Metal Clad vs Gas Insulated Switchgear (GIS): Which One is Right for Your Substation? - Zhejiang Beiye Electric Co.,Ltd ...

Metal Clad vs Gas Insulated Switchgear (GIS): Which One is Right for Your Substation?

Sep 22, 2025

Choosing the right high voltage switchgear for a substation is a critical decision that impacts safety, reliability, and cost. When faced with the choice between Metal Clad Switchgear and Gas Insulated Switchgear (GIS), it’s essential to understand their core differences to make an informed decision for your specific project. This guide breaks down everything you need to know.

What is Metal Clad Switchgear?

Metal Clad Switchgear is a type of electrical switchgear where all components—like the circuit breaker, busbars, and instrument transformers—are enclosed in separate grounded metal compartments. This design ensures that each section is isolated, preventing a fault in one area from spreading to another. The use of air as the primary insulation medium makes it a robust and well-understood technology, often used in medium voltage applications in a wide variety of industrial and commercial settings.

KYN28-12 Metal-clad Removable AC Metal-enclosed Switchgear

What is Gas Insulated Switchgear (GIS)?

Gas Insulated Switchgear (GIS), on the other hand, uses an insulating gas, typically sulfur hexafluoride (SF6), to insulate the live parts. All components are contained within sealed, gas-filled metal enclosures. This technology is known for its compact design and high reliability, as the gas provides excellent insulation and arc-quenching capabilities. GIS is widely used in high voltage and extra-high voltage applications, especially where space is a major constraint.

SH-SRM-12 Series SF6 Gas Insulated Switchgear

Metal Clad vs GIS: 6 Key Differences

When comparing Metal Clad vs GIS, these six factors are the most important to consider.

1. Size & Space Requirements

This is arguably the most significant difference. GIS is incredibly compact, often requiring as little as 10% of the space of a comparable Metal Clad Switchgear installation. This makes GIS the preferred choice for urban substations, large industrial plants, and other locations where real estate is at a premium. Metal Clad Switchgear is much larger and requires significant space for installation, operation, and maintenance.

2. Maintenance & Inspection

Metal Clad Switchgear is designed for easy access. Components are in separate compartments, allowing for routine inspections and maintenance without de-energizing the entire system. While this makes maintenance more straightforward, it also exposes the components to environmental factors like dust and moisture. GIS, with its sealed enclosure, requires significantly less maintenance. The components are protected from the environment, leading to a “fit-and-forget” mentality for many operators. However, when maintenance or repair is needed, it is more complex and requires specialized skills.

3. Installation Complexity

Installing Metal Clad Switchgear is generally less complex. The units are typically assembled at the factory and then transported to the site for installation. The installation process is well-established and relatively quick. GIS installation is more complex and time-consuming. Because of the sealed, gas-filled nature, installation requires specialized technicians to assemble the modules and ensure a perfect gas seal to prevent leaks.

4. Cost Considerations

The upfront cost of GIS is typically higher than that of Metal Clad Switchgear. This is due to the advanced materials, manufacturing processes, and specialized components. However, when you factor in the long-term total cost of ownership, the comparison can change. The lower maintenance requirements and smaller space footprint of GIS can lead to significant savings over the lifetime of the substation, potentially offsetting the higher initial investment.

5. Safety & Reliability

Both technologies offer high levels of safety and reliability, but in different ways. The compartmentalized design of Metal Clad Switchgear enhances safety by isolating faults and protecting personnel. The use of air insulation is also non-toxic and non-flammable. GIS provides superior safety due to its fully enclosed, gas-insulated design. There are no exposed live parts, and the SF6 gas is an excellent insulator and arc-quenching medium, which minimizes the risk of explosions and fires.

6. Applications & Suitability

Metal Clad Switchgear is a versatile and reliable solution for a wide range of applications, including industrial plants, commercial buildings, hospitals, and utilities. It is a workhorse in medium voltage systems (up to 38kV). GIS is the ideal solution for high voltage applications (above 72.5kV) and is perfectly suited for substations in densely populated areas, offshore platforms, wind farms, and other sites where space is severely restricted.

How to Choose the Right Switchgear

The choice between Metal Clad vs GIS comes down to balancing your project’s unique needs.

  • For limited-space installations and high voltage applications: GIS is the clear winner. The compact design and excellent performance at high voltages make it the most suitable and efficient choice.
  • For medium voltage projects with ample space: Metal Clad Switchgear is often the more cost-effective and practical solution. Its ease of maintenance and straightforward installation can save you time and money.

Consider your budget, available space, required voltage level, and long-term maintenance strategy to make the best decision for your substation.

FAQs

What are the advantages of metal-clad switchgear?

Metal Clad Switchgear is known for its ease of maintenance, robust design, lower initial cost, and clear separation of components, which enhances safety.

What is the difference between metal-clad and metal-enclosed switchgear?

Metal-clad switchgear has all its major components (like the circuit breaker, busbars, and instrument transformers) in separate, grounded metal compartments. Metal-enclosed switchgear, on the other hand, houses all or some of the components in a single common metal enclosure without the internal barriers. Metal-clad switchgear is a specific, more robust type of metal-enclosed switchgear.

Which is better for limited-space installations: Metal Clad or GIS?

GIS is significantly better for limited-space installations due to its compact design, which can be up to 90% smaller than an equivalent Metal Clad Switchgear unit.

Can Metal Clad switchgear handle high voltage applications as well as GIS?

No, Metal Clad Switchgear is typically used for medium voltage applications (up to 38kV). GIS is specifically designed for high voltage and extra-high voltage applications (above 72.5kV), where its superior insulation capabilities are essential.

What are the typical applications of Metal Clad and GIS switchgear?

Metal Clad Switchgear is used in industrial facilities, commercial buildings, power generation plants, and utility substations. GIS is commonly found in urban substations, wind and solar farms, offshore platforms, and applications requiring a compact and reliable solution for very high voltages.

Conclusion

Both Metal Clad Switchgear and Gas Insulated Switchgear (GIS) are powerful technologies, each with distinct advantages. Your final decision should be guided by your project’s specific needs, including space constraints, voltage level, and budget. At BYYOU, we specialize in providing high-quality switchgear solutions tailored to your unique requirements. Contact us today to learn more about how our expertise can benefit your substation project.

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