Cable Fault Detection Using Periodic Signal Delay
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Solution Overview
Problem
Distributed reflectometry methods face interference issues due to unsynchronized reflectometers, requiring post-processing to discriminate signals and being less effective for long cables, especially with zero-average signals and full-scale pulses, which can lead to measurement disturbances.
Innovation Solution
Introducing a controlled delay between the signals injected by reflectometers, allowing for synchronized signal injection and acquisition without the need for post-processing, and ensuring compatibility with any test signal, including zero-average signals, to minimize interference and enhance measurement accuracy for long cables.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If distributed reflectometry is used to monitor long cables with multiple reflectometers, then the monitoring distance and fault detection capability are improved, but signal interference between unsynchronized reflectometers increases
Solution Approach 1:
The patent applies periodic action by using cyclic delay patterns where each reflectometer introduces a delay that is a multiple of a base delay value. This creates periodic temporal separation between signals from different reflectometers, allowing the system to maintain extended monitoring distance while managing signal interference through predictable, repeating delay cycles.
Solution Approach 2:
The patent changes the temporal parameter (delay) of each reflectometer's signal injection. By assigning different delay values to different reflectometers based on their positions and synchronizing them cyclically, the system resolves signal interference while maintaining the ability to monitor long cable distances.
2Measurement precision
If post-processing discrimination is applied to eliminate interference from multiple reflectometers, then measurement precision is improved, but processing complexity and time increase
Solution Approach 1:
The patent applies preliminary action by pre-configuring delay values for each reflectometer before signal injection. This preliminary temporal separation is built into the system setup, eliminating the need for complex post-processing discrimination algorithms and reducing both processing complexity and time while maintaining measurement precision.
3Use of energy by moving object
If full-scale pulses are used for testing very long cables, then signal energy is maximized for better detection, but capacitive discharge transitions cause measurement disturbances
Solution Approach 1:
The patent converts the harmful capacitive discharge effect into a beneficial temporal separation mechanism. By carefully selecting delay values that account for the discharge transition duration, the system uses the discharge effect to naturally separate signals in time, transforming what was previously a source of measurement disturbance into a useful tool for interference management.
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
This approach eliminates the need for signal discrimination post-processing, maintains measurement precision across long distances, and supports full dynamics of converters, effectively locating faults in very long cables by canceling mutual interference between reflectometers.
Implementation Method 1
Reflectometry consists of transmitting a signal on a cable or a network of cables and then measuring the echoes returned due to the reflections of the signal injected on the singularities, or impedance discontinuities, of the cable.
Data Source
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AI summary
A method for testing a cable by distributed reflectometry comprising the following steps: - injecting a first periodic signal (SA) into the cable and a second periodic signal (SB) comprising the same number N of periods and the same number M of samples per period as the first signal (SA), - acquiring a measurement of the reflection, on the impedance discontinuities of the cable, of each of said first and second signals (SA, SB), - averaging said measurements of the reflection of at least one of said first or second signals (SA, SB) over all of the periods of same to produce at least one reflectogram, - determining the positions of faults in the cable from at least said reflectogram, said method being characterised in that each period of said second signal (SB) is injected into the cable with a delay or an advance of a predetermined absolute value that increases for each successively injected period.