Insulators are used in electrical equipment to support and separate electrical conductors without allowing current to pass through the insulators. Silicone rubber is the most widely used polymeric insulation material for high voltage products. Our composite insulators have excellent performance in all climates and harsh conditions such as coastal, desert, and industrial environments.
Composite insulators with silicone rubber insulation possess unique properties and are installed all over the world. YIPENG offers a wide range of insulators, and together with our flexible production method can deliver composite insulators that will meet your requirements.
The main component of the composite insulator is a silicone rubber sheath. Silicone rubber is formed by the linkage of high-molecule polymers of polydimethylsiloxane and organic oxygen compounds; the main chain is formed by a silicon-oxygen bond. Since the bond energy of the silicon-oxygen bond is larger it has good thermostability and can work at temperatures of −100 to +350°C. Silicon rubber has good ozone resistance performance, and whereas butadiene-propylene propylene butadiene rubber can be readily broken, under room temperature tension on ozone of 150 ppm, however, silicone rubber can last for several months and not be broken.
Composite insulators can take wind and rain and have good self-cleaning performance under wind and rain, so need checking for pollution only once every 4–5 years, and requiring less time for the repair and power interruption. Since the core rod has higher extension strength, composite insulators can result in very light overall weight. Their weight is only 10–20% of the weight of porcelain insulator strings of the same voltage class. Their length can be shortened by more or less 10% in the same voltage class, which can greatly reduce the labor of workers in transportation and field operation.
The composite insulator has many advantages, but also disadvantages, e.g., the loss of hydrophobicity, the risk of the core rod becoming brittle and breaking, lightning strike, and birds droppings, which can all make composite insulators lose efficiency.
Since the diameter of the sheds of the composite insulator is less, the minimum electric arc distance is less than for the same length of porcelain insulator strings, and the lightning withstand level is also less than for the same length of porcelain insulator strings.
After a lightning strike, the only effect on composite insulators is some white electric erosion; there is no change in their insulating property. But attention must be paid to the erosion of both ends of the fitting.
The internal insulation distance of composite insulators is nearly equal to that of the external insulation, and the structure is in the group of puncture-proof insulators, and therefore does not have the problem of having to detect zero value insulators, and this greatly reduces the workload of operation maintenance.
The material of sheds and sheaths of composite insulators are silicone rubber and the surface is a low-energy surface. The creepage distance of composite insulators is bigger and the diameter of the umbrella shed is smaller, and the surface has hydrophobicity and migration of hydrophobicity. Even in a humid and polluted environment, the shed surface of composite insulators will not form a continuous water film; therefore, its antipollution performance is superior to that of a porcelain insulator.
Composite insulators have been introduced as a good alternative to ceramic and glass insulators. After nearly 30 years of launching the first type of composite insulators and making design improvements and consuming materials, they are used as well-known and suitable products in HV.
In the resin insulators, the oxygen composition with certain plastics is made in the form of a polyidison; that is, together with the composition, large molecules are produced. In order to harden the compound, usually, additional materials such as quartz are added, and finally, the resin is made up by heating and casting. These types of insulators are not used in open space due to their lack of ultraviolet radiation in the sun and are used only in interior spaces and inside panels.
Composite insulators play a vital role in power transmission by supporting and insulating high-voltage power lines. Compared to ceramic or glass types, they’re lighter, more pollution-resistant, and ideal for harsh environments such as coastal or industrial zones.
But behind these advantages lie hidden risks. Internal defects, such as debonding of the sheath and core rod, air holes inside the sheath, faults, and poor bonding, together with ageing and contamination, can lead to partial discharges, interface breakdown, and even flashovers, threatening the safety of the network.
This article covers the structure, working principles, types, and key benefits of composite insulators, while also revealing the potential issues engineers must not overlook.
Maybe many people don’t know what is a composite insulator. It is made by combining two or more materials, like a steel core, polymers, and other composites. Its main job is to separate electrical conductors from the ground in power systems, stopping dangerous current leaks while keeping power lines stable. Unlike old-style ceramic or glass insulators, these are lighter, tougher, and better at handling harsh weather or physical impacts. That’s why they’re now a go-to choice for modern power grids!
They are cleverly designed to balance electrical insulation, strength, and durability. Here’s how they’re built:
Core Rod: This is the backbone of the insulator, usually made of fiberglass-reinforced plastic (FRP). It’s super strong and holds everything together, even in tough conditions like heavy winds or heavy loads. Think of it as the “spine” that keeps the insulator stable and reliable.
Tips: Some models also have cores made of insulating silicone rubber, steel, or other polymer materials.
Composite Insulating Shell: Made from durable polymer materials like silicone rubber or EPDM, this outer shell acts as the insulator’s “protective coat.” Its standout feature is water resistance, which stops water and dirt from sticking to the surface. This helps reduce risks like leakage currents and flashovers. By blocking electricity from passing through internal metal parts (like the steel core), it keeps power systems running safely and smoothly.
Lightning Protection Layer: Old-school glass or ceramic insulators could crack or burn when struck by lightning. Modern composite insulators solve this with a special layer, often made of metal or conductive materials. If lightning hits, this layer creates a safe discharge path, redirecting the electrical surge to the ground. This shields both the insulator and power lines from damage.
End Fittings: These are the connector parts at both ends of the insulator, usually built from metal or composite materials. Their job is to attach the insulator to power equipment or support structures. Designed to handle heavy loads—like strong winds, ice buildup, or vibrations—they keep the insulator securely in place while maintaining system safety.
To ensure the reliability and safety of composite insulators in high-voltage applications, manufacturers adhere to international and national standards. In the United States, the American National Standard for Insulators—Composite Suspension Type (ANSI/NEMA C29.12- ) provides comprehensive guidelines on design, testing, and performance requirements for these insulators.
They might look simple, but they play a vital role in power systems. By combining smart designs with advanced materials, they safely isolate electricity and support heavy power lines. Here’s how they work in four key ways:
Link to Electric Powertek
Blocking Electricity Leaks: The outer layer of a composite insulator is made of special polymer materials that act like a shield. These materials stop electricity from flowing between power lines and the metal towers holding them up. Even under high voltage, the insulator’s surface won’t let electricity pass through, keeping the system safe.
Staying Strong in Tough Conditions: Inside every insulator is a tough core rod, usually made of fiberglass. This rod gives the insulator its strength. Whether facing strong winds, heavy ice, or extreme temperatures, the core rod keeps power lines steady and prevents collapses.
Stopping Dangerous Sparks (Flashovers): High voltage can cause sparks to jump along an insulator’s surface. To prevent this, they have umbrella-like “sheds” that create a longer path for electricity to travel. The sheds are coated with silicone rubber, which repels water and stops conductive films from forming. Some insulators also have metal rings (called grading rings) attached to spread out the electric field evenly, reducing spark risks.
Fighting Water and Dirt: The silicone rubber coating on the sheds doesn’t just block sparks—it also resists water, dust, and grease. In wet or polluted areas, this keeps the insulator’s surface clean and dry, preventing short circuits or power failures.
Why It All Matters
When power flows through lines, composite insulators do two critical jobs:
Their insulating materials keep electricity moving only through the cables, never leaking into the towers.
Their strong core rods hold up heavy cables, even in harsh weather.
By balancing electrical safety and physical strength, these insulators keep power grids running smoothly and reliably.
They come in different types, each designed for specific jobs and environments. Here are the most common ones:
Composite Line Post Insulators: Often called High Voltage Composite Insulators, these are used on upright posts in high-voltage power lines. They handle extreme electrical stress while keeping power lines securely attached to structures like steel towers.
Composite Pin-Type Insulators: Also known as Composite Pin Insulators, these are mostly used in power transmission lines and substations, especially for high or ultra-high voltage systems. They’re designed to hold single power lines at suspension points, keeping electricity isolated from support structures like poles or towers.
Cross-Arm Insulators: These insulators are mounted on the horizontal cross-arms of power towers. Their job is to support power lines while blocking electricity from leaking between the cables and the tower. By safely holding the cables, they keep the grid stable and reduce the risk of outages.
Composite Post Insulators: Sometimes called Line Post Insulators, these are installed on vertical posts in high-voltage transmission systems. They’re popular for their strong electrical insulation, durability in tough weather, and lightweight design, which makes them easier to transport and install.
High Strength: Composite insulators are very strong. They can handle heavy forces like strong winds, ice build-up, or vibrations without breaking. They can hold between 40 and 210 kN (around 9,000 to 47,000 pounds), so they’re great for storms and extreme weather. (Learn how composite insulators outperform porcelain types in mechanical strength in our comprehensive comparison here.).
Lightweight Design: They’re much lighter than ceramic or glass insulators. This makes them easier to carry, install, and maintain, especially in hard-to-reach areas like mountain power lines.
Rust and Corrosion Resistance: The materials used (like fiberglass and silicone rubber) don’t rust or corrode easily. This makes them perfect for coastal areas, humid climates, or places with heavy air pollution.
Survives Heat and Harsh Weather: The polymer parts can handle extreme heat and cold without cracking or aging. They stay strong through years of sun, rain, or snow.
Stays Clean in Dirty Conditions: Their smooth, slippery surface (often silicone rubber) stops dirt, dust, or salt from sticking. Even if they get dirty, rain usually washes them clean, preventing power leaks.
Saves Money Over Time: While they might cost about the same as traditional insulators upfront, they last longer and need less maintenance. Fewer replacements mean lower costs in the long run.
Works Almost Anywhere: You’ll find composite insulators in power lines (even ultra-high-voltage ones), substations, and city grids. They adapt well to deserts, forests, coasts, or industrial zones.
In short, these versatile insulators work everywhere from giant power grids to wind turbines and train tracks. Their combination of strength, safety, and weather resistance makes them the go-to choice for keeping our modern world powered up.
Composite insulators are a crucial component in modern electrical systems. They provide mechanical support and electrical insulation for high-voltage power lines. Thanks to their lightweight design, durability, and ability to resist environmental factors, they have an edge over traditional porcelain or glass insulators.