Liquid immersed transformers, how do they work?

Liquid immersed transformers, or liquid-insulated transformers, are established as the most economical, safe, and sustainable technology for the electrical network.

Transformers are a key element of the electrical network that, depending on their typology, offer a series of advantages to modify electrical energy in the most efficient way possible. If we recently learned how these elements worked, today we are going to delve into the operation and advantages of one of the best-known alternatives: liquid immersed transformers, also known as submerged transformers. Technical checks position this type of transformers as the most competitive, but why? First, let’s take a brief stop to see what their operation and main characteristics are.

The main characteristic that defines this electrical machinery is that a large part of the internal elements of the piece are completely submerged in dielectric liquid (in some cases it can be oil), which acts as one of the insulating materials to transfer energy in the electromagnetic induction process by which electricity is transformed according to the needs of the network. Thus, this liquid fulfills three main insulating properties:

• Electrical insulation: The dielectric liquid incorporated into the transformer’s elements has high-strength dielectric properties that help prevent short circuits by acting as a separator between windings (a circuit of electrical wires) and the transformer’s core. Additionally, not having corrosive sulphurs or inorganic acids avoids the wear of the conductors and metallic elements of the piece.
• Thermal insulation: Another of its insulating functions is to act as a coolant to dissipate the heat generated during its operation, reducing the risks caused by overheating of this element. This is due to its low viscosity, allowing for proper heat transfer to the exterior.
• Environmental insulation: Furthermore, the dielectric liquid acts as a perfect ally to increase the transformer’s lifespan and thus the operability of the electrical network, protecting its coils against environmental elements such as moisture and dust. Its resistance to emulsions with water prevents oxidation and facilitates the formation of internal sludge. Added to this, the oil serves as an ally for preventing issues caused by cold weather in the electrical network, as this type of insulating liquid has a low freezing point.

Among the types of dielectric liquids, there are distinctions between silicone compounds, mineral, ester, or vegetable origins; something that will vary according to the technical requirements of the installation in various aspects. Therefore, it is quite common to refer to them as submerged transformers, given the wide variety of insulating liquids they use.

Main advantages of submerged transformers

Well, now that we know what distinguishes this type of transformers, let’s move on to analyze what its main advantages are – we have already seen some – according to the most relevant criteria when choosing one technology over another to provide service to the network.

Dielectric transformers and safety criteria

One of the most relevant criteria from the perspective of the electrical network’s operability is safety, both from the network’s perspective and for those who work with it, as electricity is a daily element in our lives that requires very important safety measures. In that sense, liquid immersed transformers have proven to be the best possible solution in both ways, as we can see in the following infographic.

Oil transformers operate better under high electrical loads, allowing them to respond despite overvoltages that may exist in the network. Additionally, due to their type of insulation, these transformers have greater resistance to the overheating typical of thermal stress situations; something that also translates into greater durability by better withstanding both overloads and voltage transients.

Liquid immersed transformers and installation and maintenance costs

As important as the previous point is the cost that the installation and maintenance of a critical element of the network, such as a transformer, entails for network operators and users. In this sense, oil-insulated transformers are clearly more competitive compared to their dry counterparts. Not in vain, the fact that they do not require a protective enclosure significantly reduces their initial cost; something that also extends to the fact that, by not needing accessories for cooling -due to the thermal properties of the oil-, they achieve better cooling and heat dissipation at a lower cost.

Moreover, this type of transformers are extremely easy to install and maintain in outdoor conditions, where they also do not require additional enclosures to protect them from the elements, resulting in a longer lifespan by replacing their dielectric oil (in high-power models) and requiring less maintenance due to the low insulating loss rate during service.

For all these reasons, the TCO -total cost of ownership- of an liquid immersed transformer is much lower than that of its dry counterparts, which end up being more expensive and costly to maintain.

Liquid immersed transformers and sustainability criteria

However, if we talk about relevant criteria, sustainability or environmental aspect turns out to be one of the most important. The electrification of our economy must be based on sustainable and efficient electrical networks, something that is contributed by the constructive typology of transformers.

Thus, we observe that submerged transformers have a lower acoustic impact during their use thanks to the lower level of induction necessary through the oil, affecting the surrounding life to a lesser extent. Similarly, and related to acute climatic phenomena caused by climate change, this type of transformers have less sensitivity to the environment, reducing significantly the risk of being affected by floods or storms. A point that makes them especially competitive in areas with a high risk of flooding.

If we analyze the product lifecycle, something that will allow us to know if the technological solution will accompany us sustainably, submerged transformers have a lower environmental impact in the main category of Global Warming Potential (Carbon Footprint) according to the Life Cycle Assessment (LCA). Additionally, they have higher efficiency during the usage phase, which is the main impact of LCA (90%), and load records higher than those indicated by the index itself, resulting in even greater performance from the perspective of energy efficiency.

For all these reasons, submerged transformers have become the majority reference within the electrical network. Are you interested in delving into the technical advantages of this type of insulation? Get in touch with us so that we can assist you with your project: