The insulation structure of vacuum circuit breakers mainly determines their physical dimensions, voltage levels, and application scenarios. The core purpose of different insulation designs is to ensure reliable dielectric strength within and outside the circuit breaker under high voltage conditions.
Air-insulated Circuit Breaker
This is the most traditional and structurally simple form.
Structural Features:
All live components such as the vacuum interrupter, conductive circuit, and support insulators are exposed to the air.
Insulation between phases and between phases and ground (the switchgear enclosure) is entirely dependent on air gaps.
To achieve sufficient insulation distance, its volume is usually very large.
Working Principle:
Main insulation: Relying on a sufficiently long air path to isolate high-voltage live parts from the grounded enclosure.
Phase-to-phase insulation: Relying on a large air gap to isolate live parts of different phases.
Advantages and Disadvantages:
Advantages: Intuitive structure, relatively simple manufacturing process, low cost, and easy for inspection and component replacement.
Disadvantages: Large volume: Due to the relatively low insulation strength of air (about 3 kV/mm), a large safety distance is required. Susceptible to environmental influences: Moisture (condensation), dust, salt spray, chemical pollution, and small animal intrusion can significantly reduce its insulation performance, leading to flashover accidents. Therefore, auxiliary equipment such as heaters and ventilation systems must be provided for the switchgear.
common insulation cylinder vacuum Circuit Breaker
This structure was developed to overcome the shortcomings of pure air insulation and is currently the most mainstream technology in the medium-voltage field.
Structural Features:
On the basis of air insulation, solid insulation materials, typically silicone rubber or epoxy resin, are added to critical insulation areas (such as the moving and static ends of the vacuum interrupter).
A common form is the vacuum interrupter being enclosed in a silicone rubber bushing with skirts.
Working Principle:
Main insulation: Shared by "solid insulation material + air". The silicone rubber skirts not only provide additional creepage distance but also effectively prevent pollution flashover due to their hydrophobicity.
Phase-to-phase insulation: Mainly still relies on air, but insulating partitions are usually added to enhance it.
Advantages:
Significantly improves pollution flashover and moisture resistance, with stronger environmental adaptability.
Can be made more compact than air-insulated circuit breakers at the same voltage level.
Better maintainability, with main components still accessible.
Disadvantages: Higher cost than air-insulated circuit breakers, and still not as compact as solid-sealed pole-type circuit breakers.
embedded poles type vacuum circuit breaker
This is currently the most advanced and compact form.
Structural Features:
The vacuum interrupter and its upper and lower connection terminals and other main conductive components are integrally cast in epoxy resin through an automatic pressure gel process to form a solid insulation module - the "pole".
Working Principle:
Main insulation: Almost entirely provided by epoxy resin. Epoxy resin has extremely high insulation strength (about 20 kV/mm), which is 6-7 times that of air.
Phase-to-phase insulation: Due to the strong main insulation provided by epoxy resin, the distance between phases can be designed very small, greatly reducing the overall size of the circuit breaker.
Advantages:
Extremely compact: The smallest volume, making it highly suitable for space-constrained applications (such as ships, mines, and box-type substations).
High reliability: Completely sealed, completely avoiding environmental influences (moisture, dust, chemicals), truly achieving "maintenance-free".
High safety: The epoxy shell provides good protection and makes it difficult to touch live parts.
Disadvantages:
Highest manufacturing cost.
Once the internal vacuum interrupter or insulation components are damaged, they cannot be repaired separately; the entire pole must be replaced, resulting in high maintenance costs.
Summary and Selection
The development history of these three insulation structures reflects the trend of vacuum circuit breakers towards miniaturization, high reliability, and maintenance-free.
Selection Criteria: Cost and space insensitivity: Traditional air-insulated circuit breakers can be considered.
Balancing performance, cost and maintenance: Composite insulated circuit breakers are the most common and rational choice at present.
Extremely limited space, harsh environment and the highest reliability requirements: Solid-sealed pole circuit breakers should be given priority, although the initial investment is higher, the reliability advantage throughout the entire life cycle may be more valuable.
our VTZ Serious Vacuum circuit breaker
VTZ-12 vacuum circuit breaker has many advantages:VTZ-12 vacuum circuit breaker is produced by Shaanxi West Power Tongzhong Electrical Co., Ltd. (special model of Tongzhong Electrical Co., Ltd.) is an indoor switchgear for rated voltage 12kV, AC 50/60Hz. It adopts a modular operating mechanism and is suitable for various industrial and mining enterprises, as well as power grid equipment. It can be used as a handcart unit for use with KYN28A-12 switchgear, or as a fixed unit with relevant mechanical interlocking, making it suitable for XGN2 and other fixed cabinets.
1.Peformance of circuit breaker：
E2-C2-M2
2.Convenient maintenance:
the modular mechanism design allows for easy replacement of the closing and opening coils without the need for dismantling other components. This eliminates the need for testing or adjustment after replacement, ensuring users to replace them independently, making subsequent maintenance more convenient.
3.High conductivity performance:
the product features a well-designed conductive circuit that meets 1.1 times the rated current temperature rise level.
4.Wide application range:
the product series has a wide application range, rated currents from 630A to 5000A, and rated breaking currents from 20kA to 50kA. It is suitable for all environments within an altitude of 4500 meters and an operating temperatures from -40°C to 40°C.
Supports intelligent customization:
a. It can add a wireless temperature monitoring solution with self-powered design to ensure safety and maintenance-free operation.
b. It has a mechanical characteristics monitoring solution to provide real-time monitoring of circuit breaker operating data for early detection and resolution of potential problems.
c. It has a motorized cabinet entry solution to allow remote operation for ensuring personal safety.
d. Real-time component aging can be detected by partial discharge testing.
contact us
Shaanxi West Power Tongzhong Electrical Co., Ltd.
Contact: Ms.Grace Liu (Director of Sales Department)
Email:xdtz04@westpowerelectric.com
Mobile: +86 18091765882(WhatsApp/Wechat/skype )
