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On-Load Tap Changer (OLTC) is a vital component in power transformers, enabling the adjustment of the transformer's output voltage while it remains energized and under load. This function is crucial for maintaining the stability and efficiency of electrical power networks by compensating for fluctuations in voltage levels due to changes in load or transmission distances. Regular maintenance of OLTC is essential to ensure their reliable operation, prevent failures, and prolong the transformer's lifespan. Here are some key aspects of OLTC maintenance:

1. Visual Inspection

• External Condition: Check for any signs of oil leaks, damage to the housing, or corrosion on the external parts.

• Breathers and Silica Gel: Inspect breathers for blockages and replace silica gel if it has changed color, indicating moisture absorption.

2. Oil Analysis and Management

• Oil Sampling: Regularly sample and analyze transformer oil for dielectric strength, acidity, moisture content, and the presence of particles or sludge. Contamination can harm OLTC mechanisms.

• Oil Filtration/Replacement: If analysis shows deteriorated oil quality, consider filtration or replacement as per recommendations.

3. Electrical Tests

• Contact Resistance Test: Measure the resistance of the tap changer contacts to detect overheating or impending failure due to wear.

• Timing Test: Verify that the OLTC operates within specified time limits to prevent overloading and ensure smooth transitions between taps.

4. Mechanical Tests and Lubrication

• Mechanical Operation Check: Perform functional tests to verify correct mechanical movement and alignment of the mechanism.

• Lubrication: Regularly lubricate moving parts following manufacturer guidelines to reduce wear and tear.

5. Control and Monitoring System Check

• Control Circuit Inspection: Ensure all control switches, relays, and indicators function correctly.

• Monitoring System Calibration: Calibrate sensors and verify the accuracy of monitoring systems to ensure early detection of anomalies.

6. Routine Tap Changer Exercise

• Regularly exercising the OLTC, typically every few months, helps keep the mechanism free from seized parts and ensures its readiness for operation.

• Regular and proactive maintenance not only extends the life of the OLTC and transformer but also minimizes unexpected downtime and associated costs.