Causes of Dry-Type Transformer Aging and Maintenance Guide

Dry-type transformers play a critical role in power systems. Over time, aging affects their performance and service life. Understanding the causes of transformer aging and applying effective maintenance strategies is key to ensuring a stable and reliable power supply.

Causes of Dry-Type Transformer Aging

1. Natural Aging of Components

Switch blades exposed to air are prone to corrosion, causing poor contact or short circuits over time.

Insulation materials, such as epoxy resin, deteriorate at high temperatures—becoming brittle and reducing insulation effectiveness.

2. Overload Operation Loss

Prolonged overload increases current and magnetic flux, causing overheating of windings and cores.

Heat accelerates insulation degradation, decreases transformer efficiency, and shortens lifespan, especially in peak load conditions.

3. Environmental Factors

Humidity, dust, and pollution weaken insulation strength and promote failure risks.

Contaminants impair heat dissipation and can lead to partial discharge and insulation damage.

4. Insulation Moisture Hazards

Moisture forms conductive channels in insulation, dramatically reducing its strength.

Damp insulation is prone to electrical breakdown and short circuits, especially in rainy seasons or basements.

5. Vicious Cycle of Long-Term Overload

Overload raises temperatures, accelerating insulation aging, which further increases overheating risk—creating a destructive feedback loop.

6. Influence of Environmental and Temperature Fluctuations

High ambient temperatures worsen heat dissipation and cause internal temperatures to rise.

Frequent temperature changes induce expansion and contraction, loosening connections and accelerating aging.

7. Electrical Aging and Stress Aging Effects

Partial discharge, thermal stress, and vibration stress degrade insulation and reduce transformer reliability.

These factors damage internal components over time, increasing failure risk.

Dry-Type Transformer Maintenance Methods

1. Regular Inspection and Monitoring

Temperature Monitoring

Use infrared thermometers to monitor winding, core, and connection temperatures.

Ensure winding hot spot temperature (F-class insulation) does not exceed 155°C.

Vibration and Noise Monitoring

Monitor with vibration sensors to detect loose or deformed components.

Investigate noise exceeding 85dB promptly as it indicates possible internal faults.

Appearance Inspection

Check for insulation cracks, discoloration, and dust accumulation regularly.

Clean surfaces to improve heat dissipation and prevent insulation damage.

2. Electrical Performance Testing

Insulation Resistance Test

Measure winding-to-ground resistance using a megohmmeter.

For Class F insulation, resistance should be ≥ 500 MΩ at 20°C.

DC Resistance Test

Ensure winding resistance deviation is less than 2%.

Significant deviation suggests loose connections or winding faults.

Withstand Voltage Test

Conduct power frequency withstand voltage tests to verify insulation strength.

Test voltage is typically 80% of the factory value.

3. Environmental Control

Ventilation and Heat Dissipation

Maintain good ventilation in transformer rooms.

Install fans or air conditioners if necessary to keep ambient temperature below 40°C.

Moisture and Dust Protection

Use dehumidifiers in humid environments and seal cabinets to prevent dust ingress.

Clean insulation surfaces regularly to maintain insulation integrity.

Load Management

Install overload protection devices to prevent long-term overload operation.

Ensure automatic tripping when current exceeds rated limits.

4. Preventive Maintenance

Bolt Tightening

Check and tighten connection bolts every 1–2 years to prevent increased contact resistance and heating.

Insulation Repair

Repair minor insulation damage using insulating paint or tape.

Replace windings if insulation is severely aged.

Short-Circuit Protection

Install fast-acting fuses or current-limiting reactors to protect windings during short circuits.

By following these dry-type transformer maintenance methods, operators can effectively extend transformer lifespan, minimize faults, and ensure stable and reliable power system performance.