Medium Voltage Substations.

Grupo Edmar
Oct 6
5 min read

October 6, 2025 - Medium Voltage Substations

Medium Voltage Substations.

Have you ever wondered how electricity travels from the generating plant to your factory, hospital, or even your office building? There's a crucial point along the way, a true control center that ensures the power arrives safely and efficiently: the Medium Voltage (MV) Substation .

They're not as well-known as the large high-voltage towers, but they are, without a doubt, the heart of the distribution grid. Let's reveal exactly what they are and why they're so vital to the functioning of our modern lives.

What is a medium voltage substation?

Simply put, an MV substation is a facility designed to modify the parameters of electrical energy , primarily the voltage level. Think of it as an electrical "customs office." Electricity arrives at a very high voltage (ideal for traveling long distances with fewer losses), and the substation reduces it to a medium voltage level (generally between 1 kV and 35 kV, although the most common voltages are 13.2 kV, 23 kV, and 34.5 kV), which is the ideal voltage for distribution in local areas and to large consumers.

Their purpose goes beyond mere transformation; they are also responsible for protecting the grid from faults (such as short circuits), monitoring it to ensure the quality of supply, and ensuring a continuous and safe flow. Essentially, they are the point where energy traveling along major electrical highways is diverted and prepared to enter the "streets" of the city or industrial zone.

The Strategic Importance of the Electric Grid.

Medium voltage is the essential "bridge" between the transportation of large amounts of energy ( high voltage ) and final consumption ( low voltage ). Without these substations, it would be impossible to distribute energy to large consumers viably. Attempting to use high voltage directly would be inefficient and very dangerous.

Who needs a Medium Voltage Substation?

Large Industries and Factories: To power heavy machinery that requires a lot of power (typically more than 100 kW of installed load). This is where the efficiency of a good transformer makes a difference in operating costs.
Shopping Centers and Corporate Buildings: Where the installed load exceeds the Low Voltage limits. Think of air conditioning, elevators, and all lighting.
Hospitals and Airports: Due to their high demand and the critical need for a stable supply, redundancy and protection systems are crucial here.
Large Urban Developments and Distribution Zones: To bring power to the smaller transformation centers that supply the neighborhoods. This is the first point of massive disconnection from the local grid.

Types of Medium Voltage Substations.

Not all are the same. They can be classified in several ways, but one of the most common is based on their primary function and design:

Step-Down Transformer Substations: These are the most common. Their primary function is to reduce the transmission line voltage (high or medium-high voltage) to the MV levels used for distribution. These are the ones found supplying large industrial complexes. A practical example: receiving 115 kV and reducing it to 23 kV.
Switching Substations: Their function is not to change voltage, but rather to connect and disconnect different circuits or lines. They act as nodes to reconfigure the grid in the event of a fault or for maintenance. They are vital for isolating sections without interrupting service to an entire region.
Step-up substations: These are located near generating plants (wind, solar, etc.). Their function is to increase the generated voltage (which is usually low or medium-low) to high voltage levels so that it can be transported over long distances with reduced losses.
Classification by Design: They are also classified according to their installation: Outdoor (outdoors, very common for high powers), Armored or Compact (where the equipment is encapsulated, ideal for urban or indoor areas, and where the distribution cells enter).

Key Components: The essential machinery.

A medium-voltage substation is a complex set of equipment that works in perfect synchronization. Here are the details of the "main equipment" for any installation:

Power Transformer: This is the central component and performs the magical voltage conversion. To ensure maximum efficiency and durability in your project, it's essential to choose a transformer from a trusted manufacturer like Grupo Edmar , as they are the heart of the operation.
Switchgear: Devices that allow a circuit or piece of equipment (such as a transformer) to be physically isolated for de-energized maintenance. Their operation is mechanical and is extremely important for personnel safety.
Power Circuit Breakers: These are used to interrupt the current in a circuit (with or without load) under normal conditions or, critically, during a fault (short circuit). They are responsible for the dynamic protection of the substation.
Lightning arresters: These are the substation's protective devices. They divert transient overvoltages (such as those caused by lightning or sudden surges in the grid) to ground, protecting vital and expensive equipment like the transformer.
Instrument Transformers (PTs and CTs): These are small but crucial pieces of equipment. They reduce high voltage and current values to safe levels so they can be measured and interpreted by protection relays and meters.

Substations and Cells: What's the Difference?

It's easy to confuse the terms, but we'll explain it simply:

The MV Substation is the general concept, the complete installation that contains all the equipment (transformer, lightning rod, protection and switching elements, etc.).
Electrical Distribution Panels are a modern and compact way to organize and protect control and switching elements (switches, disconnectors, fuses) in the medium-voltage sector. Instead of having separate equipment outdoors, they are housed within robust metal enclosures (often filled with insulating gases such as SF6 or solid insulation), which increases safety, minimizes the risk of arc flash, and significantly reduces the required space.
In many industrial installations or buildings, the substation consists of a transformer and a switchgear bank.

Security and Reliability.

MV is powerful and therefore dangerous if not handled properly. Therefore, the design and maintenance of an electrical substation are top priorities. The ultimate goal is operational continuity .

A well-designed substation should:

Ensure personnel safety with isolation, mechanical and electrical interlocks, and clear de-energization protocols.
Ensure supply reliability through rapid protection systems and redundancy in key equipment.
Comply with local and international regulations (such as the NOM in Mexico), an aspect in which Grupo Edmar will always provide you with the support of a team with extensive experience so that your project is 100% regulated.

The Future: Smarter Substations.

With the arrival of smart grids and the rise of renewable energy, medium-voltage substations are becoming smarter and more automated . This is no longer science fiction, but an operational necessity.

New monitoring and control systems based on digital communications allow:

Detect and isolate faults almost instantly, minimizing service interruption time (known as Self-Healing ).
Dynamically manage load to optimize energy efficiency and reduce losses.
Integrate distributed energy sources (such as solar and wind farms) into the main grid safely, accommodating the two-way flow of energy.

A medium-voltage substation is much more than a set of cables and devices; it's a strategic investment in the continuity, safety, and efficiency of your operation. Choosing quality equipment and an experienced partner like Grupo Edmar ensures that this "electrical customs" operates flawlessly, protecting your assets and guaranteeing the energy flow your business needs to continue growing. By investing in the quality of our transformers , you are investing in the future of your company. If you're about to start a project, contact us! We're ready to provide you with the equipment and advice you need.