What is a medium voltage switchgear and what is it used for?

The medium voltage switchgear is one of the most recognizable elements of the electrical grid, and its role is crucial for the proper operation of the grid

Observing the electrical grid is similar to to look at a vast and complex spider web—endless lines that intertwine and form nodes through which electrical energy flows to meet our needs as consumers. These nodes contain numerous technological elements, which are part of the so-called electrical equipment, and are located at various points. Each has a different function, but all share a common goal: ensuring that energy reaches the final consumption points continuously, efficiently, and safely. While we have already detailed the main components of this electrical equipment and their global functions, today we will be focusing on one of the most relevant and well-known systems: the medium voltage switchgear, also known as distribution switchgear.

These technological marvels—resulting from decades of development and engineering applied to the electrical energy field—are key players in ensuring that the electrical grid is managed effectively. They help prevent the potential collapse of the rest of the electrical equipment in case of a voltage, current, and/or frequency issue, which would impact final consumers and must be avoided at all costs. Switchgear receives electricity and distributes it to the transformer, allowing it to adjust the incoming voltage. In simpler terms, it acts like a giant switch at the scale of electrical voltages.

Furthermore, the switchgear goes beyond this role, protecting the transformer and the rest of the elements in the distribution chain, such as the low-voltage switchboard, from possible grid disturbances. In other words, switchgear functions like large protective fuses that prevent damage to the other components in situations of voltage fluctuation.

Wherever a final user needs electricity, medium voltage switchgear is present. They are used to distribute electrical energy from high-voltage transmission lines to final consumers, specifically for industrial applications like factories, mining operations, or connecting renewable energy sources such as solar, hydroelectric, or wind power to the grid. Hence, these elements are vital to the operation of the electrical grid in particular and our society in general.

What technology do these distribution switchgears use?

To perform all these functions, switchgear operates under significant electrical voltage. Electricity flows through them—either at high or medium voltage—requiring a stable, safe, and reliable technological solution that meets the technical requirements of each installation. This is no easy task from a design and manufacturing standpoint. Electricity enters through the electrical grid and must be conducted to other components or interrupted as needed.

The most advanced medium voltage distribution switchgear uses a technology known as GIS (Gas Insulated Switchgear). This solution uses gases of different kinds as insulators to create a sealed barrier inside the metal enclosure where the dynamic elements of the switchgear interact, allowing for safe and efficient operation. Among these gases, SF6 (sulfur hexafluoride) stands out, having been the dominant insulator in the industry for decades, along with new and innovative solutions based on industrial natural air, like those implemented by Ormazabal in their cgm.zero24 and sbp.zero24 solutions. This technology is the result of over 10 years of continuous research and represents an evolutionary step in sustainable technology.

Types of medium voltage switchgear

As mentioned earlier, switchgear can operate in different configurations depending on the overall electrical installation needs. One of the major advancements in switchgear technology is the ability to interconnect multiple units, commonly referred to in the electrical industry as “switchgear linking.” This development allows for various configurations of switchgear, each with its specific function, to work together in a unified system. The circuit passes through several units, each serving a unique purpose, to create a complete solution.

Types of switchgear by function

Among the different types of switchgear, the following are the most common:

• Incoming/Outgoing Switchgear: Connects and disconnects electrical installations that enter or exit the switchgear system.
• Busbar Switchgear: Used as mechanical protection for conductors connected to busbars, typically found in installations that do not require electrical protection.
• Fuse protection Switchgear: Offers protection based on fuses to medium-voltage transformers.
• Circuit Breaker Switchgear: Provides transformer protection with the ability to operate and restore the circuit much faster than traditional protection switchgear.

Types of switchgear by distribution phases

To understand the different types of medium voltage switchgear, it’s essential to recognize their functions in the distribution system. Depending on the power requirements of the installation or node, switchgear is classified into two categories: primary distribution and secondary distribution.

• Primary Distribution Grid: This is the phase of the electrical distribution system where electricity reaches substations to be transformed and distributed at medium voltage to the next stage of the grid or directly to electro-intensive consumers, such as industrial operations.
  • Primary Distribution Switchgear: Located further from consumption points, primarily in electrical substations, they act as large switches to protect the rest of the installations. These can also be found in high-demand industrial consumers or power generation sources like renewable energy substations.

• Secondary distribution grid: This phase adapts voltage levels to safely and efficiently approach consumption points, such as homes, offices, and hospitals. It relies on medium voltage substations to step down the voltage for low-voltage use by the final user.
  • Secondary distribution switchgear: Found near consumption centers, these switchgear units are vital for transforming voltage from medium to low. They are typically located in substations or near the final consumer, alongside other critical medium voltage equipment. Their role in protecting and interrupting the grid ensures the supply to consumers and protects the grid against possible disturbances.

Key components of a distribution switchgear

Although switchgear is a key element of electrical equipment, it consists of several internal components. Let’s explore the main ones:

• Metal enclosure: The structure housing the internal elements, serving as a sealed compartment for the flow of electricity. It is divided into different sections based on the type of switchgear.
• Internal wiring: The set of cables that conducts electricity and connects the internal components.
• Insulators: Epoxy elements like bushings or connectors that act as insulators between different sealed parts, ensuring safe operation.
• Circuit breakers: Devices that interrupt the flow of current in a circuit, designed to protect equipment from overcurrent or short circuits.
• Disconnectors: Used to isolate parts of the electrical system for maintenance or repair, often in conjunction with circuit breakers.
• Fuses: Protect equipment by interrupting the flow of current when it exceeds a certain level (short circuit current).
• Relays: Act as controllers to trigger protective measures when faults are detected, ensuring the safety and operation of the switchgear. Relays, along with remote devices, transmit real-time data and can receive control orders from control centers.
• External controls: Mechanical or digital devices that operate the internal functionalities of the switchgear, from digital displays to manual keys or lever operations for opening or closing circuits.

Ormazabal: experts in electrical solutions for the grid

At Ormazabal, we are dedicated to transforming the electrical grid into an infrastructure of the future: more reliable, resilient, and sustainable. With over 55 years of experience designing and manufacturing electrical solutions, we focus on digitalizing the grid to integrate more renewable energy, enable sustainable mobility, and ensure power supply to buildings and infrastructure with critical energy needs.

As part of our Route to Zero, we have launched our innovative fluorinated gas-free product lines, using industrial natural air insulation for public distribution up to 24 kV: cgm.zero24 and sbp.zero24. These solutions offer the most complete alternative to SF6 insulation on the market, ensuring zero changes, zero uncertainties, and a more sustainable electrical grid.

Want to know more? Contact us: