Reflectometry Fault Detection in Wired Electric Networks
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Solution Overview
Problem
Current methods for detecting faults in electrical cables using reflectometry face challenges in precision due to limitations in sampling rate and signal duration, particularly in on-board systems where high-frequency signals are attenuated, leading to insufficient accuracy and economic and technical constraints.
Innovation Solution
A method and device utilizing reflectometry with adaptive threshold comparison and desynchronized signal injection and sampling, employing Field Programmable Gate Array (FPGA) and analog-digital converters operating at lower frequencies, to improve fault detection and location precision by simulating higher sampling rates without increasing cost or complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the sampling rate is increased to improve measurement precision, then fault detection precision is improved, but device cost and complexity increase
Solution Approach 1:
The patent divides the sampling process into multiple sequential low-rate sampling operations instead of using a single high-rate sampler. By segmenting the measurement into N sequential samples taken at lower rate Fe, the system achieves equivalent precision to a single high-rate sample without requiring expensive high-speed ADC hardware.
Solution Approach 2:
The patent employs periodic injection of test signals and periodic sampling at intervals Te to accumulate multiple samples over time. This periodic approach allows the system to achieve high measurement precision through temporal averaging of N periodic samples, replacing the need for continuous high-speed sampling.
2Measurement precision
If the sampling rate is increased to improve measurement precision, then fault detection precision is improved, but economic cost increases
Solution Approach 1:
The patent uses multiple low-cost, low-speed ADC components that can be easily manufactured, replacing expensive high-speed ADC hardware. Each ADC operates at modest sampling rate Fe and can be implemented using standard, inexpensive components, making the overall system more economically viable.
Solution Approach 2:
By segmenting the high-precision measurement task into N sequential low-precision samples, the system avoids the need for expensive high-speed conversion hardware. The cumulative information from N low-cost samples provides equivalent diagnostic value to a single high-cost high-speed sample.
3Measurement precision
If the duration of the injected signal is decreased to improve measurement precision, then fault location precision is improved, but signal attenuation increases
Solution Approach 1:
The patent uses periodic repetition of the test signal injection N times, allowing each individual signal pulse to maintain adequate duration for low attenuation while the periodic repetition provides the temporal resolution needed for precise fault location. The cumulative effect of N periodic injections improves precision without requiring each individual signal to be ultra-short.
Solution Approach 2:
The system performs preliminary signal conditioning and adaptive threshold setup before the actual measurement sequence, allowing the use of longer-duration test signals that suffer less attenuation. The preliminary calibration phase enables accurate fault detection even with lower-frequency, longer-duration signals that propagate better through the cable.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enhances fault detection precision in electrical networks by improving sampling efficiency and reducing signal attenuation, allowing for accurate fault location with reduced economic and technical burdens, particularly suitable for on-board applications.
Implementation Method 1
reflectometry is a method based on the principle of radar which consists of injecting a wave into a medium and analyzing the reflected wave using the phenomena of wave propagation in physical media
Implementation Method 2
injecting a test signal into a cable of the network, recovering a signal reflected on the cable
Data Source
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AI summary
The invention relates to a method for detecting and locating defects by reflectometry in a wired electric network that comprises the following steps: feeding a test signal into a wire of said network; collecting the signal reflected on said wire and sampling said reflected signal at a frequency of Fe=1/Te; repeating N times the preceding steps, N being an integer; for each fed test signal, collecting n samples of the corresponding reflected signal, n being an integer; analysing the M=n*N collected samples in order to detect and locate a defect in the wired electric network. The method is characterised in that the collected samples are compared with a predefined adaptive threshold for each diagnosis, on the basis of the test signal fed into the tested wire.