What Are the Common Failures of AIS Voltage Transformers?

Hey everyone! I’m Felix, a 10-year veteran in the power system industry. Today, we’re going to dive into an important topic — what are the common failures of Air Insulated Switchgear (AIS) voltage transformers? How do you identify these issues, and how can they be resolved? Let’s get started!

1. Insulation Damage
The Problem You Might Encounter：

One of the most frequent issues is insulation damage. This typically happens due to aging insulation materials, overvoltage surges, contamination, or mechanical damage after prolonged operation.

How to Detect It?

• Visual Inspection: Check for cracks on the casing and ensure that seals are intact.

• Insulation Resistance Test: Use a megohmmeter to measure insulation resistance. If it’s below the standard value (e.g., 500 MΩ), there’s likely a problem.

Solutions

• For minor aging or contamination, clean and locally repair the affected areas.

• In cases of severe damage, replace the damaged insulation parts or even the entire unit.

2. Open Circuit on the Secondary Side
The Problem You Might Encounter

Another headache is an open circuit on the secondary side. This usually occurs because of wiring errors, poor connections, or faults in secondary equipment. When this happens, your protection system may fail, which is quite dangerous!

How to Detect It?

• Check Wiring: Ensure all connections are tight and secure.

• Use a Multimeter: Measure continuity in the secondary circuit. If there’s a break, you have an open circuit.

Solutions

• Tighten loose connections and correct any wiring mistakes.

• If the issue lies with the secondary equipment itself, repair or replace the faulty device.

3. Core Saturation
The Problem You Might Encounter

When the magnetic flux density in the core exceeds its saturation point, core saturation occurs. This results in significant measurement errors, affecting the accuracy and reliability of the system.

How to Detect It?

• Observe Output Signals: If you notice unstable or unusually large output signals from the voltage transformer, it might be experiencing core saturation.

• Professional Testing: Use specialized instruments like harmonic analyzers to check the core's operational status.

Solutions

• Adjust load conditions to avoid prolonged overload.

• Consider replacing the voltage transformer with one suitable for higher voltage ratings if necessary.

4. Oil Leakage in Oil-Immersed Voltage Transformers
The Problem You Might Encounter

For oil-immersed voltage transformers, oil leakage is a significant concern. Aging or damaged seals can cause leaks, which not only affect insulation performance but can also lead to fires in extreme cases.

How to Detect It?

• Regular Patrols: Look for signs of oil around the equipment.

• Infrared Thermography: Sometimes small leaks invisible to the naked eye can be detected using infrared cameras.

Solutions

• Promptly replace old seals.

• In severe cases, shutdown for repairs or replacement of the entire unit may be required.

5. Excessive Error
The Problem You Might Encounter

Over time, due to manufacturing defects, wear, or environmental factors, the error in voltage transformers may exceed allowable limits. This impacts both metering accuracy and protective functions.

How to Detect It?

• Regular Calibration: Perform calibration at specified intervals to ensure the error remains within acceptable limits.

• Online Monitoring: Some advanced systems use online monitoring to track error trends in real-time.

Solutions

• Calibrate or adjust voltage transformers that exceed error limits.

• Replace units if they cannot meet requirements.

Conclusion

To sum up, common failures of AIS voltage transformers include insulation damage, open circuits on the secondary side, core saturation, oil leakage in oil-immersed units, and excessive error. Not only should we learn how to identify these issues, but we must also know how to effectively resolve them. Remember, prevention is always better than cure — regular maintenance, keeping the working environment clean and dry, installing appropriate overvoltage protection devices, and performing periodic error calibrations are key measures to ensure proper operation.

I hope this article helps fellow professionals! If you have any questions or want to share your experiences, feel free to leave a comment or send me a message. Let’s learn together and improve collectively!

— Felix