Air-Insulated vs Gas-Insulated Switchgear: Key Differences for Medium Voltage Systems
A2Z Energy explains the key differences between air-insulated and gas-insulated switchgear for medium voltage power distribution projects.
Medium voltage switchgear is one of the most important components of electrical distribution systems. It helps protect, control and distribute electrical power safely in industrial facilities, substations, infrastructure projects, commercial buildings and energy networks.
Two commonly used technologies in medium voltage applications are air-insulated switchgear (AIS) and gas-insulated switchgear (GIS). Both solutions are used for similar power distribution purposes, but they differ in terms of insulation method, footprint, maintenance requirements, environmental resistance and investment cost.
At A2Z Energy, we support our partners with project-based medium voltage switchgear solutions through reliable sourcing, technical coordination and Türkiye-based manufacturing partners.
What Is Air-Insulated Switchgear?
Air-insulated switchgear, also known as AIS, uses air as the main insulation medium between live parts and grounded sections. It is one of the most widely used switchgear technologies in medium voltage distribution systems.
AIS solutions are generally preferred because of their simple structure, easy accessibility, cost efficiency and proven operational performance. They can be used in many standard medium voltage applications where installation space is available and regular maintenance access is possible.
Air-insulated switchgear may include circuit breakers, load break switches, disconnectors, earthing switches, busbars, current transformers, voltage transformers, protection relays and control equipment.
Advantages of Air-Insulated Switchgear
Air-insulated switchgear offers several advantages for project-based power distribution applications.
Cost Efficiency
AIS is generally more economical compared to gas-insulated alternatives. This makes it a practical solution for projects where budget control is important.
Easy Maintenance Access
Since the equipment structure is more accessible, inspection, maintenance and component replacement can be carried out more easily.
Proven Technology
AIS has been used for many years in medium voltage systems and is considered a reliable solution for many industrial and infrastructure projects.
Flexible Application
It can be used in transformer substations, distribution centers, industrial facilities, renewable energy plants and commercial projects.
Limitations of Air-Insulated Switchgear
Although AIS is reliable and widely used, it may not be the best choice for every project.
The main limitation is space requirement. Since air is used as the insulation medium, larger clearance distances are required between live parts. This usually means AIS needs more installation space compared to gas-insulated switchgear.
AIS may also be more affected by environmental conditions such as humidity, dust, pollution and temperature changes. For this reason, site conditions should be evaluated carefully before selecting the switchgear type.
What Is Gas-Insulated Switchgear?
Gas-insulated switchgear, also known as GIS, uses gas insulation inside a sealed structure. In many modern designs, the switching and insulation sections are placed inside compact and sealed compartments.
GIS is especially preferred when space is limited, environmental conditions are challenging or higher operational reliability is required. Its compact structure allows more equipment to be installed in a smaller area compared to traditional air-insulated systems.
Depending on the product design, GIS solutions may use different gas insulation technologies. Some modern systems are designed with SF6-free dry air technology, which helps reduce environmental impact.
Advantages of Gas-Insulated Switchgear
Gas-insulated switchgear provides strong advantages in projects where compact design, reliability and reduced maintenance are important.
Compact Design
GIS requires less installation space than AIS. This makes it suitable for urban substations, compact transformer stations, industrial plants and projects with limited available area.
Higher Environmental Protection
Because the main switching parts are placed inside sealed compartments, GIS is less affected by dust, humidity, pollution and external environmental conditions.
Lower Maintenance Requirement
Sealed gas-insulated systems generally require less routine maintenance compared to traditional open-access switchgear designs.
High Reliability
The compact and protected design helps reduce the risk of external contamination and supports stable long-term operation.
Limitations of Gas-Insulated Switchgear
The main limitation of GIS is the higher initial investment cost. Due to its compact design, sealed structure and advanced insulation technology, GIS is generally more expensive than AIS at the purchasing stage.
Maintenance and service operations may also require more specialized technical knowledge. For this reason, after-sales support, spare parts availability and technical documentation should be evaluated before selecting a GIS solution.
AIS vs GIS Comparison Table
| Feature | Air-Insulated Switchgear — AIS | Gas-Insulated Switchgear — GIS |
|---|---|---|
| Insulation medium | Air | Gas insulation inside sealed sections |
| Space requirement | Requires more installation space | More compact design |
| Initial cost | Generally more economical | Generally higher investment cost |
| Maintenance access | Easier access to components | Requires more specialized service approach |
| Environmental resistance | More affected by dust, humidity and pollution | Better protected against environmental effects |
| Application area | Standard MV distribution projects | Space-limited and demanding projects |
| Flexibility | Easy expansion and modification | More compact but less flexible for field changes |
| Reliability | Proven and reliable technology | High reliability under suitable design conditions |
| Best use case | Cost-effective and accessible MV systems | Compact, protected and high-reliability systems |
Which One Should Be Selected?
There is no single correct answer for every project. The right choice between AIS and GIS depends on the technical and commercial requirements of the project.
Before selecting the switchgear type, the following criteria should be evaluated:
Available installation space
Project budget
Rated voltage and current
Short-circuit level
Internal arc requirement
Environmental conditions
Maintenance strategy
Service continuity expectations
Indoor or outdoor installation conditions
Future expansion requirements
Applicable standards
Delivery and after-sales support
If the project has enough space and requires a cost-effective, easy-to-maintain solution, AIS may be a suitable choice.
If the project has limited space, harsh environmental conditions or higher reliability expectations, GIS may provide a stronger technical solution.
Application Areas
Air-insulated and gas-insulated switchgear can be used in many medium voltage power distribution projects.
Common application areas include:
Industrial facilities
Transformer substations
Compact substations
Energy distribution networks
Renewable energy plants
Commercial buildings
Infrastructure projects
Hospitals and public facilities
Data centers
Transportation and railway projects
Mining and heavy industry facilities
Urban power distribution systems
The final selection should always be made according to the project’s technical requirements and operating conditions.
A2Z Energy Approach
A2Z Energy supports international partners with project-based medium voltage switchgear and electrical infrastructure solutions from Türkiye.
Our role is to help customers evaluate their project requirements and coordinate suitable AIS or GIS solutions through reliable manufacturing partners. We focus on technical suitability, clear communication, quality-focused sourcing and long-term cooperation.
Whether the project requires air-insulated switchgear, gas-insulated switchgear, compact substations, transformer kiosks or other medium voltage equipment, A2Z Energy aims to provide dependable support for international energy projects.
Conclusion
Air-insulated and gas-insulated switchgear are both important technologies in medium voltage power distribution.
AIS is generally preferred for cost-effective, accessible and proven medium voltage applications. GIS is preferred when compact design, environmental protection and lower maintenance requirements are more important.
Choosing the right switchgear technology requires a project-based technical evaluation. With reliable sourcing capability and Türkiye-based manufacturing partners, A2Z Energy supports contractors, distributors, industrial companies and project developers with suitable medium voltage switchgear solutions.