Questions and Answers
The drain valve must remain open during the entire fluid draining process.
False
Drainage of insulating fluid should capture approximately 2 liters.
True
Removing the return flange is the final step before changing the filter cartridge.
False
Insufficient insulating fluid in the oil compartment can lead to damage in the on-load tap-changer.
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Filter cartridges lose their function if stored for more than 4 years.
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It is important to affix the securing element with warning sign back onto the drain valve after draining.
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The oil filter unit cover must be removed before the filter cartridge can be accessed.
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To change the filter cartridge, no bolts need to be removed from the oil filter unit cover.
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The insulating fluid level in the oil conservator should exceed the 'Maximum' mark for safe operation.
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The return flange vent screw is used to vent the oil filter unit.
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During filter cartridge installation, the cartridge is centered manually before closing the cover.
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The oil filter unit must be filled with insulating fluid after installing the filter cartridge.
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Function tests are performed before venting the on-load tap-changer head.
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It is advisable to leave the stop-cocks on the feed flange closed during the commissioning process.
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The installation of the filter cartridge requires the use of 4 bolts.
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The tightening torque for the lifting eye bolts is lower than that for the M10 bolts.
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The insulating fluid used in the oil filter unit must have a dielectric strength of at least 60 kV/2.5 mm.
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The combined filter cartridge can be removed from its container and installed in the pump unit at any time before commissioning.
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It is advisable to keep stop-cocks open during the oil filling procedure to facilitate easier filling.
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The maximum allowable water content in the insulating fluid should be 12 ppm.
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The filter cartridge will not be centered automatically upon closing the cover of the oil filter unit.
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The procedure requires the use of a wrench size of 14 to remove the bolts from the oil filter unit cover.
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Two lifting eye bolts (M10) should be used with a tightening torque of 30 Nm during the filter cartridge installation.
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The oil filter unit components are fully vacuum proof, allowing stop-cocks to be open during filling.
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Study Notes
Filter Cartridge Installation and Maintenance
- Secure the new filter cartridge and o-ring into the oil filter unit's receiving flange; it will center automatically upon closing the cover.
- Fill the oil filter unit with insulating fluid.
- Attach the cover using 6 bolts (M10, wrench size 17, tightening torque 30 Nm) and 2 lifting eye bolts (M10, tightening torque 30 Nm).
- Connect the return flange to the stop-cock and open all stop-cocks on the feed and return flanges.
- Vent the oil filter unit via the return flange's vent screw.
- Vent the on-load tap-changer head using air-vent valve E1.
- Vent the feed pipe connection on the on-load tap-changer head.
Function Testing and Safety Warnings
- Conduct a function test as outlined in the relevant section.
- Ensure the insulating fluid level in the oil conservator is maintained between "Minimum" and "Maximum" marks to prevent explosion risks.
- During maintenance, if the water content or dielectric strength of the insulating fluid is out of specified limits, replacement is necessary.
Changing the Filter Cartridge
- Close the stop-cocks on both feed and return flanges before commencing maintenance.
- Position a container to capture approximately 2 liters of insulating fluid below the drain valve.
- Drain the insulating fluid by removing the securing element on the drain valve and allowing fluid to flow.
- Close the drain valve post-drainage and reaffix the securing element.
- Detach the return flange from the stop-cock and remove the cover of the oil filter unit by taking out securing bolts and lifting eye bolts.
- Carefully pull the old filter cartridge out using the handle; storage beyond 4 years degrades cartridge function.
- Obtain a new filter cartridge, ensuring that it has been stored for no longer than 4 years, and only remove it from its packaging immediately prior to installation.
Essential Installation Guidelines
- Keep stop-cocks closed during the entire oil filling process to avoid vacuum damage to oil filter unit components.
- Open stop-cocks only after oil filling is complete.
- The insulating fluid must exhibit a dielectric strength of ≥ 60 kV/2.5 mm and a water content ≤ 12 ppm as per relevant IEC standards.
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Description
Test your knowledge on the maintenance criteria for on-load tap-changers, including water content and dielectric strength compliance. This quiz will cover essential steps for changing filter cartridges and understanding replacement criteria.
