How does a transformer substation work?

The transformer substation is an element that, despite our lack of knowledge, is essential for the electricity grid to work like a Swiss watch

Many of us have walked past or over a transformer substation without knowing it – or maybe we did. Whether walking through the city or the countryside, these key elements in our daily lives are strange everyday objects that, unless you have an electrician friend or have read an article about how energy reaches our homes, we rarely come to understand and identify. The truth is that very few people understand the true importance of these transformer substations and how they make sure that, thanks to a crucial and innovative technological development, we use energy in our homes, workplaces or different public facilities. In short, these unknowns, whose function we are going to reveal today, are one of those everyday mysteries that so fascinate people who are in the habit of asking themselves questions. Are you curious? Then let’s go for it.

Let’s take it one step at a time. Perhaps the main thing is to explain, very quickly, how the electricity grid works. We, the consumers, are part of a long chain where the continuous availability of energy and the security and intercommunication of the infrastructure are absolutely necessary. The electricity grid is a kind of spider’s web made up of various elements such as cables, switchgear, poles, towers, substations, etc.

In short, and to be clear, energy comes from different electricity generation sources that can be classified into two main groups: traditional or renewable.

The traditional sources are far away from us – think of a combined cycle power station on the outskirts of our city – so the electricity has to be transported efficiently to city centres: this is where the power is switched to high voltage. This is transported via cables on high-voltage pylons to an electrical substation, where the voltage can be lowered and reduced from high to medium voltage. This reduces risks and leaves the energy ready to be distributed to consumption points.

In contrast, the energy generated by renewables undertakes a substantially different journey, as it is transported directly at medium voltage to the substations located in the vicinity of our cities. In addition, in many cases this energy is generated inside the buildings themselves, equipped with systems such as photovoltaic panels, allowing direct access to their power supply systems.

This is all very well, but when do the famous transformer substations come into play? Well, they act as the great controllers and distributors of energy in the great web that is the electricity grid. If we were to speak in footballing terms, the transformer substations would be the creative midfielders, crucial for spreading the play intelligently and weighing up, at all times, where to pass the ball. Located at the outlets of the substations to our electricity grids, the TSs (in abbreviated form) distribute and distribute electrical energy to areas of consumption thanks to sophisticated grid protection and automation systems, such as those implemented by Ormazabal, a leading company in the sector. In this way, the spider’s web is transformed around the consumption points into interconnected rings thanks to the work of the TSs.

All this makes it possible to ensure the supply, the rational utilization of resources and the safety of the electricity consumption environment, achieving an efficient, safe and sustainable electricity distribution, capable of supplying and adapting to the different existing energy demand needs. Without our strange friends we would have a big problem, as we would run out of electricity. That is how important they are. They are present in residential areas, shopping centres, factories, hospitals, railways, roads, petrol stations… and the list goes on.

Now that we know what they do, all that remains is to find out what they are made of and how they work.

What does a transformer substation consist of, what types are there, and how does it work?

A transformer substation consists of five main elements:

  1. Enclosure: This is the substation’s outer layer. It can be made of prefabricated concrete, sheet metal or even brick.
Concrete enclosures
Concrete enclosures insulate and protect the critical elements of the transformer substation.
  1. Transformer: This is the main electrical element of the TS, which increases or decreases the voltage of an electrical circuit for its subsequent distribution.
Transformers are fundamental to the operation of the electricity grid.
  1. Switchgear: This element, which is at the heart of the substation’s complexity and technological development, is used for different functions depending on its type, but it is like a large switch that cuts power off or lets it flow. To this end, technological development has been fundamental, providing a solution that allows the grid to operate at medium voltage values with total safety for the operator and the grid in the most adverse conditions.
Ormazabal CGMCOSMOS 2LV Switchgear
Ormazabal CGMCOSMOS 2LV Switchgear
  1. Protection Relays: Intelligent protection, measurement and control elements are implemented in association with this switchgear. They allow electricity companies as well as private and industrial customers to continuously monitor current values, voltage values and fault history, and to operate the grid remotely if necessary. A genuine revolution.
The relays are integrated into the operability of the switchgear.
  1. Low voltage switchboard: This element distributes the energy and protects it on its way to our homes. Having transformed -reduced- the voltage value in the transformer, the current value increases and this element distributes and protects this current value in a certain number of outlets that will end up in our homes.

As in other respects, transformer substations fall into different categories according to their use. No doubt while walking through a park you have seen some oval-shaped vents amid the grass; or maybe on the outskirts of an industrial estate you have noticed some sort of concrete blocks with metal doors, various electrical signs and the unmistakable seal of quality that is the Ormazabal brand. Well, they are transformer substations, and these are two of the clearest examples of some of the types that exist depending on their physical location. Let’s take a look at each one in turn:

Infografía de un centro de transformación estándar y sus elementos
  • TS in prefabricated enclosure: Perhaps the most common type and the easiest to spot if we look carefully enough. They are concrete blocks of different sizes, ranging from three to eight metres long, with access through metal doors. They represented a genuine revolution when Ormazabal launched them on the market, reducing installation times from one month to just a couple of days. Sometimes, with the aim of using their structure as a large canvas, they are customised with drawings representative of the place where they are located. You may not realise it, but you’ll almost certainly go past one of them every day.
 Transformer substation
A transformer substation can also be a wall mural (Photo by Óscar Daniel López)
  • Underground TS: This type of substation is hidden in order to coexist with urban spaces, either for pedestrian or vehicle traffic or for aesthetic reasons. Easily recognised by their vents -which some would mistakenly call chimneys-, they are accessible through a trap door located on top. Some models, such as those developed by Ormazabal, are floodable in order to guarantee grid safety and service capability even in the wettest conditions.
Ormazabal underground transformer substation
Infographic of the inside of an Ormazabal underground transformer substation.
  • Semi-buried TS: This is a solution that buries a significant part of its structure while still providing accessibility through two small doors. It is relatively common to see this type of substation in urban areas.
half-buried transformer substation
This is what a half-buried transformer substation looks like.
  • TS in a civil works building: Whether located on the ground floor of a building and separated from the public thoroughfare by a ventilated metal “façade”, or inside a civil works brick building, this type of TS was the most traditional until the advent of prefabricated enclosures.
  • Outdoor TS: Very recognisable in rural areas, they are located at the top of a high-voltage tower. With hardly any protection, as they are at the mercy of the weather, this type is not used with power ratings above 160 kVA.

In any case, the incoming lines (the connection to the grid) of these substations that we see in our cities, are underground; the only visible ones are those in areas with high voltage pylons located outside city centres.

How does each TS work, in detail?

Now that we know what components make up a transformer substation and what types there are, all that remains is to find out how the substations work.

When the energy arrives at the transformer stations via the electricity grid, it is distributed through the medium voltage switchgear. Normally, the most common configuration used by electricity companies is that of an input and output ring with a protection switchgear designed to protect each transformer in the event of a problem such as a network overload.

Thus, the transformer is responsible for reducing the voltage value, allowing the output current value to increase and obtaining a large amount of current, which is then distributed through the low-voltage switchboard to numerous outlets.

This is how, once the transformer substation has managed to adapt the current to its ideal value for consumption in our homes, the energy is channelled to our sockets; making everything work correctly.

This is why every transformer substation is crucial in protecting and securing the electricity supply.