Maintenance of On-Load Tap-Changer
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Questions and Answers

What is the correct sequence for refitting the coupling tube after inspection?

  • Refit the coupling tube without checking for mechanical damage
  • Refit immediately without checking alignment
  • Refit following instructions for removal in reverse order, ensuring alignment of adjustment marks (correct)
  • Refit only the outside of the coupling tube

    • When should the vacuum interrupters be replaced?

  • Every year regardless of usage
  • Every 300,000 tap change operations
  • After 600,000 tap change operations (correct)
  • Only when visual damage is present

    • What should be visually checked during the maintenance of transition resistors?

  • Their color and material type
  • For unusual appearances (correct)
  • For signs of rust only
  • Their alignment with the installation points

    • What must be assured before refitting the diverter switch insert in the oil compartment?

    <p>That all six insulating shims are present in the energy accumulator carrier</p> Signup and view all the answers

    How often should the varistor connection leads and their fasteners be replaced?

    <p>After 600,000 tap change operations</p> Signup and view all the answers

    What should be done if signs of leakage paths or discharge marks are observed?

    <p>Immediately contact MR Technical Service for inspection</p> Signup and view all the answers

    What is the purpose of aligning the red adjustment mark during coupling tube assembly?

    <p>To correctly position the coupling tube for optimal functioning</p> Signup and view all the answers

    What is the first step in removing the tap-change supervisory control?

    <p>Take tap-change supervisory control plug connector out of bracket</p> Signup and view all the answers

    What is the significance of checking the mechanical condition of the coupling tube?

    <p>To ensure that there are no leakage paths or discharge marks</p> Signup and view all the answers

    What could result from improperly removing the tap-change supervisory control?

    <p>Damage to the on-load tap-changer and transformer</p> Signup and view all the answers

    How many nuts and locking elements may need to be removed from the mounting plate when taking out the tap-change supervisory control?

    <p>3 or 4, depending on the model</p> Signup and view all the answers

    What is the purpose of the Teflon strip mentioned in the removal process?

    <p>To prevent damage to the stud bolt during removal</p> Signup and view all the answers

    What action should be taken with the oil suction pipe before removal?

    <p>Remove cable ties from the oil suction pipe</p> Signup and view all the answers

    What should be done with the lead of the tap-change supervisory control before pulling out the diverter switch insert?

    <p>It needs to be swivelled to avoid damage</p> Signup and view all the answers

    Which of the following is NOT a step in removing the tap-change supervisory control?

    <p>Unscrewing the oil suction pipe</p> Signup and view all the answers

    What is the primary risk associated with removing the tap-change supervisory control without care?

    <p>Damage to the on-load tap-changer and transformer</p> Signup and view all the answers

    What should be done with lock tabs, lock disks, lock nuts, and the on-load tap-changer head cover o-ring after removal?

    <p>Replace them once removed</p> Signup and view all the answers

    Which type of screws should be used with the on-load tap-changer?

    <p>Self-locking screws with thread coating</p> Signup and view all the answers

    How should the diverter switch insert's energy accumulator be positioned before insertion?

    <p>It should be locked at its dead center</p> Signup and view all the answers

    What is required for the alignment of the diverter switch insert during installation?

    <p>The red markings must face opposite each other</p> Signup and view all the answers

    What should be ensured about the screw connection points before installing components?

    <p>They should be free of oil and grease</p> Signup and view all the answers

    What is the consequence of correctly aligning the diverter switch insert?

    <p>It guarantees compatibility with the oil compartment</p> Signup and view all the answers

    Which of the following is NOT a recommended practice for installing the diverter switch insert?

    <p>Ignoring the adjustment marks</p> Signup and view all the answers

    What must be checked before lowering the diverter switch insert into the oil compartment?

    <p>The tap selector coupling must be in the adjustment position</p> Signup and view all the answers

    What is the correct distance between the upper edge of the diverter switch insert coupling tube and the head flange during installation?

    <p>10 ± 2 mm</p> Signup and view all the answers

    What is the first step in the correct order of installation for the oil suction pipe?

    <p>Insert the oil suction pipe into the on-load tap-changer head.</p> Signup and view all the answers

    What must be installed before the oil suction pipe according to the installation order?

    <p>Diverter switch insert</p> Signup and view all the answers

    What is the purpose of the locking washers when securing the mounting plate?

    <p>To prevent loosening due to vibration</p> Signup and view all the answers

    What should be checked to ensure the tap-change supervisory control is installed correctly?

    <p>That the drive shaft feather key is seated properly</p> Signup and view all the answers

    Which part is directly fastened to the retaining bracket during the installation process?

    <p>Oil suction pipe</p> Signup and view all the answers

    What must be connected outside its bracket during the final steps of installation?

    <p>Plug connector</p> Signup and view all the answers

    What damage is explicitly mentioned as a risk during improper installation?

    <p>Damage to the on-load tap-changer</p> Signup and view all the answers

    What is the first step to collect drained oil from the on-load tap-changer?

    <p>Place a bucket under the drain valve.</p> Signup and view all the answers

    What must be done before opening the head cover of the on-load tap-changer?

    <p>De-energize the tap-change supervisory control.</p> Signup and view all the answers

    Which auxiliary circuits must be de-energized to prevent hazards?

    <p>Tap-change supervisory control and pressure relief device.</p> Signup and view all the answers

    What action should be taken after approximately 10 liters of oil have been drained?

    <p>Seal the air-vent valve E1 with a screw cap.</p> Signup and view all the answers

    What precaution is necessary regarding the sealing surfaces when removing the head cover?

    <p>They must be checked for sound condition.</p> Signup and view all the answers

    Why is it important to avoid operating electric devices during the maintenance procedure?

    <p>There is a risk of creating sparks.</p> Signup and view all the answers

    What should be ensured about the o-ring during maintenance?

    <p>It should be in sound condition.</p> Signup and view all the answers

    What might occur if parts fall into the diverter switch oil compartment?

    <p>It may cause contamination.</p> Signup and view all the answers

    Abbreviations such as OI, DS, and MC stand for Operating Instructions, Diverter Switch, and Main Contact respectively.

    <p>True</p> Signup and view all the answers

    The highest voltage for equipment, represented as Um, is measured in watts.

    <p>False</p> Signup and view all the answers

    The symbol for 'Fill with oil' appears in the notation conventions section of the technical documentation.

    <p>True</p> Signup and view all the answers

    The signal word DANGER indicates a situation that, if not avoided, could lead to minor injuries.

    <p>False</p> Signup and view all the answers

    The notation conventions section is primarily concerned with legal and binding regulations.

    <p>False</p> Signup and view all the answers

    Hazard communication in the technical file uses a format that includes warnings and specifies actions to take.

    <p>True</p> Signup and view all the answers

    TDCa and TDCb refer to on-load tap-changer indicators.

    <p>False</p> Signup and view all the answers

    The implication of a tightening torque symbol in the documentation is related to proper maintenance practices.

    <p>True</p> Signup and view all the answers

    The maintenance manual (MM) is not listed as an abbreviation in the document.

    <p>False</p> Signup and view all the answers

    Environmental protection regulations must be disregarded during operation and maintenance.

    <p>False</p> Signup and view all the answers

    The term 'Caution' indicates a situation that could result in death or serious injury.

    <p>False</p> Signup and view all the answers

    Pictograms in warning notices can indicate the presence of combustible substances.

    <p>True</p> Signup and view all the answers

    The information system described is aimed at complicating the understanding of procedures.

    <p>False</p> Signup and view all the answers

    Reading the technical file carefully is necessary to familiarize oneself with the product.

    <p>True</p> Signup and view all the answers

    A 'Notice' signal indicates measures to be taken to prevent life-threatening situations.

    <p>False</p> Signup and view all the answers

    Warning of dangerous electrical voltage is illustrated with a specific pictogram.

    <p>True</p> Signup and view all the answers

    Warnings about tipping hazards are conveyed through specific warning notices.

    <p>True</p> Signup and view all the answers

    The general safety information chapter in the technical file contains trivial details.

    <p>False</p> Signup and view all the answers

    The maximum permitted measured current for a filled oil compartment is 10 A DC.

    <p>False</p> Signup and view all the answers

    DC resistance measurement requires that the measured current must be 0 A when changing the operating position.

    <p>True</p> Signup and view all the answers

    The measured DC current can be up to 100% of the rated current of the transformer winding to ensure accurate measurements.

    <p>False</p> Signup and view all the answers

    Operating conditions for on-load tap-changers can be monitored without interruption of measured current at all times.

    <p>False</p> Signup and view all the answers

    The DC resistance measurement process is the same for both empty and oil-filled compartments.

    <p>False</p> Signup and view all the answers

    The DC current restriction during measurement is primarily for safety and to maintain the integrity of the transformer.

    <p>True</p> Signup and view all the answers

    The maximum measured DC current in an oil compartment empty is 50 A.

    <p>False</p> Signup and view all the answers

    DC resistance measurement can be performed continuously without any need to stop the measured current.

    <p>False</p> Signup and view all the answers

    The highest voltage for the VRC OLTC variant is 175 kV.

    <p>False</p> Signup and view all the answers

    The motor-drive unit can be operated while the on-load tap-changer is not coupled without risking damage.

    <p>False</p> Signup and view all the answers

    The maximum weight limit for the diverter switch insert is 120 kg.

    <p>True</p> Signup and view all the answers

    The withdrawal height of the diverter switch insert during maintenance is measured in liters.

    <p>False</p> Signup and view all the answers

    The oil quantity for oil change in the VRF OLTC variant is stated in liters.

    <p>True</p> Signup and view all the answers

    The oil change for the VRE OLTC variant requires a quantity of 1380 liters.

    <p>False</p> Signup and view all the answers

    The maximum withdrawal height for VRD OLTC variant during maintenance is 1840 mm.

    <p>True</p> Signup and view all the answers

    It is acceptable to not block the motor-drive unit against electrical operation during adjustments.

    <p>False</p> Signup and view all the answers

    Filling the diverter switch oil compartment with insulating oil should reach the lower edge of the coupling shaft.

    <p>False</p> Signup and view all the answers

    A damaged o-ring can lead to oil escaping from the on-load tap-changer, causing potential damage.

    <p>True</p> Signup and view all the answers

    The on-load tap-changer head cover can be sealed with a screw cap without any specific tightening torque requirement.

    <p>False</p> Signup and view all the answers

    It is acceptable to skip cleaning the sealing surfaces before placing the on-load tap-changer head cover.

    <p>False</p> Signup and view all the answers

    The venting process only applies to the on-load tap-changer head and does not involve the oil conservator.

    <p>False</p> Signup and view all the answers

    It is essential to match the red triangular marks on both the on-load tap-changer head and cover during assembly.

    <p>True</p> Signup and view all the answers

    The dielectric strength and water content of insulating oil are irrelevant as long as oil is present in the diverter switch.

    <p>False</p> Signup and view all the answers

    The vent pipe connection S on the on-load tap-changer head does not need to be closed again after venting.

    <p>False</p> Signup and view all the answers

    Study Notes

    Maintenance of On-Load Tap-Changer

    • Place a bucket (10 liters) under the drain valve to collect drained oil before opening the drain valve.
    • Use a screwdriver to lift the valve tappet on air-vent valve E1; oil level will decrease automatically.
    • Close the drain valve after draining approximately 10 liters of oil; securely seal air-vent valve E1 with a screw cap.

    De-energizing Tap-Change Supervisory Control

    • If equipped, de-energize the tap-change supervisory control before opening the head cover.
    • Ensure all circuits, including auxiliary devices, are de-energized to prevent accidents.

    Removing On-Load Tap-Changer Head Cover

    • Loosen screws with locking washers on the head cover to remove it.
    • Check sealing surfaces and o-rings for sound condition; ensure no parts fall into the diverter switch oil compartment.

    Handling Tap-Change Supervisory Control

    • Remove the tap-change supervisory control carefully to avoid damaging connecting leads.
    • Disconnect the plug connector and remove mounting nuts and locking elements.
    • Take out the supervisory control along with the mounting plate and drive shaft.

    Removing Oil Suction Pipe

    • Detach cable ties from the oil suction pipe and pull it out of the on-load tap-changer head.
    • Swivel the lead of the tap-change supervisory control to avoid damage while extracting the diverter switch insert.

    Visual Inspection and Maintenance

    • Perform a thorough visual inspection of the coupling tube for mechanical or electrical damage.
    • Ensure proper alignment of adjustment marks during reassembly of the coupling tube.

    Inspections and Replacements

    • Visually check transition resistors for unusual appearances.
    • Replace vacuum interrupters after 600,000 tap change operations; consult MR Technical Service for assistance.
    • Verify that all six insulating shims are present before reassembling parts.

    Installation Precautions

    • Only use new lock tabs, nuts, and screws once; ensure screw connections are free from oil and grease.
    • Follow the correct order of installation to prevent damage to components.

    Inserting Diverter Switch Insert

    • Ensure the tap selector coupling is in the correct adjustment position before inserting the diverter switch.
    • Position the diverter switch insert to align red markings on the energy accumulator and tap-changer head.
    • Check that the distance between coupling tube and head flange is approximately 10 ± 2 mm.

    Final Assembly Steps

    • Insert the oil suction pipe and secure it with a cable tie on the retaining bracket.
    • Reinstall the tap-change supervisory control with correct seating of the drive shaft feather key and secure the mounting plate with nuts and washers.
    • Compliance with European and national laws, including accident prevention and environmental protection regulations, is mandatory.
    • Technical files and supporting documents must always be accessible for future reference.

    Notation Conventions

    • Abbreviations define specific terms related to the equipment:
      • OI: Operating instructions
      • DS: Diverter switch
      • OLTC: On-load tap-changer
      • MR: Maschinenfabrik Reinhausen GmbH
    • Symbols indicate actions or specifications, such as tightening torque, visual inspections, and use of tools.

    Hazard Communication System

    • Warnings follow a standard format: type of danger, consequences, and recommended actions.
    • Signal words indicate severity:
      • DANGER: Risk of death or severe injury.
      • WARNING: Could result in serious injury.
      • CAUTION: Risks minor injuries.
      • NOTICE: Prevents property damage.
    • Pictograms visually represent dangers, such as electrical voltage or combustible substances.

    General Safety Information

    • Detailed maintenance instructions are crucial for safe operation.
    • Emphasis on understanding the technical file for effective maintenance practices.

    Maintenance Scope and Intervals

    • DC resistance measurements should not exceed defined limits to avoid transformer overheating.
    • Maximum measured currents vary based on the oil compartment state:
      • Empty: Maximum of 10 A DC.
      • Filled: Maximum of 50 A DC.

    Preparatory Work for Maintenance

    • Use of a crane or MR lifting device is necessary for the safe handling of the diverter switch insert, which has a maximum weight of 120 kg.
    • Procedures must ensure that the motor-drive unit is not activated unless coupled to avoid equipment damage.
    • Important measures include filling oil compartments appropriately, replacing O-rings to prevent oil leaks, and maintaining clean sealing surfaces.

    Oil Quantity and Maintenance Details

    • Specific oil quantities for different OLTC variants are provided, depending on the highest voltage for equipment.
    • The importance of maintaining adequate dielectric strength and water content in insulating oil to prevent transformer and on-load tap-changer damage is emphasized.

    Steps for Inserting Diverter Switch Insert

    • Move on-load tap-changer to the adjustment position, record current operating position, and ensure proper filling of insulating oil.
    • Installation and tightening procedures for the on-load tap-changer head cover must be followed precisely to avoid leaks and ensure proper sealing.

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    Related Documents

    VACUTAP® VR I HD Maintenance Manual PDF

    Description

    This quiz covers essential procedures for maintaining an on-load tap-changer. It includes steps for draining oil, de-energizing supervisory control, and removing the head cover for inspection. Understanding these processes is crucial for ensuring operational safety and efficiency.

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