On-Load Tap-Changer Actuation Using Current Zero-Crossing Detection
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Solution Overview
Problem
Existing on-load tap-changers are actuated without considering inrush occurrences, leading to potential unsafe switching operations.
Innovation Solution
A method and device that utilize a control device to detect current profiles, determine zero crossings and intervals, derive a characteristic variable, and compare it with a limit value to safely pause or terminate actuation during inrush events.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the on-load tap-changer is actuated immediately after the switching command without considering inrush, then the switching operation speed is improved, but the safety and reliability of switching operations deteriorates
Solution Approach 1:
The control device performs preliminary detection of the current profile and determination of zero crossings before actuating the on-load tap-changer. By analyzing the current profile in advance and identifying suitable actuation moments (zero crossings), the system ensures safe switching operations while maintaining operational efficiency. This preliminary analysis allows the system to wait for optimal conditions rather than actuating immediately.
2Reliability
If the control device monitors current profile and determines zero crossings to prevent inrush, then the safety of switching operations is improved, but the device complexity and actuation time increase
Solution Approach 1:
The patent replaces complex mechanical monitoring systems with an electronic control device that uses sensor-based current profile detection. The control device processes electrical signals to determine zero crossings and control actuation timing, substituting mechanical complexity with electronic control. This approach maintains safety while reducing overall system complexity through modern electronic measurement and control techniques.
3Reliability
If the actuation is paused or terminated based on characteristic variable analysis, then the reliability of switching operations is improved, but the productivity and switching frequency decrease
Solution Approach 1:
The control device uses periodic current zero crossings as the basis for actuation timing. By synchronizing the tap-changer actuation with the natural periodic zero crossings of the current profile, the system ensures reliable switching at optimal moments. This periodic approach based on AC current characteristics allows frequent switching operations while maintaining reliability, as zero crossings occur regularly in AC systems.
Data Source
AI summary
A method for actuating an on-load tap-changer using a control device, a sensor, and a drive is provided. The control device receives a switching command for actuating the on-load tap-changer. The sensor detects a current profile. The control device determines multiple consecutive times for current zero crossings of the current profile and multiple intervals between the multiple consecutive times of the current zero crossings. The control device derives a characteristic variable from the multiple intervals and compares the characteristic variable with a limit value. The control device terminates or pauses the actuation based on determining that the characteristic variable exceeds the limit value and performs the actuation by controlling the drive based on determining that the characteristic variable satisfies or falls below the limit value.