Electrical Engineering Standards and Methods

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Questions and Answers

What is the first step required to lower the oil level in the tap changer head?

Open the sample valve of the return pipe

Loosen the screws at the coupling bracket

Close the stop valve between oil conservator and tap changer head (correct)

Open the drain valve of the tap changer head

Which precautions should be taken when handling the switching oil during maintenance?

Avoid any electrical equipment near the work area

Ensure open flames are present for safety

Use any type of pumping equipment available

Handle the oil as if it were a flammable liquid (correct)

What should be monitored through the inspection glass while draining oil from the tap changer head?

The oil level in the conservator

The color of the switching oil

The support plate of the diverter switch unit (correct)

The temperature of the oil

Which action is necessary to uncouple the drive shaft at the upper gear unit?

Loosen 6 screws M6/w.s.10 at the coupling bracket Signup and view all the answers

Why is it important to avoid open fire during the oil handling process?

Explosive gases can accumulate under the tap changer cover Signup and view all the answers

What quantity of oil should ideally be drained from the tap changer head?

10 liters Signup and view all the answers

What must be taken into consideration concerning the pumping equipment used during maintenance?

It must be suitable for flammable liquids Signup and view all the answers

Which component's operation should be initiated if an oil filter unit is present?

The sample valve of the return pipe Signup and view all the answers

What is the maximum allowable number of tap change operations for the diverter switch units of the tap changer before replacement is required?

800,000 operations Signup and view all the answers

For the M II 350 D on-load tap changer with a rated current of up to 350 A, how many tap change operations can it perform without requiring any MR oil filter?

40,000 operations Signup and view all the answers

If a transformer performs 15,000 tap change operations per year, when is the first mandatory inspection interval?

After 20,000 operations Signup and view all the answers

What is the recommended inspection interval after the first inspection is carried out?

4 years Signup and view all the answers

What should be done when a tap changer reaches approximately 1,000,000 switching operations?

Contact Technical Service Signup and view all the answers

Which of the following is a requirement for transformers operating under high switching operation conditions?

Use a stationary oil filter unit Signup and view all the answers

What measurement method is referenced for testing oil quality in transformers?

Karl-Fischer method Signup and view all the answers

How many tap change operations can the M III 600 D perform with an MR oil filter?

80,000 operations Signup and view all the answers

What action should be taken before removing the upper supporting cylinder?

Dismount the link for the tap change supervisory control system Signup and view all the answers

Which components are used to secure the link for the tap change supervisory control system?

Two studs M5 with lock nuts Signup and view all the answers

What should be avoided to prevent damage to the diverter switch unit?

Dropping any parts during disassembly Signup and view all the answers

What type of screws are used for the connection of the supporting cylinder?

M8 x 20 screws with lock nuts and washers Signup and view all the answers

What cleaning method is recommended for the supporting cylinder?

Cleaning with a brush and transformer oil Signup and view all the answers

What could lead to creeping paths that may damage the system?

Unclean surfaces of the support cylinder and insulating shaft Signup and view all the answers

Before starting the disassembly, what should be ensured regarding small parts?

The number of small parts is complete Signup and view all the answers

What type of risks does dropping parts during disassembly pose?

Potential blockage of the diverter switch and damage to system components Signup and view all the answers

What is the maximum torque specification for attaching the supporting cylinder with lock nuts?

22 Nm Signup and view all the answers

Which components must be securely fastened with lock nuts when assembling the diverter switch unit?

Supporting plate and supporting cylinder Signup and view all the answers

What is the purpose of the diverter switch pole W in the assembly process?

To ensure alignment with diverter switch pole U Signup and view all the answers

How many screws are required to attach the lower supporting cylinder of pole W?

8 screws Signup and view all the answers

What should be checked regarding the resistor leads of diverter switch pole W during assembly?

Clearance to the upper screen ring Signup and view all the answers

Which part must be assembled first when setting up the diverter switch unit?

Lower insulating shaft Signup and view all the answers

Which operation should be performed to verify the mechanical function of the device?

Operate the diverter switch several times Signup and view all the answers

What is the role of the 2 washers provided with each screw in the assembly process?

To distribute load and prevent loosening Signup and view all the answers

What does the notation '50%' suggest in the context provided?

A maximum threshold for component wear Signup and view all the answers

When should the contacts be evaluated for replacement according to the value mentioned?

When the wear tolerance has reached a 50% level Signup and view all the answers

What consequence may arise from not replacing the contacts when necessary?

Increased operational costs due to inefficiency Signup and view all the answers

What is indicated by the letter 'R' appearing multiple times in the context?

Repeated instances of wear measurement Signup and view all the answers

What could the series of numbers '5555' signify in maintenance documentation?

A identification code for maintenance history Signup and view all the answers

What strategy should be implemented when the wear indicator reaches critical levels?

Conduct immediate inspections and potential replacements Signup and view all the answers

Why is it critical for documentation to indicate the need for replacement?

To maintain consistent operational efficiency Signup and view all the answers

What does the symbol 'x' followed by percent signs imply in the context?

A representation of variable operational levels Signup and view all the answers

Study Notes

Transformer Tap Change Operations

Several transformers are detailed (M III 350 D, M III 500 D, M III 600 D), each rated for specific current capacities.
Inspection intervals are based on experience with conventional oil qualities and the number of tap change operations.
A tap selector in the tap changer is generally maintenance-free, but special cases may require Technical Service consultation after approximately 1,000,000 operations.
Diverter switch units must be replaced after 800,000 operations.

Inspection and Maintenance Schedule

Initial inspection required after 20,000 tap change operations, if yearly operations exceed 15,000.
Further inspections occur every four years.
Recommended use of stationary oil filter units for upkeep.

Handling Procedures

Switching oil is flammable; handle with care, avoiding open flames and using appropriate pumping equipment.
During maintenance, lower the oil level by closing the stop valve and opening the drain and bleeder valves.
Approximately 10 litres must be drained until the diverter switch unit support plate is free of oil.

Diverter Switch Maintenance

Uncoupling of the drive shaft involves loosening screws at the coupling bracket for clearance.
Care must be taken to visually inspect and ensure cleanliness of surfaces to avoid damage from creeping paths.
Proper assembly of the diverter switch is vital; ensure all parts are clean and accounted for to prevent operational blockages.

Important Assembly Steps

Remove supporting components in reverse order, checking for mechanical functionality during reassembly.
Max torque requirements are specified for attachment screws to prevent damage.
Final checks for sufficient clearance in electrical components are crucial before testing the diverter switch unit's operation.

Safety Precautions

Strict measures need to be followed to avoid dropping parts into the switch unit which could lead to malfunctions.
Series of corrective actions and checks are outlined to confirm readiness before final installation of the diverter switch unit.

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Description

This quiz focuses on various electrical engineering standards and measurement methods, including tap change operations and oil quality assessments based on established publications. Deepen your knowledge of inspection intervals and IEC standards through this informative quiz.