
Understanding High Voltage Switchgear: Types, and Applications
Understanding High Voltage Switchgear: Types, and Applications https://www.theelectricalguy.in/wp-content/uploads/2025/01/Blog-post-thumbnails-1024x576.jpg 1024 576 Gaurav Joshi Gaurav Joshi https://secure.gravatar.com/avatar/87a2d2e0182faacb2e003da0504ad293?s=96&d=mm&r=gIn the complex world of electrical systems, high voltage switchgear plays a crucial role in managing and protecting circuits operating at higher voltage levels. Let’s dive into the essentials of high voltage switchgear, its applications, and the technologies shaping modern power systems.
What Is High Voltage Switchgear?
High voltage or HV switchgear is equipment designed to control, protect, and isolate electrical circuits operating at voltages above 52 kV. It ensures the safe and efficient operation of electrical grids, preventing equipment damage and safeguarding personnel during maintenance or fault conditions.
Note – International Electrotechnical Commission (IEC) defines 52kV & above (upto 800kV) as high & extra high voltage.
Key Locations for High Voltage Switchgear in Power Systems

In a typical power system, you will find high voltage switchgear at:
- Primary Transmission: Power generated at 11 kV in generating stations is stepped up to higher voltages for transmission over long distances. High voltage switchgear is essential at this stage to manage and protect the system.
- Secondary Transmission: As power is transmitted to various load centers, voltages are stepped down for distribution. High voltage switchgear continues to play a vital role in ensuring smooth operations and system protection.
Voltage Ratings for High Voltage or HV Switchgear
In India and other countries following International Electrotechnical Commission (IEC) standards, common high voltage ratings include:
- 72.5 kV
- 145 kV
- 245 kV
- 420 kV
- 800 kV
These rated voltages are indicative of the robust designs required to handle such high energy levels. Different countries may have different voltage ratings based on the history and type of standard they follow.
Types of High Voltage Switchgear
High voltage switchgear is broadly classified into three main types:
1. Air Insulated Switchgear (AIS)

This technology uses air as the insulating medium between phases. Here lets clarify two concepts –
- Insulation within the phase – this is the insulation provided within the phase. It can be SF6 or vacuum.
- Insulation between the phase – this is the insulation provided between the two phases. Here it is provided by Air and hence the hame of the technology is Air Insulated Switchgear or AIS.

- Insulation: Inside circuit breakers, SF6 gas or vacuum typically provides insulation within a phase, while air is used between phases.
- Applications: Due to its outdoor installation requirements and large spatial footprint, AIS is commonly found in 70-72% of global substations*.
- Voltage Range: Available from 72.5 kV to 800 kV.
- Limitations: Requires higher space to maintain dielectric strength and demands frequent maintenance.
2. Gas Insulated Switchgear (GIS)

Here, an insulating gas, usually SF6, replaces air for insulation between phases.
- Compact Design: GIS systems are highly compact, making them ideal for areas with space constraints or high land costs, such as urban substations.
- Factory-Assembled: All components—circuit breakers, transformers, and disconnectors—are integrated within a metal enclosure.
- Indoor Installation: GIS is often installed indoors due to its compact design and environmental protection requirements.
Here is our basic guide on Gas Insulated Switchgear.
3. Mixed Technology or Hybrid Switchgear

This combines elements of both AIS and GIS technologies.
- Space Efficiency: Offers a compromise between the large space requirements of AIS and the high costs of GIS.
- Selective Use: Hybrid systems are suitable when budget constraints preclude full GIS solutions but land availability is limited.
- Applications: Less common than AIS and GIS.
Emerging Trends in High Voltage Switchgear
The insulation technology landscape is evolving. Previously dominant technologies like air blast and oil circuit breakers have largely been replaced by SF6 gas systems. However, environmentally friendly alternatives are emerging as industries move away from SF6 due to environmental concerns.

Conclusion
High voltage switchgear is integral to the reliability and safety of modern power systems. Understanding the types and applications of switchgear helps in making informed decisions for system design and maintenance. As technology advances, the industry continues to innovate with solutions that balance performance, environmental responsibility, and cost-effectiveness.
Stay tuned for more insights as we explore medium voltage switchgear and its role in power distribution in upcoming discussions!
FAQs
High voltage switchgear typically operates at voltages above 52 kV, with standard ratings ranging from 72.5 kV to 800 kV in systems following IEC standards.
High voltage switchgear is used in primary and secondary transmission systems to control, protect, and isolate electrical circuits in power distribution networks.
There are three main types:
Air-Insulated Switchgear (AIS): Uses air as an insulating medium.
Gas-Insulated Switchgear (GIS): Uses gas, typically SF6, for insulation.
Hybrid or Mixed Technology Switchgear: Combines features of AIS and GIS.
Switchgear and other high-voltage equipment where the insulation to earth and between phase conductors is mainly provided by air at atmospheric pressure.
Metal-enclosed switchgear and other high-voltage equipment where the insulation is obtained, at least partly, by an insulating gas other than air at atmospheric pressure. The gas is usually SF6.
Mixed technology switchgear combines AIS and GIS components, balancing space efficiency and cost. It is used in scenarios where land is constrained but GIS costs are prohibitive.
GIS is preferred where space is limited or where land costs are high because it offers a compact design with better dielectric properties, despite being more expensive upfront.

Watch the video on High voltage switchgear –
References –
*CIGRE Report presented in CIGRE Green book of Substation
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Gaurav Joshi
Gaurav, also known as TheElectricalGuy, is an accomplished electrical engineer with over 8 years of experience in the high and medium voltage switchgear industry. In addition to his professional endeavors, Gaurav has made significant contributions to the global electrical engineering community through his highly successful YouTube Channel. With over 195K subscribers and a prestigious silver play button from YouTube, he has become a trusted resource for electrical engineers worldwide. Gaurav's dedication to sharing knowledge extends to the creation of comprehensive courses, which have already attracted over 3000 students eager to enhance their skills in the field.
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