Electrical Engineering: Contact Shell Detachment
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Questions and Answers

What is the maximum permissible difference for the contact layer thickness between main switching and transition contacts?

  • 1.5 mm
  • 2.5 mm (correct)
  • 0.3 mm
  • 2.6 mm (correct)
  • What should be done if the difference in thickness between main switching and transition contacts reaches the permissible limit?

  • Replace the contacts (correct)
  • Increase the contact pressure
  • Perform regular maintenance
  • Adjust the mechanical sequence
  • Which tools are suggested to measure the thickness of the contact layers?

  • Caliper
  • Micrometer
  • Vernier gauge (correct)
  • Digital scale
  • What is the consequence of the difference between main switching and transition contacts exceeding stipulated limits?

    <p>Mechanical switching sequence failure</p> Signup and view all the answers

    What condition is implied if the contact wear is significantly high?

    <p>Potential failure of mechanical sequence</p> Signup and view all the answers

    In the operation sequence mentioned, which components are emphasized?

    <p>Main contacts and transition contacts</p> Signup and view all the answers

    If the operating conditions are unfavorable, what should be the action taken?

    <p>Inspect and potentially replace contacts</p> Signup and view all the answers

    What happens to the contacts if they are expected to reach critical wear before the next scheduled inspection?

    <p>They must be preemptively replaced</p> Signup and view all the answers

    What type of screws need to be loosened first during the detachment of the contact shell?

    <p>M 8 x 20 screws</p> Signup and view all the answers

    Which components must be cleaned with special care during the cleaning process?

    <p>All insulating parts</p> Signup and view all the answers

    How many screws must be loosened when removing the contact shell?

    <p>Total of 14 screws</p> Signup and view all the answers

    What is the installation requirement for the outer arc chutes when reassembling?

    <p>They must be refitted in their original position.</p> Signup and view all the answers

    What type of oil should be used for cleaning the contact shell and related parts?

    <p>Transformer oil</p> Signup and view all the answers

    What tools are primarily used to perform the loosening and detaching of screws?

    <p>Hexagon socket wrench</p> Signup and view all the answers

    Which washers are associated with the M 8 x 25 screws?

    <p>Both standard and dished washers</p> Signup and view all the answers

    What additional component must be withdrawn when working on the on-load tap changer type M 111?

    <p>Arc chutes</p> Signup and view all the answers

    What is the purpose of prying in a chucking wedge during the reattachment of the contact shell?

    <p>To hold back the movable contact system</p> Signup and view all the answers

    Which component should not have screws inserted during the initial reattachment process?

    <p>The resistor leads</p> Signup and view all the answers

    What is the maximum torque for tightening M6 x 20 screws during the fixation of each contact shell?

    <p>5 Nm</p> Signup and view all the answers

    When detaching the transition resistor shell, how many screws M8 x 25 need to be unlocked and loosened?

    <p>2 screws</p> Signup and view all the answers

    Which additional component needs careful attention to prevent distortion during the transition resistor shell reattachment?

    <p>The resistor leads</p> Signup and view all the answers

    What is the correct attachment for the potential connection on the contact shell?

    <p>1 hexagon socket screw M6 x 10</p> Signup and view all the answers

    What type of washer is used with each M8 x 25 screw during the reattachment of the transition resistor shell?

    <p>Both washer and dished washer</p> Signup and view all the answers

    What should be done after tightening the screws during the reattachment process?

    <p>Remove the chucking wedge</p> Signup and view all the answers

    What is one necessary step when remounting the diverter switch unit?

    <p>Align the marks on the support plate and tap changer head.</p> Signup and view all the answers

    What must be done after the motor drive has stopped during the operational checks?

    <p>Ensure that the motor drive unit will not restart when the push button is pressed.</p> Signup and view all the answers

    Which component is involved in operating both columns by one step?

    <p>Drive unit</p> Signup and view all the answers

    What torque specification is given for securing both types of screw installations?

    <p>22 Nm</p> Signup and view all the answers

    What is the function of the triangle markings on the tap changer head?

    <p>To ensure proper orientation during installation.</p> Signup and view all the answers

    Which type of screws are prescribed for standard design installations?

    <p>M8 x 20</p> Signup and view all the answers

    What is the last step after cranking the motor drive to return the coupled column?

    <p>Return it to the same position as the un-coupled column.</p> Signup and view all the answers

    What action must be taken concerning the oil conservator?

    <p>Fill with new oil up to its original level.</p> Signup and view all the answers

    What is the purpose of venting the suction pipe in the motor drive operation?

    <p>To release any trapped air or pressure</p> Signup and view all the answers

    When adjusting the axial clearance after stopping the motor drive, what is the recommended distance?

    <p>3 mm</p> Signup and view all the answers

    Which step should be taken after the motor drive has stopped and the time relay has dropped?

    <p>Check the bellows and greasing of ball joints</p> Signup and view all the answers

    What must be ensured regarding the transformer during operational tests of the motor drive?

    <p>It is de-energized</p> Signup and view all the answers

    Why is it necessary to grease coupling bolts and O-rings before operating the motor drive?

    <p>To reduce wear and tear on the shafts</p> Signup and view all the answers

    Which component is specifically mentioned as needing lubrication if necessary?

    <p>The upper gear unit</p> Signup and view all the answers

    What should be done regarding the diverter switches before conducting operational tests?

    <p>They must not be disconnected</p> Signup and view all the answers

    What action is associated with the tap changer during a successful motor drive operation?

    <p>Checking symmetrical coupling to the tap changer</p> Signup and view all the answers

    Contacts should be replaced if the value of 8 is reached or expected to be reached before the next inspection.

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

    The mechanical tap-change operation sequence includes main contacts denoted as A and B.

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

    Transition contacts are referenced with the notation a1, b1 in the main operation sequence.

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

    The operational sequence of main switching contacts is denoted by the letters D and E.

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

    Section 1.1 describes the sequence of both mechanical tap-change and electrical contacts.

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

    The correct mechanical switching sequence of the diverter switch is guaranteed as long as the difference between main switching and transition contacts does not exceed stipulated limits.

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

    Main switching contacts are not specified within the given context, making them irrelevant to the operation.

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

    If the difference between main switching and transition contacts is less than the given limits, correct mechanical switching may still not be ensured.

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

    A significant increase in the difference between main switching and transition contacts can lead to a failure in the diverter switch operation.

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

    Diverter switches are unaffected by variations in contact thickness between main switching and transition contacts.

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

    Maintaining the appropriate contact layer thickness between switching contacts is crucial for ensuring reliable device operation.

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

    The configuration of the diverter switch remains the same regardless of the contact wear experienced during operation.

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

    The maximum torque for securing the cover on the tap changer head is 34 Nm.

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

    It is unnecessary to ensure that the gasket fits properly when putting the cover on the tap changer.

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

    The horizontal drive shaft should be coupled to the upper gear unit using 6 screws M6 with a max torque of 9 Nm.

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

    The position of the tap-changer is irrelevant when reconnecting the leads for the monitoring circuit.

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

    A new O-ring is recommended to be replaced only if the original seal is broken.

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

    Reinstalling the position indicating disc is done before coupling the columns.

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

    Column motor drive synchronization is necessary for the operation of columns 1 and 2.

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

    The torque specification for securing M10 bolts for the head cover is 17 Nm.

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

    The tap-change monitoring circuit allows the motor drive to continue running even if the simultaneous operation between columns 1 and 2 is disturbed.

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

    The protective relay RS 2001 must be energized before the transformer can be switched off by the circuit breakers.

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

    It is absolutely necessary to operate the motor drive electrically or by cranking if the transformer is energized.

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

    Before returning to service, it is important to check that the tap changer and transformer are undamaged.

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

    In the event of serious trouble with the tap changer or motor drive, repairs should always be attempted on site.

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

    When the tap-change monitoring circuit responds, the motor drive must immediately stop.

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

    Reconnecting the transformer is permitted without any prior checking.

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

    The swing boom has a range of 270°.

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

    The operating test of the protective relay is not necessary unless a response is indicated.

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

    The specified angle for operation is 20°.

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

    The notation 'nr' indicates a quick-release mechanism in the operation.

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

    The content includes a diagram for mounting components.

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

    The representation of 'AEE' relates to electrical efficiency measurements.

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

    The operation sequence can vary based on the swing boom's range.

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

    The content suggests that additional support is unnecessary during operation.

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

    A visually pleasing layout is not crucial in technical layouts.

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

    Study Notes

    Detaching the Contact Shell

    • Loosen 6 hexagon socket screws (M8 x 20, self-locking) for the resistor connection.
    • Unlock and loosen 1 screw (M8 x 25) on both sides of the contact shell, each with a washer and a dished washer.
    • Unlock and loosen 8 screws (M6 x 20) to remove the contact shell.

    Removing the Arc Chutes

    • Withdraw the arc chutes from the on-load tap changers (types M Ill 350 A, M 111500 A, and M 111600 A).
    • For M 111500 A and M 111600 A models, ensure the two outer arc chutes are refitted in their original positions due to their split sidewalls.

    Cleaning the Diverter Switch

    • Clean the contact shell, all arc chutes, and the movable contact system using transformer oil and a brush.
    • Clean insulation parts with special care to avoid damage.
    • Note the thickness measurements for main switching and transition contacts, which should remain within 2.5 to 2.6 mm to ensure correct mechanical switching operation.

    Reattaching the Contact Shell

    • Reattach the contact shell in reverse order of removal, ensuring the arc chutes are seated properly.
    • Fixation requires specific screws: 8 screws (M6 x 20, max torque 5 Nm) and 2 screws (M8 x 25, max torque 22 Nm).
    • Do not insert screws for resistor leads immediately after tightening.

    Detaching and Reattaching Transition Resistor Shells

    • Loosen a hexagon socket screw (M6 x 10) for the potential connection and two screws (M8 x 25) on the transition resistor shell.
    • Clean the transition resistor shell and the resistor before reattaching, avoiding lead distortion.
    • Ensure correct torque settings when reattaching: 4 screws (M6 x 20, max torque 5 Nm) and 2 screws (M8 x 25, max torque 2 Nm).

    Final Assembly Steps

    • After reattaching the transition resistor shell, attach the resistor connection screws (6 screws, max torque 5 Nm).
    • Lower down into the oil compartment carefully, monitoring triangle markings for alignment.
    • Operate the motor drive unit to engage both columns and ensure proper function of the motor drive relay and tap changer.

    Additional Checks

    • Perform an operational test of the tap-change monitoring circuit.
    • Ensure that the transformer cannot be energized during tests, maintaining ground connections.
    • Check that the motor drive unit functions properly and that all components are aligned before finalizing the assembly.

    Maintenance and Operation of Diverter Switch Tap Changer

    • Replace contacts upon reaching the maximum number, or if expected to exceed before the next inspection.
    • Follow specific mechanical tap-change operation sequence for main and transition contacts.
    • Monitor for any discrepancies in the switching sequences to ensure proper functioning.

    Installation and Drive Shafts

    • Ensure motor drive unit and columns are in the same operating position for correct coupling.
    • Complete provisional coupling of motor drive and column, making sure positions are symmetric.
    • Reinstall horizontal drive shaft and secure the head cover with bolts, ensuring correct torque.
    • Reset protective relay and lock the hood to maintain safety standards.

    Oil Filling Procedure

    • Fill new oil into the diverter switch oil compartment to the recommended level, ensuring proper gasket fit.
    • Replace O-rings if necessary to prevent leakage.

    Tap-Change Monitoring Circuit

    • This circuit prevents the motor drive from running if simultaneous operation between columns is disrupted.
    • Immediate actions required if the protective relay activates: check the tap changer and transformer.

    Protective Devices

    • Circuit breakers should turn off the transformer immediately if the protective relay activates during operation.
    • Inspect tap changer and transformer for damage before reconnecting to power.

    Emergency Response

    • In case of serious troubles with tap changer or motor drive, consult an authorized representative or manufacturer.
    • Ensure that operations do not resume until the cause of any issues is identified and resolved.

    Safety Instructions

    • Never operate the motor drive while the transformer is energized if any alerts are triggered by the protective relay.
    • Confirm undamaged status of both tap changer and transformer before returning to service.

    General Tips

    • Regularly check the tap-change monitoring circuit functionality to ensure operational equality between columns.
    • Maintain readiness of the motor drive unit for efficient electric operation.

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    Description

    This quiz covers the detailed procedures for detaching the contact shell, including the loosening of various hexagon socket screws. It also addresses the removal of arc chutes as part of the process. Perfect for students or professionals looking to enhance their understanding of electrical components.

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