Air insulation switchgear adopts air as insulation medium and realizes the insulation and arc extinguishing function of electrical components through the open structure design. The working principle can be summarized as follows:
1.Insulation Mechanism: Air as a natural barrier
Air Gap Insulation
Electronic components of automatic identification systemssuch as circuit breakers and circuit breakers are exposed directly to air, utilizing air molecules as insulators. When voltage is applied between components, the air gap forms a natural barrier to the free flow of current. The design does not require enclosed gas or solid insulating materials and is therefore simple in structure and cost-effective.
Electric Field Uniformity
The concentration of electric fields and the risk of partial discharges are reduced by optimizing conductor shape (e.g., the use of rounded corners and uniform electric field structures) and component layouts. For example, the main circuit a metal-clad removable switchgear is designed with a uniform electric field to ensure stable operation even at high voltage.
2.Arc Extinguishment Mechanism: elongation of arc and Natural Cooling
Arc generation and hazards
When the circuit breaker is turned on, an arc occurs when the moving contact is separated from the static contact. Arc temperatures can reach thousands of degrees Celsius and can damage contact points, causing explosions or fires that must be extinguished quickly.
Air Arc Extinguishing Principle
Automatic identification systems use a combination of arc elongation and natural cooling to extinguish fires:
Arc elongation: Metal grids inside the groove divides the length of the arc into short knots, each lengthening further as it travels between the metal grids.
Natural cooling: As the arc length increases, the heat dissipates, rapidly dispersing heat into the air, causing the arc temperature to fall below the threshold required to sustain combustion, and ultimately extinguishing arc.
Typical Application Scenarios
When air circuit breaker (such as a die shell circuit breaker) interrupts the short circuit current, pull the arc to the arc slot and quickly extinguish the arc with the above mechanism. This method is cost-effective and suitable for low and medium voltage applications (e.g., 6kV to 750kV power grids).
III. Structural Advantages: Open design flexibility.
Modular Combination
The AIS product portfolio includes components such as circuit breakers, instrument transformers, and circuit breakers, allowing for flexible configuration according to specific needs. For example, the Siemens NXAirS series supports voltage levels ranging from 12kV to 40.5kV and has a new 1400mm panel width option to meet different capacity requirements.
Convenience of maintenance and expansion
The open structure allows for direct observation of the state of repair and replacement components. For example, metal cladding removable switches with drawers or plug-ins can quickly isolate problematic modules to minimize power outages.
Environmental Adaptability
Suitable for industrial park substation with beautiful environment and plenty of space. Its open structure is good for heat loss, but must be protected from parts corrosion in harsh environments such as humidity and salt mist.
IV. INTRODUCTION INTRODUCTION Typical Product and Technology Evolution
Traditional AIS Equipment
Structure: open steel frame, exposed member.
Strengths: Low cost, easy installation, high flexibility.
Limitations: Large footprint, reliability influenced by environmental impact.
Modern AIS Innovations
Compact design: For example, the ABB UniSafe series utilizes composite insulation technology to reduce overall size and construction investment. Intelligent Upgrade: Integrated ABB AbilityTM intelligent solutions to Achieve Hazard Warning and Device Health Management.
Eco-friendly materials: Reduce carbon emissions by using recyclable and biodegradable PT materials.
V. Application Scenarios and Market Positioning.
Key players in Medium-Voltage Power Grids
AI) will remain to occupy a significant position in the mid-voltage switching equipment market by 2024, and is widely used in 6kV-750kV digital substations, power plants, industrial substations, etc.
Complementarity with GIS Equipment
Artificial intelligence: Low cost, high flexibility, suitable for broad space applications.
GIS (Gas-Insulated Switchgear): SF6 gas insulation, small size, high reliability, suitable for high altitude, high humidity and other harsh environments. In the field of medium voltage, the two complement each other, and due to cost advantages, industrial substations are still dominated by automatic control.
