Wet Type Transformers: Managing Moisture and Contaminants



Transformers are vital devices used in power distribution networks to transfer electrical energy efficiently from one circuit to another. Among various types, wet type transformers are commonly utilized due to their high reliability and effectiveness. However, these transformers, like any electrical equipment, are susceptible to moisture and contaminant-related issues that can degrade their performance and lifespan significantly. This article explores the importance of effectively managing moisture and contaminants and provides solutions to mitigate potential problems.

Understanding Wet Type Transformers

A wet type transformer, also known as a liquid-immersed transformer, is filled with a dielectric fluid, usually mineral oil. This dielectric medium provides insulation and cools the transformer, preventing overheating. Wet type transformers are widely used in both medium and high-power applications due to their excellent cooling capabilities, high insulation properties, and good heat transfer characteristics. However, their performance can be compromised if moisture and contaminants gain access to the system.

Importance of Managing Moisture and Contaminants

Moisture and contaminants are the primary causes of transformer failure and reduced operational lifespan. The presence of moisture can lead to insulation breakdown, corrosion, and increased vulnerability to electrical faults. If not properly managed, contaminants such as dust, dirt, and conducting particles can deteriorate insulation, result in short circuits, and impair the cooling system. Timely detection and management of these issues are crucial to maintaining the efficiency and reliability of wet type transformers.

Dealing with Moisture Issues in Wet Type Transformers

Moisture can enter a wet type transformer through various sources, including ambient air, pole-mounted transformers, temperature fluctuations, and even during routine maintenance or repairs. To effectively deal with moisture-related issues, several preventive measures can be implemented:

1. Sealing and Gasket Maintenance: Maintaining properly sealed gaskets and ensuring the transformer's housing remains airtight significantly reduces moisture ingress. Regular inspection and replacement of damaged or worn-out gaskets are essential to avoid potential leaks.

2. Breathers and Desiccants: Desiccant breathers are installed on wet type transformers to control moisture. These devices use desiccant material to adsorb moisture from the air entering the transformer, preventing it from reaching critical components. Regular monitoring and replacement of desiccant cartridges are necessary to ensure their continued effectiveness.

3. Dehydration: Periodically dehydrating the transformer's insulating oil can remove existing moisture. Methods such as vacuum or heat treatment are commonly employed to reduce moisture levels. Dehydration should be performed according to manufacturer recommendations and industry standards to prevent potential damage to the transformer.

4. Winding Insulation Drying: If moisture has penetrated the transformer's winding insulation, proper drying techniques should be implemented. Utilizing specific drying ovens or applying controlled heat and vacuum techniques can eliminate moisture within the winding.

Contaminant Control Measures for Wet Type Transformers

Alongside moisture, contaminants pose a significant threat to the performance and longevity of wet type transformers. Proper management and control of contaminants are essential to minimize the risk of failures and maximize the transformer's lifespan. Here are some effective measures:

1. Filtration: Installing high-quality oil filtration systems at critical points can remove contaminants, ensuring the oil remains clean and free of particles. Regular oil sampling and analysis can help determine the appropriate filtration requirements and frequency.

2. Regular Inspections: Conducting routine visual inspections of the transformer's exterior can help identify potential sources of contaminants. Dust, dirt, and vegetation should be removed promptly to prevent them from entering the system.

3. Contaminant Monitoring: Monitoring the levels of contaminants, such as dissolved gases and solids, present within the transformer's oil, can provide valuable insights into its condition. Analyzing oil samples through dissolved gas analysis (DGA) and other diagnostic techniques can help identify potential issues before they escalate.

4. Oil Reclamation: In some cases, the transformer's oil may become contaminated beyond acceptable limits. Oil reclamation systems can effectively remove impurities, gases, and moisture from the oil, allowing it to be reintroduced into the transformer, reducing waste and minimizing environmental impact.

5. Routine Maintenance: Following a well-defined maintenance schedule, including inspections, oil sampling, and testing, can ensure early detection and swift corrective actions, preventing larger issues from arising.


Effective management of moisture and contaminants is crucial to maintaining the optimal performance and extending the operational life of wet type transformers. Implementing preventive measures such as sealing and gasket maintenance, breathers, desiccants, regular oil filtration, inspections, and monitoring is essential to minimize the risks associated with these issues. By prioritizing the management of moisture and contaminants, power distribution networks can ensure the reliability and longevity of their wet-type transformers, contributing to a stable and efficient electrical supply system.


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