Liquid dielectric transformers: how do they work?

Transformers immersed in liquid dielectric are formed as the most economical, safe and sustainable technology for the electrical grid

Transformers are a key element of the electrical grid that, depending on their type, offer a series of advantages for modifying electrical energy in the most efficient way possible. If we recently learned how these elements work, today we are going to delve into the operation and advantages of one of the best-known alternatives: transformers immersed in liquid dielectric, also called submerged transformers. Technical checks establish this type of transformer as the most competitive, but why? First, let’s take a quick look at how it works and what its main features 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 liquid dielectric (in some cases it can be a type of organic 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 has three main insulating properties:

• Electrical insulation: The liquid dielectric incorporated into the transformer elements has high rigidity dielectric properties that help prevent short circuits by acting as a separator between the windings (electrical wire circuit) and the transformer core. Furthermore, since it does not contain corrosive sulfur or inorganic acids, wear of the conductors and metallic elements of the part is avoided.
• Thermal insulation: Another of its insulating functions is to act as a coolant to dissipate the heat generated during operation, reducing the risks caused by overheating of this element. This is due to its low viscosity, which allows for proper heat transfer to the outside.
• Environmental insulation: Furthermore, the liquid dielectric acts as a perfect ally to increase the useful life of the transformer, and therefore the operability of the electrical network, protecting its coils from environmental elements such as humidity and dust; and its resistance to emulsions with water prevents oxidation and facilitates the formation of internal sludge. In addition, the oil stands out as an ally in preventing the effects of cold on the electrical network, and this type of insulating liquid has a low freezing point.

Within the types of liquid dielectrics, there are compounds of silicone, mineral, ester or vegetable origins; something that will vary depending on the technical requirements of the installation in several ways. Therefore, it is quite common to refer to them as immersed 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 transformer, let’s analyze what their main advantages are – we have already seen some – according to the most relevant criteria when choosing one technology or another to serve the network.

Liquid dielectric transformers and safety criteria

One of the most relevant criteria from the point of view of the operation of the electrical network is that of security, both from the point of view of the network itself and of those people who work with it, and electricity is an everyday element of our lives that requires very important security measures. In this sense, liquid dielectric immersed transformers have proven to be the best possible solution in both senses, as we can see in the following infographic.

And the fact is that oil-filled transformers perform better under high electrical loads, allowing them to respond despite any overvoltages that may exist in the network. Furthermore, due to their type of insulation, they have greater resistance to overheating typical of thermal stress situations; something that also translates into greater durability by better withstanding both overloads and voltage transients.

Liquid dielectric transformers and installation and maintenance costs

Just 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, transformers immersed in liquid dielectric are clearly more competitive with respect to their dry counterparts. Not in vain, the fact that they do not require a protective enclosure significantly reduces their cost from the outset; Something that also extrapolates to the fact that, since they do not require cooling accessories – due to the thermal properties of the oil – they achieve better cooling and heat dissipation at a lower cost.

On the other hand, this type of transformer is extremely easy to install and maintain in outdoor conditions, and does not require additional enclosures to protect them from the elements. This also translates into a longer lifespan when replacing the dielectric liquid (in high-power models) and less maintenance due to the low rate of insulation loss during service.

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

Liquid dielectric transformers and sustainability criteria

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

Thus, we observe that submerged transformers have a lower acoustic impact during use thanks to the lower level of induction required by means of the oil, affecting life around them to a lesser extent. Similarly, and related to acute weather phenomena caused by climate change, these types of transformers are less sensitive to the environment, so the risk of being affected by floods or storms is significantly reduced. A point that makes them especially competitive in those areas with a high risk of flooding.

If we stop to analyze the life cycle of the product, something that will allow us to know if the technological solution will accompany us in a sustainable way, submerged transformers have an LCA (life cycle analysis) with a lower impact in the main category Global Warming Potential (Carbon Footprint). In addition, it has greater efficiency during the use phase, which represents the main impact of the LCA (90%), and load records higher than those indicated by the index itself, which translates into even greater performance from the point of view of energy efficiency.

This is why submerged transformers have become the most popular option in the electrical grid. Are you interested in learning more about the technical advantages of this type of insulation? Contact us so we can help you with your project: