What are the functions and types of insulation parts for high and low voltage switchgear?

What are high- and low-voltage switchgear insulation components?

Insulation components are non-metallic functional components used in high- and low-voltage switchgear to isolate live components, support and secure conductors, and prevent electrical short circuits and ground faults. They must possess extremely high electrical insulation strength, mechanical strength, and stability.

​​​​​​​

Main Functions of Insulators

Electrical Insulation (Core Function): Ensures sufficient insulation distance between charged objects at different potentials (e.g., between phases, between phases and ground) to prevent current breakdown.

Mechanical Support and Fixing: Supports heavy or critical conductive components such as busbars, circuit breakers, and disconnectors, ensuring their stability under conditions such as electrodynamic forces and vibration.

Safety Protection: Forms an isolation barrier to protect personnel and equipment from accidental electric shock.

Improves Electric Field Distribution: Certain specially designed insulating components (such as grading rings and shielding covers) can optimize electric field distribution and reduce partial discharge.

 

Commonly Used Materials

 

The performance of insulation materials directly determines the quality and reliability of insulation components.

Material Type	Key Features	Common Applications
Epoxy Resin	High strength, high insulation, and excellent arc and chemical resistance. It can be molded into complex shapes through casting and APG processes, offering dimensional stability. It is currently the mainstream material.	Insulators, bushings, partitions, circuit breaker housings, and current transformer castings.
SMC/DMC (Unsaturated Polyester Bulk Molding Compound)	It offers excellent mechanical strength, electrical insulation, and heat resistance, while being relatively cost-effective and suitable for large-scale press molding.	Insulator boxes, mechanism covers, brackets, and partitions for low-voltage switchgear.
Nylon (PA)	It is tough, wear-resistant, and self-lubricating, but is susceptible to moisture absorption and has slightly poor long-term heat resistance.	Small structural components such as nuts, screws, wire clips, and guide rails.
Polycarbonate (PC)	It offers high impact strength, transparency, and heat resistance, but offers only moderate chemical resistance.	Observation windows and instrument housings.
Polytetrafluoroethylene (PTFE)	It offers extremely excellent resistance to high and low temperatures, chemical corrosion, and dielectric properties, with an extremely low coefficient of friction, but at the expense of high cost and moderate mechanical strength.	Special insulation and arc-resistant components for high-voltage environments.
Ceramic	It offers ultra-high hardness, high-temperature and arc resistance, and resistance to aging, but also offers limited performance and brittleness.	High-voltage fuse housings and insulators.

Development trend: Environmentally friendly, flame retardant, and halogen-free materials are the future development direction to meet stricter safety and environmental standards.

 

Main Types and Products

Based on their function and form, insulating components can be divided into the following categories:

Insulators

Function: Used to support and secure busbars (main circuit conductors).

Types: Post insulators, wall bushing insulators.

Material: Primarily epoxy resin castings.

Partitions and Baffles

Function: Provide isolation within the switchgear, separating different compartments (such as the circuit breaker compartment, busbar compartment, and cable compartment) to achieve "metal enclosed armor" and "internal fault arc protection."

Material: SMC board, epoxy resin board, etc.

Mechanism Accessories and Structural Parts

Function: Insulating components for operating and interlocking mechanisms, such as connecting rods, levers, and gears.

Material: Nylon, POM (polyoxymethylene), reinforced engineering plastics.

Busbar Clamps and Sealing Components

Function: Clamp and secure the busbar to prevent displacement due to short-circuit electromotive force.

Material: SMC, nylon, epoxy resin.

Sealed Pole

Function: This represents a significant advancement in vacuum circuit breaker technology. The vacuum interrupter and associated conductive components are integrally cast in epoxy resin.

Advantages: Compact structure, excellent insulation performance, dust and moisture resistance, and maintenance-free. It has become a standard feature of medium-voltage vacuum circuit breakers.

 

Key Performance Requirements and Testing

Electrical Performance

Power Frequency Withstand Voltage: The ability to withstand short-duration power frequency high voltage.

Impulse Withstand Voltage: The ability to withstand lightning impulse voltage.

Partial Discharge: A key indicator for determining whether there are minor defects within the insulation. The lower the requirement, the better.

Creeping Distance: The shortest path measured along the insulation surface. Must meet the requirements of the corresponding pollution level.

Mechanical Performance

Flexural Strength/Compressive Strength: The ability to withstand mechanical loads.

Impact Toughness: The ability to withstand shock and impact.

Thermal Performance

Thermal Resistance Grade (e.g., B, F, H): Ensures performance does not degrade under long-term operating temperatures.

Flame Retardancy (e.g., UL94 V-0): Prevents the spread of fire.

Environmental Performance

Weather Resistance: Resists the effects of UV rays and temperature fluctuations.

Chemical Corrosion Resistance: Resists corrosion by chemicals such as acids, alkalis, and salts.

 

Frequently Asked Questions and Precautions

Aging: Insulation materials will gradually degrade (age) under prolonged electrical, thermal, and mechanical stress, requiring regular inspection and maintenance.

Condensation and Contamination: In humid and contaminated environments, a conductive film of water can easily form on the insulation surface, leading to creepage (flashover) incidents. Ensure temperature and humidity control within the cabinet (e.g., by installing a heater) and maintain regular cleaning.

Mechanical Damage: Cracks and gaps caused during installation or transportation can significantly reduce insulation strength.

Improper Material Selection: Unsuitable materials can deform and crack over time, causing serious failures.

Design Flaws: Improper insulation structure design can lead to electric field concentration and partial discharge.

 

Summary

Although insulation components aren't active components of switchgear, they are the unsung heroes that ensure the safe and reliable operation of the entire system. From material selection and structural design to production processes and on-site installation, every step is crucial. As switchgear evolves towards miniaturization, intelligence, and high reliability, insulation components are increasingly required to meet higher standards of performance, environmental friendliness, and integration.

 

Are you also troubled by the following issues?

Rapid aging of insulation components, leading to frequent equipment failures?

Concerned about substandard insulation performance, posing a safety hazard?

Seeking cost reduction and efficiency improvement, but can't find the optimal balance between quality and price?

Shaanxi Huadian Insulation Components is the solution for you!

We provide more than just products; we deliver value throughout the entire equipment lifecycle:

Improve equipment reliability: Fundamentally eliminate unplanned downtime caused by insulation problems, ensuring continuous power supply.

Reduce overall costs: Ultra-long service life and extremely low failure rates significantly reduce your maintenance and replacement costs.

Strengthen brand reputation: Stable core components are the best proof of the high-quality switchgear you deliver to your customers.

Accelerate project delivery: A stable supply chain and efficient delivery capabilities ensure worry-free project progress.

 

Welcome to inquire and negotiate, we will provide free selection guidance and sample testing according to your needs.

Email:pannie@hdswitchgear.com.

Whatsapp/Wechat:+8618789455087