Vacuum Circuit Breaker Insulation Structures: A Comparison of Assembled, Embedded, and Insulated Tube Designs

In the development of medium-voltage power distribution systems, vacuum circuit breaker (VCB) insulation structure has undergone continuous evolution. Currently, embedded poles and insulating tube poles are the established solutions adopted by leading vacuum circuit breaker manufacturers globally. Renowned for their reliability and environmental adaptability, they satisfy the stringent requirements of most industrial and commercial applications. Concurrently, discussions regarding assembled pole vacuum circuit breakers—characterized by their modular and removable “open-type” structures—are gaining momentum, driven by low-carbon design philosophies and diverse perspectives on the future of the industry.

Technical Evolution of Vacuum Circuit Breaker Insulation

The vacuum circuit breaker working and its structural design have always centered on the balance between two core elements: heat dissipation efficiency and dielectric strength. It is through technical explorations and breakthroughs at different stages that the transition from traditional structures to modern mainstream solutions was formed:

• The Technical Starting Point – Traditional Open-Type Structures: From the perspective of technical evolution, early structures were mostly open-type, where the vacuum interrupter was directly fixed onto insulating supports. These supports, typically made of iron, aluminum alloy, or copper, featured a simple, transparent design with excellent heat dissipation. However, due to the substantial air clearance required (e.g., >125mm for 12kV), the equipment footprint was large, and the insulation level was vulnerable to environmental contamination or foreign objects, requiring relatively high standards for the installation environment. This original natural convection cooling logic, while limited by the material technology of the time, is being re-evaluated today for its thermal advantages in specific high-standard, controlled environments.
• Total Protection via Embedded Poles: With the maturation of material science and automatic pressure gelation (APG) technology, embedded pole stru emerged. By encapsulating the vacuum interrupter in high-performance epoxy resin, it resolved the external environmental interference issues that early structures struggled to handle. This marked the transition of vacuum circuit breakers into a phase of high reliability and extreme compactness.
• The Balanced Path of Insulating Tube Solutions: During technical iterations, the insulating tube structure simultaneously became a mainstream choice. This solution seeks a scientific balance between insulation protection and physical heat dissipation. Through a semi-enclosed tube structure, it ensures operational safety while effectively mitigating the temperature rise pressure faced by fully enclosed structures under high-current conditions.

Embedded Pole VCBs: Reliability in Harsh Environments

Embedded pole vacuum circuit breakers are recognized as the global standard for high reliability, ensuring peak performance even in complex environments.

• Technical Principle: Using the APG process, the vacuum interrupter and primary circuit are encapsulated in high-performance epoxy resin. Heat is primarily dissipated through conduction via the resin, requiring materials with high thermal conductivity.
• Core Advantages: This design is particularly superior in environments with heavy dust or high humidity. The physical encapsulation eliminates the risk of insulation failure caused by dust ingress, condensation, or small animals.
• Compact Design: Thanks to the superior dielectric strength of epoxy resin, phase-to-phase distances can be significantly reduced (e.g., to 135/150mm), meeting the demand for miniaturized and compact medium voltage switchgears.

Insulating Tube VCBs: Balancing Thermal Performance and Maintainability

For applications prioritizing continuous current-carrying capacity and maintenance flexibility, insulating tube vacuum circuit breakers offer a highly balanced solution.

• Structure Design: This solution integrates the vacuum interrupter and supports within an insulating tube, utilizing fewer components while achieving high assembly precision.
• Thermal Advantages: The semi-open structure naturally facilitates air convection, effectively reducing temperature rise and enhancing current-carrying capacity during heavy-duty operations.
• Maintenance Flexibility: The installation and commissioning process for the vacuum circuit breaker is straightforward. Specifically, the accessibility of VCB components like insulating pull-rods greatly simplifies preventive maintenance and adjustments.

Sustainability Trends: Assembled Pole Vacuum Circuit Breakers

In specific application scenarios or project selections, the assembled pole vacuum circuit breaker is gaining attention for its specialized performance and low-carbon maintenance potential. This interest is rooted in deep considerations of the operating environment and equipment lifecycle:

• Selection Logic Under Strict Environmental Control: Some customers with high requirements for power distribution safety prioritize ventilation and are concerned about the potential moisture absorption risks associated with embedded poles in specific conditions. To fundamentally prevent insulation issues caused by condensation, these projects often aim to eliminate traditional cable trench layouts, preventing water accumulation and humidity from entering the switchgear.
• Thermal Optimization in Controlled Conditions: In distribution rooms with metal steel structures, environmental control is often very strict (e.g., using positive pressure control to prevent corrosive gases and pests). With temperature and humidity closely monitored and risks controlled, customers prefer the air convection cooling advantages of the assembled pole vacuum circuit breaker. This ensures that the temperature rise remains within ideal limits during sustained high-current operation.
• Component-Level Maintenance for Low-Carbon Goals: From a sustainability perspective, the removable and modular design of the assembled pole structure offers a unique alternative. Unlike embedded poles, where the epoxy resin is difficult to recycle after disposal, this design supports the recycling of key components. When the vacuum interrupter reaches the end of its service life, operators can replace only the interrupter while retaining the insulating supports. This approach significantly reduces epoxy waste and aligns with circular economy goals.

Conclusion: Balancing Reliability and Sustainability

In summary, the evolution from early open-type designs to modern embedded and insulating tube technologies demonstrates that vacuum circuit breaker insulation selection must be based on actual operating conditions, balancing extreme safety requirements with low-carbon commitments.

Based on this principle, embedded poles remain the reliable choice for harsh conditions involving high humidity and heavy dust. Meanwhile, insulating tube designs provide a superior balance between thermal performance and ease of maintenance. Furthermore, the emergence of the assembled pole vacuum circuit breaker offers a versatile alternative to meet the growing demand for low-carbon O&M and optimized cooling in specific environments. As industry participants, Liyond Electric is committed to providing technical solutions tailored to our customers’ specific needs, ensuring maximum system reliability while actively fulfilling our commitment to sustainable development.