Moisture: The Silent Killer of Transformers

Transformers are crucial components in power systems, providing voltage transformation and electrical isolation.

These devices are designed to operate for many years, but their performance and lifespan can be significantly affected by the presence of moisture.

Moisture in transformers can cause a range of problems, including increased oxidation and aging of transformer oil, reduced dielectric strength, and corrosion of transformer components.

In this article, we’ll explore the negative effects of moisture on transformers, methods of detecting and preventing moisture, and why it’s important to address moisture in transformer maintenance.

How Moisture Affects Transformers

To understand how moisture affects transformers, we first need to understand the role of transformer oil.

Transformer oil is used to cool and insulate the transformer’s internal components, such as the core and windings.

The oil provides a dielectric barrier between the windings and the transformer’s metal components, allowing electrical energy to flow through the transformer without causing damage. The oil also helps to dissipate heat generated during operation.

Moisture can enter transformers in several ways, including through leaks in the transformer tank, faulty gaskets or seals, or through inadequate venting.

Once moisture enters the transformer, it can begin to react with the oil and other materials present, leading to a range of negative effects.

Read also my article: Moisture and transformer oil- a deadly combination!

Negative Effects of Moisture on Transformers

Increased Oxidation and Aging of Transformer Oil

Moisture can react with transformer oil to increase the rate of oxidation, which breaks down the oil and reduces its effectiveness as a dielectric fluid.

As transformer oil oxidizes, it produces sludge and acids, which can clog or damage the transformer’s internal components.

Oxidation can also reduce the oil’s ability to dissipate heat, leading to further damage.

Formation of Sludge and Acids in Transformer Oil

As mentioned, moisture can react with transformer oil to produce sludge and acids, which can build up in the transformer’s tank and on its internal components.

This sludge and acid buildup can lead to the clogging of oil passages and damage to the insulation between the windings and transformer core. This can cause the transformer to overheat and eventually fail.

Reduced Dielectric Strength of Transformer Oil

Moisture in transformer oil can also reduce its dielectric strength, which is the ability of the oil to withstand electrical stress without breaking down.

This reduction in dielectric strength can lead to electrical arcing within the transformer, causing damage to the windings and other internal components.

Corrosion of Transformer Components

Moisture can also cause corrosion of the transformer’s metal components, including the core, windings, and tank.

This corrosion can weaken the components and reduce their lifespan, leading to the potential failure of the transformer.

Methods of Detecting Moisture in Transformers

Detecting moisture in transformers is critical to preventing its negative effects. Some common methods of detecting moisture in transformers include the use of moisture meters and sensors, as well as sampling and analysis of transformer oil.

Moisture meters and sensors can detect the presence of moisture in the transformer’s oil or on its internal components, while sampling and analysis can provide more detailed information about the condition of the transformer oil and any contaminants present.

Methods of Preventing and Removing Moisture from Transformers

Preventing and removing moisture from transformers is crucial to maintaining their performance and lifespan.

Some common methods of preventing and removing moisture include the use of desiccants and breathers, vacuum filling and dehydration of transformer oil, replacement of contaminated transformer oil, and regular maintenance and testing of transformers.

Desiccants and breathers are used to prevent moisture from entering the transformer’s tank, while vacuum filling and dehydration can remove moisture that has entered the transformer.

Replacement of contaminated transformer oil is another option for removing moisture and other contaminants from the transformer, and regular maintenance and testing can help identify and address any issues before they become more serious.

Why Addressing Moisture in Transformer Maintenance is Important

Addressing moisture in transformer maintenance is critical to ensuring the safe and reliable operation of power systems.

Moisture can cause significant damage to transformers, leading to costly repairs or even complete failure.

By detecting and preventing moisture in transformers, power system operators can help extend the lifespan of these critical components and avoid potentially dangerous and expensive failures.

In addition, addressing moisture in transformer maintenance can help improve the efficiency of power systems.

Moisture can reduce the effectiveness of transformer oil as a dielectric fluid and can cause the transformer to overheat, leading to energy losses and decreased efficiency.


Moisture in transformers can cause a range of negative effects, including increased oxidation and aging of transformer oil, formation of sludge and acids, reduced dielectric strength, and corrosion of transformer components.

Detecting and preventing moisture in transformers is critical to maintaining their performance and lifespan, and a range of methods are available for doing so.

By addressing moisture in transformer maintenance, power system operators can help ensure the safe and reliable operation of their systems and improve their efficiency.

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