Parallel Arc Detection via Discrete Wavelet Transforms
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Solution Overview
Problem
Conventional circuit breakers fail to detect parallel arc faults effectively, leading to potential fires as electrical wiring deteriorates in older homes, as these faults do not trigger the instantaneous trip function due to lower peak current levels.
Innovation Solution
An apparatus and method utilizing a current sensing device, detection unit, and microcontroller that decompose load current signals using discrete wavelet transforms to identify parallel arc faults by comparing sum of discrete wavelet coefficients to predetermined thresholds, generating a trip signal when conditions are met.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional thermal-magnetic trip devices are used, then overcurrent and short circuit protection is provided, but parallel arc faults are not detected effectively
Solution Approach 1:
The patent replaces the mechanical thermal-magnetic trip mechanism with an electronic detection system using discrete wavelet transforms. The microcontroller analyzes current waveforms through digital signal processing, computing wavelet coefficients and comparing them against thresholds to detect parallel arcs, substituting mechanical response with electronic intelligence.
Solution Approach 2:
The patent changes the detection parameter from simple current magnitude (thermal-magnetic) to wavelet transform coefficients that capture transient arc characteristics. By analyzing the mathematical decomposition of current signals into different frequency components, the system detects subtle arc patterns that conventional magnitude-based devices miss.
2Measurement precision
If discrete wavelet transform analysis is implemented, then parallel arc detection accuracy is improved, but processing complexity increases
Solution Approach 1:
The patent segments the current signal analysis into distinct wavelet coefficient components through discrete wavelet transform. By decomposing the complex current waveform into separate frequency-band coefficients, the system analyzes each segment independently, improving detection accuracy while managing computational complexity through structured breakdown.
Solution Approach 2:
The patent creates a mathematical representation (wavelet coefficients) that copies essential features of the original current signal. This transformed copy captures arc characteristics more effectively than the raw signal, allowing accurate detection while simplifying the actual processing by working with coefficient values rather than full waveform data.
3Reliability
If wavelet coefficient summation method is used, then detection reliability is improved, but computational requirements increase
Solution Approach 1:
The patent applies partial action by summing only the relevant wavelet coefficients that correspond to arc fault frequencies, rather than processing the entire signal spectrum. This selective summation of specific coefficient components provides sufficient detection reliability while minimizing the computational energy required compared to exhaustive signal analysis.
Data Source
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AI summary
An apparatus to perform parallel arc fault current interruption (AFCI). The apparatus includes a current sensing device (10) disposed in the electrical circuit to sense an electrical load, the current sensing device (10) configured to produce an output signal representative of a load current passing therethrough, a detection unit (302), in signal communication with the current sensing device and configured to receive the output signal produced by the current sensing device, the detection unit (302) being configured and disposed to output a secondary signal based on the output signal, and a microcontroller (306) coupled to the detection unit (302), being responsive to computer executable instructions which, when executed by the microcontroller (306), cause the microcontroller (306) to receive and to decompose the secondary signal via discrete wavelet transforms to thereby obtain discrete wavelet coefficients, and to compute a sum of the discrete wavelet coefficients, and to compare the sum of the discrete wavelet coefficients to a predetermined threshold, and to generate a trip signal when the sensed load current is above a predetermined threshold and the sum of the discrete wavelet coefficients cooperatively indicate that predetermined threshold conditions for trip signal generation are satisfied