An inflatable cabinet is a type of switchgear that seals high-voltage electrical equipment (such as circuit breakers, disconnectors, grounding switches, current transformers, voltage transformers, etc.) in a metal shell filled with insulating gas. Inflatable cabinets usually use sulfur hexafluoride (SF6) as the insulation and arc extinguishing medium, which is widely used in high-voltage and ultra-high-voltage power systems because of its excellent insulation performance and arc extinguishing ability.

1. The structure and composition of the inflatable cabinet

The main components of an inflatable cabinet include:

Metal shell: made of stainless steel or aluminum alloy, with good sealing and mechanical strength, filled with insulating gas (such as SF6) inside.

Circuit breaker: used to make and break circuits, usually vacuum circuit breakers or SF6 circuit breakers.

Disconnector switch: used to isolate the circuit to ensure that the equipment is completely disconnected from the power supply during maintenance.

Grounding switch: used to ground the equipment to ensure the safety of the operator.

Current transformers (CT) and voltage transformers (PT): used to measure current and voltage, provide protection and control signals.

Busbar: used to connect various electrical equipment and transmit electrical energy.

Air chambers: Electrical equipment is sealed in separate compartments, and each air chamber is filled with insulating gas to ensure electrical isolation between devices.

Operating mechanism: used to control the operation of circuit breakers, disconnecting switches, and grounding switches, and is usually equipped with manual and electric operating mechanisms.

Monitoring system: Modern inflatable cabinets are often equipped with intelligent monitoring systems that monitor gas pressure, equipment status, and electrical parameters in real time.

2. Main features of inflatable cabinets

Compact design: Thanks to the gas insulation, the gas-filled cabinet is much smaller in size than conventional air-insulated switchgear (AIS), saving space.

High reliability: SF6 gas has excellent insulation and arc extinguishing properties, which can effectively prevent arc and short circuit faults.

Strong adaptability: The inflatable cabinet is suitable for all kinds of harsh environments (such as high altitude, humid, and heavily polluted areas), and is not affected by external climatic conditions.

Low maintenance: Since the equipment is sealed in a metal housing, it is virtually impervious to dust, moisture and corrosion, resulting in minimal maintenance.

Long life: Inflatable cabinets are usually designed to last more than 30 years.

Environmental friendliness: While SF6 is a potent greenhouse gas, modern gas cabinets use sealing technology to ensure extremely low gas leakage rates, while also developing environmentally friendly alternative gases.

3. Technical parameters of the inflatable cabinet

Rated voltage: 12kV, 24kV, 36kV, 72.5kV, 145kV, 245kV, 420kV, etc.

Rated current: 630A, 1250A, 1600A, 2000A, 2500A, 3150A, 4000A, etc.

Rated short-circuit breaking current: 20kA, 25kA, 31.5kA, 40kA, 50kA, etc.

Gas pressure: usually 0.4~0.6MPa (gauge pressure), depending on the design.

Degree of protection: The enclosure is usually IP67 and the internal compartment is IP6X.

Gas leakage rate: The annual leakage rate is usually less than 0.5%~1%.

4. Application field of inflatable cabinet

Substation: Used in high-voltage and ultra-high-voltage substations as the core equipment for power distribution and control.

Urban power grid: It is suitable for urban substations with limited space to meet the needs of high load density.

Industrial and mining enterprises: It is used in the power distribution system of large industrial and mining enterprises to provide reliable power supply.

Renewable energy: It is used for grid connection and distribution of new energy projects such as wind farms and photovoltaic power stations.

Rail transit: power supply system for subway, high-speed rail and other rail transit.

5. Advantages of inflatable cabinets

Space-saving: Due to the use of gas insulation, the volume of the inflatable cabinet is 50%~70% smaller than that of the traditional switchgear, especially suitable for places with limited space.

High safety: SF6 gas is much more insulating than air, effectively preventing arcing and short-circuit faults, while the metal housing provides additional mechanical protection.

Strong environmental adaptability: the inflatable cabinet is suitable for harsh environments such as high altitude, humidity and serious pollution, and is not affected by external climatic conditions.

Low maintenance costs: Since the equipment is sealed in a metal casing, there is little to no need for routine maintenance, reducing O&M costs.

6. Maintenance and maintenance of inflatable cabinets

Gas Pressure Monitoring: Regularly check the pressure of SF6 gas to ensure that it is within the normal range.

Leak detection: Use a gas leak detector to detect gas leaks and ensure good sealing performance.

Mechanical parts inspection: Regularly check the flexibility and reliability of the operating mechanism to ensure that the switch is operating properly.

Cleaning & Anti-corrosion: Keep the outside of the cabinet clean to prevent corrosion and contamination.

7. Environmental issues of inflatable cabinets

SF6 gas is a potent greenhouse gas with a global warming potential (GWP) of 23,500 times that of carbon dioxide. Therefore, the environmental protection of inflatable cabinets has attracted much attention. Currently, the industry is taking the following measures:

Reduced leakage rate: The gas leakage rate is kept to a very low level through improved sealing technology.

Gas Recovery: When equipment is decommissioned or repaired, SF6 gas is recovered to prevent it from being released into the atmosphere.

Alternative gases: Research and development of environmentally friendly alternative gases, such as dry air, nitrogen, fluoronitrile (C?) F? N) and so on to reduce dependence on SF6.

8. Future development of inflatable cabinets

Intelligent: Inflatable cabinets will increasingly integrate intelligent monitoring systems for remote control, fault diagnosis and condition assessment.

Environmental protection: With the improvement of environmental protection requirements, the inflatable cabinet will gradually adopt environmentally friendly insulating gas to reduce the dependence on SF6.

Modular design: The inflatable cabinet will be more modular, making it easy to install, expand, and maintain.

With its compact design, high reliability and low maintenance cost, inflatable cabinets are widely used in high-voltage power systems. With the continuous advancement of technology, inflatable cabinets will make greater breakthroughs in intelligence and environmental protection, providing more efficient and sustainable solutions for the power system.