Arc Detection Using Wavelet Coefficients
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Solution Overview
Problem
Conventional current interrupters fail to accurately distinguish between series arcs and normal load currents, particularly when a series arc occurs, leading to potential failure to trip in case of arcing faults.
Innovation Solution
An apparatus with a current sensing device, detection unit, and microcontroller that decomposes secondary signals using discrete wavelet transforms to generate a trip signal when specific threshold conditions are met, effectively differentiating between normal and arcing currents by analyzing detailed and approximate coefficients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional current sensing methods are used, then the device complexity is low, but the measurement precision is insufficient to distinguish series arcs from normal load currents
Solution Approach 1:
The current signal is segmented into multiple frequency components using wavelet packet transform, separating the signal into approximation coefficients (low frequency) and detail coefficients (high frequency). This segmentation allows targeted analysis of arc-specific high frequency components while filtering out normal load current components.
Solution Approach 2:
The analysis transitions from single-domain time analysis to multi-domain analysis by computing wavelet coefficients in both time and frequency domains. This dimensional transformation enables identification of arc faults through frequency-based characteristics that are not apparent in the time domain alone.
2Reliability
If simple current threshold comparison is used, then the ease of operation is high, but the reliability is insufficient to detect arcing faults accurately
Solution Approach 1:
Wavelet packet transform coefficients serve as an intermediary between the raw current signal and the final arc detection decision. These coefficients act as a mediator that transforms the complex signal analysis into comparable metric values that can be evaluated against thresholds.
Solution Approach 2:
The simple mechanical threshold comparison is replaced with a sophisticated signal processing system using wavelet transforms. This substitution replaces direct current magnitude comparison with frequency-domain coefficient analysis, enabling reliable arc detection while maintaining automated operation.
3Measurement precision
If high-frequency sampling is performed to capture arc characteristics, then the measurement precision improves, but the loss of time increases due to longer processing periods
Solution Approach 1:
The wavelet packet transform decomposition is performed on pre-collected signal segments rather than in real-time continuous processing. By preparing and analyzing fixed-length signal windows in advance, the system achieves high-resolution frequency analysis without introducing excessive processing delays.
Solution Approach 2:
The system processes only the necessary frequency components (detail coefficients at specific decomposition levels) rather than analyzing the entire frequency spectrum. This partial action approach focuses computational resources on arc-relevant high frequency components, reducing overall processing time while maintaining detection precision.
Data Source
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AI summary
An apparatus for facilitating interruption of current in an electrical circuit is provided and includes a current sensing device (10) in the electrical circuit to service an electrical load, the current sensing device (10) being productive of an output signal representative of a load current passing therethrough, a detection unit (30), in signal communication with the current sensing device (10) such that the output signal is received by the detection unit (30), the detection unit (30) being configured and disposed to output a secondary signal based on the output signal, and a microcontroller (80) to receive and to decompose the secondary signal into detailed and approximate coefficients, and to generate a trip signal for use in interrupting an operation of the electrical circuit when a current of the sensed load is above a predetermined threshold and the detailed and approximate coefficients cooperatively indicate that threshold conditions for trip signal generation are satisfied.