Transformers are critical components in power distribution networks, and their longevity depends on proper maintenance. One of the biggest threats to transformer windings is corrosion, often caused by moisture ingress. If left unchecked, moisture can lead to insulation degradation, reduced dielectric strength, and even catastrophic failures.

How Moisture Causes Corrosion in Windings

Moisture enters transformer windings through:

Breathing action due to temperature fluctuations

Damaged gaskets or seals

Improper storage or maintenance

When moisture combines with oxygen and contaminants, it accelerates oxidation and corrosion in copper or aluminum windings. This leads to increased resistance, hotspots, and eventual winding failure.

Controlled Hot Air Drying: An Effective Solution

One of the most reliable methods to prevent moisture-related corrosion is controlled hot air drying. This process involves circulating dry, heated air through the transformer to evaporate trapped moisture.

Key Benefits of Hot Air Drying:

Removes Moisture Efficiently – Hot air (typically 80–100°C) evaporates moisture from windings and insulation.

Prevents Corrosion – By eliminating moisture, oxidation and corrosion risks are minimized.

Restores Dielectric Strength – Dry insulation improves electrical performance.

Non-Invasive & Cost-Effective – Unlike vacuum drying, hot air drying requires less equipment and downtime.

Best Practices for Controlled Hot Air Drying

To ensure effective moisture removal:

Monitor Temperature – Excessive heat can damage insulation; maintain optimal drying temperatures.

Use Dry Air Sources – Air should be dehumidified to avoid reintroducing moisture.

Check Moisture Levels – Use insulation resistance (IR) and polarization index (PI) tests to verify dryness.

Seal the Transformer Post-Drying – Prevent re-entry of moisture using nitrogen blankets or desiccants.

Conclusion

Corrosion in transformer windings is a preventable issue with proper moisture control. Controlled hot air drying offers an efficient, cost-effective way to protect windings, extend transformer life, and ensure reliable power distribution. Regular maintenance and moisture monitoring are essential to keeping transformers in optimal condition.

By adopting proactive drying techniques, utilities and industries can reduce failures, cut maintenance costs, and enhance transformer performance for years to come.

Need help with transformer maintenance? Consult an expert to implement the right drying solution for your equipment.