can quickly adapt to ground wire hardware. They also have certain angle adjustment capabilities to adapt to the force deformation of the towers.

2) Core advantages

• Adapt to the working characteristics of ground wires. Ground wires have no rated operating voltage and only need to withstand lightning overvoltage. Therefore, the insulation configuration of ground wire type insulators precisely matches the requirements, avoiding excessive design, and the cost is 30% to 40% lower than that of line pollution-resistant insulators.
• Strong wind vibration and fatigue resistance. Ground wires are always in the high air environment, and they are prone to high-frequency vibration due to wind force. The ground wire type insulator optimizes the gluing structure, can effectively absorb vibration energy, avoid cracking at the connection between the steel foot and the glass component, and has a fatigue life of over 30 years.
• Low operation and maintenance cost. The zero-value self-breakage feature enables visual inspection of deteriorated insulators without climbing the tower for detection. Only regular inspections and replacement of self-burst pieces are required, significantly reducing the operation and maintenance workload of the ground wire system.
• Excellent lightning resistance performance. The glass material itself has strong arc resistance and will not suffer permanent insulation damage after lightning strike, maintaining mechanical strength and insulation performance, reducing the risk of ground wire failure caused by lightning faults.

3) Applicable scenarios

• Overhead ground wires / lightning protection wires of 110kV to 1000kV transmission lines;
• Ground wire systems in harsh environments such as coastal areas, high altitudes, and industrial pollution zones;
• Ground wires of large-span lines that need to withstand extreme loads such as strong winds and icing;
• Transmission line ground wire projects that need to reduce radio interference.

4) Selection and operation maintenance key points

• Select the rated breaking load based on the mechanical tension of the ground wire. It is usually 2.5 to 3 times the maximum operating tension of the ground wire;
• In polluted areas, the creepage distance should be appropriately increased, and models with creepage ratio ≥ 18mm/kV should be selected;
• For large-span ground wires, priority should be given to models with a rated mechanical breaking load ≥ 100kN.
• In plain clean areas, conduct inspections every 12 months, and in harsh environments, every 6 months;
• Pay special attention to rusting of the steel cap and steel foot, cracks in the umbrella skirt, and self-burst pieces, and replace deteriorated insulators in a timely manner;
• In coastal salt spray areas, the steel cap and steel foot can be sprayed with anti-corrosion coatings to extend the service life.