The three-position vacuum circuit breaker is a high-voltage switchgear that integrates three functions: vacuum circuit breaker, disconnector, and earthing switch. It boasts excellent electrical and mechanical performance, reliable and stable operation, and a long service life. The main circuit uses solid-sealed poles, improving the circuit breaker's environmental adaptability and insulation reliability. Reliable mechanical and electronic performance, extended mechanical and electrical lifespan, make maintenance-free operation possible. It can be used in 3.6-12kV power systems as a protection and control unit for power distribution equipment in industrial and mining enterprises. It is suitable for various types of loads and applications involving frequent operation and multiple short-circuit current interruptions. This product features a complete mechanical and electrical interlocking system, ensuring extremely high operational stability and reliability, guaranteeing the safety of operators and equipment, and ensuring electrical safety.
Key components and the meaning of "three-station"
Vacuum Interrupter:
Responsible for interrupting and closing load current and fault current (short-circuit current). This is the core function of the circuit breaker, utilizing vacuum as the arc extinguishing medium, possessing extremely strong arc extinguishing capabilities.
Three-Position Isolating/Grounding Switch:
This is the origin of the "three-position" concept. It is usually connected in series with the vacuum interrupter and installed in the same gas-filled enclosure. Its moving contact can move between three predetermined mechanical positions:
Working (Closed) Position: The circuit is connected, and current can flow through the vacuum interrupter and the three-position switch.
Isolation (Open) Position: The vacuum interrupter is open, and the moving contact of the three-position switch is also disconnected from the stationary contact, forming a visible electrical isolation gap that meets safety standards. This is crucial for ensuring safety during equipment maintenance.
Grounding Position: In addition to isolation, the line side (usually downstream, such as the cable side) is directly connected to the grounding grid. This is to release residual charge on the line during maintenance and prevent accidental energization, ensuring personnel safety.
Common Operating Mechanism:
Usually driven by a spring operating mechanism. Through precise mechanical and electrical interlocking design, one mechanism can control the opening and closing of the vacuum interrupter and drive the three-position switch to switch between the three positions in the correct sequence. Interlocking is the core of ensuring safe operation and preventing misoperation (such as closing with grounding).
Main Advantages
Extremely High Reliability and Safety:
All live parts are sealed in an inert gas environment, unaffected by external factors such as moisture, dust, dirt, and small animals.
Mechanical interlocks fundamentally prevent misoperation, such as "closing the circuit breaker with the ground switch closed" or "opening the disconnector under load."
Compact Structure, Saving Space:
Integrating three functions into one gas chamber, the volume is significantly smaller than the traditional "circuit breaker + independent disconnector + independent grounding switch" arrangement (AIS). It is particularly suitable for space-constrained locations, such as urban substations, wind/solar power substations, railway traction substations, and large industrial and mining enterprises.
Maintenance-Free or Low Maintenance:
The components in the sealed gas chamber are essentially maintenance-free. The vacuum interrupter has a very long lifespan, typically reaching tens of thousands of mechanical operations. The main maintenance work involves checking the mechanism performance and gas pressure.
Fast Operation and High Mechanical Life:
Using a spring mechanism, operation is fast and reliable. The integrated design reduces external connections, resulting in a long mechanical life.
Environmentally Friendly Trend:
More and more new products are using dry air, nitrogen, or mixed gases as insulation media, replacing traditional SF₆ gas, making them more environmentally friendly.
Comparison with traditional layout methods
| Features | Three-position vacuum circuit breaker | Traditional air-insulated switchgear |
|---|---|---|
| Structure | Integrated, modular, and sealed design | Distributed, open-air design |
| Function Integration | Circuit breaker + disconnector + earthing switch | Circuit breakers, disconnectors, and earthing switches are independent |
| Insulating Medium | Vacuum (arc extinguishing) + SF₆/dry air, etc. (insulation) | Air (primarily) |
| Environmental Impact | Almost unaffected | Highly susceptible to pollution, humidity, and weather conditions |
| Footprint | Very small | Very large |
| Safety | High, with built-in interlocking | Relies on external interlocks and operating procedures |
| Maintenance | Infrequent maintenance, long service life | Numerous components, requiring regular cleaning and inspection |
Selection
The VS1(VEGM)-12GD can be installed in small fixed cabinets, ring main units, or transformer substations.
The main circuit of the indoor high-voltage three-position vacuum circuit breaker is arranged longitudinally, with the disconnector at the top, the vacuum circuit breaker in the middle, and the grounding switch at the bottom. The operating mechanism, circuit breaker mechanism, and interlocking mechanism are located at the front of the switch. This switch can be installed upside down.
Selection is a systematic process that requires comprehensive consideration of technical parameters, application scenarios, and standards. The following are the key steps and elements:
Step 1: Clarify Core Electrical Parameters
Rated Voltage: Must be ≥ the system's highest operating voltage. Common values in China are 12kV and 40.5kV.
Rated Current: Selected based on the load current, considering future expansion. Common ratings: 630A, 1250A, 1600A, 2000A, 2500A, 3150A.
Rated Short-Circuit Breaking Current: One of the most critical parameters. Must be greater than or equal to the expected short-circuit current at the installation point. Common ratings: 20kA, 25kA, 31.5kA, 40kA.
Rated Short-Time Withstand Current & Rated Peak Withstand Current: Must match the breaking current and test the equipment's dynamic and thermal stability.
Mechanical Life: Vacuum circuit breakers themselves have a long lifespan (10,000-30,000 operations), but the mechanical life of the operating mechanism and three-position switch is a key indicator, usually requiring more than 10,000 operations.
Insulation Level: Power frequency withstand voltage and lightning impulse withstand voltage values must comply with national standards.
Step 2: Determine Functions and Configuration
Operating Mechanism:
Manual Spring Operating Mechanism: Low cost, no auxiliary power required, but slow operation speed and no remote control.
Electric Spring Operating Mechanism: The most common configuration. Allows for local/remote electrical control and features such as automatic reclosing.
Permanent Magnet Mechanism: Simple structure, fewer parts, high reliability, fast opening and closing speed, representing a high-end development direction.
Protection and Measurement Integration:
Is a built-in protection relay required? Modern equipment often integrates microprocessor-based protection and control devices (such as overcurrent, instantaneous overcurrent, and ground fault protection).
Are current/voltage sensors required? Traditional CT/PTs are gradually being replaced by smaller sensors (such as Rogowski coils and voltage dividers).
Communication Interface: Does it support protocols such as Modbus and IEC 61850 for distribution network automation?
Control of the Three-Position Switch:
Confirm whether the operation is manual or electric. Electric operation facilitates "five-prevention" interlocking and remote control.
Gas Compartment and Airtightness:
For gas-insulated types, attention should be paid to the gas compartment material (stainless steel is best), annual leakage rate (usually required to be < 0.5%/year), and pressure monitoring device.
Step 3: Application Scenarios and Installation Environment
Indoor vs. Outdoor:
Indoor: Standard cabinet types are sufficient.
Outdoor: Requires specialized modules from outdoor packaged substations (European or American type), or outdoor ring main units that can withstand sunlight and rain.
Main Grid vs. User End:
Power Grid Companies: Have extremely high requirements for standardization, reliability, and communication protocols, and usually have a strict list of approved brands and models.
Industrial and Commercial Users: Are more concerned with cost-effectiveness, footprint, and ease of use.
Space Constraints: In confined spaces such as basements or offshore platforms, solid insulation or compact environmentally friendly gas-insulated equipment is preferred.
Environmental Requirements: In areas or projects where the use of SF₆ gas is explicitly prohibited, dry air/nitrogen insulation or solid insulation types must be selected.
Contact Us
Shaanxi Huadian Electric Co., Ltd. mainly produces and sells a series of products including indoor and outdoor high-voltage disconnectors, high-voltage load switches, high-voltage vacuum circuit breakers, grounding switches, and surge arresters. Among these, our company's three-position vacuum circuit breaker is particularly popular and highly regarded by customers due to its outstanding quality. Our products are reliable, and we possess all the necessary certifications, ensuring you can purchase with confidence. We also provide bidding authorization and OEM manufacturing services. If you have any questions or needs regarding our products, please feel free to contact us. We look forward to hearing from you.
Email:pannie@hdswitchgear.com.
Whatsapp/Wechat:+8618789455087
