On-Load Tap Changer Timing at Current Zero Crossings
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Solution Overview
Problem
Existing load tap changers lack accuracy in actuation and fail to protect vacuum switching tubes due to immediate actuation without considering the current zero crossings, leading to increased wear and tear.
Innovation Solution
A method and device that utilize a control device and sensor to predict future current zero crossings, adjusting the actuation time of the load tap changer to align with these crossings, accounting for the mechanical inertia of the drive train, thereby minimizing arc duration and wear on vacuum interrupter tubes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a conventional on-load tap changer uses a gear mechanism with multiple gears and intermediate shafts to achieve bidirectional rotation, then the tap changer can switch between different connection positions, but the device complexity increases and the number of moving parts increases leading to higher failure risk
Solution Approach 1:
The gear mechanism is segmented into a first gear engaged with the drive shaft for one rotation direction, and a second gear engaged with the drive shaft for the opposite rotation direction. This segmentation allows independent control of each gear, eliminating the need for complex intermediate shafts and bidirectional coupling mechanisms.
Solution Approach 2:
Instead of using a single bidirectional gear system with intermediate shafts, the invention inverts the approach by using two unidirectional gears that can be independently selected. The control system switches between first and second gears based on the desired rotation direction, simplifying the mechanical structure while maintaining bidirectional capability.
2Adaptability or versatility
If the on-load tap changer uses multiple moving parts including intermediate shafts and multiple gears, then bidirectional rotation is achieved, but the reliability decreases due to increased failure risk from more moving parts
Solution Approach 1:
The invention extracts and removes the intermediate shafts from the gear mechanism, retaining only the essential first and second gears directly engaged with the drive shaft. This extraction eliminates unnecessary moving parts that could fail, while the bidirectional rotation capability is preserved through selective engagement of the two gears.
Solution Approach 2:
The invention inverts the conventional approach by using two simple unidirectional gears instead of one complex bidirectional gear system with intermediate shafts. This inversion reduces the number of moving parts and potential failure points while maintaining the ability to control rotation in both directions.
3Adaptability or versatility
If a gear mechanism with intermediate shafts is used to control rotation direction, then tap position switching is achieved, but the ease of operation deteriorates due to complex control requirements
Solution Approach 1:
The invention applies dynamic control by selectively engaging the first gear for one rotation direction and the second gear for the opposite direction based on real-time operational needs. This dynamic switching is controlled by a control system that monitors the desired tap position and activates the appropriate gear, simplifying the control logic compared to managing multiple intermediate shafts.
Solution Approach 2:
The control system is segmented into distinct control paths for the first gear and second gear, allowing independent and simple control of each gear's engagement. This segmentation reduces the control complexity by treating each gear's engagement as a separate, straightforward decision rather than managing a complex interconnected system of multiple shafts and gears.
Data Source
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AI summary
The invention relates to a method for actuating an on-load tap-changer (4) by means of a drive (3), a sensor (5), and a controller (2), wherein - the controller (2) receives a switch command to actuate the on-load tap-changer (4); - a current curve is detected via the sensor (5); a start time (T0) at which the actuation of the on-load tap-changer (4) would be started is determined in the current curve; - a temporal offset (TV) is added to the start time (T0), and the time (TB) at which the actuation would potentially be started is determined therefrom; - the point in time (TG) of the next zero-current crossing after the point in time (TB) at which the actuation would potentially be started is determined; - the temporal difference (TD) between the point in time (TB) at which the actuation would potentially be started and the point in time (TG) of the next zero-current crossing is determined; - the temporal difference (TD) is added to the start time (T0) in order to determine a new start time (T1) for the actuation therefrom; and - the actuation of the on-load tap-changer (4) is started at the new start time (T1) by means of the the drive (3).