Medium Voltage Switchgear: Air-Insulated Vs Gas-Insulated – How To Choose?

Medium Voltage Switchgear: Air-Insulated vs Gas-Insulated – How to Choose?

Introduction

At the same voltage level, why are some switchgear cabinets large and inexpensive, while others are small and costly?

The answer often comes down to the insulation method.

Medium voltage switchgear is mainly divided into two types by insulation medium: air-insulated (AIS) and gas-insulated (GIS/C-GIS) . Each has its advantages and trade-offs. The right choice depends on your project environment, available space, and budget.

This article compares the two from four angles — size, environmental adaptability, maintenance, and cost — to help you decide.

1️⃣ Air-Insulated Switchgear (AIS): Traditional, Mature, Economical

Air insulation is the most traditional switchgear solution. The high-voltage live parts inside — busbars, circuit breakers, disconnectors, contacts — are all exposed to air, relying on air‘s insulating properties for safety.

Key features:

• Insulation medium: air

• Construction: exposed components, larger cabinet size

• Mature technology, widely used

• Requires more space in the electrical room

Advantages:

• Low cost, good value for money

• Mature technology, reliable

• Simple maintenance, easily available spare parts

Disadvantages:

• Large size, takes up more space

• Sensitive to installation environment (dust, moisture, salt spray)

• Requires regular cleaning of insulation components to prevent flashover

2️⃣ Gas-Insulated Switchgear (C-GIS): Compact, Sealed, Maintenance-Free

Gas-insulated switchgear seals all high-voltage components — circuit breakers, busbars, disconnectors, instrument transformers — inside a stainless steel tank filled with SF6 or another insulating gas.

Key features:

• Insulation medium: SF6 or other insulating gas

• Construction: fully sealed, compact cabinet

• Unaffected by external environment

Advantages:

• Very compact — for the same voltage level, footprint is only 1/3 to 1/5 of air-insulated switchgear

• Fully sealed — unaffected by dust, moisture, or salt spray

• Maintenance-free or very low maintenance

• High reliability

Disadvantages:

• High cost (initial investment 30–50% higher than air-insulated)

• SF6 is a greenhouse gas — subject to strict environmental regulations

• If the gas tank leaks, specialized equipment is required to refill

3️⃣ Comparison Table

4️⃣ When to Choose Air-Insulated?

Best for air-insulated:

• Indoor electrical rooms, clean and dry environment

• Limited budget, seeking good value

• Sufficient space, not concerned about cabinet size

• Have maintenance capability for regular cleaning

Typical applications:

• General factory electrical rooms

• Commercial building distribution rooms

• Residential community substations

• Small to medium substations

In short: Clean environment, tight budget, maintenance capability available — choose air-insulated.

5️⃣ When to Choose Gas-Insulated?

Best for gas-insulated:

• Harsh environments (heavy dust, moisture, salt spray, corrosive gases)

• Extremely limited space (urban substations, underground distribution rooms)

• Very high reliability requirements, minimal maintenance desired

• Sufficient budget

Typical applications:

• Coastal substations

• Underground distribution rooms

• Mines and chemical plants

• Compact urban substations

In short: Harsh environment, limited space, difficult maintenance — choose gas-insulated.

6️⃣ Quick Selection Table

Conclusion

Neither air-insulated nor gas-insulated is absolutely better — it‘s about what fits your project.

• Air-insulated (AIS): Traditional, economical, mature — suitable for clean indoor projects with limited budgets

• Gas-insulated (C-GIS): Compact, sealed, maintenance-free — suitable for harsh environments and space-constrained projects

Consider these factors when choosing: installation environment, space availability, budget, and maintenance capability.

We supply both types. If you are unsure which one fits your project, send us your project details and we will recommend the right solution.

Contact us:
Web: https://yqsxdl.en.made-in-china.com/
WhatsApp: +195 1818 9858
Mail: lunahe927@gmail.com