Arc Fault Branch Isolation Using FFT Power Spectral Density
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Solution Overview
Problem
Existing methods for detecting and isolating series arc faults in DC power systems on aircraft are inadequate, as they fail to accurately determine the source of the arc fault signature, leading to unnecessary shutdowns of non-faulted electrical connections.
Innovation Solution
A system and method that utilize the Fast Fourier Transform (FFT) to convert sampled current data into the frequency domain, calculate power spectral density (PSD), and compare it to predetermined limits to detect arc faults. By applying Kirchhoff's current law and analyzing current divisions across different electrical branches, the method determines the source of the arc fault signature and isolates it to a single load.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If arc fault detection is performed by analyzing voltage and current waveforms in a large DC power system, then arc fault signatures can be detected, but the source of the arc fault signature cannot be determined, leading to unnecessary shutdowns of non-faulted electrical connections
Solution Approach 1:
The patent divides the large DC power system into multiple electrical branches, each monitored by its own arc detection device. Each device analyzes voltage and current waveforms locally to detect arc fault signatures and determine their source within that specific branch. This segmentation allows for precise localization of arc faults without causing system-wide shutdowns, as only the affected branch is isolated when an arc fault is detected.
2Reliability
If arc fault detection systems are implemented in aging aircraft with deteriorated wire insulation and loose terminal connections, then arc faults can be detected, but the bundled wiring configuration makes it difficult to isolate the specific source of the arc fault
Solution Approach 1:
The patent segments the bundled wiring into individual electrical branches, with each branch equipped with its own arc detection device that monitors voltage and current waveforms. This allows the system to identify which specific branch within the bundled wiring contains an arc fault, even when wire insulation is deteriorated or terminal connections are loose. The segmentation approach transforms an otherwise indistinguishable bundled wiring problem into a set of individually monitorable branches.
3Power
If DC power systems operate at 270VDC and higher voltages to achieve more electric aircraft goals, then power delivery capability is improved, but the risk of sustained arcs and catastrophic failures increases
Solution Approach 1:
The patent implements continuous monitoring of voltage and current waveforms in each electrical branch, with arc detection devices providing real-time feedback about arc fault conditions. When an arc fault is detected in a high-voltage DC power system, the system immediately responds by isolating the affected branch, preventing sustained arcs from causing catastrophic failures. This feedback mechanism enables safe operation at 270VDC and higher voltages by rapidly detecting and mitigating arc hazards.
Data Source
AI summary
An arc fault detection system senses current flow in a power source branch and in one or more load branches in an electrical system. Over a frequency range divided into a predetermined number of frequency bins, a controller records and tallies the branch having largest magnitude of power spectral density for each frequency bin. The branch having highest total tally is determined to be the branch in which the arc fault occurred and can then safely be isolated from the electrical system.