On-Load Tap Changer Crowbar Protection for Fast Voltage Switching
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Solution Overview
Problem
Existing on-load tap changers for power transformers, particularly in wind power installations, face issues with voltage instability, slow response to rapid voltage changes, and potential damage from undefined switching states in thyristor-based systems, leading to inefficiencies and safety concerns.
Innovation Solution
An on-load tap changer module with a control device, tap changers, and a crowbar that provides a predetermined current path to adjust the transformation ratio and protect against overvoltage, using toggle diode structures and thyristors for rapid switching and auto-start capabilities, ensuring safe and reliable operation without external activation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If mechanical switches are used in conventional tap changers, then the transformation ratio can be adjusted, but the response speed is slow and cannot respond to rapid voltage drops and/or overvoltages
Solution Approach 1:
The patent replaces mechanical switches with electronic valves or switches (thyristors) to achieve rapid switching responses. This substitution eliminates mechanical inertia and contact wear, enabling the tap changer to respond quickly to voltage fluctuations while maintaining reliability through electronic control mechanisms.
2Speed
If thyristor-based tap changers are used, then rapid response to voltage dips and/or overvoltages is achieved, but the thyristors may fail and cause damage to the transformer
Solution Approach 1:
The patent implements a crowbar device as a protective mechanism that activates before thyristor failure can cause damage. The crowbar provides a controlled short-circuit path that limits voltage stress on thyristors during transient overvoltage events, preventing catastrophic failure while maintaining the rapid response capability of the thyristor-based system.
Solution Approach 2:
The crowbar acts as an intermediary protective element between the thyristors and the transformer. It intervenes during abnormal voltage conditions to redirect current flow, protecting the expensive transformer from damage caused by thyristor failures or undefined switching states.
3Speed
If thyristor-based tap changers are used, then rapid switching is achieved, but undefined switching states during start-up can result in voltages reaching or exceeding supply voltage level
Solution Approach 1:
The patent employs a control device that activates the crowbar during start-up and transient conditions before the thyristors are fully controlled. This preliminary protective action ensures that even if thyristors are in undefined switching states, the crowbar prevents dangerous voltage buildup by providing a controlled discharge path.
4Adaptability or versatility
If mechanical tap changers are integrated in the transformer, then voltage regulation is achieved, but the system requires oversizing to handle voltage variations between -20% and +20%
Solution Approach 1:
The patent replaces mechanical tap changers with electronically controlled thyristor-based tap changers. This enables continuous and rapid adjustment of the transformation ratio to handle wide voltage variations (-20% to +20%) without requiring oversized transformer components, as the electronic system can dynamically adapt to voltage changes rather than relying on fixed mechanical taps.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution ensures reliable, low-maintenance, and efficient operation of power transformer systems by rapidly responding to voltage fluctuations and protecting against transient high voltages, preventing damage and ensuring safe operation even during power failures or disruptions.
Implementation Method 1
at least one crowbar for voltage limitation which is adapted to provide a predetermined current path for determining a predetermined transformation ratio of the power transformer when a predetermined threshold voltage value is exceeded
Data Source
AI summary
The invention relates to an on-load tap changer module (1, 15), in particular a power electronic on-load tap changer module, for adjusting a transformation ratio of a power transformer (2) having at least one transformer winding providing at least one tap (3), having: a control device (6), at least one tap changer (7) which can selectively be connected and disconnected by means of the control device (6) in order to adjust the transformation ratio of the power transformer (2), and at least one crowbar (11) for voltage limitation, which is adapted, when a predetermined threshold voltage value is exceeded, to provide a predetermined current path for determining a predetermined transformation ratio of the power transformer.The invention relates further to an assembly consisting of a power transformer (2) and an on-load tap changer module (1, 15) and to a method for operating an on-load tap changer module.