Transformer On-load Tap-changer Quiz

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Questions and Answers

What is essential for ensuring equal current splitting during the operation of on-load tap-changers?

A split tapped winding and split main winding (correct)

A complete bypass of the diverter switch

Bridging of parallel contacts

A higher transition resistance in the parallel windings

In applications with enforced current splitting, what must not be bridged?

The parallel contacts (correct)

The main transformer winding

The voltage between parallel tapped windings

The impulse voltage resistance

What must the transformer manufacturer specify regarding impulse voltage resistance?

The resistance required between parallel tapped windings (correct)

The maximum current rating

The type of impulse voltage generated

The number of on-load tap-changer models available

What condition is necessary for the leakage impedance in on-load tap-changers?

It must be three times that of the transition resistance Signup and view all the answers

What purpose does the VACUTAP® VT® on-load tap-changer serve in dry-type transformers?

To allow for interrupt-free voltage adjustment Signup and view all the answers

What distinguishes on-load tap-changers from off-circuit tap-changers regarding enforced current splitting?

On-load tap-changers require active current division Signup and view all the answers

Which application does not require enforced current splitting?

Non-active current splitting configurations Signup and view all the answers

Which component is responsible for the mechanical operation of the on-load tap-changer in dry-type transformers?

Motor-drive unit Signup and view all the answers

What must be ensured when loading with impulse voltage in a transformer with parallel tapped windings?

Voltage must be monitored between windings Signup and view all the answers

What design feature allows the single-phase modules of the VACUTAP® VT® to form a three-phase system?

Direct assignment to transformer legs Signup and view all the answers

What aspect of the on-load tap-changer operation is highlighted by its interrupt-free capability?

Voltage stability during load changes Signup and view all the answers

In which scenario do different models of tap-changers need to be applied?

With and without enforced current splitting Signup and view all the answers

Which of the following is NOT a function of the oil conservator in an on-load tap-changer system?

Houses protective relays Signup and view all the answers

Why is the VACUTAP® VT® on-load tap-changer considered a single-phase module?

It connects to only one phase of the transformer Signup and view all the answers

What is the significance of the last digit in the designation I 651 for the VACUTAP® VM® on-load tap-changer?

It specifies the number of parallel main switching contacts for single-phase models. Signup and view all the answers

In the designation VACUTAP® VM® I 651-123/B-10191W, what does the 'B' refer to?

Tap selector size. Signup and view all the answers

Which feature is essential for ensuring a non-interchangeable tap-changer designation?

Specific characteristics of the on-load tap-changer model. Signup and view all the answers

What does the basic connection diagram identifier signify in the tap-changer designation?

It illustrates the wiring and connections for installation. Signup and view all the answers

How can the tap selector of an on-load tap-changer be adapted?

To fit the required number of positions and tapped winding circuit. Signup and view all the answers

What does 'Um' represent in the context of the VACUTAP® VM® on-load tap-changer designation?

Highest voltage for equipment in kilovolts. Signup and view all the answers

What determines the distinguishing features of on-load tap-changer models?

The specifications and requirements of the application. Signup and view all the answers

The term 'maximum rated through-current Ium' refers to what aspect of the tap-changer?

The highest load the tap-changer can handle under normal operation. Signup and view all the answers

Study Notes

Enforced Current Splitting

Enforced current splitting is relevant for single-phase on-load and off-circuit tap-changers that handle large rated through-currents.
Different tap-changer models are required for applications both with and without enforced current splitting, despite having the same rated through-current.

Electrical Properties

Parallel contacts in systems with enforced current splitting must remain unbridged to avoid operational issues.
Voltage must be monitored between parallel tapped windings when subjected to impulse voltage, with specific resistance requirements established by the transformer manufacturer.

On-load Tap-changers

Equal current splitting on parallel contacts is critical during diverter switch operation, necessitating split tapped and main windings.
Leakage impedance between parallel main windings should be at least three times the transition resistance of the tap-changer.
The on-load tap-changer's model designation is uniquely determined based on its design features to prevent interchangeability.

Example Type Designation

Example designation for VACUTAP® VM® on-load tap-changer: I 651-123/B-10191W
- I: Indicates single-phase operation.
- 651: Maximum rated through-current (650 A) and number of parallel contacts.
- 123: Highest voltage for equipment (123 kV).
- B: Tap selector size.
- 10191W: Basic connection diagram reference.

Tap Selector Configurations

Tap selectors can be customized for varying numbers of positions and winding circuits, allowing flexibility in transformer design.
On-load tap-changer systems include components such as a motor-drive unit and protective relays for enhanced operation and safety.

On-load Tap-changers for Dry-type Transformers

VACUTAP® VT® is specifically designed for dry-type transformers, facilitating interrupt-free voltage adjustments.
It's a single-phase module that attaches directly to the transformer leg and includes a mechanical operation motor-drive unit.
Multiple single-phase modules can be combined to form a three-phase system.

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Description

Test your knowledge of transformers, specifically focusing on on-load tap-changers and their components. This quiz will cover the schematic presentation and operational aspects related to motor-drive units and protective relays. Enhance your understanding of transformer technology through this interactive quiz.