Air-Insulated vs Gas-Insulated Switchgear: When to Use Which

🕒 6 min

Switchgear is the foundation of every safe and reliable electrical distribution system. Whether it’s a manufacturing plant, commercial building, or renewable energy setup, switchgear ensures protection, control, and isolation of electrical circuits.

But as industries modernize, engineers often face a crucial question —
👉 Should we use Air-Insulated or Gas-Insulated Switchgear?

Both types serve the same core purpose — protecting electrical networks — but they differ significantly in design, application, and performance.

In this blog, we’ll dive deep into the differences between Air-Insulated Switchgear (AIS) and Gas-Insulated Switchgear (GIS), focusing particularly on Low Voltage (LV) switchgear applications. We’ll also help you decide which type best suits your specific operational needs.

What is Switchgear? – A Quick Overview

Before comparing the two, let’s understand what switchgear actually does.

Switchgear includes a combination of electrical devices like circuit breakers, fuses, isolators, relays, and control panels that regulate, protect, and isolate electrical systems.

The purpose is to:

• Interrupt fault currents
  
• Prevent short circuits
  
• Safely de-energize equipment for maintenance
  
• Ensure continuous power supply
  

In LV switchgear systems, these functions become even more critical since they protect sensitive machinery and personnel in commercial and industrial environments.

Air-Insulated Switchgear (AIS) – Definition and Features

As the name suggests, Air-Insulated Switchgear uses air as the primary insulation medium to separate live electrical components. It’s the traditional and most widely used switchgear type in Low Voltage switchgear applications.

Key Features of Air-Insulated Switchgear:

• Insulating Medium: Air (natural or ambient).
  
• Voltage Range: Typically used up to 1 kV (for LV systems) and up to 36 kV for MV systems.
  
• Construction: Components are installed in air-filled metal enclosures.
  
• Accessibility: Easy to inspect, repair, and modify.
  

Advantages of Air-Insulated Switchgear:

✅ Cost-Effective: Uses air as insulation, reducing manufacturing and maintenance costs.
✅ Simple Design: Easy to install and maintain without special tools or gas handling equipment.
✅ Environmentally Friendly: No greenhouse gases involved.
✅ High Reliability: Proven technology used globally for decades.
✅ Easier Customization: Ideal for modular setups and control panels.

Limitations of Air-Insulated Switchgear:

• Requires more physical space due to air gaps.
  
• Slightly higher maintenance due to dust and environmental factors.
  
• May not be ideal for humid or dusty industrial sites without additional sealing.
  

Best suited for:

• Commercial buildings
  
• Factories
  
• Utilities with available space
  
• LV switchgear systems needing flexibility and affordability
  

Gas-Insulated Switchgear (GIS) – Definition and Features

Gas-Insulated Switchgear, or GIS, uses SF₆ (sulfur hexafluoride) or other gas mixtures as the insulation medium. The gas prevents arcing and allows for compact, sealed designs.

In GIS, all live parts are enclosed within grounded, gas-tight metal housings. This makes it extremely safe and compact — ideal for modern high-density infrastructure.

Key Features of Gas-Insulated Switchgear:

• Insulating Medium: SF₆ gas or SF₆-free alternatives (e.g., fluoroketone-based mixtures).
  
• Voltage Range: From LV up to ultra-high-voltage applications (1 kV to 800 kV).
  
• Design: Fully enclosed and sealed, maintenance-free units.
  

Advantages of Gas-Insulated Switchgear:

✅ Compact Footprint: Occupies up to 80% less space than AIS.
✅ High Safety: Completely enclosed — minimal risk of electric shock or arc flash.
✅ Reliable in Harsh Environments: Unaffected by dust, humidity, or pollution.
✅ Low Maintenance: Sealed enclosure reduces inspection frequency.
✅ Long Service Life: Can operate 30+ years with minimal upkeep.

Limitations of Gas-Insulated Switchgear:

• Higher Initial Cost: Due to gas insulation and sealing technology.
  
• Environmental Concerns: SF₆ is a potent greenhouse gas if released.
  
• Special Handling: Requires trained personnel for gas monitoring and refilling.
  

Best suited for:

• Urban substations with space constraints
  
• Offshore platforms and tunnels
  
• Wind and solar energy systems
  
• Mission-critical facilities (data centers, hospitals)
  

Technical Comparison: AIS vs GIS

Parameter	Air-Insulated Switchgear (AIS)	Gas-Insulated Switchgear (GIS)
Insulating Medium	Air	SF₆ or eco-gas
Space Requirement	High	Low
Installation Cost	Lower	Higher
Maintenance	Periodic	Minimal
Environmental Impact	Eco-friendly	SF₆ can be harmful if leaked
Reliability in Harsh Environments	Moderate	Excellent
Operational Safety	Good	Superior
Lifespan	20–25 years	30+ years
Best For	Conventional installations	Space-limited or critical systems

When to Choose Air-Insulated Switchgear

Selecting Air-Insulated Switchgear makes sense when:

1. Space is not a constraint.
   
   • Example: A manufacturing unit or control room with ample floor area.
     
2. Budget sensitivity exists.
   
   • AIS offers an economical solution without compromising on safety.
     
3. Frequent maintenance is acceptable.
   
   • Panels are easily accessible for inspection or retrofitting.
     
4. Low environmental contamination.
   
   • Ideal for indoor installations in clean, dry conditions.
     

Real-world example:
A food processing plant using multiple motor control centers (MCCs) can efficiently deploy Low Voltage switchgear with air insulation for easy access and cost-effective scalability.

When to Choose Gas-Insulated Switchgear

Opt for Gas-Insulated Switchgear when:

1. Space is limited.
   
   • Ideal for metro stations, data centers, or underground substations.
     
2. High reliability is required.
   
   • GIS systems provide sealed safety and minimal downtime.
     
3. Environmental conditions are harsh.
   
   • Works well in dusty, humid, or salty air environments.
     
4. Safety is paramount.
   
   • Fully enclosed design reduces arc-flash risks and exposure.
     

Example:
A metro station substation where compactness and uninterrupted power are priorities benefits greatly from GIS technology.

Low Voltage Focus: AIS vs GIS in LV Switchgear

In the context of LV switchgear, both AIS and GIS technologies have evolved to offer remarkable protection and performance.

• LV Air-Insulated Switchgear dominates traditional setups such as distribution boards and control panels. It’s favored for modular expandability, ease of wiring, and cost-efficiency.
  
• LV Gas-Insulated Switchgear, though newer, is gaining traction in automation-intensive industries where compactness and reliability are essential.
  

Performance Comparison in LV Systems:

Feature	LV AIS	LV GIS
Panel Size	Larger	Compact
Maintenance Needs	Regular	Minimal
Safety Level	Standard	High
Installation Environment	Indoor, clean	Any environment
Lifecycle Cost	Low upfront	Low long-term

Environmental Considerations: Moving Toward SF₆-Free GIS

One growing concern around gas-insulated switchgear is its reliance on SF₆ gas, which has a global warming potential (GWP) nearly 23,500 times higher than CO₂.

However, manufacturers and suppliers like Balaji Switchgears Pvt. Ltd. are now promoting SF₆-free alternatives, such as vacuum-based or fluoroketone gas insulation systems, that maintain the same electrical performance with lower environmental impact.

These green switchgear options align with India’s sustainability goals and the global shift toward eco-friendly Low Voltage switchgear.

Installation and Maintenance Differences

Air-Insulated Switchgear:

• Requires regular visual inspection.
  
• Easy to replace or retrofit components.
  
• Suitable for facilities with in-house electrical staff.
  

Gas-Insulated Switchgear:

• Installation is quicker once pre-tested units arrive on-site.
  
• Gas pressure monitoring systems ensure long-term performance.
  
• Maintenance cycles can extend up to 10 years or more.
  

When working with a trusted supplier like Balaji Switchgears Pvt. Ltd., clients also benefit from post-installation technical support, ensuring compliance with IEC and IS standards.

Cost and ROI Perspective

While GIS carries a higher initial price tag, its longer lifespan, minimal maintenance, and smaller space requirement often justify the investment in high-value installations.

AIS, on the other hand, offers a lower entry cost and faster customization, making it ideal for cost-conscious industrial users.

ROI Tip:

When evaluating ROI, consider total lifecycle costs — including installation, space usage, maintenance, and downtime risk. Often, a compact GIS may offset its higher cost through operational savings over 15–20 years.

Balaji Switchgears: Helping You Choose the Right Switchgear

At Balaji Switchgears Pvt. Ltd., we understand that every project has unique technical and spatial requirements. That’s why we offer expert guidance and access to both air-insulated and gas-insulated switchgear solutions from globally trusted brands.

Our solutions combine:

• High safety standards (IEC/IS compliant)
  
• Custom-built LV switchgear assemblies
  
• Energy-efficient designs for long-term reliability
  

Whether you’re designing a high-rise building, industrial plant, or renewable energy facility, our experts help you determine the right switchgear for optimal safety, space utilization, and cost-efficiency.

Conclusion

Choosing between air-insulated switchgear and gas-insulated switchgear depends on your environment, budget, and performance goals.

• Go with AIS when you value simplicity, affordability, and easy maintenance.
  
• Choose GIS when compactness, reliability, and safety come first.
  

As the electrical landscape evolves, modern Low Voltage switchgear solutions from Balaji Switchgears Pvt. Ltd. ensure your system remains efficient, compliant, and future-ready — no matter which insulation technology you choose.