What is an operation and switching substation and how does it work?

A key component of the medium voltage grid, the operation and switching substation is an integral part of our daily lives

By closely examining the functioning of the electrical grid, we can understand how its various elements interact and comprehend the operation of this vast network that transports and distributes energy from generation to consumption. Today, we will focus on a specific part of the grid: we will delve into the distribution grid in general—which efficiently and safely distributes electricity to consumption points after it has been transformed to the necessary values for use—and into the operation and switching substation in particular. Will you join us on this journey through the grid?

As you may know, electrical energy is generated through different sources (renewable, non-renewable, etc.) that, depending on their type, may be far from consumption centers (homes, offices, hospitals, factories, electric vehicle charging stations, etc.) or not. When this energy is generated far from the consumer, it must be transformed, transported, and distributed through the grid to be usable. This is why, if you look around, you will see various recognizable elements such as high voltage cables, substations, transformers, or, relevant to this discussion, operation and switching substations. Since we have discussed the other elements on previous occasions, today we will try to explain the last of these components of electrical equipment.

We can define an operation and switching substation as an electromechanical element that is part of the distribution grid. Its core is a set of medium voltage switchgears, and its main purpose is to connect, but above all, protect the public distribution grid, as well as manage the derivation—private installation—without harming the rest. Its main purpose is to connect the public distribution grid with a third-party installation. This is achieved by switching and opening the electrical current through the switchgear, which act as large switches and fuses for the connected installation, protecting it from any type of alteration it might suffer. For example, one of these units would close the electrical connection to a residential building, ensuring that none of the appliances or community services (boiler, elevator, heat pump, etc.) are affected in case a storm causes an overvoltage in the grid. You probably now understand the importance of these elements.

Where can we find these substations?

Operation and switching substations are located in easily accessible places to ensure maintenance by specialized personnel, both in enclosed and open areas, always protected from unauthorized access. These elements can be observed in most public services or key infrastructures such as airports, hospitals, or the commercial and industrial sectors.

Typically, we find them in:

• Public distribution grids
• Electrical substation control centers
• End users of electrical energy
• Renewable generation

Types of operation and switching substations

We can identify these substations by their enclosures, which, depending on the country, type of installation, or technical needs, can be metallic or concrete. They come in various sizes and configurations to meet the requirements of each project, always prioritizing their integration into the environment, reducing visual, environmental, and acoustic impact, and ensuring insulation from harsh environmental conditions for a long service life.

What are their main functions?

Among the various functions of an operation and switching substation, some are fundamental for enhancing the digitalization and automation of the electrical grid:

• Switching and connection of electrical energy according to grid situation and demand
• Protection of electrical consumption elements connected to the grid
• Measurement and evaluation of real-time metrics: intensity, voltage, power, switchgear states, etc.
  • Generation of periodic reports
• Detection of possible alterations or faults
  • Sending alerts
• Digitized remote control
  • Handling situations without physical presence
• Automation of operations
  • Prediction of scenarios

What elements make up an operation and switching substation?

• Prefabricated concrete or metallic enclosures: Key to maintaining optimal conditions for environmental protection and operational safety, the enclosures serve as containers for the operational elements. Although they may seem simple, their compact and modular design allows for a wide variety of configurations according to project needs.

• Medium voltage distribution switchgears: The switchgear, which represents the complexity and technological development of the substation, is used for different functions depending on its type, but essentially acts as a large switch that cuts or lets electrical energy flow. The technological development achieved allows for safe operation of the grid at medium voltage values, even under adverse conditions. They are typically interconnected, forming different configurations that adapt to the consumer’s needs.
• Protection, control, and automation units: These elements are among the main innovations in the medium voltage grid in recent years. Their functions, which include remote control of medium voltage switchgears, report generation, diagnostics, and automation, have enabled the grid to become smarter, making these units a key ally in grid modernization.
• Low voltage switchgears (optional): Responsible for dividing the current to be safely transported directly to consumption points, the LV switchgear distributes and protects the energy for our homes.
• Supply cables (external to the installation): These are the main arteries for transporting electrical energy within the secondary distribution grid. Although they may appear to be simple cables, they are designed to handle significant electrical currents, minimizing losses and prioritizing safety. They are also protected by overload and short-circuit protection devices and connected to measurement and monitoring devices for proper management and tracking of the grid.

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