Overhauling of 105MVA Transformer On Load Tap Changer (OLTC) MR OILTAP-M

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Overhauling of 105MVA Transformer On Load Tap Changer (OLTC) MR OILTAP-M

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An on-load tap changer (OLTC) is a vital component in power transformers, responsible for regulating voltage levels by adjusting the transformer's taps while the transformer is energized. Overhauling an OLTC involves a comprehensive inspection, maintenance, and potential repair or replacement of its constituent parts to ensure optimal performance and longevity. Overhauling an OLTC is based on two factors, one is number of operations count and second is years of service life. This particular video shows the Overhauling of 105MVA Transformer OLTC which is MR OILTAP-M type. It has two main parts one is Diverter Switch which is inside OLTC tank and other is Selector Switch which is inside transformer tank. Here's a detailed description of the process:
1-Initial Assessment and Preparation:
-Before beginning the overhaul, the transformer and OLTC are thoroughly examined to assess their condition and identify any existing issues.
-Safety precautions are paramount, including isolation procedures to ensure the transformer is de-energized and properly grounded before any work begins.
-Relevant documentation, including service records, manufacturer manuals, and technical specifications, are gathered for reference throughout the process.
2-Disassembly:
-The OLTC is carefully disassembled by qualified technicians, following manufacturer guidelines and best practices.
-Each component, including contacts, diverter switches, insulation materials, and mechanical linkages, is methodically removed and inspected for signs of wear, damage, or corrosion.
3-Cleaning and Inspection:
-All disassembled parts undergo a thorough cleaning process to remove dirt, oil, and other contaminants.
-Visual and tactile inspections are conducted to identify any visible defects such as pitting, erosion, or warping. Non-destructive testing techniques like ultrasonic testing may also be employed to detect internal flaws.
4-Repair or Replacement:
-Components showing signs of wear or damage are either repaired or replaced with genuine manufacturer-approved parts.
-Common repair tasks may include regrinding and polishing contacts, replacing worn insulation materials, or repairing damaged mechanical linkages.
-Replacement parts are carefully selected to match the original specifications, ensuring compatibility and optimal performance.
5-Lubrication and Assembly:
-Proper lubrication is essential for smooth operation and longevity of the OLTC mechanism. High-quality lubricants, recommended by the manufacturer, are applied to moving parts during reassembly.
-Components are meticulously reassembled according to the manufacturer's specifications, taking care to align and adjust parts accurately.
6-Functional Testing:
-Once reassembly is complete, the OLTC undergoes rigorous functional testing to validate its performance under simulated operating conditions.
-Electrical tests are conducted to verify contact resistance, insulation integrity, and continuity of electrical circuits.
-Mechanical tests assess the smoothness of operation, alignment of moving parts, and overall mechanical stability.
7-Adjustment and Calibration:
-If required, adjustments are made to the OLTC settings to ensure precise voltage regulation within specified tolerances.
-Calibration procedures are performed to verify the accuracy of tap position indicators and other control mechanisms.
8-Documentation and Reporting:
-Detailed documentation is prepared, documenting all aspects of the overhaul process, including findings, repairs, replacements, adjustments, and test results.
-Any recommendations for future maintenance or upgrades are noted, along with a record of parts used and work performed.
9-Recommissioning:
-Once the overhaul is successfully completed and documented, the transformer and OLTC are recommissioned in accordance with established procedures, and normal operation is resumed.
10-Follow-up Monitoring and Maintenance:
-Regular monitoring and maintenance schedules are established to ensure the continued reliability and performance of the OLTC and the transformer as a whole.
-Periodic inspections, testing, and lubrication are carried out as part of ongoing preventive maintenance efforts.
In summary, overhauling an OLTC involves a systematic and thorough process encompassing assessment, disassembly, cleaning, repair or replacement, reassembly, testing, calibration, documentation, and recommissioning. By following best practices and adhering to manufacturer guidelines, this process helps to ensure the safe, efficient, and reliable operation of power transformers in electrical power systems.