Standard Type: Umbrella-shaped insulators are the oldest type of suspension insulator. They are characterized by their simple structure, low cost, and suitability for clean areas. They are commonly used in AC transmission lines.
Disc Type: Disc-shaped suspension insulators are the most common and important type of line insulator. These insulators consist of an iron cap, porcelain insulating parts, and feet bonded together with cement adhesive. A thin buffer layer, usually asphalt, is applied to the surfaces of the steel feet and iron cap in contact with the adhesive. Elastic pads are placed between the porcelain parts at the top of the steel feet. The porcelain surfaces are generally glazed white, and the iron cap and steel feet are all hot-dip galvanized. A suitable gap is left between the lower edge of the cap and the insulating parts to prevent stress damage to the insulating parts during material expansion.
Disc-shaped suspension porcelain insulators mainly come in two types: ball-and-socket connections and slot connections. Ball-and-socket connections are non-directional and have the advantage of easy assembly and disassembly, especially facilitating live insulator replacement. Therefore, ball-and-socket connections are generally used on high-voltage, ultra-high-voltage, and extra-high-voltage lines. The slotted connection structure has relatively simple connecting hardware, but it is not convenient for live-line work and is generally used in lower voltage level lines in my country. To ensure that the insulator does not fall out of the string during operation, each insulator is equipped with a locking device. In the ball-and-socket connection structure, a locking pin is used for locking, while in the slotted connection structure, a cylindrical pin is used, secured with a cotter pin or a hump pin.
Bell-shaped insulators: These umbrella-shaped insulators have a longer underside ridge, allowing for a larger creepage distance. The inner cavity under the umbrella is less prone to moisture absorption and has a higher pollution withstand voltage, making them more suitable for use on AC and DC transmission lines in coastal, foggy, humid, and saline-alkali areas.
Double and triple umbrella types: These two shapes have smooth, open undersides, resulting in good self-cleaning performance from wind and rain, and a low natural dirt accumulation rate. Combined with a larger creepage distance, this gives the product a good pollution withstand voltage level, making the umbrella structure even more advantageous in dusty environments. These umbrella-shaped insulators are called "aerodynamic type," and they are suitable for various operating conditions, especially AC and DC transmission lines in heavily polluted, high-altitude, and arid desert regions.
"Hat type" insulators have an exceptionally large umbrella disc diameter, a smooth, edgeless underside, and a streamlined structure. They have excellent self-cleaning properties and low dirt accumulation. They are used by inserting them into the upper and middle parts of the suspension strings of AC and DC line insulators. The extra-large disc diameter helps to suppress line flashover caused by icicles and bird droppings.
