Selection and Maintenance of Insulators on High-Voltage Power Lines

The Important Role of Insulators
On high-voltage power lines, we often see strings of insulators. What exactly is their purpose? These insulators, like guardian deities on the high-voltage lines, play a crucial role in ensuring safety. Through them, we can guarantee smooth current transmission while preventing the current from causing damage to the surrounding environment and equipment.

​The Installation Process of Insulators
Why are strings of insulators hung on high-voltage lines? And how exactly do they work?
Next, let's understand the installation process of insulators. First, workers use tools to gently prop up the connections on both sides, creating the necessary distance for installing the new insulator. Then, they securely place the new insulator into position and quickly remove the tools to complete the installation process. This seemingly simple series of operations actually safeguards the power supply for thousands of households.

​02 Principles of Insulator Operation​

​Principles and Material Selection
How do insulators actually work?
Besides glass-type insulators, we commonly see white, ceramic-like insulators. While they provide fixation, their core function is insulation. Since high-voltage lines typically exceed 10,000 volts and span vast distances, if they were simply wrapped in insulation like household wires, the shell thickness for a 500,000-volt line would reach 17 centimeters. This would not only be prohibitively expensive but also the increased weight would extend the required spacing between support structures.
Furthermore, thick insulation layers would hinder the heat dissipation of the high-voltage lines, potentially causing safety hazards. Therefore, high-voltage lines are usually exposed directly to the air.

​Design Evolution and Challenges
However, this creates a problem: when the high-voltage line passes by a utility pole, current could flow down through the concrete and steel reinforcement into the ground, creating a hazard.
To solve this problem, insulators were added between the line and the pole. They were designed with a disc shape to reduce the electric field concentration that causes flashover (arcing). But another problem arose: the disc shape could allow rainwater to accumulate, and current could potentially track along the water path. This led to the gradual evolution of the umbrella-shaped design, which reduces the risk of current leakage and rainwater accumulation, resulting in the insulator shape we recognize today.

​Pollution and Maintenance Measures
Simply put, insulators block current flow by using insulating materials and their unique shape design. However, while insulators meet basic insulation needs under normal conditions, if their surface becomes contaminated and then wetted, soluble substances can dissolve in the water and form a conductive film on the surface. This can lead to intense electrical discharge phenomena (flashover), potentially causing equipment outages or damage.
Contaminants such as industrial dust, smoke particles, salty/alkaline dirt, and even bird droppings can easily cause insulator flashover. To prevent this dangerous situation, insulators need regular cleaning. One method is washing them using high-pressure water guns. Additionally, the pollution flashover characteristics can be improved by increasing the number of insulator discs in a string or by applying special coatings to the insulator surfaces, thereby ensuring the safe operation of the high-voltage power lines.